Archive for February, 2009

Why worry about the mechanics of running?

February 28, 2009

Does speculation about the theory of running make any difference to how fast you can run?  I have been observing and reading and talking and thinking about running mechanics since recommencing running again, about two years ago.  Has this made any difference to how fast I run?  The ultimate test is racing performance and I have run  too few races to draw any definite conclusions.  Furthermore, asthma has hindered my attempts to get fit, so even two years experience is scarcely enough to draw any definitive conclusions.  However, I think I can draw some practical conclusions that have the potential to improve my running.  These are my top 10 learning points:

1)      Short time on stance is more efficient because there is less braking but very short time on stance increases the risk of injury because ground reaction forces are greater.  So a very short time on stance makes sense for a sprinter but is more risky for a marathon runner.

2)      Landing with the foot only a short distance in front of the centre of gravity (COG) minimizes braking and facilitates short time on stance

3)      Holding the pelvis forwards facilitates landing a short distance in front of the COG.

4)      High cadence is more efficient because the amount of energy wasted in compensating for free fall under the influence of gravity is less when the distance is covered in a large number of smaller strides compared with fewer long strides – but beyond a certain point, high cadence becomes inefficient; probably the limit is determined by the optimum speed of the ratcheting interaction between the muscle proteins actin and myosin.  The question of whether or not this limit is fixed by your genes or alternatively might be improved with training is uncertain. 

5)      Landing with a rigidly extended knee increases risk of injury but landing with a very soft knee (low tension in quads) prevents a brisk recovery of impact energy via elastic recoil.  When speed is the highest priority, a fairly high degree of tension in quads is best. In longer races, less tension in the quads might be safer, but too little tension will result in wasted energy.

6)      The optimum point of contact between foot and ground at footfall depends on speed, and should be further forward under the ball of the foot at higher speeds. Except when sprinting, it is highly desirable to allow the heel to drop to the ground during stance to minimize risk of injury to the Achilles tendon and calf muscles

7)      Some of the benefits of training, such as strengthening of bones and connective tissues accumulate slowly over a period of many months or years; training at fast speed before building up the required strength creates high risk of injury.

8 )      Running requires a moderate degree of development of many muscle groups.  The muscular functions that are especially important to develop are: 

·        ability of the quads and calf muscles to capture impact energy at foot fall. This requires eccentric contraction.

·        ability of the hamstrings to arrest the forward motion of the swinging leg in late swing phase to as to allow the foot to fall only a little in front of the COG. This also requires an eccentric contraction.

·        strength of the hip abductors (eg glutes) to prevent the pelvis tilting to the unsupported side during stance.

·        Strength of the trunk muscles to allow a relaxed carriage of the pelvis in a forwards position.

9)      There is some evidence to suggest that running produces cumulative damage to muscles even in the absence of overt injury, so it is probably best to have mixed program that includes cross training.

10)  There is unlikely to be one running style that is best for all purposes. It is necessary to make choices and seek a balance that best meets one’s priorities  Perhaps the best illustrations of this are provided by the requirement of short time on stance and relatively high tension in quads at footfall when running fast, but due to the risk of injury, a somewhat longer time on stance and less tension in quads is preferable when running long distances.

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If gravitational torque is a red herring, how do we run fast?

February 24, 2009

In his comment on my post yesterday, Ewen reported that he has a heart rate around 153 when race walking 1500m in 8 minutes, and a similar heart rate when running 1500m in about 5:40.  He assumes that in both instances he has a similar cadence of around 180 steps per minute, and therefore is able to compute his stride length as 1.04 metres when walking and 1.47 metres when running.  He concludes that walking is not a very efficient form of locomtion – at least at these speeds.  In fact, once we want to move at speed faster than about 7 Km per hour (8.5 min /Km) most people find that running is more efficient (i.e uses less energy per Km at a given speed). This is improved efficiency achieved by becoming airborne during each stride. 

 

If we want to accelerate from rest or from a jogging pace, we can unbalance ourselves by displacing our centre of gravity forward of our supporting foot.  As Jack Nirestein (or Nicholas Romanov) might point out, unbalancing ourselves in this way generates gravitational torque that produces a head forwards and down rotation, so that we naturally increase our speed.  However, gravitational torque is largely irrelevant to the distance runner, because we actually spend most our time running at near constant speed. 

 

Gravitational torque cannot provide forward propulsion at constant speed, because any torque producing a head forward and down rotation during part of the gait cycle must be counteracted by an oppositely directed torque at some other part of the gait cycle if we wish to remain upright.  In fact, allowing an appreciable gravitational torque to develop at any point in the gait cycle when running a constant speed is actually inefficient because the need to apply a force to reverse that torque results in waste of energy. 

