Granted that races at distance ranging from 5000m to marathon are run at a paces either a little above or a little below the anaerobic threshold, the greatest determinant of efficiency is the ability to achieve a high pace at threshold so as to minimise the amount of fuel-inefficient anaerobic metabolism.    If the goal is efficiency, much of one’s training efforts should be directed at this raising the threshold pace.  Whether this goal is best achieved by emphasis on high volume or high intensity training (or both) remains a controversial topic, but that is not the question I will focus on in this post.   Instead, I will return to the less important but nonetheless intriguing question of running style.

Almost certainly, the most important issue in considering the effects of running style on efficiency is minimization of risk of injury.  Injury impairs not only performance at the time of injury but also leads to missed training and loss of aerobic fitness.  Unfortunately, the evidence suggests there might be a trade-off between mechanical efficiency and safety.  I think this can be illustrated most readily by examining solving the equations of motion of the running body (though if you are willing to accept my calculations, you do not need to do the maths yourself – I will illustrate the results pictorially).  The complete solutions of the equations describing a multiply-jointed body made of viscoelastic tissues (i.e. tissues in which change of shape depends on how rapidly the force is applied) is of course horrendously complex.  Nonetheless a great deal can be learned by focussing on the equations that describe the motion of the centre of gravity of the body (COG).  If we know the time course of the external forces acting on the body – namely gravity; ground reaction force (GRF); and wind resistance – it is possible to perform an accurate computation of the motion of the COG.

On the surface of the earth, the force of gravity is constant.  It is the product of mass multiplied by the acceleration due to gravity (g), which has the value 9.8 metres/second/second (or 32 feet/sec/sec in Imperial units).  Ground reaction force is the reaction of the ground to the push of the body against the ground.  We can measure the push of the body against the ground quite precisely using a force plate, and therefore, since action and reaction are equal and opposite, we can deduce the GRF. Estimation of wind resistance is trickier, and for the purpose of this post, I will assume that wind resistance is negligible.   I have presented the equations and a description of how I solved them, in the calculations page (see the sidebar).

Ground reaction forces

For simplicity I have assumed that the vertical component of ground reaction force (vGRF) varies sinusoidally while the runner is on stance, as shown in figure 1.   This is a moderately good approximation to real data for a forefoot runner, and is convenient from the computational point of view.   vGRF rises rapidly from zero after footfall, reaches a peak at mid-stance and then falls away to zero as the runner approaches take-off.  I do not think the main conclusions I will draw will be appreciably influenced by the exact shape of the time course of vGRF, though at the price a little more computation, I could solve the equations using real data for vGRF.

One crucial feature regarding vGRF is that the value of vGRF averaged over the entire gait cycle must equal the downward force of gravity (mg, where m is mass) since gravity acts constantly throughout the gait cycle.  Otherwise, there would be a net vertical impulse that would either cause the runner to continue to float upwards after the completion of the gait cycle if average vGRF exceeded mg, or alternatively to be pulled to the ground if average vGRF was less than mg.  One inevitable consequence is that when time on stance is short compared with the total period of the gait cycle, peak vGRF must be high (as is illustrated by the ochre dashed curve in figure 1) compared with the situation where time on stance is a large faction of the total duration of the gait cycle (as illustrated by the dashed blue line in figure 1).

Fig 1: vGRF (dashed line) and hGRF (solid line) for relatively long time on stance (blue) and short time on stance (ochre). Vertical lines denote footfall, mid- stance and take-off. (Force units are Newtons)

Once vGRF is known, the horizontal GRF (hGRF) can readily be computed assuming the total GRF acts along the line from point of support to the COG (as shown in equation 5 on the calculations page).  The hGRF associated with a sinusoidal  time course of vGRF is depicted by the solid ochre and blue lines in figure 1.   In early stance, vGRF is negative, indicating that it exerts a braking effect on the runner.   Early in the stance phase magnitude of hGRF increases as vGRF increases, but because hGRF is only appreciable when the line joining point of support to COG  is oblique, the magnitude of hGRF begins to decrease despite the continued rise in vGRF as the runner approaches mid-stance.  By mid-stance, the COG is directly above the point of support, total GRF is vertical and hGRF is zero.  After mid-stance, the line from COG to point of support is directed obliquely backwards, so hGRF is now directed forwards and has an accelerating effect on the runner that reveres the braking effect in early stance phase.   One feature of interest is that when the runner spends a long time on stance, the peak magnitude of hGRF is almost the same as when the runner spends only a short time on stance, despite the much greater peak vGRF when stance is short.  The reason is that when time on stance is short, the line from COG to point of support is never far from vertical so hGRF does not rise as high is it would if this line was more obliquely inclined.   The fact that the magnitude of peak hGRF is similar for both short and long times on stance means that the braking effect is actually much greater when time on stance is longer, because the braking force acts for a longer time.

Vertical and horizontal components of velocity

Figure 2 depicts the time course of the velocity of the body in both vertical and horizontal direction throughout the gait cycle, based on the solution of equations 1 and 2 shown on the calculation page.

Fig 2: Vertical velocity (dashed line) and change in horizontal velocity from airborne phase, V(a), due to braking and acceleration. Blue: long stance; Ochre: short stance. Running speed: 4 m/sec.

If we focus first of all on the vertical velocity in the case where time on stance is a large proportion of the total gait cycle (the dashed blue line), we see that starting from the high point at mid-flight, downwards velocity increases at a steady rate under the influence of the uniform accelerating effect of gravity.  After foot-fall, as vGRF rises, the rate of acceleration slows and once vGRF exceeds mg, the downwards acceleration ceases, though the body still continues to move downwards at a decreasing rate until mid-stance, by which time vertical velocity is zero.  After mid-stance, the body accelerates upwards under the influence of vGRF.  Once vGRF has fallen below mg, the acceleration diminishes, though the velocity remains upwards.  After the body becomes airborne, vGRF is zero and the upwards velocity continues to decrease at a constant rate as gravity retards the ascent.  By the middle of the airborne period (the end of the cycle in figure 2) the vertical velocity is zero.

In the case in which time on stance is short (the ochre dashed line in figure 2), the constant increase in downwards velocity during the airborne phase continues for a longer period than when time on stance is long (blue dashed line).  Consequently, when stance time is short, the downwards velocity is much greater at foot-fall.   As vGRF rises in the first half of the stance phase, the downwards velocity decreases reaching zero at mid-stance.  After mid-stance, the high vGRF causes a greater upwards acceleration than in the case where time on stance is longer, so that upward velocity at take off is higher.  The body rises to a greater height before its ascent is arrested by gravity in the middle of the airborne phase.  Using equation 3 to compute distances travelled, in the case where horizontal velocity at mid-stance is 4 m/sec, it can be shown that in the case when peak vGRF is 2mg, the total vertical distance travelled between mid-stance and airborne peak is 5.8 cm whereas it is 9.8 cm when peak vGRF is 4mg.

In contrast, in the case of horizontal velocity (solid lines in figure 2) the amount of slowing between footfall and mid-stance is appreciably greater when time on stance is longer, because, as we have seen, the braking force (hGRF) is of similar magnitude but acts for a longer period of time.

Implications for efficiency

What do these calculations tell us about mechanical efficiency?  It is important to note that a substantial proportion of the kinetic energy of the falling body is absorbed and stored as elastic energy during the first half of stance, and is recovered by elastic recoil after mid-stance.  The proportion that is recovered is likely to be higher when time on stance is short because tendons and muscle as viscoelastic, meaning that up to a certain point, they are more elastic when the force is applied over a shorter period of time.  In similar manner, some of the kinetic energy lost due to the braking effect of  hGRF in early stance can be stored as elastic energy and recovered after mid-stance.  Again, the proportion recovered is likely to be higher when time on stance is shorter.  However, irrespective of whether time on stance is short or long, only a proportion of the kinetic energy lost during the first half of stance can be recovered.  Thus, in general efficiency will be less when the total amount of work that must be done to reverse the braking effect and to elevate the body back to its peak height is large.  We have already seen that the braking effect is greater when time on stance is long, whereas the amount of upwards acceleration required to elevate the body to its peak height is greater when time on stance is shorter.  Which of these effects demands more energy?

Energy required

The amount of work done when a force is applied can be computed using equation 6.  The results are shown in table 1 for a running speed of 4 m/sec.

Table 1: the work done after mid-stance to reverse the braking effect by hGRF and to elevate the body from mid-stance to peak height in mid-flight. Less of the required energy is derived from elastic recoil at longer time on stance (i.e lower vGRFmax)

At both short and long times on stance, the energy required to overcome braking is greater than the energy required to elevate the body from its low point at mid-stance to its high point in the airborne phase.  Thus, the sum of the amounts of energy required to overcome braking and to elevate the body is substantially greater when time on stance is longer.  Since the proportion of energy recovered by elastic recoil is likely to be less under these circumstances, it is clear that mechanical efficiency is less when time on stance is long.  It should be noted that these calculations refer to the work done to counteract the effects of external forces acting on the body.  Some additional work is also done repositioning the limbs, and at very high running speeds this can become appreciable, but is beyond the scope of this discussion.

Conclusions

The calculations confirm that mechanical efficiency is increased by shorter time on stance.  Although many coaches believe this, it is not universally accepted, so it is re-assuring to see that the equations provide a clear confirmation.  In practice a shorter time on stance can be achieved though stiffening the hip, knee and ankle joints by applying greater tension in the muscles that flex and extend these joints, especially the hamstrings and quads.  The BK method of running developed by Frans Bosch and Ronald Klomp focuses on decreasing time on stance via plyometric drills that develop the strength necessary to maintain adequate leg stiffness.   However, the equations also provide a clear warning regarding the increased ground reaction force.  As shown in figure 1, when time on stance is short, the peak vertical forces acting on the body are much larger, and the potential risk of injury is potentially greater.

It is noteworthy that in the late stages of a marathon, many runners automatically increase their time on stance.  This is probably due in part to the fact that as muscle strength diminishes it is harder to maintain the required tension in the hamstrings and quads, but also might be an unconscious defensive reaction to protect the body from injury at a stage where tired muscles are less able to withstand stress.

