Cautious optimism

The goal and the strategy

The evidence suggests that my strategy to overcome my recent acute fatigue syndrome with short sessions that include some moderate intensity running might be working.  The goal is to re-train my brain to accept that my body can safely cope with producing at least a moderate power output.  In my post last Monday (31^st Aug), I compared the Poincare plot of heart inter-beat intervals recorded during an elliptical staircase session during a mild setback on my path to recovery, with a plot from a similar session in mid-July before the onset of fatigue.  The feature of interest was the extensive spread of points across the 45 degree line on 31^st August, indicating excessive input from the parasympathetic nervous system.  This was apparently responsible for the fact that my heart rate could not rise above 143 bpm (averaged over 5 sec intervals), when I increased my power output from 200 to 240 watts.  I had to rely on anaerobic metabolism to generate the increase in power.  This was extremely demanding and in retrospect it was not surprising I found it very difficult to maintain 240 watts for more than a few minutes.  Clearly if I want to be able to produce a moderate power output, it was necessary to teach my non-conscious brain that it could relax the tight control at least a little.

Executing the strategy

During the past week I have done three elliptical sessions and two runs, each relatively short but each including a small amount of moderate intensity activity.  The increase in my heart rate from resting to standing during the orthostatic tests in the mornings has stabilized around 5 bpm – still a rather small increase, but probably within my normal range.  Encouraged by the signs of recovery, I repeated an elliptical staircase session on Friday.  To avoid the risk of stressing my heart too much, I spent only 2 minutes at each level of power output in contrast to 4 minutes at each level on previous occasions.  When I increased my power-out to 240 watts, my pulse rose to 147 bpm.  Although producing this power output required some effort, it was not so crushingly difficult as it had been when my maximum heart rate had been clamped at 143 bpm by my tyrannical parasympathetic nervous system, on 31^st August. 

Here are the Poincare plots for the three elliptical staircase sessions: mid-July, 31^st  August and Friday (4^th September).  The plot for Friday’s session is not fully comparable with the other two, because it was recorded after only 27 minutes of exercise, compared with 52 minutes in the other two sessions, and furthermore, the plot is based on a sample of heart beats over 1 minute rather than 2 minutes (because the plots can be misleading during a period of increasing heart rate immediately after an increase in power output).  Nonetheless, the three plots are as comparable as can be achieved in the circumstances.  The crucial point of interest is that the spread of points at right angles to the 45 degree line, which represents parasympathetic activity, is back to a level similar to that in mid-July.  This amount of spread is represented by the quantity, SD1, which was 4 ms  in mid-July; 13.4 ms on 31st August and 3.1 ms on 4^th September.   This provides further confirmation that the over-zealous parasympathetic nervous system that had clamped my cardiac output on 31^st Aug, forcing me to employ anaerobic metabolism to produce even a moderate power output, had learned by yesterday that it could safely allow the rise in heart rate necessary to generate 240 watts aerobically.         

Poincare plots of interbeat intervals in the upper aerobic zone during elliptical sessions before the onset of fatigue (July); during fatigue (August); and during recovery (September)

It is of course ironic that I am celebrating being able to push my heart rate to 147 in order to achieve a power output of 240 watts.  In June, I was pleased when I managed to produce 240 watts at a heart rate of 141.  However, in June my heart rate increased steadily as power output increased.  As I increased output from 200 to 240 watts, heart rate rose from 132 bpm to 141 bpm – in other words, in June, my relatively low heart rate was not due to clamping by the parasympathetic nervous system, but simply the result of being fitter.  ( It is not surprising that my aerobic fitness has decreased somewhat since early June, due to my illness and the fatigue that developed in its aftermath.  The increase in heart rate at 240 watts from 141 bpm in June to 147 bpm yesterday appears to reflect a decrease of around 4% in my aerobic capacity.  That is not too bad in light of the severity of my illness in June/July.)

A short tempo run

Encouraged by the apparent success of my strategy of short, moderately intense training sessions, yesterday (Saturday) I decided to do a 4Km tempo run.  In my only previous running session this week, I had done an easy 5Km including 4 stride-outs of 200-300m at a pace of around 4:45 /Km.  At the time, it would have required great effort to have increased to a pace any faster than this.  Nonetheless, because of my growing confidence, yesterday I decided to aim for a pace of 4:40 /Km for the 4Km run.

After warming up, I set off running comfortably with a gentle breeze behind me and reached the half-way point in 9:18 (4:39 min/Km) with an average heart rate of 138 bpm.  I anticipated that when I turned into the wind, it would no longer feel like a gentle breeze.  As expected, I had to increase the effort and my heart rate rose rapidly to 145, but I felt fine.  I covered the return journey in 9:20 despite the head-wind, giving a total of 18:38 (4:39.5 /Km).   I arrived home very pleased with my progress.