 

So how can we minimize the wasteful generation of gravitational torque?  Perhaps it might seem paradoxical but we do this by becoming airborne. If we spend an appreciable fraction of the gait cycle in the air, we minimize the effects of gravitational torque because gravity can only exert a torque when a part of us is anchored to the ground.  However becoming airborne also uses energy.  Due to elasticity of muscles and tendons at footfall we can recover some, but not all, of the energy spent lifting ourselves upwards against gravity.  So, if we wish to run we are faced with one of two alternatives: spending energy lifting ourselves upwards to become airborne only to see an substantial fraction of this energy dissipated as we fall back to earth, or allowing gravity to rotate us face forwards and downwards, only to have to then apply an opposite torque during the early part of the next stance phase, to correct this rotation.  Running is indeed a dance with a devil named gravity.  Hence the name of the series of articles on the mechanics of running that I wrote last year and have posted in the pages listed in the side bar of this blog: ‘Running: a dance with the devil’.

 

If gravitational torque is largely irrelevant when running at constant speed, what should we do if we wish to maintain a fast pace?  We might consider increasing cadence.  In fact the faster the cadence the less energy we waste on lifting our body against gravity because we fall less during a series of short fast steps than during a series of longer slow steps of the same total duration.  Hence, efficient runners tend to adopt a fast cadence (180 steps per minute or perhaps more) even at slow speeds.  Unfortunately, beyond a certain cadence, rapid turnover is no longer efficient.  I suspect this is because there is a limit to the maximum rate at which the actin and myosin protein filaments that form the contractile machinery within our muscle fibres can cycle through the sequence of engagement, ratcheting and release that occur when a muscle contracts.  So once we have reached maximum cadence, which might be 180 steps per minute or maybe 200 steps per minute for some people (eg Haile Gebresalassie) what can we do?  Most of us reach near maximum cadence at all speeds faster than a jog.  If we want to go any faster than a jog, we must increase stride length.

 

But this is where the task become a bit tricky.  If we reach out with our leading leg before footfall so that we strike the ground with the foot well in front of the centre of gravity, we suffer a braking force that places great stress on joints; dissipates our momentum; and places us in a position where gravity exerts a backwards torque.  So reaching out with the leading leg is both dangerous and inefficient.  As almost all experts on efficient running emphasize, at footfall the foot should be moving backwards relative to the body so it touches down at near zero speed relative to the ground, as near to directly underneath the centre of gravity as possible (though it must touch down at least slightly in front of the COG if we wish to remain upright unless we are running into a very strong headwind).

 

If we cannot afford to reach forwards, how can we increase stride length?  The answer is by propelling ourselves higher into the air at lift off.  In fact, most of the force that generates the upwards propulsion is actually delivered mid stance – during the latter part of stance the centre of gravity is already moving upwards as we remove the weight from the supporting foot.  Once we are airborne momentum carries us forwards, without need for forward propulsion except to overcome wind resistance.  So the answer to going faster than a jog is simply to push up more strongly in mid stance.  Probably about 50% of this push can be obtained from elastic recoil, but elasticity is far from 100% efficient, so we must achieve a substantial l part of the required work be achieved by active muscular contraction.  That is why we need to be fit to sustain a fast pace.  No amount of skillful technique can replace the need to be fit if we want to run far and fast.

 

So why bother with technique?  In fact many elite runners over the years have simply replied ; ‘don’t bother; just get fit’ or words to that effect.  I wasn’t an elite athlete or even a serious competitor.  I was actually far more interested in mountaineering during the years when I might have achieved my peak as a runner, but I did run marathons in less than two and a half hours without ever spending a minute thinking about technique.  Furthermore, I rarely suffered any injury.  I am inclined to think that was probably due to the fact that carrying a heavy pack up and down hills and mountains had given me a fairly rugged frame.

 

So why do I now have a blog with the words ‘Efficient Running’ in the title?  Because as I approach my mid 60’s I no longer have the natural bounce that used to propel me upwards on each stride with relative ease, and because I no longer have the rugged frame that allowed me to run 100 miles a week without thinking about injury, forty years ago.  I now need to pay more attention to just how it is done. 

 

I certainly do not yet know how it is best done, though I suspect that there is no single answer that will fit the needs of every individual, or indeed all of my own goals.  I appreciate the comments that people make and I am learning.  At this stage, I am fairly certain that merely increasing my cardiac output by aerobic training will not be enough.  I believe that I need to increase my muscular strength, but I also need to know how to apply that strength to best effect. 

 

I believe that I need to increase the power of eccentric contractions in my quads and calves to allow me to capture energy at footfall and return it with added push in mid-stance to initiate the next airborne phase.  I suspect that this should not be a conscious push.  Indeed, while I think the theory of Pose is misguided, I think that Nicholas Romanov’s emphasis on the subjective sense of a quick, light footfall is probably the best subjective experience to aim for, if one is to become airborne quickly enough.  However, because I would like to be still  running in my eighties, I am also concerned about the possibility that too much eccentric contraction (running fast and far too often) might produce lasting microscopic damage.  I am intrigued by the possibility that increased antioxidants in the diet might diminish this risk.