So far we have not addressed the issue of cadence.  For a given proportion of the gait cycle spent on stance, the magnitude of peak vGRF required to achieve a specified proportion of the gait cycle airborne is lower at high cadence because both airborne time and stance time decrease at higher cadence.  In my next post I will discuss cadence.  The interim conclusion is that there is a trade off between mechanical efficiency and risk of injury.  Efficiency can be increased by spending a shorter period of the gait cycle on stance, but the risk of injury is greater.  Therefore, a style which entails greater leg stiffness should be adopted cautiously, and requires careful conditioning of the muscles, tendons and joints to allow them to withstand the greater forces.

Perhaps to the non-runner, the enigma is why runners are so devoted to their sport.  It is of course relatively easy to comprehend the mind of the elite athlete striving for Olympic glory, but a surprising passion is found  across the entire spectrum for those whose ambition is to run 10 Km in an hour to those aiming to run a half-marathon in that time.  In the internet era, running has become a major social event.  On web-sites such as Fetch Everyone, hundreds of runners not only record hundreds of thousands of training miles, diverse races and numerous hard-won PB’s,  but also engage in a wide range of chatter, most of it mutually supportive but sometimes it is bitchy and at other times ribald.   The austere amateur spirit that permeated athletics when it was largely the preserve a small group of dedicated, almost monastic, individuals in the 1950’s has given way to something of a carnival.  Though of course the ribald graffiti occasionally uncovered on medieval monastic cell walls suggest that monasticism has always been only a thin veil over seething passion.

John Hadd

But to runners the enigma of the heart is more profound.   Sadly, this was illustrated by the recent death of John ‘Hadd’ Walsh.  He was the founder and a guiding spirit of the Malta marathon in the 26 years since its inception, but by virtue of his generous spirit, thoughtful analysis of heart physiology, and pugnacious writing, his influence extended far beyond the island of Malta and shaped the training programs of runners worldwide.    He was devoted to his wife, the marathon runner, Carol Galea.   He was 8 years her senior, and declared that he would train with a dedication sufficient to ensure that he lived to be 108, so they would not be separated prematurely.  Tragically, his promise was not fulfilled as he died, apparently of a totally unanticipated heart attack, during an early morning run at age 56 [2].  Though a personal tragedy, his death, along with the occasional reports of other untimely deaths of athletes and coaches, might merely be taken as confirmation of the widespread acceptance that running does indeed place an immediate stress upon the heart, but overall, the health benefits of running far outweigh the risks [3].

However the picture is a little more complex.   While at least some premature cardiac deaths among athletes are due to previously unidentified congenital defects, or to unsuspected coronary artery disease in those who take up running in middle age, the challenging question is: does endurance training actually produce persisting damage to the heart?

Two of the greats

The evidence is extensive and controversial, but before dipping into the vast body of scientific evidence, it is illuminating to look at the cases of two other athletes.  The first, Wally Hayward, a legendary figure in the history of the Comrades Marathon, did almost make it to his hundredth birthday.    Hayward first won that gruelling hilly 90 Km ultra-marathon between Durban to Pietermaritzburg  in 1930 at age 21; he was the winner again on four occasions in the 1950’s; and became the oldest person to complete the race when he staggered across the finishing line at age 80 in 1989.    He died in 2006 a few months before his 98^th birthday.   At age 70, at a stage when he had engaged in regular training for 52 years, he underwent extensive physiological testing [4]. A treadmill exercise test revealed no ischaemic ECG abnormalities and an excellent functional capacity (VO2max = 58.6 ml/kg/min).  His overall fitness was exceptional for a 70 year-old.  The only two abnormalities reported were frequent premature atrial contractions (PACs) and moderately increased thickness of the left ventricular wall.

The second case is that of Emil Zatopek, world record holder at 5000m and 10,000m in the 1950’s and winner of gold medals in the 5000 m, 10,000m and marathon in the Helsinki Olympics in 1952.   Unlike Wally Hayward, he retired from competitive running at age 35, after 17 years of training that had included a hitherto unheard of combination of intensity and volume.   He continued to be active in the Communist Party in his native Czechoslovakia, but due to his support for the democratic wing of the party during the Prague Spring in 1968, he was banished to work in a uranium mine.  At age 71, three years after his after his rehabilitation as a national hero by Vaclav Havel in 1990, he underwent extensive medical and physiological testing at the Institute of Sports Medicine in Prague [5].   Perhaps as a legacy of the privations of the uranium mine his muscles were flabby and he was a pale shadow of his former self, though it is noteworthy that his joints were remarkable free of the degenerative changes common in his age group.   Of particular interest in the current context, his heart showed some ischaemic changes and he had both atrial fibrillation and ectopic ventricular contractions.

Ventricular hypertrophy and PACs

General conclusions should not be drawn from anecdotes of exceptional athletes.  Nonetheless, the two abnormalities reported in Wally Hayward, hypertrophy of the muscular wall of the left ventricule and frequent premature atrial contractions are both well documented features of the elderly athlete’s heart.  For example, in a study comparing 11 elderly male athletes (mean age 73) with a life-long history of strenuous exercise with matched controls (mean age 74), Jensen-Urstad and colleagues [6] found that 9 of the 11 athletes had more than 100 premature atrial contractions in24 hours compared with 4 of the controls, while 8 of the athletes had multiform ventricular ectopics (indicating multiple maverick electrical sources in the ventricles) compared with 2 of the controls.

Of course ventricular hypertrophy in athletes is only to be expected.  It contributes to the powerful contraction of the well-trained heart.  Unlike the hypertrophy associated with pathological conditions in non-athletes, in which there is decreased blood supply to the heart muscle via myocardial capillaries,  the hypertrophy in athletes is usually accompanied by normal or increased capillary density [7].

Cardiac damage and remodelling

Nonetheless it is probable that the remodelling of cardiac muscle produced by endurance training involves some breakdown of muscle cells, similar to that which can readily be observed in skeletal muscle following intense training.  For example, following demanding endurance events, increased levels of the cardiac enzyme troponin are found in the blood stream, implying damage to heart muscle cells.  Immediately after the 2004 Otztal Radmarathon, troponin levels in the cyclists’ blood were increased 10 fold relative to baseline, and returned to baseline one week later [8].

In skeletal muscle, the muscle cells damaged by training are rebuilt stronger than before.  The persistence of collagen fibres that formed a scaffold during repair is of little importance provided the fibres become well aligned along the direction of pull of the muscle.  On the other hand, heart muscle is different.  Cardiac muscle performs not only physical work of contraction, but the muscle cells themselves from part of the conducting system that initiates and transmits the electrical signal that triggers contraction.   If the heart is to pump efficiently, this electrical signal must be transmitted across the myocardium from the sinoatrial node in the right atrium via the atrioventriclar node to the ventricles, in a well coordinated manner.  It is plausible that misplaced collagen fibres might upset the orderly transmission of the signal and perhaps even cause maverick muscle cells to take over the pace-maker role, generating ectopic beats.  As reported by Jensen-Urstad [6], premature atrial beats and also multiple maverick ventricular sources are substantially more frequent in elderly athletes than in age-matched non-athletes.

Atrial fibrillation

Premature atrial contractions are of little functional importance, but the crucial issue is whether they can lead to the chaotic ill-coordinated contraction that is atrial fibrillation.  In a large population-based study of men and women aged 55-75 in Denmark, Binici and colleagues found that a frequency of premature ectopic atrial contractions greater than 30 /hour, or runs of more than 20 consecutive atrial ectopic beats, was associated with an almost three fold increased risk of hospital admission for atrial fibrillation in the follow-up period of approximately 6 years [9].  There is also worrying evidence of a similar risk in endurance athletes.    The anecdotal account of Emil Zatopek’s atrial fibrillation is consistent with the findings of several large, well designed scientific studies.  For example in an 11 year follow-up study of 252 marathon runners, with mean age 39 at recruitment, the risk of symptomatic atrial fibrillation, based on an observed annual onset rate of 0.48 per 100,  was 8.8 times greater than in a comparison sample of 305 sedentary men, after adjusting or other risk factors such as high blood pressure [10].

Although far less serious than ventricular fibrillation (which is usually lethal) atrial fibrillation has some life-threatening consequences.  It predisposes to the formation of blood clots in the atrium which can subsequently be released into the blood stream, causing a myocardial infarction if they lodge in the coronary arêtes or a stroke if they lodge in the brain.   However, despite the quite compelling evidence for an increased incidence of atrial fibrillation in middle-aged and elderly runners, the balance of evidence does not indicate that the commonly observed heart rhythm abnormalities lead to an increase rate of serious adverse cardiovascular events in middle-aged athletes.   For example, in a 5 year follow-up of 117 middle-aged and elderly cross-country skiers, Lie and Erikssen [11] found that while persisting abnormalities of heart rhythm and also ventricular hypertrophy were common, only 2 developed angina and none suffered a myocardial infarction.  They concluded that the ECG abnormalities were mainly related to physiological adaptation to training and that training seems to protect against coronary heart disease.

Coronary obstruction

So far, we have focussed mainly on possible disturbances of heart rhythm.  In contrast, we have noted that capillary blood supply to the myocardium is often enhanced in athletes, and coronary disease might in fact be reduced.   However, perhaps the most disconcerting study of all is a recently reported investigation of calcified plaques furring-up the coronary blood vessels of elderly men who have participated in multiple marathons.  Schwartz and colleagues found that the prevalence of calcified plaques in the coronary arteries of men who had run in the Twin Cities Marathon annually for at least 25 years was almost twice as high as in age matched sedentary comparison subjects [12].  Enigmatically, the same research group carried out a similar study in female marathoners, with the opposite result: namely, the female runners had far fewer calcified plaques than the matched comparison subjects, though it is noteworthy that the female runners had run at least one marathon annually for only a period of 10 years.   The results of both of these studies should be treated with extreme caution until they have been replicated.  Despite the evidence that the male heart is generally more vulnerable to injury than the female heart, the diametrically opposite findings in the two sexes raise doubt about the generalizability of the findings.  Furthermore, it should be noted that the finding in males might reflect the consequences of running a larger number of marathons.