 The next day

However, the crucial question is whether or not today’s orthostatic test would show any evidence of a parasympathetic clampdown indicating over-exertion yesterday.  In fact, this morning the orthostatic difference was 5.4 bpm which is virtually identical to the average value of 5.3 bpm for the entire week. 

Thus, at this stage it appears that I am recovering from the excessive parasympathetic activity that had apparently produced the feelings of severe fatigue I had suffered two weeks ago.  Overall the evidence of the past few weeks is consistent with my previous suspicion that my parasympathetic nervous system tends to be over-active.  Furthermore, the evidence of the past week supports the hypothesis that the non-conscious part of the brain that regulates the parasympathetic system can be trained to relax the tightness of its  grip on the control of heart rate.  The question of whether or not I could have achieved the same outcome simply by resting remains unanswered, though the evidence from clinical studies that graded exercise can promote recovery from fatigue inclines me to think that the low volume, moderate intensity program was the right thing to do.

Caution

I remain aware that the parasympathetic nervous system serves a crucial protective role and therefore, I must be cautious in trying to modify it.  It is likely that the parasympathetic clampdown and the associated fatigue arose because I had been a little too vigorous in the attempts in early August to regain fitness after my illness in June and July.  Therefore, I will continue carefully, but I am cautiously optimistic.

Cautiously graded exercise

After not running for several days, I decided that tonight I would do a short run of about 5Km, including a few stride-outs.  By the time I got home from work it was around 8pm, almost dark, and the rain was pelting down.  However once I had my trainers on, I was eager to go.

The chilly gust of wind that greeted me as I opened the door sent me back inside to put on a long sleeved top – undoubtedly summer has ended.   Because the last glimmer of daylight was fading rapidly, I decided to run on the sidewalk rather than my usual path along the river bank.  After a short distance I passed a young woman jogger who was dressed or perhaps more accurately, un-dressed, for mid-summer, with a large expanse of bare mid-riff between her skimpy top and shorts. As the wind whipped the rain against my face I was quite glad I had gone back for a long sleeved top, even though it was already quite soggy.

During the stride-outs over a distance of 200-300 metres at a pace of around 4:45 per Km, I managed to remain fairly relaxed, though to have run any faster would have been quite effortful.  Afterwards I thought ruefully that 4:45 was a little slower the pace I had originally intended for the half-marathon next week.  That goal is now unthinkable, but I at present I am happy that the fatigue of the past few weeks seems to be gradually receding and I am still running.

Re-evaluation

I am now completely recovered from the illness that afflicted me seven weeks ago.  The main symptoms had resolved after 4 weeks and I have gradually resumed training in the past few weeks, though prior to this morning, I my longest run had been 6.5Km, and the only session at a pace faster than 5:30 min per Km was a 4 Km tempo run.

This morning I faced the question of whether or not to abandon my plan to run a half marathon in early September. Seven weeks ago my training was progressing according to plan, and my target time of 99 minutes appeared reasonable.  After four weeks of quite debilitating illness and 3 weeks of very light training, that target is probably beyond me.  Is it even feasible to contemplate a half marathon at all, within the next 6 weeks?

Last night I had vacillated between planning a 10Km run as the first step in a prudent program directed at recovering endurance, or a moderately paced 15Km to force an answer to the question of whether or not I should persist with my plan for half marathon in early September.  This morning, the rain was beating down from an oppressive leaden sky, and my initial inclination was towards a prudent 10K.  However, rain often looks worse when seen though a glass window than it feels splashing on your face.  So I decided on the 15K, starting slowly, but with the intention of increase pace gradually to around 5:15 min/Km.

The rain was invigorating and I gradually built up pace.  During the second Km my heart rate monitor revealed some brief bursts of tachycardia (discussed below) but I felt fine so I continued to increase pace gradually, and still felt comfortable when I reached 5 min/Km.  The rain continued to pour down and my clothes and shoes became water logged.  I had set off in a pair of old, very heavy, reebok shoes because I suspected that the intrinsic muscles of my feet might have become de-conditioned in the past seven weeks, and I wanted to protect my awkwardly angled metatarsophalangeal joints from the stony sections of the riverside path.  It was probably a wise decision, but nonetheless as I splashed through the mud and slush, the water-logged reeboks felt like soggy clogs.  I had images of Emil Zatopek training in army boots and re-assured myself that I was probably giving my hamstrings and hip flexors a good work-out.  From 3 Km  to 15 Km I maintained a constant cadence of 186 strides per minute (except on the short steep hills) and I gradually increased my stride length from 104 cm to 110 cm.  I finished comfortably with an average overall pace of 5:11 min per Km and a heart rate of  664 beats/Km.