 

Although upward propulsion is paramount, getting airborne is not the only role of the legs muscles when running.  It is also necessary to get the swinging leg forward quickly so that it is in position to support the body at subsequent footfall.  This requires two actions. The first is acceleration of the leg forwards relative to the torso.  This is probably achieved best by a well coordinated simultaneous contraction of the hamstrings (to flex the knee) and the hip flexors, such as iliopsoas.  The second action is a neatly timed deceleration of the swinging leg relative to the torso, so that it drops to the ground just slightly in front of the centre of gravity, with the foot moving backwards relative to the torso and at near zero velocity relative to the ground.  This action requires an eccentric contraction of the hamstrings, together with a gentle tensioning of the quads to modulate the action.  The quad tensioning needs to be subtle, so that the leg is not too stiff on impact, if minimizing risk of injury is a priority.

 

While I am fairly confident with this outline of the muscular actions, there are many subtleties, such as contraction of the hip abductors (mainly glutes) in mid-stance to prevent the pelvis tilting down on the unsupported side.  Even more important is the question of the mental image required to achieve this series of muscular contractions with a degree of fine control that defies conscious direction.  So I still have much to learn.

Cadence, Heart, Lungs, Nirenstein, Pose and a Humorous but Horrible Video

February 22, 2009

Rick posted some interesting comments on my recent blog about elliptical cross training.  He pointed out that Haile Gebresalassie averages over 200 steps per minute, whereas I had recommended 180 (i.e. 90 left, 90 right).  Like most of the variables associated with running it is unlikely that there is one magic number that it best for all individuals at all speeds. 

 

A few simple principles of physics demonstrate that for a given pace, there is less up and down motion at higher cadence and probably less risk of injury. When falling under the influence of gravity, the body accelerates continuously. Hence the average speed of fall is greater when the body is airborne longer. The total height of falling is greater during a few long airborne periods than during a larger number of short airborne periods of the same total duration. The mathematics demonstrating this is given in the calculations page in the side bar of my blog.  Similarly the total amount of impact energy that must be absorbed is greater with when the strides are longer at a given speed. The repeated impact with the ground creates risk of repetitive stain injuries in runners, and under the assumption that the risk rises as the force of the impact increases, the risk of injury is almost certainly less with fast short steps that it is with slower cadence and longer strides.

 

However, if you want to maximize efficiency as well as safety the issues are a little more complex. There comes a point where short fast steps become inefficient. I think this point might be reached when length of time on stance becomes too short to allow optimum recovery of energy via elastic recoil of tissues, unless the stiffness of the leg at footfall is increased. The evidence from observing elite athletes suggests that the optimum is probably around 180 steps per second for the majority.  In general sprinters tend to have a slightly greater cadence, possibly because they land with a slightly stiffer leg which recoils more rapidly.  The increased risk of repetitive strain injury is less of a concern when you take about 30 steps in the entire race compared with several hundred thousand steps in a marathon.  However, if you are prepared to run the risk of tendon and joint injuries (especially Achilles tendon injury) then you might run faster marathon if you land with a stiffer leg and higher cadence.

 

At footfall, Haile Gebresalassie takes the weight fairly far forward on his foot, an action that is likely to maximize the storage of elastic energy in his calf muscles.  It may be that one of the several factors that have made him the world marathon record holder is the efficiency with which he recovers impact energy via elastic recoil.  However, I understand that he has required two operations to repair his Achilles tendon.  I personally am cautious about placing too much emphasis on recovery of impact energy via elastic recoil. I therefore aim for a relatively soft landing at a cadence around 180.

 

Rick also points out that by emphasizing loss of leg strength and elasticity as the cause of the decreased stride length that characterizes older runners, I  fail to take account of the decrease in pumping action of the heart and the decrease in efficiency of breathing that also occur with age.  He is absolutely right to emphasize the importance of loss of cardiac and respiratory function.  The reason I focus on leg muscle changes is that I think there maybe more scope for developing better strategies for delaying the loss of leg strength and elasticity.

 

 

With regard to cardiac efficiency, the majority of people suffer a decrease in maximum heart rate as they age.  One factor in this is probably the slow but inexorable decline of the sympathetic nervous system which produces adrenaline.  It is interesting to note that in his recent post ‘Bad, Mad, Glad’, Ewen reported a personal high maximum heart rate recording during the last lap of an exciting race in which he won a silver medal (see link in side bar).  I suspect his adrenaline levels were a bit higher than usual.  However, apart from increasing adrenaline levels, I do not know of anyway of increasing maximum heart rate. The other main cardiac measure is stroke volume. This does appear to respond to training and indeed increasing stroke volume is one of the main goals of aerobic training.  I regard resting heart rate as an indirect measure of stroke volume, and have been pleased that during my recent phase of elliptical training my resting heart rate has fallen from around 53 to around 43, implying that 43 beats is enough to supply the baseline oxygen and nutritional requirements of my body.  Maybe my metabolism has become more efficient, but I suspect a major factor is an increased stroke volume. 

 

The increase in required respiratory effort has also been something I have thought about but on account of my asthma, I have placed my main emphasis on minimizing the irritation of my bronchi and bronchioles.  However, I have noticed that even when I am not wheezing my respiratory effort in the upper aerobic zone is greater on the elliptical than when running.  I do not know why, but speculate that due relatively greater use of fast twitch fibres I am generating more lactic acid and therefore increasing blood acidity which might be expected to provide a greater drive to respiration.  Blowing off more carbon dioxide will decrease blood acidity and compensate for the increase in lactic acid.  If this is the case, then an added advantage of the elliptical is that I will be working my respiratory muscles harder and potentially minimizing the loss of respiratory muscle strength as I grow older. 