At least for the time being, the majority of the evidence suggests that despite the fairly high likelihood that long term endurance training will lead to an increased number of premature atrial contractions, the overall effect of endurance training is to increase life expectancy.    In future posts I will examine the evidence in greater detail, and also describe my discoveries about my own heart rhythm since acquiring a heart rate monitor that records the time intervals between consecutive beats.   More formal investigations have demonstrated that my heart is functioning well.  Nonetheless, in light of the growing evidence that elderly endurance athletes face a significant risk of atrial fibrillation, my current opinion is that monitoring heart rate beat by beat is indeed a sensible way of screening for possible increases in frequency of premature atrial contraction.  It would of course be foolish to make any definitive diagnosis based on one’s own observations using equipment that is demonstrably fallible.  It would be similarly foolish to curtail an activity that I enjoy passionately, when even the risk of atrial fibrillation is less daunting than the risk of a sedentary life style.

References

[1] Jankowski M, Bissonauth V, Gao L, Gangal M, Wang D, Danalache B, Wang Y, Stoyanova E, Cloutier G, Blaise G, Gutkowska J. 2010 Anti-inflammatory effect of oxytocin in rat myocardial infarction. Basic Res Cardiol. 105(2):205-18.

[2] Times of Malta, Saturday, September 17, 2011. Malta marathon founder dies  [http://www.timesofmalta.com/articles/view/20110917/athletics/malta-marathon-founder-dies.385085]

[3] Thompson PD, et al. (2007) Exercise and acute cardiovascular events placing the risks into perspective: a scientific statement from the American Heart Association Council on Nutrition, Physical Activity, and Metabolism and the Council on Clinical Cardiology. Circulation. 115(17):2358-68.

[4] Maud PJ, Pollock ML, Foster C, Anholm JD, Guten G, Al-Nouri M, Hellman C, Schmidt DH. (1981) Fifty years of training and competition in the marathon: Wally Hayward, age 70–a physiological profile. S Afr Med J. 31;59(5):153-7.

[5] Novotný V, Brandejský P, BaráckováM, Boudová L, Vilikus Z, Streda A, Novotný A.(1994) Medical and anthropological study of a world and Olympic champion, long-distance runner, 35 years after the end his racing career. Sbornik Lekarsky (Journal of Czech Physicians and the Czech Medical Society) 95(2):139-55.

[6] K Jensen-Urstad,F Bouvier,B Saltin,M Jensen-Urstad (1998) High prevalence of arrhythmias in elderly male athletes with a lifelong history of regular strenuous exercise.Heart 79:161–164

[7] Hudlicka O, Brown M, Egginton S. (1992) Angiogenesis in skeletal and cardiac muscle.  Physiol Rev. 72(2):369-417.

[8] Neumayr G, Pfister R, Mitterbauer G, Eibl G, Hoertnagl H. (2005) Effect of competitive marathon cycling on plasma N-terminal pro-brain natriuretic peptide and cardiac troponin T in healthy recreational cyclists. Am J Cardiol.;96(5):732-5.

[9]  Binici Z, Intzilakis T, Nielsen OW, Køber L, Sajadieh A. (2010) Excessive supraventricular ectopic activity and increased risk of atrial fibrillation and stroke. Circulation. 121(17):1904-11.

[10] Molina L, Mont L, Marrugat J, Berruezo A, Brugada J, Bruguera J, Rebato C, Elosua R. (2008)  Long-term endurance sport practice increases the incidence of lone atrial fibrillation in men: a follow-up study. Europace. 10(5):618-23.

[11] Lie H, Erikssen J. (1984)  Five-year follow-up of ECG aberrations, latent coronary heart disease and cardiopulmonary fitness in various age groups of Norwegian cross-country skiers. Acta Med Scand. 216(4):377-83.

[12] Schwartz JG, Merkel-Kraus S, Duval S, Harri K, Peichel G, Lesser JR, Knickelbine T, Flygenring B, Longe TR, Pastorius C, Roberts WR, Oesterle SC, Schwartz RS (2010) Does long term endurance running enhance or inhibit coronary artery plaque formation? A prospective multidetector CFA study of men completing marathons for least 25 consecutive years.  J. Am. Coll. Cardiol. 55;A173.E1624

However, a little below the horizon scanned by the national newspapers, there has been what seems to me, an even more amazing transformation. In the 1950’s and 60’s the newspaper headlines focussed on the exploits of legendary figures who were household names. In Australia, where I grew up, our parochial heroes were John Landy, and then Herb Elliot and later Ron Clark. Across the Tasman Sea there was Peter Snell, while the names of the great European middle and long distance runners, Bannister, of course, but also Zatopek and a long list of others, were household names even in Australia. In contrast, club athletics earned only a few column inches in local newspapers. Nonetheless, even at this more modest level, athletes were mostly a dedicated band of fit young men and women. I ran for a D grade club. My memory of finishing times from 45 years ago is hazy, but as far as I remember, even at D grade level, the entire field in a 5000m typically crossed the line within the span from 16 to 18 minutes. I doubt that I would have recognized 20 minutes as a meaningful time for 5000m. Even at this level, running was not a sport for individuals without at least a modest talent for athletics. Despite the apparent decline in distance running in Europe and the Anglophone world, in my eyes, the really dramatic development over the past half century has been the transformation of distance running from the sport of a few dedicated fit young men and woman to something that might almost be called a mass participation sport, occurring far away from the hubbub of the big city marathons.

In England, and to a less extent, in many countries world-wide, this transformation is illustrated most clearly by the phenomenon of Parkrun. Parkrun grew out the Bushy Park time trials, initiated by Paul Sinton-Hewitt in 2004. At the beginning, a handful of runners from local clubs in southwest London met on Saturday mornings to run a timed 5Km along the paths of Bushy Park in Teddington. In large part due to the dedication and creativity of Paul, but also of course, due to the input from many volunteers, and eventually, funding from commercial sponsors, Parkruns occur every Saturday morning in hundreds of sites, in Britain and other countries, extending from Denmark to Australia.

Perhaps least typical is the Parkrun at Camp Bastion in Afghanistan. I know little about that particular Parkrun, but suspect that the event often occurs in circumstances of duress. I doubt the atmosphere is quite like the Christmas truce on the Western front in 1914, when British and German troops put down their weapons and played football together in the snow. Camp Bastion perhaps demonstrates the far reach of Parkrun, but more typical Parkruns occur in relaxed and sociable circumstances in the congenial surroundings of leafy city parks. The runners span the range from world class athletes such as Mo Farah and Craig Mottram to individuals for whom merely completing 5 Km is a triumph.

A few months ago, a weekly Parkrun was established at Colwick Park, a delightful space of grassy banks and woodland surrounding two small lakes beside the River Trent on the outskirts of Nottingham. This morning, I decided that Colwick Parkrun offered me a good opportunity to make an attempt at my short term goal of running 5Km in 25 minutes. So I arrived shortly before 9am on a cool Autumn Saturday morning to find that the park was alive with runners warming up. There had been quite a lot of rain in the past few days, and there were a few extensive puddles on the paths. In other places, soggy wet autumn leaves covered the paths as they meandered through the trees, but on the whole, the surface was not bad, and it was an ideal day for running.

I have not actually raced a 5Km (or a 5000m) since the 1960’s so I was not sure how to fine tune my pace, but as my primary goal was to break 25 minutes, I set-off at a pace little faster than 5 min/Km. I covered the first Km in 4:50. However it was already clear that it would be a struggle to sustain that pace for another 4 Km, so I eased back a little, and 20 or 30 runners passed by. Despite the large field, in the second Km I was largely on my own. As I approached the one very minor ascent on the otherwise completely flat course, about 50 metres ahead of me was a youngster who had clearly misjudged the early pace and was now struggling. This gave me the opportunity to claw back one of the places I had lost while being overtaken by so many at the end of the first Km. However, I suspect that the 50 year age gap between us was much more a handicap to him than to me, so overtaking him could scarcely be regarded as an achievement. A further 100 metres ahead was a group of three men and a young woman, and as they climbed the minor ascent, the young woman had dropped back a few metres. I thought that here was a quarry worth pursuing. There is no cause for mock gallantry in these mixed age and mixed gender races: it seemed to me that in this instance, the thirty five year age gap separating us was certainly to her advantage rather than mine and more than compensated for any effects of gender difference, so the race was on. However, I could not summon the power to make any inroads into the gap. In fact, the gap widened as the second Km went by in 4:58. During the third Km the young woman was still in psychological contact with the group ahead of her, and I was falling yet further behind. In the 3rd Km my pace had slipped to 5:02 and in the 4th Km slipped even further to 5:05. By this stage it was clear that the group ahead were out of reach, and even my 25 minute target was in jeopardy. I was interested to note at the finish that the young woman had not only maintained contact with the group of three men, but had overtaken all of them.

Meanwhile, from midway through the fourth Km, I could hear feet behind me. I didn’t look around but estimated that there were probably three runners rapidly closing the gap. Now I was the quarry and the task was not only to make sure I didn’t drop any further behind my 5 min/Km target schedule, but to avoid being overtaken in the run to the finish. I held out until 150 metres from the end when one of the three men sprinted past. I did however hold off the other two, covering the final Km in 4:54, giving me a finishing time of 24:49. So I achieved my primary goal, but it had been a considerable effort. I was 56th in a field of 121, and thirteenth on age grading. I still have a long way to go to get back to my fitness of two years ago. But it is delight to have at last joined the Parkrun community.

There is little doubt that before building up intensity, it is crucial to do enough low intensity running to condition sinews and muscles to protect them against injury.  At the end of the summer, I had gradually built-up volume with low intensity running – enough, I think, to prepare my sinews and muscles for moderately intense interval sessions provided I keep the number of reps low enough to avoid serious fatigue.   So the debate hinges mainly on the question of whether a high volume of low intensity running is essential to build a sound aerobic base, and the related question of whether speed sessions help or hinder base-building.

Lessons from Ed Whitlock

There is no doubt that at least for some athletes, a large volume of low intensity running works well.  In the Toronto Waterfront Marathon earlier this month, Ed Whitlock set a new M80-84 world record of 3:15:54.  Whitlock is famous for training slowly – typically he runs 15-20 miles daily, in monotonous 500m circuits of Evergreen Cemetery near his home in a Toronto suburb, at 9 min mile pace.  While this pace is not all that slow for an 80 year old, compared with his marathon racing pace of 7:30 min/mile, 9 minute mile pace is fairly relaxed.   He only occasionally does intervals.