So what conclusion should I draw?  I felt relaxed and comfortable throughout.  My only subsequent musculo-skeletal discomfort is some tenderness of the tissues overlying my metatarsophalangeal joints, confirming the anticipated de-conditioning of my feet during the past seven weeks.  My larger muscles appear to have coped well.  I could almost certainly run much faster in a half-marathon race.  The heavy shoes and muddy surface probably cost me several minutes.

However, I am not sure that my former target of 99 minutes (4:42 min per Km) is within reach   Today’s performance is very similar to my training runs in early June.  At that stage, with three months preparation ahead of me, I was confident of achieving my target. Now, with only a month of training ahead, I doubt that 99 minutes is feasible, but am fairly confident that if all goes well during August, I can achieve a time of 102 min; maybe even 100 min.  So I have set myself a provisional target of 100 min.

The Polar RS800CX

My new Polar RS800CX Heart Rate Monitor has provided me with lots of fascinating information, but at this stage, I am not sure what to make of it all.

Quality of the engineering

My first impression is that it is not as well engineered as I had anticipated for a Polar product.  Sometimes the facilities if offers do not appear to work reliably; for example the first time I attempted to use the Own Optimizer test of training stress and recovery, it failed to give the beep after three minutes to signal that it was time to stand up.  At other times it gives warnings of problems that do not appear to exist.  At this stage I am monitoring the situation to determine whether any of these problems is sufficiently troublesome to justify returning the device to Polar.  On account of the large number of clever options it provides, I suspect that have yet to learn many of its subtleties.

I am not sure about the S3 foot pod. It definitely gives unreliable estimates of distance if not mounted very firmly.  I am not yet convinced that it is reliable even when firmly mounted.  Sometimes it fails to communicate with the wrist-mounted watch/computer for a period of 10-15 seconds, and I am trying to ascertain if this is caused by running near large metal objects.  However, despite occasional evidence of minor unreliability, my interim conclusion is that it is useful to have a reasonably reliable estimate of pace during training.

Heart rate variability

The more interesting thing is the information the RS800CX provides about my heart. There is no doubt the information is interesting, though whether this will allow me to train more effectively remains to be seen.   I have been doing a recording each morning while seated and relaxed.  This confirms that I produce a healthy amount of high frequency heart rate variability at approximately the respiratory frequency suggesting good function of the parasympathetic nervous system; the system that promotes relaxation and recovery.    Figure 1 shows a typical 5 minute segment of resting heart rate.  The fluctuations occur at approximately the breathing frequency (6 breaths per minute).

Figure 1: Five minutes of resting HR

I will be interested to see how the resting heart rate variability changes once I beginning training more heavily.  As I anticipated, I am frustrated by the Polar Own Optimizer, which merely gives a single number indicating recovery status.  It maybe that for a person who is not interested in the physiology, a single number is all that they want, but I suspect that reducing the relatively complex information contained within the heart rate recording to a single number creates the risk of erroneous interpretation in some circumstances.

So far, I am finding a strong correlation between the various indices of parasympathetic function derived from HRV and low resting heart rate.  Maybe a simple observation of resting heart rate would be less prone to misinterpretation, though it should be noted that in the more severe form of the over-training syndrome, resting heart rate is likely to be mis-leadingly low due to over-compensation by the parasympathetic nervous system.  So even a simple measurement such as resting HR needs to be interpreted in light of the overall evidence

Erratic HRV

The most interesting thing I have discovered about my own heart is that despite a healthy amount of heart rate variation associated with parasympathetic activity, my heart rate also exhibits some more erratic variability.  Sometimes during warm-up I get brief runs of rather dramatic tachycardia, during which my heart beats much faster than the anticipated maximum rate of the normal pacemaker in the sinus node.  With my old primitive HRM, I occasionally observed these events, but attributed them to malfunction of the monitor.  However, with the detailed record of R-R intervals provided by the RS800CX I can examine these events in much greater detail, and they do appear to arise from aberrant initiation of the heart beat.  However I cannot be certain of their origin until I record a full ECG.   Figure 2 presents a comparison of a selected (atypically bad) one minute segment of the HR record during warm-up, with a typical one minute segment recorded in the mid-aerobic range.  During the atypical warm-up segment, there is no evidence of fluctuation at the breathing rate, but instead there are erratic fluctuations including bursts of a few beats at a heart rate over 200 per minute, which is far above the maximum rate of my normal sinus node pace-setter (around 160 bpm).  In the mid-aerobic segment the fluctuations are fairly regular at approximately the breathing rate (around 45 breaths per minute).