 

Finally Rick points out that he has been greatly helped by adopting Jack Nirenstein’s running technique.  Jack Nirenstein advocates a technique that has some similarity to the Pose technique advocated by Nicholas Romanov. The cardinal theoretical principle is the use of gravity to promote a fall forwards.  Perhaps the most interesting puzzle that I have conjured with in my recent attempts to understand running technique is the claim that gravity can provide net forward propulsion.  There are people who undoubtedly find that the Pose technique or the Nirenstein technique are helpful, but it simple consideration of the laws of physics suggests that the theoretical basis of these techniques cannot be correct. 

 

It is true that when the centre of mass of the body is in front of the point of support during stance, that gravity will exert a torque that causes an increase in rotaion in a head forwards and downwards direction.  This is very beneficial when accelerating and indeed it well illustrated by the exaggerated forward lean of a sprinter propelling him or herself from the blocks.  However, unless this head forwards and downwards rotation is counteracted by a forceful application of torque directed in the opposite direction, the runner will inevitable suffer a face down crash within a few strides.. This is an inevitable consequence of the law of conservation of angular momentum. 

 

The Pose coach, Cabletow, whom I regard as the person with the best intuitive grasp of running mechanics that I have ever met (I would venture to speculate that he has a more sound intuitive grasp that Nicholas Romanov himself), recently commented on the Fetch efficient running thread that my application of the principles of physics applies only to stick men.  Unfortunately that is not so.  One or two of the approximate models that I have proposed for the purpose of calculations are indeed approximations that apply to stick men, but the basic conservation laws of physics such as the law of conservation of energy and the laws of conservation of both linear and angular momentum apply to flexible human beings as much as to rigid sticks.. 

 

Some time ago there was a humorous but horrible illustration of the law of conservation of angular momentum in one of those humorous but horrible television programs that show home videos of domestic accidents and other forms of everyday mayhem.  The video clip (which was also published on You Tube but I am afraid I do not have the link) showed a man descending down a slide holding an infant in his arms.  At the bottom of the slide, the man landed on his feet and stepped forwards as he began to rotate to the upright position.  However, because the combined centre of gravity of the man-infant combination was so far forward, he could not get his foot forward quickly enough to plant it in front of his centre of gravity at footfall.  With each step, the man-infant combo accumulated angular momentum-in a head forward and downward direction (unfortunately also an infant forward and downward direction).  They continued to accelerate forwards but also to rotate out of control.  After about 11 steps they suffered the inevitable face-down crash.  The video clip did no make it clear whether or not the infant was hurt, but I hope not.

 

The forward lean proposed by Pose and by Nirenstein is good for acceleration but must be counteracted by a force that exerts an opposing torque at some point in the gait cycle if a face down crash is to be avoided.  Thus, as far as I can see the theoretical basis of both Pose and the Nirenstein methods is fundamentally flawed.  As I have stated here on my blog before, I believe that the Pose method has some very good features.  I am prepared to accept the same of the Nirenstein method, though I have not attempted to practice it.  In particular by taking the focus away from a powerful push off and claiming that gravity provides net forward propulsion, these two methods maximize relaxation while running and minimize the risk of dangerous over-striding.  However, if the goal is to maximize speed without compromising safety, I think one of the goals is to work out how best to develop and apply a powerful push off without over-striding.   I suspect that a major part of the answer is a well timed deployment of hamstrings and other hip extensors in mid-airborne phase to arrest the forward trajectory of the leg relative to the trunk

 

So I am grateful to Rick for his interesting comments.  For me they illustrate the issues that have been at the heart of a lot of my ponderings in the past year or so.

More thoughts on elliptical cross-training

February 16, 2009

In my post yesterday I suggested that although elliptical cross training might have many benefits for the runner, it might not be good for promoting the required neuromuscular coordination.  Ewen asks whether one factor is the lower cadence on the elliptical. In fact I aim for an elliptical cadence in the range 80-90 complete gait cycles per minute which is similar to my cadence when running (around 90 left steps and 90 right steps per minutes).  I did some testing of my efficiency (i.e. heart rate v power output) at different cadences and found that there is not a great deal of difference between 70 and 90 gait cycles per minutes.  Around 80 appeared marginally more efficient than  70 but not much different from 90.  However,as I mentioned yesterday, the striking difference between elliptical cross training and running is the amount of downwards push required, presumably due to the lack of elastic recoil on the elliptical.

 

Although the action of elliptical is intermediate between running and cycling insofar as the involvement of trunk muscles on the elliptical is similar to running (especially if you do not use the handles), the leg action on the elliptical feels somewhat similar to cycling.  I am not a triathlete, but I understand that for the first few minutes after the bike-to-run transition, running feels awkward, and that this awkwardness can be at least partially reduced by increasing cadence towards the end of the cycling.  I suspect that the awkwardness is due to the change  from recruitment of fast twitch fibres employed to power concentric contraction, to a greater dependence on slow twitch fibres and eccentric contraction.   (I would be interested to know what triathletes understand about this).