However I think that there are some additional aspects of Whitlock’s running history that need to be taken into account.  As a young man Whitlock was a fairly fast runner – competing with and occasionally beating some of the legendary figures of British distance running in the 1950’s.  When he took up running again in his early 40’s, while living in Montreal, he concentrated on middle distances.  In a Runners Web interview in 2003, he reported that this best times during those years in Montreal were 1:59.9 and 4:02. He described his training as ‘a fair amount of road work but the serious stuff was track interval work outs under coaching supervision’.  I suspect that he built up some fairly powerful type 2a (aerobic fast twitch) muscle fibres in those sessions.   In more recent years, he has balanced his long slow training sessions with frequent races, and his racing paces are fast – typically under 6 minutes for a mile and around 6:50 /mile in 10K.   Frequent racing at these speeds no doubt keeps those type 2a fibres in good condition.

and from Faija Singh

The other amazing veteran performance in this year’s Toronto Waterfront Marathon was 100 year old Fauja Singh’s 8:11:06, also a world record.  The most impressive feature is not the time itself but simply that he is the first 100 year old to complete a marathon.  Fauja also trains fairly slowly – typical he run/walks 10-15Km a day, though he does do some track training and he holds the world M100 records for virtually all distances from 100 metres (23.14 sec) to the marathon.

Despite their predominantly high volume/low intensity training, both Ed Whitlock and Fauja Singh illustrate that if you want to sustain a reasonable pace over the longer distances as the years go by, it is important to maintain some speed in your legs.  I think the greatest enemy of speed in the veteran years is the loss of type 2a fibres.   For a runner whose goal is to run a reasonably fast race over any distance shorter than an ultra-marathon, building up  the type 2a fibres is almost as important as building up the type 1  (slow twitch) fibres.  The specialist ability of the elite marathon runner is the ability to maintain a pace at the upper boundary of the aerobic zone for several hours. This demands not only endurance but enduring muscle power.

Renato Canova

Perhaps the most successful marathon and half-marathon coach of all time is Renato Canova.  His protégés include Moses Mosop, Florence Kiplagat, Abel Kirui and Wilson Kiprop.  Not only has he coached some of the world’s finest half marathon and marathon runners, but he has also been more prepared than any other leading endurance coach to discuss his ideas with the running community, most notably though his frequent and comprehensive contributions to Let’s Run forums.  He claims that his principles are based on observation of many leading athletes of the past two decades; extensive discussion with other coaches and a good grounding on science, particularly detailed evidence about energy metabolism derived from lactate testing in many athletes.

A key feature of Canova’s approach is periodization that leads to a final period of training that is specific for the target event.  In the case of marathon training, the goal of the specific period is to develop the capacity to maintain marathon pace for increasingly long distances.  However long runs at MP are potentially stressful and therefore, must follow earlier phases that are designed to build an adequate foundation for this demanding final phase.  Of course most coaches advocate some form of periodization which starts with base building and leads to more specialized training.  However, there is a crucial conceptual difference between Canova’s periodization and the periodization recommended by a coaches such as Maffetone and Hadd,.  Whereas Maffetone and Hadd argue that exceeding anaerobic threshold can interfere with the building of an aerobic base, Canova does not and therefore he is more inclined to recommend a greater mixture of different types of session within each phase of the periodization.  As I have discussed in previous posts, there is only a little evidence that speed sessions might damage aerobic fitness, but substantial evidence that training at the upper end of the aerobic zone is an efficient way to produce increases in aerobic capacity.

The four phases of marathon preparation identified by Canova are a general phase in which the emphasis is on developing an all-round base; a foundation phase designed to build endurance via fairly high volume of low intensity running.; special preparation which increasing the capability to maintain marathon pace and a little faster; specific training in which the goal is to accustom the body  to running at marathon pace or even a little faster for distances in the range 25-35 Km.

Looking backward to move forward

For present purposes, I am interested in the general phase, whose goal is the development of an all round base.  I think this is the phase in which each individual has to weigh up his or her own current strengths and weaknesses, based on a life-time history of running.  My own personal experience suggests that for me, a crucial component of building an all round base includes building up muscle coordination and strength.   This is the foundation for ensuring that even in the subsequent higher volume, relatively low intensity phase I can maintain a reasonable pace, bearing in mind that beyond that phase comes a specific training phase in which the body must become accustomed to sustaining marathon pace for 25-35 KM.

Over forty years ago I became a marathon runner almost by accident.  At that time, I was involved in a fairly wide range of interests and activities, one of which was club level track athletics.  My main event was the 5000m but I wasn’t especially gifted.  My principal objective at interclub meetings was gaining points for my club.  As a result I ran in events as diverse as 400m hurdles, 3000m steeplechase and 5000m, though I cannot remember ever winning any interclub event, at any distance.   The majority of my training consisted of tempo runs and fartlek around the local suburban streets.  During the winter I ran cross county races on weekends when I was not involved in other activities, such as mountaineering.  One year in the late 1960’s I entered a marathon, with very little specific marathon preparation.  In those days there were few marathons and this one happened to be the South Australian state championship.  Rather to my surprise, I won it.  In retrospect, I think the conclusion is that while I have very limited natural speed, I have a modicum of natural endurance.  Whether this is a product of my genes or the fact that I used to run to and from school as a youngster, I do not know.  Whatever, the origin of my endurance, it appeared that the main requirement to allow me to put this endurance to use in a marathon was enough tempo running and fartlek to compensate for my lack of natural speed.  I only ever ran about four marathons in those days.  I do not have a record of my best time but it was around 2:25.

Almost forty years later, in my late fifties, I decided that it was time to get fit again.  Without fully appreciating the effort it would require, I decided to prepare for a marathon at age 60.  However I was dismayed to find that whereas four decades previously my tempo pace was around 5:30 to 5:45 minutes per mile, and I had rarely trained at paces slower than 6 minutes per mile, now it was a struggle to run faster than 6 min per Km.  So I decided my first task was to get my tempo pace up to something between 4 and 4:15 minutes per Km.  After about six months of tempo sessions, fartlek and a few interval sessions, I did a time trial over a 10 K cross country route in 41 minutes.  I was a bit disappointed to fail to break 40 minutes but nonetheless turned my attention to re-establishing my endurance.    For 5 months, I averaged only about 30 miles per week, but did include three long runs of 20 miles or more.  At that stage, I entered a marathon to assess my progress and allow me to set a reasonable goal for my intended M60 marathon attempt the following year.

In my previous experience, at the start of a marathon the entire field formed no more than two or three rows across the roadway.  In the intervening decades the character of marathon races had been transformed almost beyond belief.  I now found myself engulfed in a vast throng of runners in diverse outfits progressing at diverse speeds.  After feeling trapped at a snail’s pace for the first mile I broke clear of the melee with a crazy burst of speed and did not settle to a sensible pace until after three miles.  I reached the halfway mark in 93 minutes, feeling fairly comfortable.  However by 20 miles I was paying the price for my crazy escape from the melee at the beginning, and in the final few miles I struggled even to achieve 10 minute mile pace.  My finishing time was 3:27:35.  I was disappointed by my poor pace judgement but considered that the following year, after my 60^th birthday, it would be feasible to aim for a time around 3:15.  Unfortunately, my long standing asthma came back with a vengeance the following year and I gave up training.

A couple of years later I made another attempt to get back into training but was once again diverted by several misadventures, including a rather nasty fall earlier this year.  Now, I am starting again.   But now, in my mid sixties, I am acutely aware of how much muscle strength I have lost in the past few years.  Once again it is an effort to run much faster than 6 min/Km.  My past experiences suggests to me that the highest priority in my  general conditioning phase is to get some speed back into my legs.  Then I can embark on some high volume, lower intensity workouts, with the   expectation that even when running at lower intensity, I will be able to maintain at least a moderate pace, in preparation for the phase in which I will try once again to accustom myself to  sustaining marathon pace for long distances.

My current program includes a weekly interval session or hill session, a progressive run or tempo run, and one longish run (typically 15 Km), together with some easier sessions to make a total of around 50Km per week.  I am also doing some trampolining – which I hope will prove to be a satisfactory substitute for plyometrics, but more gentle on aging legs.  I will persist with this program for at least 3 months.  My first target is a 25 Min 5K, and after that I will see how much further I can increase my pace.  I hope that this will allow me not only to get some speed back into my legs, but also give me some idea of what pace to aim for in a half-marathon in spring of 2012.

Last week I did a 4×1 Km session and was reasonably pleased to maintain a pace in the range 4:33 – 4:38 min/Km for each repetition, without pushing myself too hard.    So a 25 min 5 K appears within reach, but I will have to wait patiently to see what further gains might be possible.

My major short term goal is to get some speed back into my legs.  My medium term goal is to run a reasonably fast 5Km, but because I have clearly lost a lot of fitness as a result of the misadventures of the past year, it is not clear what would be a reasonable goal.  However observation of my heart rate indicates that at a pace around 5:30/ km I am already in the mid to upper part of the aerobic zone, suggesting that a 25 min 5 Km would be a challenge at present.

For the next 4 weeks I will aim to do 5 sessions per week, including two moderately effortful sessions: an interval session (short or long) and either a tempo session at around 5:20 min/Km or a progressive run aiming to reach 5 min/Km pace for the final few Km.   The short interval sessions will be 400m repeats aiming for a pace around 4:15 min/km and in the longer interval sessions I will do 1000m repeats aiming for 5 min/Km.

Today, I was eager to see if I could sustain 4:15 pace during 400m repeats, so I decided on 4x400m.  Beforehand I used Google Earth to locate two trees 400m apart on the fields beside Fairham Brook.   However when I got there, it was not absolutely clear which of the many trees lining the brook were my 400m markers.  I set off on the first estimated ‘400m’, into a slight head wind across a grassy surface that was easy on the legs, though a little bumpy in places and definitely not ideal for fast running.  I was dismayed to find that my time was 112 sec.    I was already in the anaerobic zone,  and it was clear that running any faster would be unreasonably stressful.   After 3 minutes of easy jogging my heart rate had fallen from 95% of maximum to around 75%; I had intended to get it down to 70% before the second 400m, but even after 5 min of easy jogging it remained at around 70% so I set off, with the breeze behind me this time, but again was disconcerted to find that my time was only marginally less.  Once again I was well into the anaerobic zone.