Figure 2: One minute segments of HR during warm-up and in mid aerobic zone

I am re-assured by the fact that there is growing evidence that ventricular tachycardia (which is potentially a precursor of fatal ventricular fibrillation) tends to be a predictor of cardiac death when it is observed during recovery rather than during exercise itself.  In my case, the abnormalities are mainly present during warm-up.  When I am working fairly hard, my heart rate exhibits an apparently healthy pattern of variation. As expected, the parasympathetic influence decreases markedly as I approach maximum heart rate, but there is still an appreciable variation at the respiratory frequency.  Furthermore, during the recovery period, the parasympathetic influence re-asserts itself rapidly.  So overall, I think I have a quite healthy heart (for a 63 year old) but it may be that there is an irritable bit of muscle in the walls of my ventricles that gets impatient with my well-regulated sinus node during warm-up.   I will experiment with a more gradual warm-up.

In conclusion, perhaps my previous ignorance was bliss, but I am inclined to think that it is better to understand the situation more fully.  Any middle aged person who runs vigorously faces a small risk of a heart attack.  I suspect that in most cases, the increase in life expectancy due to the improved cardiac function produced by training far outweighs the small risk of catastrophe.   I hope that the additional information provided by my HRM will allow me to improve the odds in favour of increased life expectancy.

However, for the person who would rather avoid the intricacies of interpretation, maybe the most sensible thing is simply to measure resting heart rate each morning.  For the gung-ho individual, maybe even this seems over-academic – always looking both ways before crossing the road might provide a greater improvement in life-expectancy in proportion to effort spent.  However I am enjoying the exploration of the intricacies of heart rate variability, and I am increasingly confident that it will allow me to regulate my training more effectively.

Furman re-visited

In March I had set myself the goal of running a half marathon in 99 min in the autumn.  In my blog postings around that time, I looked into the potential advantages and disadvantages of the Furman training program: a relatively low volume, high intensity program that consists of three running sessions per week – a long run a tempo run and an interval session, all to be run at predetermined paces based on target race pace, together with several cross training sessions. 

 

At that stage I still had time for some additional base-building before embarking on a program focused on the half-marathon.  With my intended race now little over three months away, it is time to make a definite decision.  I continue to be tempted by two aspects of the Furman program: the fact that it requires only three running sessions per week augmented by cross-training, and the fact that I enjoy the sensation of running at moderately fast paces.  So to help me decide, I have looked into the evidence from two sources: information gleaned from the experiences of other bloggers who have followed the Furman program; and a review of the progress I have made during the past three month of base-building.

 

The experiences of other bloggers

I sporadically follow the blogs of a number of runners whom I would describe as dedicated amateurs: amateurs in the sense that they appear to run mainly for the love of running; dedicated in the sense that train regularly while meeting the demands of a regular job and/or family.  In recent months, I have kept an eye out for dedicated amateurs who have committed themselves to the Furman program.  In fact I have come across only two such bloggers.  Maybe this is itself tells us something, as there appear to be substantially more blogs describing programs that might be described as Lydiard-style programs.  Nonetheless, the two individuals have interesting stories to tell.  It would be unwise to draw too many conclusions from only two accounts, but the advantage of the stories of individuals is that one can assemble a richer picture of the background fitness and other individual factors that get lost in the reports of scientific studies.

 

I am not sure about the etiquette of quoting from other people’s blogs about themselves, but assume that if they have put the material in the public domain that they are happy for others to try to learn from their experiences. You can read their own accounts to get the facts; any conclusions I draw say more about me than about than about them.  Nonetheless, I will let both individuals know that I have mentioned them so they can correct any misperceptions if they wish. I would also be delighted to hear from anyone else who has tried the Furman program.

 

Charlie

http://runningnowherefast.blogspot.com/2007/08/furman-first-to-finish-program.html Charlie adopted the Furman program to prepare for the Marine Corp Marathon (in Washington DC) in October 2007. At time he was a 52 year old who had been running off and on since high school, but had begun to take running more seriously recently.  In April 2007 he had run a half marathon in 1:32:26, and a 10K in 41:58:55.  His usual training program included a large amount of cross training, including use of elliptical, stair-stepper and swimming.  He set his Furman training paces according to a planned marathon pace of 7:20 min per mile which corresponds to 3:12:00 for the marathon.  He started at the 4^th week of the 16 week Furman marathon program but at that stage had already been training hard for 5 weeks. Here is a description of the final stages of his first Furman session, a 5×1Km interval session at 5:53 min per mile  pace (3:40 /Km), following a rest day:

‘I could barely finish the fourth one…leaving me gasping for air and taking a minute more for my RI. For the fifth one I dropped the speed down to 10 mph [6 min/mile] and barely finished that one…thankful the series was over. 