 

If the downwards push on the elliptical is similar to that of cycling, then an immediate transition from elliptical to running will have some of the problems of a bike-to-run transition.   As in the bike-to-run transition, the problem might be diminished by high cadence on the elliptical, but I suspect it will always be at least a minor problem.   I sometimes use the elliptical at high cadence and low resistance to warm up for running on very cold days.  I believe it does promote muscle blood flow and joint lubrication, but I have been surprised to find that I still need to do a running warm up before I can run fluently.  Whether or not elliptical training one day affects neuromuscular coordination the next day, I d not know, but in view of the theoretical possibility of interference, I would advise a good warm up for the running session to establish good neuromuscular coordination.

 

Related to the issue of the greater push on the elliptical is the likely greater development of fast twitch fibres.  Ewen asks how well these fibres can be recruited aerobically.  The distinction between aerobic and anaerobic function is not an all-or-nothing distinction.  I suspect a moderate degree of hypertrophy of fast twitch fibres is useful for all except ultra-marathon runners.  Whenever stride length increases beyond about 1 metre, a quite appreciable push is required to launch the body along the required trajectory, and as I mentioned yesterday, elastic recoil is not adequate to achieve this.  (Since passing age 60 I have become increasingly aware of the need to push to achieve a fast pace – maybe this would be heresy to the Pose School, but until I meet an elderly Pose runner who can run fast, I will be inclined to hold onto my current opinion). At cadence of 180 steps (i.e. 90 left, 90 right) per minute, paces faster than about 5.5 min/Km require a  stride length greater than 1 metre.   A pace of 5.5min per Km, which is only a moderate marathon pace, is below lactate threshold pace for many runners, so as far as I can judge, an appreciable concentric push is required even when running in the aerobic zone.  I suspect that this is best achieved using fast twitch fibres.

 

So in conclusion, I think that the greater amount of concentric push on the elliptical might cause neuromuscular coordination difficulties during an elliptical-to-run transition, but might produce greater fast twitch hypertrophy which would be beneficial provided it is not excessive.

 

Two days ago, Ewen asked if I thought that my decreased heart rate at a given power output on the elliptical might translate into a lower heart rate at lactate threshold when running.  I do not think this is likely.  Instead I would expect that an increase in mitochondria, increased capillary density, increased pumping capacity of the heart, and increased ability to metabolize lactate would all lead to a faster pace and an increased heart rate at lactate threshold.  I would regard this as a benefit.  I just hope it is true.

Transfer of the benefits of elliptical cross-training to running

February 15, 2009

As usual, Ewen raises the important question about my post yesterday about improvements in aerobic efficiency during 3 months of elliptical cross training.  He asks whether or not the observed improvement would be expected to result in a lower heart rate in the vicinity of lactate threshold when running.  Implied in this question is the more general question: will the observed improvement in aerobic fitness lead to improved performance when running.  I do not know.

 

The definitive proof of the pudding will come when I test myself in a race.  However, many factors affect race performance. In my case, my tendency towards asthma places me at the mercy of my only partially controllable bronchi, so a particular race might be more influenced by daily fluctuations in the irritability of my bronchi than by overall change in aerobic fitness.  Therefore I need a test that is relatively unaffected by variable outside air temperature and humidity, and the muddiness of the terrain; and furthermore, produces little DOMS so it can be applied fairly frequently, allowing averaging to minimize the effect of daily fluctuations.  That is why I developed this elliptical test for aerobic fitness.  The dilemma is that I can only speculate on the likelihood that the gains in aerobic fitness on the elliptical will transfer to fitness for running.  I am still evaluating the relevant evidence, but here are my currents thoughts.

 

The goals of aerobic conditioning for running are:

1)      Increasing the number of mitochondria in muscle fibres. The mitochondria contain the enzymes that carry out oxidative metabolism; that is the combining of glucose with oxygen to generate relatively large amount of energy.  Increasing mitochondria should increase the ability to generate energy efficiently, provide enough oxygen and glucose can be delivered to the muscles.

2)      Increasing the efficiency of the heart as a pump.

3)      Promoting development of new capillaries in muscle so that blood (and hence oxygen and glucose) can be delivered to muscle fibres at a higher rate.

4)      Increasing the ability to metabolise lactate.  When the rate of supply of oxygen is insufficient, energy is produced by anaerobic metabolism  in which glucose is converted to lactate.  Although  this process is the dominant process once the ‘anaerobic threshold’ is exceeded, in fact this threshold is not an all-or-nothing threshold.  In the upper part of the aerobic zone, when oxygen delivery is not quite adequate, a certain amount of lactate is produced.  Build up of lactic acid leads to eventual transition into the anaerobic zone that can only be sustained for a limited time before rising acidity impairs muscle function.  This build up might be delayed if the ability of muscles and perhaps other tissues to remove lactate, is increased. In fact, lactate is also oxidized in mitochondria, so enhanced mitochondrial function should help delay the build up of lactate.