I completed the four  ’400m’ runs, each in a time in the range 110-112 sec, and on each occasion, well into the anaerobic zone.   On each occasion my heart rate settled to a level around 75% of max after 3 minutes of jogging at a pace which would normally produce a heart rate around 60% of max.  It was clear that I was accumulating a substantial amount of lactate during the 400m runs.   It seemed that I was even less fit that I had anticipated, and that a 25 min 5K would be out of reach for the near future.  After a careful look at my ‘400m’ marker trees, I set off for home at a gentle jog, but the continuing elevation of heart rate and respiratory rate demonstrated that I still had appreciable acidity in my blood stream.

When I got home I made a closer inspection of the trees on Google Earth.  Marrying the Google Earth aerial view with my ground level observations, it was clear that I had misidentified my intended marker trees.   In fact the markers I was using were 445m apart, so my true times were in the range 99-101 sec per 400m, corresponding to 4:10 min per Km.   I had achieved a pace slightly faster than my target pace of 4:15.  However it had been quite effortful.  Most noticeably, my ability to clear acidity from my blood stream is very poor.   Fortunately, that is perhaps the most readily trainable of the various metabolic adaptations required for 5Km racing, so all in all, it was a good opening session of my campaign.  A few hours afterwards I did a bit of bouncing on the trampoline and my legs felt reasonably springy, so I do not anticipate appreciable DOMS tomorrow.  Next week’s interval session will be 4x1000m aiming for 5 min/Km pace.  That will give me a clearer idea of just how near or far I am from a 25 min 5K.

1)      what type of training is beneficial;

2)      what aspects of running performance improve most;

3)      at what stage in a training program is breathing training most  likely to be beneficial;

4)      how great an improvement can be anticipated?

While a growing number of studies demonstrate that breathing training works in practice, the application of the findings from scientific studies carried out under standardized conditions, in a way that fits the circumstances of an individual athlete requires interpretation based an understanding of the underlying mechanisms.  Therefore it is helpful to start with a brief review of the various mechanisms by which breathing training might lead to improved performance.

The relaxation response

Improved breathing might be expected to improve running performance via several different mechanisms.  There is evidence that merely focussing on deep diaphragmatic breathing produces relaxation of unnecessary muscle tension, especially the tension in muscles of neck and shoulders which produces restrictive hunching of the shoulders.  It is also likely that the rhythmic contraction and relaxation of the abdominal muscles associated with diaphragmatic breathing minimizes the tense static contraction that results in painful cramp of abdominal muscles.   Herbert Benson, a cardiologist from Harvard and pioneer in the investigation of mind-body interactions, showed that mental centring – focussing of conscious awareness  of a location a few cm behind the navel resulted in a 5% reduction in energy  consumption at a fixed power output on an exercise bike (Benson 1975) .  Benson’s studies were performed at low power levels (corresponding to heart rate around 100 bpm) and are of little direct relevance to competitive athletes.  Nonetheless, it is very likely that the release of unnecessary shoulder tension and the maintenance of good trunk posture combats exhaustion during long races – marathons or ultramarathons – in which efficient husbanding of energy resources is crucial.

It is plausible that minimising static tension in the trunk muscles reduces the production of  toxic metabolites that prompt that the putative ‘central governor’  to impose restrictions on muscular effort during a long race.  My own experience indicates that conscious focus on diaphragmatic breathing in the later stages of a marathon can have a re-vitalising effect.   We will return in a later section to a discussion of how diaphragmatic breathing might also play a crucial role optimising the dynamic range of diaphragm muscle fibre length, thereby preventing a vicious cycle of respiratory muscle failure when the athlete is approaching a state of whole body exhaustion.

Respiratory muscle fatigue

At first sight, it appears the respiratory muscles have adequate capacity to move air at a rate exceeding that required for running.  Typically, maintaining a pace of 4 min/Km requires approximately 3 litres of oxygen per minute.   15 litres of air contains 3 litres of oxygen.  If we assume that it is inefficient to attempt to extract more than 20% of the oxygen from alveolar air during a single inspiration, maintaining a pace of 4 min/Km would require a ventilatory rate of about 75 litres of air per minute.   Peak ventilation rate for a man is typically 180-200 litres per minute.   It is clear that peak ventilation rate is more than adequate to provide the oxygen required to maintain a pace of 4 min/Km.  However breathing at anywhere near peak ventilatory rate is quite exhausting.   The diaphragm becomes exhausted quite quickly and takes a substantial time to recover.

Using a technique that assessed strength of diaphragmatic contractions by stimulating the phrenic nerve, which drives the diaphragm, after exercise, Johnson and colleagues (1996) from the Mayo Clinic in Minnesota  showed that  endurance exercise at above 85% of VO2max lasting 8-10 min caused a 15-30% reduction in the maximum force that the diaphragm could produce .  It took more than an hour for the diaphragm to recover it full strength.   However, this loss of muscle power was apparently due at least in part to increased competition for blood flow from the locomotor muscles. Reducing the load on the respiratory muscles by breathing a mixture of oxygen and helium had little effect on the time to exhaustion at 85% of VO2 max, implying that at that work rate, the principle cause of exhaustion was competition from the locomotor muscles for blood flow.  However, at 95% VO2 max, changing the load on respiratory muscles by adjusting the composition of inspired air did effect time to exhaustion, indicating that the diaphragm itself had become exhausted.  Thus, at high power output, exhaustion of the diaphragm is a limiting factor.  It seems very likely that in 3000m or 5000m races respiratory muscle exhaustion might be a limiting factor, and training designed to improve respiratory muscle endurance might be expected to improve performance.

At lower power outputs typical of 10Km to marathon pace, the major contribution to diaphragmatic exhaustion will be competition for blood from the locomotor muscles.   The most important way to minimise fatigue at these paces is to increase overall aerobic capacity and the efficiency of the entire musculature, especially the large locomotor muscles.  When it is crucial to avoid any waste of energy, ensuring maximal efficiency of the respiratory muscles is also likley to be worthwhile.    Because muscles work most efficiently when they are slightly stretched, the efficiency of respiratory muscles will be maximised by ensuring that they are working under conditions that ensure a fairly extensive dynamic range.  This is more likely to be achieved by deep diaphragmatic breathing.

Inspiratory muscle training

Inspiratory muscles can be trained by exercises that entail breathing- in through a device that contains a valve that does not open until the inspiratory muscles has produced a pre-determined reduction in air pressure in the mouth.  Thus the muscles must exert greater than usual force. Typically a training program involves one or two sets of thirty such inspirations daily for a period of several weeks.  Several commercially produced inspiratory muscle training devices are available.  One that is readily available on-line and has been used in several scientific studies is the PowerBreathe.

The majority of published studies that have tested the value of respiratory muscle training have reported benefits.  Andrew Edwards from Universal College of Learning in New Zealand and colleagues from Sheffield and Leeds in the UK, carried out a study in which two groups of 8 previously  untrained men were assigned to either respiratory training consisting of 30 daily inhalations against maximum resistance using the PowerBreathe, or 30 daily inhalations against minimal resistance (Edwards et al, 2007).  In addition both groups underwent a four week cardiovascular training program consisting of three running sessions per week (5x1000m; 3x1600m or 20 min run).   Mean inspiratory power increased 15% in the group who inhaled against maximal resistance and only 8% in the control group.  Those training against maximal resistance improved 5000m run time by 4.3% whereas the control group only improved by 2.2%.  However the magnitude of the improvement in running performance was not significantly correlated with the increase in inspiratory muscle power (possibly a consequence of lack of statistical power in such a small study),

Subsequently, Tong and colleagues (2008) from Hong Kong reported that a 6 week program consisting of 3 sets of 30 inspirations against a respiratory load increased by 50% produced a 30% increase in inspiratory muscle power; a 16 % increase in shuttle run performance; an 11% reduction in the rate of increase of perceived breathlessness; and less lactate accumulation during the shuttle run.  These beneficial effects were not seen in a control group who exercised against a minimal resistance.  The same investigators had previously demonstrated that a warm-up consisting of inspiratory muscle exercises similar to those used in the training program  improved performance and decreased the rate of rise of subjective breathlessness.  However, the warm-up produced a lesser increase in inspiratory muscle power than the training program.   They concluded that both the training program and the warm up had a beneficial effect on performance, but the mechanisms were different, with the benefits of training attributable to improved muscle function, while the warm-up merely produced greater tolerance of breathing discomfort.  My own opinion is that the benefits of the warm-up were likley to have been due, at least in part, to increased depth of inspiration resulting from greater mental focus on breathing.

More recently Lomax and colleagues from University of Portsmouth (2011) examined the independent and combined effects of an inspiratory muscle warm-up and inspiratory muscle training performed using a PowerBreathe device, on intermittent running to exhaustion.   The 12 male participants undertook four intermittent running tests, two before and two after 4-week of training consisting of 30 breaths twice daily at either 50% (experimental group) or 15% (control group) maximal inspiratory mouth pressure,.  Tests 1 and 4 were preceded by a warm-up consisting of 2 × 30 breaths at 40% of maximum inspiratory mouth pressure.   In the pre-training period, the inspiratory warm up produced significant increases in both inspiratory muscle power and distance covered in the shuttle run, in both groups.  After training, in the experimental group inspiratory muscle power increased by 20%  in the session without respiratory  warm-up and 27% in the session with warm-up.  Distance covered increased by 12%  in the session without respiratory  warm-up and 15% in the session with warm-up.   The investigators concluded that inspiratory muscle training and inspiratory muscle warm-up both increase running distance independently, but the greatest increase occurs when they are combined.