However he found the 20 mile long run that week easy and couldn’t restrain himself from increasing the pace from the planned 8 min/mile to an average of 7:15 min/mile for last 2 miles.  At the end of the week he concluded

‘My first week of the Furman program is under my belt. I found the speed intervals was my hardest day and the other two days were fairly easy.’

As he progressed through the program he continued to find the speed interval sessions hard but coped well with the other sessions.  On race day, he covered the first half of the marathon in 1:37:38, but a few miles later he developed muscle cramps and struggled to finish in 3:47:28, a very respectable performance but well short of his target.  Only two weeks later, on 11 November he entered the Richmond Marathon. He started more slowly and did the first half in 1:41:10.  This time he did not suffer cramps during the second half, and finished in the creditable time of 3:23:26, in fact a really impressive performance only two weeks after his travails in the MCM.    

So in his marathon campaign in 2007 Charlie did very well, but fell a little short of the potential indicated by his half marathon and 10K times recorded in April.  I would anticipate that a runner with a half marathon time of 1:32:26 and with legs optimally prepared for the rigors of the longer race, would be capable of a marathon in the range 3:12:00 to 3:15:00. It plausible that a larger number of long training sessions run at a less punishing pace might have resulted in better conditioning of his leg muscles, though whether or not that conditioning could be achieved in a single season by any training regimen is doubtful.     

 

Paul

http://2009marathoncampaign.blogspot.com/

The other ‘dedicated amateur’ blogger who used the Furman program is Paul.  I discovered his blog as a result of a comment he left on my blog, reporting the outcome of his recent run in the Sri Chinmoy half-marathon in Williamstown (Melbourne).  Paul is a forty year old triathlete who had run a half-marathon in 97 minutes about 15 years ago, and in February 2009, initiated his campaign to prepare for the Melbourne marathon in October.  In the first week of his campaign he completed a 500m-20km-5km. triathlon in 1:15.43, running the final 5Km in 23.:29.  Thus, at that stage he appeared to have the speed and endurance to run a half-marathon in around 98-99 minutes.  He confirmed this potential with a 10K in mid-March in 44:54, which according to the Daniels VDOT tables, corresponds to a half-marathon time of 98:30.     

At the end of March he commenced the Furman half-marathon program, starting 10 weeks out from his interim target of a half-marathon at the end May.  This is what he wrote after his first session:

‘This is hard!!! I had to complete 2x 1.5km easy (5.28min/km) and 3.5km tempo (4.38min/km) with a cool-down so a total session of 11km. I found pacing pretty hard to set and ended up running a little faster on the easy bits (7.47 and 7.56) and a little slower on the tempo sets (16.21 and 16.48).’

He didn’t find the first long run of the program any easier.  A few days later he wrote:

‘Crikey, that was a hard run today! I knew this program wouldn’t be easy, but I didn’t realise I’d find it so hard from the start.   Somewhere along the course today I realised that this program says Run #3 each week is a long run. It does not say it is an EASY long run. … In any case today was a 13km run at HMP (Half Marathon Pace) +12 sec/km…But, managed to run 63.54min against a target of 63.42min so essentially right there. But it was no gentle Sunday morning stroll.’  

However, as the weeks went by Paul started to find the long runs easier, and by the end of the program was comfortably completing the long runs at a pace around 4: 53 per Km.  He went on to record 1:33 in the Sri Chinmoy half-marathon on May 31^st.  He will soon be starting the Furman marathon program.  So, my interim conclusion from Paul’s experience is that for a runner with a sound base, the Furman half-marathon program is tough, but can produce a spectacular improvement 

A review of my own situation

In my younger days I used to enjoy the sensation of running at a moderately fast pace.  During my brief return to regular running during my fifties I had been a little frustrated by the fact that I was no longer able to run fast, but nonetheless had started to get the sense that it might again be possible, as my pace for tempo runs decreased to around 4:30 min/Km.  Then an exacerbation of my long standing asthma and also the demands of work led me to stop running for about 18 months.  On realizing how unfit I was becoming I restarted running again in 2007, but progress has been slow.  