5)      Improving neuromuscular efficiency – the ability of the central nervous system to recruit muscles in the most efficient manner.

6)      Re-modelling of tendons, ligaments and bones to withstand the stresses of running

7)      Hypertrophy of muscle fibres.  During aerobic conditioning, I believe that the main mechanism of increase in the strength of muscle is likely to be the increase in mitochondria and capillaries listed above; during anaerobic resistance training, hypertrophy is due to incorporation of additional protein into muscles.  It is nonetheless probable that some strengthening of contractile proteins occurs during aerobic conditioning.  The skinny legs of many elite distance runners suggests this strengthening makes only a minor contribution to fitness for distance running, but even a distance runner needs to be able to exert  at least a moderaltey powerful downwards push at the end of stance because elastic recoil is far from 100% efficient and therefore elastic recoil is unable to supply an adequate push to propel the body along the required trajectory in the airborne phase. 

 

So which of these processes is likely to be enhanced by elliptical cross training, which are likely to be unaffected and which might actually be harmed?

 

Development of the heart as a pump is likely to be similar for a similar work elliptical work load as for running.  Development of mitochondria and capillaries is also likely to be similar, though  there is a possibility that the development will be a little more focused on fast twitch fibres, because the concentric contractions characteristic of the elliptical training are a little to likely to recruit fast twitch fibres. The development of ability to metabolise lactate is likely to be similar for the two types of training.

 

Elliptical training is unlikely to be effective in fine tuning of neuromuscular coordination for running.  The ability to capture the gravitational energy associated with the vertical oscillations of running, in the from of elastic energy that can be recovered at lift-off, is a crucial factor in efficient running.  The elliptical does not develop the exquisite neuromuscular coordination required for this.  Similarly, elliptical cross training does not provide much stress on tendons, ligaments  and bones, and hence will not be very effective in remodeling these structures to withstand the stress of running.  On the other hand, as I discussed in my post about reactive oxygen on February 5th,  the benefits of running might be offset by permanent damage to muscle fibres.  Such permanent damage appears to be less likely with elliptical training on account of the lesser amount of eccentric contraction.

 

Finally, I suspect that elliptical training might actually produce greater hypertrophy of muscle due to incorporation of protein in the contractile machinery with the muscle fibres, than running.  Because there is minimal elastic recoil, the elliptical demands a stronger downwards push by the leg muscles. I suspect that this will be more effective in producing hypertrophy of fast twitch fibres.  Too much hypertrophy of fast twitch fibres might be harmful, though at least for oldies like myself, in whom deterioration of fast twitch fibres is likely to play a major part in the shortened stride that makes us slow, I think a moderate amount of development of fast twitch fibres is probably beneficial.

 

Summary

So in summary, elliptical cross-training is likely to increase the pumping capacity of the heart, increase mitochondria and capillaries in muscle and increase the capacity to metabolise lactate.

 

It is unlikely to do much to strengthen tendons, ligament ad bones, but on the other hand, is also much less likely to cause permanent damage to either these connective tissues or to muscles.  It will not refine the exquisite neuromuscular control required to capture gravitational energy as elastic energy, and to recover via recoil at lift-off when running.

 

It might promote a slightly greater degree of hypertophy of fast twitch fibres than an equivalent amount of running.  I am inclined to think that on balance this might be beneficial, especially for older runners.

 

As Ewen suggests, it might be useful to replace the training session the day before a high quality running session with an elliptical session to help ensure that the muscle are in good shape for the high quality session.  However, in the warm up for the quality session, it is probably all the more important to include some brief bursts of running at the quality training pace, so as to recover optimal neuromuscular coordination for running at that pace.

 

Most of this is speculation.  I hope that when the spring arrives my bronchi will allow me to assess the fruits of my elliptical sessions, in a 10K race.

Snow drops and improved aerobic fitness

February 14, 2009

I am just back from an easy 10K run in the woods and along the river bank. We are now at the mushy end of a thaw that set in two days ago. At the edge of the village, two slumping lumps of snow are all that remain of a snowman and his partner; a sad demise on St Valentine’s day.  In the woods a few drifts of mushy snow remain and some mini ice floes float in scattered puddles, but the paths are mainly mud. 

 

Staying upright is almost as difficult as it was on the sheets of icy snow last week.  Mud does not raise the spirits in the way that snow does.  However, the clumps of snow drops in full bloom provide some compensation and the thick green carpet of bluebell shoots indicate that spring is not too far away.

 

The River Trent is in spate, swollen with melt-water but still far from bursting its banks.  Nonetheless, the ancient mill race on the escarpment side of the riverside path, but connected to the river by a tunnel, is full of water.  On account of the mud it took some time before I developed a good rhythm, but in the final few Km I was running fluently and comfortably at about 5:30 min per Km.