Inadequate respiratory drive

Respiration is controlled by the respiratory centre in the brain stem.  Decreases in oxygen concentration and/or increases acidity in the blood stimulate nerve endings in the walls of the large blood vessels.  These nerve terminals send messages to the brain stem and prompt increased respiratory drive, which is transmitted to the diaphragm by the phrenic nerve and to the accessory muscles of respiration in the chest and abdomen via the somatic nerves.  When running at paces at or above lactate threshold, the accumulation of acidity in the blood results produces a strong respiratory drive.  At these paces, the major issue to consider is respiratory muscle fatigue as discussed in the previous sections.  However at slower paces, typical of an ultra-marathon or during recovery runs, it cannot be taken for granted that automatic respiratory drive will be strong enough to achieve optimal ventilation.

The classic studies by WS Fowler (1949) demonstrated that uneven alveolar filling occurs in healthy people at rest, suggesting that when demand is low, respiratory drive is inadeqaute to ensure complete filling of the alveoli.  If alveolar filling remains non-uniform when exercising in the low aerobic zone, oxygenation of the blood will be inefficient.   Adopting a breathing pattern that ensures uniform alveolar filling would be expected to improve the oxygenation of the blood.    I suspect that the rapidly-achieved reductions in heart rate at a given power output achieved by conscious focus in breathing pattern when exercising in the low aerobic zone, described in my post on 22^nd February, were probably due to a voluntary increase in depth of inspiration.  It is plausible that the mechanism was more even alveolar filling resulting in more efficient oxygenation of blood .

It is also plausible that the rapid improvements reported by Alexander Streltsov (1992) achieved by performing four inspiratory efforts preceding each expiration can be attributed to increased depth of inspiration.  Streltsov reported that his breathing technique led to improvements across the aerobic range, in international class athletes.  However I remain unconvinced that the particular ‘fractional’ breathing pattern proposed by Streltsov is necessary to achieve the benefit.  I believe that the crucial feature is deep diaphragmatic breathing, and this might be achieved by various different respiratory patterns.

Respiratory rate

What is the ideal respiratory rate?  Each breath must move a volume of air that is far larger than the capacity of the bronchial tree, as the air remaining within the bronchial tree at the end of each expiration contains stale air from which oxygen has been removed and CO2 added, and this stale air will be drawn back into the alveoli at the beginning of inspiration.  Therefore rapid, shallow breathing will be inefficient.  On the other hand, the rate at which air moves into the lungs will be greatest during early inspiration and the rate of expulsion will be greatest early in expiration when the stretched lungs recoil.  Therefore very prolonged inspiration and expiration will also be inefficient.   I have tried a number of different patterns and rates of breathing.  In my experience it is usually best to breathe at the rate that is most comfortable.

During a progressive run, I start with a 4:4 rhythm (inspiration for four steps; expiration for four steps) during warm-up, and then move to a 3:3 rhythm when running in the low aerobic zone.  When I become aware of an impulse to snatch an occasional ‘early’ inspiration before the full duration of expiration (which usually happens in mid-aerobic zone) I shift up to a 2:2 rhythm, which I can sustain up to the  lactate threshold.   If I deliberately try to prolong the inspiration ( e.g. by holding onto a 3:3 rhythm when I would feel more comfortable at 2:2) I find that my heart rate goes up a few beats per minute without an increase in pace.  However if I make a premature transition from 3:3 to 2:2, I often find that both pace and heart rate increase but without noticeable increase in effort.   Thus, in general I do not find it helpful to attempt to sustain duration of inspiration longer than is comfortable.  However, if I want to increase pace, I do find it helpful to move up to 2:2 a little sooner than I feel the need.

With regard to Streltsov’s proposal to make four consecutive inspiratory efforts before each expiration, I found that it worked well enough at the low end of the aerobic zone, and I am prepared to accept that it might be a useful training strategy to encourage a deep inspiration, but I have not found it helpful for ‘routine’ running in the mid or upper aerobic zones.

Conclusions

Both my own experiences and the scientific literature provide fairly clear evidence that attention to respiration is potentially beneficial. Both novices and experienced runners can benefit.  At low and modest paces, simply focussing on diaphragmatic breathing appears to produce more efficient running, possibly due in part to the relaxation response described by Benson, and in part to the greater efficiency associated with a large dynamic range of respiratory muscle contraction. For optimum performance at higher paces, such as 3000m or 5000m pace, it can helpful to perform inspiratory muscle training to improve respiratory muscle performance.  Specific exercises using a device such as Powerbreathe that increases the load on the breathing muscles can help increase the power and endurance of these muscles.    Furthermore, a respiratory warm-up can increase both respiratory muscle power and running performance

References

Benson H (1975) The relaxation response, New York:Morrow

Edwards AM, Wells C, Butterly R  (2007) Concurrent inspiratory muscle and cardiovascular training differentially improves both perceptions of effort and 5000-m running performance compared to cardiovascular training alone.  Br J Sports Med

Fowler WS (1949) Lung Function Studies. III. Uneven Pulmonary Ventilation in Normal Subjects and in Patients with Pulmonary Disease J Appl Physiol 2:283-299.

Johnson BD, Aaron EA, Babcock MA, Dempsey JA. (1996) Respiratory muscle fatigue during exercise: implications for performance. Med Sci Sports Exerc. 28(9):1129-37.

Lomax M, Grant I, Corbett J. (2011) Inspiratory muscle warm-up and inspiratory muscle training: Separate and combined effects on intermittent running to exhaustion. J Sports Sci. 22:1-7.

Streltsov A. (1992) The endurance reserves, http://www.iaaf-rdc.ru/eng/news/0027e.html

Tong TK, Fu FH, Chung PK, Eston R, Lu K, Quach B, Nie J, So R (2008) The effect of inspiratory muscle training on high-intensity, intermittent running performance to exhaustion. Appl Physiol Nutr Metab. 33(4):671-81.

After a period of several months the progress in increasing fitness slows down.  Although capillary development continues slowly over a period of years, the increases in aerobic capacity are only perceptible on a timescale of months.  The athlete scarcely remembers those early days when the most pressing question appeared to be how to improve breathing.  By this stage, many are preoccupied with an attempt to identify the training program that will eke out further improvements in the capacity of the heart to pump blood and of the muscles to extract and use the oxygen delivered by that blood.   A few athletes get diverted into experimenting with changes in style – such as changing from heel strike to landing on the mid-foot or fore-foot.  Despite the intense discussion about running style on blogs and forums, there is remarkably little evidence that adjustments of style lead to major improvement in performance.  Very few give a second thought to the possibility of improving the efficiency of oxygenation the blood in the capillaries in the lungs or the removal of carbon dioxide from the lungs.  Yet the few published scientific studies of the effects of training directed at improving breathing technique indicate that this can produce worthwhile additional improvements in performance in well-trained athletes.

Training to increase ventilatory capacity

For example, Leddy and colleagues (2007)  used a technically complex device that  allowed hyperventilation while carbon dioxide level was maintained constant, to train a group of experienced runners to breathe more deeply.  After  10 hours of training spread over 4 weeks, the runners had increased their ventilatory capacity and achieved a 50% increase time to exhaustion during  treadmill running test at 80% of VO2 max on the day after training, and also on further testing 1 week later.  Furthermore 4 mile run time decreased by 4% and this improvement was maintained for a period of at least 3 months.  The findings demonstrate that experienced runners can be trained to increase their ventilatory capacity and that this increase is associated with improved running performance, sustained for several months after the completion of the training.

Although the procedure used by Leddy was too cumbersome for everyday use by amateur runners, the findings suggest the possibility that simply focussing on breathing more deeply while running might result in better performance.  In fact I had discovered many years ago that the most effective strategy to maximize my speed in the final few hundred metres of a long distance race, such as a marathon, is to devote my conscious attention to breathing a deeply as possible in the final Km.  Typically during a race such as a HM or marathon I breathe at a rate 3 steps per inspiration and 3 steps per expiration for most of the race; during the final Km I increase the breathing rate to a 2:2 pattern.   While the capacity to increase pace at the end of a marathon is important if the main goal is to beat an evenly matched opponent, when the primary goal is to record a fast time, the average pace during the first 41 Km is more important than the pace in the final Km.  So it is more pertinent to ask whether or not efficiency when running below lactate threshold can be improved by more effective breathing.

Fractional breathing

I was therefore intrigued when Rick raised the issue of breathing patterns on his blog a few months ago.   He provided a link to an article by a Russian chemist, Alexander Streltsov (1992), reporting that breathing efficiency could be improved by a technique called fractional breathing: a breathing pattern in which the duration of inspiration is longer than expiration.  The runner makes 4 consecutive inspiratory efforts followed by an expiration, thereby prolonging and deepening the inspiration.   The rationale for the method does not make much sense to me.  Streltsov states that the reason from prolonging inspiration is to ensure that the inspiratory period matches the time it takes for oxygen to attach to haemoglobin (approximately 0.8 seconds).  His argument appears to imply that oxygen can only be transferred to blood during inspiration.  While it is true that the alveoli expand during inspiration and deflate during expiration, they do not deflate entirely due to a natural lubricant called surfactant, which reduces surface tension in the alveolar walls.  The volume of air in the alveoli rises to a peak at the end of inspiration and falls to a minimum at the end of expiration, but the average volume during expiration is not greatly different from that during inspiration.  Furthermore the concentration of oxygen rises and falls during the breathing cycle but the average value during inspiration tends to be similar to that during expiration.  Therefore, oxygen exchange can occur during both the inspiratory and expiratory phase.  As I understand it, the efficiency of oxygen transfer will be maximised by ensuring the concentration of oxygen averaged over the entire cycle is a high as possible.  One of the most important issues is the fact that during the first part of inspiration, the air reaching the alveoli is the stale dead-space air that had remained within the bronchial tree following the previous expiration.  So breathing will only be effective if the volume of air inspired in each breath is much greater than the dead-space volume.  This certainly suggests that deep breathing is likely to be more effective, but does not provide a clear justification for unequal breathing. However it is possible that extending the duration of inspiration will result not only in maximum filling of the lungs but also in a rapid expulsion of air during expiration, so perhaps fractional breathing is an effective way of maximising the depth of breathing.

Steltsov provides some quite impressive evidence for improvement of respiratory efficacy achieved by several international Russian athletes when using fractional breathing.   For example, middle-distance runner, Olga Nelubova, decreased her HR from 118 to 111 when running at an easy  pace (3 m/sec) in the low-aerobic zone, after only 4 days of training in the new breathing technique – a far more rapid improvement than would be expected simply to the cardiovascular improvement produced by 4 days of aerobic training.