For two years I trained mainly at fairly low intensity, rarely covering more than 50Km in a week, and averaging around 35 Km per week.  In September of both 2007 and 2008 I had run a half-marathon, on each occasion recording a time of 101:xx minutes.  I decided that this year I would make a more determined effort to increase training intensity and have set myself the goal of a half-marathon in 99 minutes in the coming September.

When I reviewed the options for a training plan in March, I had weighed up the merits of either a Lydiard-style relatively high volume program or a Furman high intensity program.  I realized that I did not have an adequate fitness base to enable me to tackle the Furman recommended training paces, especially the recommended pace for the majority of the long runs (half-marathon pace + 12 sec /Km) .  For a target half-marathon time of 99 min the recommended long run pace is 4:54 min/Km.  I therefore decided to defer the decision until after I had spent a further 10-12 weeks building up my fitness base.  As stated above, now is the time to make the decision.

In the past three months, my asthma has continued to be an intermittent problem, leading to mild wheeziness and a 35-45 % fall in expiratory flow rate after a vigorous training session.  Furthermore, the fact that I often arrive home from work after 8pm in the evening, tired and hungry, has curtailed my plans to do really solid base building.  The mainstay of my training has been back-to back moderately long runs in the lower aerobic zone on the week ends, with several short evening sessions during the week.  Typically I have done one session of uphill strides; a fartlek run of 6-8 km; an easy run with some alactic sprints and an elliptical cross-training session most weeks.  I have averaged a little over 50 Km per week.  During this time my aerobic fitness has continued to improve slowly.  

As I have mentioned previously on my blog, I find that heart beats per Km for runs in the aerobic zone over easy terrain when not stressed is a fairly consistent indicator of my aerobic fitness.  When I recommenced training in 2007, my score on this measure was over 800 beats/km, by February 2009 it was around 700 beats/km and now it is typically 650-660 beats/Km.  I estimate that a value of 645 beats/Km would represent adequate aerobic fitness for a 99 min half marathon.   On my current training schedule, I would anticipate achieving this level by September, so there is little reason to change my current schedule for the purpose of increasing aerobic fitness.

However, the other main requirement for achieving my half-marathon target is conditioning my leg muscles to cope with a pace of 4:42 min/Km for 21Km without substantial muscle damage.  How near am I to achieving that goal?  My back-to back longish runs on the week-ends have demonstrated that I can fairly easily maintain a pace around 6 min/Km for 20Km.  Yesterday (Saturday) I decided that I would test my ability to increase the pace during a 16Km run.

Unfortunately, as is often the case, I had had a busy week at work and I felt very lethargic as I warmed up.  Even after a few stride-outs over distances of 50-150 metres I still felt very sluggish.  So I decided that the most practical thing was to start at a pace of around 5:10 min/Km, which I anticipated would be in the lower aerobic zone, and increase pace steadily with the hope of reaching and maintaining the my intended half-marathon pace over the final few Km.

I covered the first 4Km in around 20:30, with a heart rate in the lower aerobic zone as expected.  I continued to feel sluggish but nonetheless enjoyed the sensation of gradually increasing my pace.  With 4 Km to go my legs still felt heavy but I was by now near to my intended race pace and really enjoying feeling of running faster.  I covered the final 4Km in 18:48 min (4:42 min/Km), which was exactly my target pace.  My time for the 16Km was 80 minutes and mean heart rate 130 beats/min, corresponding to 650 beats/Km.  Although my average pace was modest, this run clearly extracted a price from my muscles. I awoke with appreciable stiffness in my leg muscles, and during an easy 8Km recovery run, my heart rate was 696 beats/Km.  Experience has taught me that an increase of this magnitude indicates a moderate degree of over-reaching.  If I take it easy tomorrow I expect that I will have recovered completely by Tuesday.

So what conclusions should I draw?  I am fairly confident that irrespective of the specific training strategy I adopt, provided I continue to train regularly for the next three months, my aerobic fitness (i.e capacity to deliver oxygen to my muscles at the required rate) will be adequate to allow me to achieve my target half-marathon pace while remaining within the aerobic zone.  However my leg muscles are still far from adequately conditioned for the task of maintaining this pace for the required distance.  The two ingredients missing from my recent program are tempo runs in the upper aerobic zone, and longish runs (around 16 Km) at a pace not far below race pace. 

The tempo sessions and fast longish runs might be provided by the Furman program.  However, I do not anticipate the demands my job becoming any less in the next few months, and I do not relish the prospect of fitting two very demanding midweek sessions into my current work schedule.  Furthermore, I do not want to abandon my current back-to-back longish runs on weekends entirely, as I think these runs have served me well so far.   Therefore, I think it is probably more practical to continue with a weekly program that includes 5 or 6 running sessions, including at least one tempo run and a hill session each week, and longer runs on the weekend that alternate from week to week.  One week I will do a fairly fast run of around 16Km (aiming for the Furman recommended long run pace of 4:54 min/Km)  and the following weekend I will do back-to-back  longer runs in the lower aerobic zone. 