 

In November, at the time when I decided to re-introduce several elliptical cross-training sessions into my weekly schedule, I had developed a simple test of aerobic fitness.  I record heart rate in the final 15 sec of a series of consecutive 2 minute intervals.  At the beginning of each interval I increase the resistance but maintain a constant cadence so that power output increases in a series of 7 steps spanning the aerobic zone.  Before my run today I did this aerobic test as a warm up, and was pleased to find that my heart rate at each level of the test is about 12 BPM lower than it was on November. 

 

In part this improvement is due to the fact that my asthma is much better today.  There was scarcely a trace of a wheeze. My performance on this test fluctuates day by day depending on how wheezy I am.  It is probable that I will not do as well in future on days when the wheezing is worse.  However even if I were to take the average the most recent three tests and compare with the average of three tests done in November to smooth out the daily fluctuations, there would still be a definite improvement, perhaps by around 5 BPM at each level. 

 

 

Heart rate v power on the elliptical cross trainer

Heart rate v power on the elliptical cross trainer

 

 

 

 

This improvement has occurred over a period of three months during which I have done 2 or 3 easy (or moderate intensity) running  sessions and 3 to 5 elliptical sessions per week, apart for a few weeks in which training was curtailed by injury.  The majority of the elliptical sessions have been in the upper part of the aerobic zone (30 – 35 sessions over the three months). I have done a total of 5 sessions in which I exceeded lactate threshold, and 4 sessions in the lower or mid aerobic zone. 

 

One good thing about elliptical training is that it does not produce any appreciable leg muscle soreness on subsequent days.  This is almost certainly because of minimal eccentric contraction.  The lack of eccentric contraction during the elliptical sessions will probably have resulted in some de-conditioning of my legs, and it is unlikely that I could run anywhere near my potential best over 10K or a half marathon at present.  The interesting question is how much running will be required to re-condition my leg muscles for running.  Whatever the answer to that question, it is pleasing to know that I have been able to improve aerobic fitness substantially without stressing my legs.  

Forlorn bluebells

February 8, 2009

We still have snow on the ground after a week. This morning I went for an 11Km run in the woods and along the river bank. Where the snow was undisturbed, footfall produced a satisfying crunchy sound, but along the more heavily trampled paths, the compacted snow had become a treacherous sheet of ice. It was necessary to run with a high cadence and short steps, focusing on a allowing only a short time on stance in order to stay upright. In the woods, the bluebell shoots that had appeared prematurely a few weeks ago were struggling gamely to poke their leaf tips through the blanket of snow.

The big question

February 7, 2009

In recent weeks I have been posting my thoughts on the risks of long term muscle damage from a training program that includes a large eccentric load. In response to my recent posting ‘sloppy snow and reactive oxygen’, Ewen has posed the big question:

‘Regarding the ‘damage’ caused to muscles by excessive aerobic metabolism… do you think this is good evidence for a training program (for older athletes) that limits aerobic running and promotes higher quality running? When I say “limits”, I’m thinking a runner who might have run 80k per week in their youth, now runs 50-60k, but with higher quality. ‘

The answer is that I have not yet found enough ‘good evidence’ to justify firm conclusions, but I have found some thought provoking information based on scientific studies that allows one to make a reasonably well informed guess.

One problem with scientific studies is that at best they provide information about what happens in a particular group of runners who represent only a small selection of the huge range of variability within humankind; variability that arises from variation in genes and variation in life experiences, including training history. So each individual has to balance the scientific evidence with their own experience.

I think that there is enough evidence to justify the conclusion that abrupt increases in training load or excessive training loads can produce long term damage even in the absence of overt acute injury. It is plausible that the chronic leg weariness might be a marker for long term damage. Therefore, whatever training plan one adopts, I would strongly recommend increased recovery time whenever persisting leg weariness develops.

As to the question of whether a smaller amount of high intensity training is preferable to a larger volume of low intensity training, the answer is not clear. For me, in recent times a weekly volume of 80Km or more results in persisting leg weariness. However, in ‘oldies’, fast running without adequate preparation by gradual build up of intensity almost certainly creates risk of acute injury, and probably causes long term damage.

The elliptical cross trainer appears to require less eccentric contraction and produces less muscle aches and pains, and less persisting leg weariness, that running sessions of equivalent intensity. My own experience when I recommenced training early in 2007 is that a 6 week program based almost entirely on elliptical training produced a substantial improvement in my running performance over a distance of 6Km. However, I do not yet have good evidence that elliptical cross-training produces further improvement in running performance after the easy initial gains.

So my own current plan is to do a mixture of moderate intensity running sessions and somewhat higher intensity elliptical sessions, leavened with some easier running sessions. I will also monitor my progress to determine whether or not my strategy is producing improvement.

The question of how best to monitor progress is not easily answered. I have devised what I believe is a good test of aerobic fitness on the elliptical. I measure my heart rate over a range of power output values – this gives fairly good reproducibility from day to day, though the reproducibility is a little confounded by the daily variations in my asthma. For a test of aerobic fitness when running I will probably employ a version of the Hadd test (or the similar Maffetone test) but at present I face the difficulty that my usual running terrain is cross-country and varies according to weather.

Fortunately, I can afford to be patient as my goal is to sustain, and hopefully improve, performance over a period of 5-10 years.