My experiences with  fractional breathing

Despite being unconvinced by the explanation proposed by Streltsov to justify his proposed technique, the data suggest that his technique is worth further examination.  I decided that it would be worthwhile to try fractional breathing myself to see if it improved my efficiency.  Because I anticipated it would be easier to regulate my breathing while exercising in the low aerobic zone, it seemed sensible to start with a training program in this zone.

Steltsov maintains his technique can be applied to various forms of aerobic exercise.  Because I can assess heart rate at a fixed work-rate most precisely on the elliptical cross trainer I decided to start with a brief training program on the elliptical cross trainer.  I employed a testing procedure consisting of 26 minutes at a power output of 100 watts, after a standard 6 minute graded warm-up and a 4 minute ‘HR stabilization’ period at an output of 100watts.  The demands of this test closely resembled the demands of the low-aerobic recovery sessions that I have performed intermittently over the past two years, and during which my HR had achieved a reasonably stable plateau in recent months, so I could reasonably attribute any improvement during a brief respiratory training program to the respiratory training itself, rather than to a general increase in fitness.

The primary measure of efficiency was heart rate averaged over the 26 minute period.  Before I began the breathing training program, I recorded HR during three sessions using my usual pattern of breathing in the low aerobic zone: namely three steps per inspiration and three steps per expiration.  Then I did four 40 minutes training sessions on consecutive days,  in which I practised fractional breathing, taking 4 steps during  inspiration and 2 steps during expiration. After four training sessions I found it fairly easy to maintain the 4:2 breathing pattern.  It should be noted that unlike the Russian athletes described by Streltsov, I did not produce an overall slowing of breathing rate.  In the week following training I performed three test sessions: two using my former 3:3 breathing pattern and one using the fractional 4:2 breathing pattern.  I included tests using both the unequal and equal patterns to test whether or not the inequality was essential for achieving the benefits. Then six weeks later, I did a further test session, using my usual 3:3 breathing pattern.

In the two baseline tests prior to training, average HR during the 26 min at 100watts was 116 and 117 BPM.  In the two tests in which breathing pattern was 3:3, in the week following the four training sessions, average HR during the test was 111 and 110, while in the test in which the breathing pattern was 4:2, the average HR was 108.  Six weeks after the training, average heart rate during the test when breathing with a 3:3 pattern was 111 bpm.  These results indicate an improvement of approximately 6 percent after training.  This improvement was maintained for six weeks. Furthermore after training, my efficiency was only marginally better when using the 4:2 fractional breathing pattern, than using my usual 3:3 breathing pattern.  It appears I had increased the effectiveness of breathing, probably by increasing the depth of each inspiration and the forcefulness of expiration.

Interpreting the evidence

This evidence is little more than anecdotal, but it is of noteworthy that the magnitude of the improvement in my HR was similar to that achieved by the Olga Nelubova. It is not clear whether or not I achieved improvement by exactly the same mechanism as the Russian athletes. Unlike Olga Nelubova, I exhibited no overall slowing of my respiratory rate.  My breathing rate was 27 breaths/min before and after training, whereas Nelubova’s rate was 33 before training and 21 after training.   The main reason that I did not adjust my overall breathing rate is that on the elliptical machine, it is easiest to maintain a constant work-rate by employing a constant cadence, and I naturally adjust breathing rate to be an integral multiple of step rate.  Therefore producing a gradual change in breathing rate as training proceeded would have required an unnatural decoupling of step rate and breathing rate

The fact that I exhibited a similarly improved performance when tested using a 3:3 pattern indicates that unequal duration of inspiration and expiration is not essential, though it is possible that the use of an unequal pattern during training promoted both deeper inspiration and more forceful expiration and hence increased the efficiency of the training.   I was definitely more conscious of my abdominal wall moving out during inspiration and inwards during expiration both during training and in the testing sessions.   So, I suspect that in my case the major factor contributing to the improvement was simply due to moving a larger volume of air during each breath.

Exercise in the low aerobic zone is not directly relevant to racing.  However if conscious focus on breathing improves efficiency of exercise even in the low aerobic zone, it is likely that even greater benefits would be obtained in the mid and upper aerobic zones that are characteristic of marathon  racing.   Streltsov reported benefits throughout the aerobic range.

It would be premature to draw any definitive conclusions, especially as it is unclear how similar the mechanism of change in my breathing were to that in the Russian athletes.  Nonetheless at this stage I am inclined to think that it is worthwhile paying greater attention to breathing technique

References:

Leddy JJ et al (2007) Isocapnic hyperpnea training improves performance in competitive male runners Eur J Appl Physiol 99:665–676

Streltsov , A (1992)   The endurance reserves, http://www.iaaf-rdc.ru/eng/news/0027e.html

This challenge raises four of the major unanswered questions regarding training for distance running:

1)      what is the role of resistance training?

2)      what is the role of plyometrics?

3)      what is the role of stretching?

4)      when should these forms of exercise be performed?

While there is no doubt that aerobic capacity is of paramount importance in distance running, the available evidence suggests that leg strength and stiffness play a role.   Many studies show that less flexible runners are more efficient (e.g. J Strength Cond Res 23(1):158-62, 2009; J Orthop Res.8(6):814-23 1990.)

Anecdotal evidence supports this.  Although it is probable that several things, including an increase in aerobic capacity, contributed to Paula Radcliffe’s transformation from a non-medal winner in Sydney in 2000 to the world’s best female marathon runner in 2003, I think that one important contribution was the introduction of hopping and other plyometric exercises which increased her jump height in association with a decrease in her flexibility. In his article on Radcliffe in International Journal of Sports Science & Coaching (Vol 1 • Number 2 • 2006) Anthony Jones reports in the period 1996 to 2003 her vertical jump height increased from 29 cm to 38cm while her ‘sit and reach distance’ decreased from 8cm to 3 cm.

However the anecdotal evidence regarding the world’s all-time greatest distance runner, Haile Gebrselassie, is a less clear.  In an interview prior to his unsuccessful attempt to break his own world record, in Dubai in January 2009 , Haile made it clear that he considers that it is important to take the time to stretch all major muscle groups.  In particular, he advised: “focus on your hamstrings and calf muscles to avoid injury during the race.”   According to Constantine Njeru, Geb includes both jumping on the spot and stretching during the cool-down after a session.   I was a little surprised to see plyometrics included in the cool-down, but I note that Terrence Mahon (former coach of Ryan Hall) also recommends hopping at the end of a training session.

The anecdotal evidence suggests the need for a compromise between stiffness and flexibility, and furthermore raises the issue of how one might sensibly integrate plyometrics, which tend to promote stiffness, with stretching, which reduces stiffness.  Because the question of whether or not plyometrics, stretching, or both, are useful for a distance runner probably depends on a complex interplay between an individual’s genes, their past training experience and the way in which these forms of exercise might be integrated into a training program, it is unlikely that either anecdotal evidence, or scientific studies that compare outcome of a particular form of training with another in a random selection of athletes, will provide a clear answer.   I think the only way to decide what is best is to weigh up the evidence from anecdote and from scientific studies of training procedures, with an estimate of what makes sense in light of muscle physiology.

What makes muscle-tendon units stiff?

Muscle-tendon units perform two types of function: they can either move or stabilise joints. Many studies have provided very clear evidence that in order to run efficiently the muscle tendon units that act at hip, knee and ankle must act as stiff springs to maximise the rapid capture and release of elastic energy after footfall.  However there is much uncertainty about the best way to achieve the flexibility that allows our joints to move with minimal resistance yet have the stiffness necessary to stabilize them

I think it helpful to examine more carefully the nature of the mechanisms that produce stiffness.  There are two main factors that contribute to the stiffness of a muscle-tendon unit.

1)      Isometric contraction of the muscle.  This requires the formation of temporary cross bridges between the actin and myosin molecules in the muscle, and consumes energy.  These cross bridges can be created and released within a fraction of a second.

2)      The formation of fibrous collagen bands which are more permanent.  They are produced over a period of hours or days as a result of inflammation due to tissue damage and do not require energy to maintain them.  The collagen molecules are helical proteins; in other words they are miniature coiled-up springs that can undergo compression or extension.  They can contract in response to small electric currents generated by collateral nerve terminals that branch off from the nerve supplying the muscle to terminate on the surface of the tendon.  However the time scale of this contraction and its subsequent release is much slower than the making and breaking of actin-myosin cross-links within the muscle fibre.

Cleary if we are to have adequate mobility we cannot rely only on permanent collagen fibres to stabilise the joint.  Furthermore, if the stiffness is due to collagen fibres we are more likely to tear the muscle when a sudden force is applied, so we would be at great risk of injury.

However, if we have very few collagen fibres so that our muscles are very floppy when not actively contracting, it is likely to be difficult to build up enough tension quickly enough at footfall to produce the required stiffness, and furthermore, the isometric contraction will consume energy.  If we were as floppy as a new born baby, we would probably be very inefficient at running.

If our goal is to run fast and injury free we need the right balance between stiffness due to isometric contraction and stiffness due to collagen. I believe that the right balance depends on how well we have trained our nervous system to contract the muscles very quickly at precisely the right time in the gait cycle.   If we have trained our nervous system well, we can rely more on muscle contraction and less on collagen, allowing us to run efficiently with low risk of injury.

However the picture is even more complex, because the way in which muscle contraction is controlled is very complex.

Feedback control of muscle contraction

There are two main feedback systems that control the tension of the muscle-tendon unit – the system that senses muscle tension via the intrafusal fibres within the muscle spindles that are attached in parallel with the body of the muscle, and the system based on  Golgi tendon organ that is attached to the tendon near the point where the tendon becomes a sheath that envelopes the muscle.

The intrafusal system

Nerve ending attached to the intrafusal fibres detect tension in the muscle and can initate a rapid reflex contraction mediated via a single synapse with the alpha motor neuron in the spinal cord responsible for driving a contraction of the muscle.  This reflex which occurs in less than  1/10^th of a second is responsible for the stretch-shortening cycle that is activated during plyometrics.  A sudden sharp stretch produces a strong concentric contraction of the muscle.    The strength of this contraction can be enhanced by plyometric training.  It is probable that this stretch-shortening cycle contributes to the elastic recoil during stance while running.  The force of footfall produces an eccentric contraction of the major leg muscles, and the associated stretch would be expected to initiate a powerful reflex contraction.