Maybe this medium intensity/medium volume plan is neither fish nor fowl, but I think it will more enjoyable than a rigid Furman schedule and I suspect it will be adequate to allow me to achieve my goal this year.

Maximising aerobic development

The study by David Bishop and colleagues that Ewen drew my attention to in his comment on my post on base-building on April 12th, demonstrates that interval sessions in the upper part of the aerobic zone produce a marked stimulus to development of mitochondria, and this stimulus to aerobic development is decreased, but not abolished, by acidosis (Medicine & Science in Sports & Exercise:Volume 40(5) Supplement p S33, 2008). Although Bishop and colleagues produced acidosis artificially by administering ammonium chloride, it is likely that marked acidosis arising from highly anaerobic exercise would have a similar effect.

Thus, this study does imply that mixing highly anaerobic work (sufficient to produce marked acidosis) with aerobic work within a session will produce less aerobic development than might be achieved by a purely aerobic session. Although the study does not directly compare lower aerobic with upper aerobic sessions, it certainly demonstrates that upper aerobic work produces a major stimulus to development of mitchondria and hence suggests that the most efficient way to promote development of mitochondria within a limited time is upper aerobic work.

I would expect that fartlek would also be an efficient way to produce aerobic development provided the effort epochs do not become severely anaerobic.  A session that I have been experimenting with recently consists of 6 to 8 uphill stride-outs for about 250 metres on a 1 in 10 gradient grassy path though woodland, separated by easy-paced downhill recoveries. I find this session is not at all stressful (in fact I really enjoy it). By the end of each uphill stride-out, I am near the ventilatory threshold. I do this session in place of the ½ effort sessions in a Lydiard program, because it takes only about 20 minutes (not including warm-up) and hence fits more easily into the time I have available. I hope this will provide good aerobic development while also strengthening my legs.

My current weekly program consists of one longish low aerobic run, a progressive run that gets me near lactate threshold for 5-8 Km (my current equivalent of Lydiard’s ¾ effort session); the uphill strideouts (my replacement of Lydiard’s ½ effort sessions); several easy runs that include a few short ‘alactic’ sprints at the end; and an elliptical session. Overall this program is intended to build an aerobic base while also strengthening my legs and promoting good neuromuscular coordination, with a relatively limited commitment of time. However, it is reasonable to assume that if time was not an issue, I might achieve as much aerobic development by running in the lower aerobic zone for a longer period.  A greater proportion of lower aerobic work would be expected to produce greater development of fat-burning capacity, but less development of type 2a (fast twitch aerobic) muscle fibres than my current program.

I consider that the study by Bishop and colleagues confirms that Lydiard’s recommendation of a moderate amount of upper aerobic work and a large amount of lower aerobic work during base-building is good advice. However, I also think this study indicates that Lydiard’s claim that no further aerobic development can occur once one starts anaerobic development is not correct. Even in a session in which aerobic threshold is exceeded some development of mitochondria will occur. Nonetheless, if you want to achieve aerobic development while also developing speed endurance during a phase of mixed training, it would probably be most efficient to do some entirely aerobic sessions and some separate interval sessions

A race on New Years Day

I run mainly because I enjoy primitive low tech interaction with the natural world, and also because I enjoy the occasional fleeting experiences of powerful efficiency when I get into a good rhythm. I also quite like the extra spice provided by racing – the challenge of achieving a personal best and the psychological contest with the other runners – though the battle is mainly with one’s own psyche. Last year I ran only two races and I have decided that this year I will run a few more races.

Today I set out for an easy 18-20Km run to Attenborough. Shortly after joining the riverside path heading northeast towards Clifton Bridge I could see a family – dad, mum and two young girls – on bicycles about 500 metres ahead of me. What better day than New Years Day to implement my plan for more racing, so the race was on. I didn’t know how far we would be racing, and the family were starting with two advantages: they were already 500 metres ahead, and they were on bicycles. However I also had two secret weapons: While I didn’t know whether the race would be over 3 Km, 5 Km or 10 Km, they didn’t even know they were in a race. Secondly, I knew that about 2Km ahead was the gate to a field that was home to two friendly horses. Sure enough, I overtook them in time to hear the younger daughter saying ‘Goodbye horsey’ while dad was pushing onwards toward the up-ramp to Clifton Bridge with a demeanour that said: ‘We’ll all freeze to death if we hang around here patting horses’ I strode into the lead up the long incline to the bridge, but about 600m later, coming off the down-ramp, dad and elder daughter whizzed past me at a speed I could not have hoped to match. I turned southwards along the river bank towards Attenborough while the family continued onwards towards Nottingham. I was still ahead of mum and younger daughter. So my first ‘race’ for the year could be considered a drawn match.