Sloppy snow and reactive oxygen

February 5, 2009

In the past eight years, snow in the east midlands has never remained on the ground for more than 24 hours, but this week we have had lingering snow for five days. It snowed again last night and continued in the morning. Unlike the initial flurries of crisp polar snow on Sunday, today’s precipitation was typical sloppy English snow, created as a result of a weakening stream of cool sub-arctic air from the east meeting warm moist maritime air from the southwest. When I set out for work the slope down the escarpment to the river was treacherous, so I decided to run to work rather than cycle. The riverside path was delightful as the fresh snow was largely undisturbed, but elsewhere was mush. Apart from free flowing traffic on the few major roads that had been gritted, the roads were in chaos. I am sure that running was preferable to any other form of transport today. The round journey to and from work is about 15 Km. I was pleased that there was no trace of discomfort in my hamstring

This week, in my continuing attempt to assemble the evidence about possible long term muscle damage from forms of training such as downhill running; plyometrics or simple long runs, that entail large amounts of eccentric muscle contraction, I have been looking into the mechanism of damage at the cellular level. There is very strong evidence, which I will review in greater detail in a later post, that sudden increases in amount of strenuous exercise cause damage to muscle via the generation of re-active forms of oxygen – various atomic and molecular forms of oxygen with an extra electron attached. These are generated by aerobic metabolism and cause damage within the muscle fibres. Furthermore, the generation of these reactive forms of oxygen is much greater in the elderly. At first sight, this appears to provide clear-cut support for the value of supplementary antioxidants such as vitamin C.

However, as with almost all processes in the human body, there are natural compensation processes. Training helps build up chemical processes that neutralise the reactive forms of oxygen. Inappropriate supplementation with anti-oxidants might at least in principle diminish this natural intrinsic protective process. On the other hand, in the elderly, the development of natural ability to counteract over-reactive forms of oxygen is more sluggish. So far, I have not managed to identify evidence establishing whether eccentric and concentric muscle contractions differ in their ability to promote protection.

So what can we conclude. As is often the case, the evidence is not adequate to allow definitive conclusions, but several guidelines appear sensible.

1) this evidence confirms that sudden increases in training load are more likely to result in long term damage, even when there is no overt injury.

2) slow build up of training load is likely to help build up of the ability to counteract oxidative damage.

3) plentiful natural anti-oxidants in the diet (eg vitamin C from citrus fruits etc) are likely to be beneficial. As an ‘oldie’, I am veering towards adding supplements, but want to look further into the possible danger of suppression of intrinsic defence mechanisms before consuming an amount in excess of that in the diet that humans have adapted to over our evolutionary history.

Polar snow

February 1, 2009


Ewen, as you imply, De Castella’s demanding 10 mile sessions including fairly fast down-hill running at Stromlo almost certainly contributed to his good performance in Boston, but it is intriguing to speculate that they might also have contributed to the fact that he is now ‘well and truly retired’ at 51. Of course there are many possible reasons why a former world record holder might choose to take it easy as middle age approaches.

However, it is disconcerting that some evidence indicates that elite athletes who stop training tend to deteriorate faster in middle age than sedentary individuals.   In a comparison of 64 sedentary men with 89 endurance-trained men, Pimentel and colleagues (Journal of Applied Physiology, volume 94, pp 2406-2413) found a more rapid decline in maximum oxygen uptake (VO2max) after age 50 in the endurance trained men. Not surprisingly the accelerated deterioration was associated with reduced training volume, though the causal mechanism was not established. In a 30 year follow-up study of men who had participated in the 1966 Dallas bed rest study in their youth, McGuire and colleagues (Circulation, 104, 1350-1357, 2001) found that the cardiovascular deterioration due to 3 decades of aging was less than that due to 3 weeks of bed-rest at age 20. Of special note with regard to the mechanism of deterioration, they found that the decrease in VO2max could be attributed mainly to decreased ability of muscle to extract oxygen from blood. In other words, the deterioration with age was largely due to deterioration within the muscles, though whether this deterioration was merely a loss of aerobic enzymes, or to the loss of fibres, and/or capillaries is unknown.

In the 4th edition of his book ‘Lore of Running’, Tim Noakes proposes that the springiness of muscles is significantly compromised by large numbers of runs over 21k, and he advocates that runners seeking a sustained quality running career should minimise eccentric muscular damage. So, I will continue to be cautious about forms of training that focus on eccentric contraction. Maybe the most important thing is allowing adequate recovery, especially when the legs start to show signs of cumulative fatigue over several consecutive days.

With regard to the recovery from my recent hamstring injury, my easy 7 Km run today went well despite the rather stripey weather. Fitful sunshine alternated with brief flurries of snow. Although the flurries were brief, the flakes were small and compact, typical of polar snow borne by a north-easterly airstream. Nonetheless it was good to be out of doors. After a gentle warm up, I gradually increased pace up to 5:30 min per Km for the 6th Km and was not aware of any discomfort in my hamstring. So I hope that after a week or two of gentle running I will be able to return to moderately intense efforts by mid February.