However the intrafusal system is more complex than this.   There are two types of intrafusal fibre: ‘nuclear bag’ fibres that respond to a rapid stretch, and ‘nuclear chain’ fibres which are viscoelastic and respond to more sustained tension.  As far as I am aware, the circuitry is not fully understood, but it is probable that the nerves from these nuclear chain fibres send signals to the cerebellum (at the base of the brain) and the cerebellum computes the required steady state level of activity that is required to maintain posture.   However, if the local milieu around the nuclear chain fibres is too acidic or otherwise unfavourable to the generation of nerve signals, the transmission of the signal regarding current muscle tone is obstructed and the cerebellum sends a signal to increase muscle tone.  Thus, the muscle might develop a potentially damaging hypertonic state in which the muscle remains in a sustained over-contracted state.  In this hyper-contracted state the muscle pulls on the tendon and is likely to trigger the build-up of additional collagen fibres at the junction of muscle and tendon, making the muscle even stiffer.

The Golgi tendon organ

Nerve fibres from the Golgi tendon organ send signals to the spinal cord (and probably to the brain) indicating the amount of tension in the tendon.  In the spinal cord the incoming nerve from the Golgi organ synapses on an interneuron.  In some circumstances, it appears that the interneuron acts on the alpha motor neuron to inhibit muscle contraction – a so-called autogenic inhibitory reflex.   It was once thought that this mechanism was responsible for the potentially protective release of tension in a muscle that is maintained in a stretched state for a sustained period.  More recent evidence suggests that that inhibitory process might, at least in some circumstances be mediated via the intrafusal system.   Furthermore, in other circumstances, the Golgi tendon organ can initiate an autogenic excitatory response that produces an increase in muscle tone.   This mechanism appears to play a part in the lift-off from stance.

The net effect of feedback control of muscle tone

It appears that both the intrafusal system and Golgi tendon organ system are able to initiate either increases or decreases in muscle tone under appropriate circumstances.  However, as far as the athlete is concerned, the three important conclusions regarding the regulation of muscle tension are:

1)      rapid stretch of the muscle promotes a rapid concentric contraction – the stretch shortening cycle.

2)      Sustained stretching tends to produce a release of muscle tension via an autogenic inhibitory response.

3)      When the muscle environment is too acidic or otherwise unfavourable, the signal providing feed back about muscle tone to the cerebellum might be impaired resulting in potentially damaging hypertonic contraction.  This hypertonic state is likely to promote the deposition of additional collagen fibres at the junction of muscle and tendon.

The effect of muscle tension on collagen at the junction of muscle and tendon

When the nerve innervating a muscle sends an excitatory signal, a collateral signal to tendon in the vicinity of the junction of muscle and tendon promote tensioning of the coiled collagen springs.  This is likely to trigger the laying down of more collagen making the muscle stiffer.  However, the tension in the muscle produced by a slow contraction of the muscles sustained over a period of 8-10 seconds appears to be able to reverse this process.   Thus slow contractions appear to be capable of reducing the excessive stiffness due to excessive build up of collagen.   A sudden, very strong muscle contraction, especially a strong eccentric contraction, is likely to tear the collagen fibres and damage the muscle.

How is the stiffness of the muscle-tendon unit regulated during running?

Recordings from the motor nerves that drive the leg muscles reveal that shortly before footfall there is a burst of activity in the muscles controlling hip and knee (quads and hams) that generates an isometric contraction that is maintained through stance.  This contraction would also be expected to stiffen the collagen springs.  Thus, a potentially trainable muscle contraction appears to make a major contribution to creating the rigid strut that is required to capture the kinetic energy of the falling body and store it as elastic energy within the tendon.  When the isometric contraction is released, possibly via a nerve impulse from the Golgi tendon organ, the rebound will propel the body upwards off stance.

If the isometric contraction is not adequate to prevent stretching of the muscles (as is likely when running downhill or when sprinting) the stretch-shortening reflex will be activated thereby generating a powerful concentric contraction that will propel the body upwards.  Unless the muscle is adequaltey conditioned, the eccentric contraction is likely to tear collagen fibres producing DOMS the following day

Practical conclusions regarding training

The first priority is to train the preloading contraction that occurs just before footfall.  This contraction is not under conscious control.  However it appears that it can be trained by drills that focus on producing a short sharp landing and lift-off from stance.  I consider that various hopping drills are best for this.  I am currently doing two-footed bunny hops and two footed hurdle jumps (6 inch hurdles) as I need to be very careful to avoid aggravating my recently inflamed knee joint.  However, once the knee has fully recovered, I will do one-footed hops and also bounding from foot to foot.

However these plyometric-type exercises are likely to produce sustained tension in the collagen springs and perhaps to induce the formation of new collagen.  While this would be expected to increase the stiffness of the muscles and thereby improve the efficiency of capture and storage of  kinetic energy, it will also make my hips and knees more resistant to movement at other phases of the gait cycle.  Furthermore, excessive stiffness due to collagen might increase the risk of injury.  In my opinion it is undesirable to allow too much build up of collagen near the muscle-tendon junction.  Therefore, after a plyometric session I engage the hams and quads in slow controlled contractions (eg squats with each cycle lasting around 10 seconds).   Furthermore, because the plyometric sessions place substantial strain on the muscle-tendon unit, I do not do these session after heavy training, at which time there are likely micro-tears that might be exacerbated by the plyometrics.  Nor do I do them before heavy training as the muscle requires time to recover.   Therefore, I only do plyometrics on a day when I intend to do light training or cross-training on the elliptical machine.

The possibility that any acid in the local environment within the muscle tissue might impede the transmission of signals regarding postural tone  from the intrafusal fibres to the cerebellum  thereby leading to a faulty computation in the cerebellum and excessive drive to the motor neurons, resulting in chronic excessive contraction and the possible build up of excessive collagen makes it essential to perform an adequate cool-down after any training session in order to stimulate blood flow that clears acid and any other toxic substances from the muscle.  After running sessions I simply jog at a pace well below the first ventilatory threshold.  After plyometric sessions, I usually do some low-aerobic elliptical cross-training.

What about stretching?  It is clear that static stretching before running is undesirable because it will result in decreased stiffness and therefore decreased efficiency, in addition to the risk of tearing of collagen fibres.  However after running and after plyometrics, either static stretching or slow contractions (e.g. slow body-weight squats) are desirable as such exercises are likely to minimise the risk of chronic hypertonic contraction and thereby minimise the build up of excessive collagen.

Finally, what is the role of resistance training for runners?   While much of the drive that gets the body airborne comes from the release of stored elastic energy, the process of energy capture is not 100% efficient and some of the energy must be generated by concentric contraction. Therefore powerful type 2A fibres are required for sprinting and also for running uphill during distance events.  Furthermore, if you plan to do plyometrics it is essential to ensure that the muscles are strong enough to withstand the eccentric contraction, so some resistance work is advisable before undertaking higher intensity plyometrics, such as bounding and single leg hopping.

A year earlier, Ritzenhein had joined a group of selected athletes in the well-funded Nike Oregon project.  The athletes live in a house in Portland, Oregon, where the bedrooms and living room have a controlled atmosphere that makes it possible to live high (that is in an atmosphere with oxygen content similar to an altitude of 12,000 feet), yet train low (near sea level), under the guidance of Alberto Salazar.  In order to adjust training load according to body physiology, various high technology devices are used to monitor heart rate variability (based on fairly sound science) and brain omega waves, which as far as I am aware is at best based on speculative science, and is perhaps as mind-boggling as the Cryosauna Space Cabin, in which temperatures of -170 degrees C are employed to hasten muscle recovery.  In my post on 4th September, I expressed some concern that Salazar had attempted to change Ritz’ running style, encouraging him to land on the mid or forefoot, despite his well know susceptibility to metatarsal stress fractures.  So far, the outcome has been disappointing.  Dathan achieved 8th place in New York, in a time of 2:12:33.

Ryan Hall was training with Terrence Mahon at Mammoth Lakes at an altitude of 7800 feet.  I was concerned by the approach to training that led to what he described as a brutal training run of 12 miles climbing from 7,000 to 10,000 feet over Tioga pass, a week before his tune–up in the Philly Rock and Roll half marathon.  He ran poorly in Philadelphia, and subsequently withdrew from Chicago.  Around the same time he also announced that he was leaving Terrence Mahon’s training group.

Meanwhile, in 2010 Kenyans and Ethiopians were again dominant.  The winners of the five World Marathon Majors were:

Berlin, Patrick Makau (Kenya, born 1985) 2:05:08

London, Tsegaye Kebede (Ethiopia, born 1987) 2:05:19

Boston, Robert Kiprono Cheruiyot (Kenya, born 1988)  2:05:52,

Chicago, Samuel Wanjiru (Kenya, born 1986) 2:06:24

New York, Gebre Gebremariam  (Ethiopia, born 1984) 2:08:14

The fastest marathon of the year was the Rotterdam Marathon, won by Patrick Makau in 2:04:48.  It is noteworthy that the oldest of the winners of the 5 Majors, Gebre Gebremariam, was born in 1984. All are younger than Ritzenhein and Hall, both of whom were born in 1982.  All the signs indicate that the Africans will continue to dominate marathon running for the foreseeable future.

In their review of the highlights of long distance running in 2010, IAAF statisticians A Lennart Julin and Mirko Jalava reported that 59 of the athletes in world top 100 marathon runners were Kenyan while 28 were from Ethiopia.  Of the top 18, 10 were from Kenya and 8 from Ethiopia.

Whatever the role of genes or high altitude training, a major factor must simply be the power of cultural expectation.  Just as Bannister’s 4 minute mile opened a floodgate, a floodgate has been opened in Kenya and Ethiopia.  Aspiring young Kenyans and Ethiopians know that times faster than 2:10:00 are not only possible but to be expected of themselves and their compatriots.  Conversely, perhaps the high tech of the Nike Oregon Project has created a barrier in the minds of US marathoners that appears as insurmountable as the 4 minute mile once did.