With regard to more serious races, although my current level of aerobic fitness is not great, I will stick to my plan to build up my speed to a moderate level in the near future and run a few shorter races in late winter or early spring, before settling in for some longer distance training in the summer and a half-marathon race in the autumn, with a ‘gold standard’ target of 96 min and a ‘silver standard’ target of 99 min.

Running and stress on the knees

In his comment on my blog about adjustments to my running style to deal with my knee problem, Andrew wondered whether he had enough patience and knowledge to adjust his running style to eliminate his knee problem. The human body is complex and each individual has a unique history, so tackling any serious musculoskeletal problem must start with individual assessment by a qualified professional. However, there are also some general principles of running style that can help reduce the stress on the knee. Adjusting running style requires some patience, but the challenge of mastering a skill can be in itself rewarding. With regard to knowledge, there is a lot of information available in books or via the internet, but if possible it is best to get a well-informed coach. The big challenge is finding the right coach, and it is probably best to do some searching of internet sources beforehand so that you can ask the right questions of a potential coach.

I did quite a lot of searching when I decided to adjust my own running style. There are quite a lot of modern schools of running technique. Reassuringly, they almost all agree on some of the key features for high performance, such as short time on stance, but they differ in regard to features that influence the amount of stress on the knee.

For example the Dutch BK method (http://www.runningdvd.com/content/en/) advises against substantial flexion of knee and ankle at footfall but instead favours a relatively rigid leg to maximise rapid recoil and minimise time on stance. This might be optimal if speed is your highest priority, but I suspect that it places a lot of stress on muscles and joints, and in my search for a technique that is kind to the joints, I decided that it was not the method for me.

On the other hand there are several modern methods that do favour a softer landing. These include Stride Mechanics, Evolution Running, and Pose. In my opinion, Stride Mechanics is the most soundly based of these methods, and Pose the least. Because I have a background in both physics and physiology, I decide to try to incorporate what I regarded as the most sensible of the ideas from these schools of thought (together with the ideas of Gordon Pirie) into a coherent framework based on the principles of physics and physiology. The current version of my synthesis is described in the series of articles under the heading ‘Running: a dance with the devil’ in the side bar of this blog. I cannot yet claim that I have proven that these ideas have led to an improvement in my own running, though they appear to have alleviated my knee problem. Furthermore, I cannot offer the type of guidance and support that a commercially developed package can offer.

Therefore, if you want a comprehensive package, I suggest starting with the material on the Stride Mechanics website (http://www.stridemechanics.com/) and consider buying the book.

The most fully developed commercial package is provided by Pose, developed by Nicholas Romanov (http://www.posetech.com/). I have spent a lot of time exploring Pose and doing my best to put the method into practice. I have been on a two day course run by Nicholas Romanov. In those two days I was fascinated but also somewhat appalled by what I perceived as psychological tricks designed to convert us into disciples. However, I was also very impressed by the intuitive grasp of running mechanics of one of the Pose coaches present (Dr Mark Hainsworth) and I learned a lot from him.

My conclusions about Pose, after much reading, thought and practice, are:

1) It does reduce stress on the knee. This was confirmed in the study by Arendse and colleagues from Tim Noakes laboratory in Capetown (Medicine and Science in Sports and exercise 36(2):272-7, 2004)

2) The recommendation to land on the forefoot increases risk of injury to the Achilles tendon and calf muscles. This was apparently also observed in the Capetown study, according to Ross Tucker, one of the scientists involved (see (http://www.sportsscientists.com/2007/09/running-technique-part-ii-scientific.html), but those findings were apparently never submitted for publication in a peer-reviewed scientific journal. In the 2004 edition of ‘Pose Method of Running’ Romanov has decreased the emphasis on forefoot landing, but many illustrations in that edition still show an exaggerated forefoot landing that creates a high risk of Achilles or calf injury.

3) The Pose principle that gravity provides the energy for forward propulsion is misleading. It implies violation of the law of Conservation of Energy. However, despite being misleading from the theoretical point of view, it might well have the desirable effect of discouraging unnecessary muscle action and thereby reduce the risk of injury. On the other hand, it might also discourage beneficial muscle action and therefore result in less powerful performance – in comparison with approaches such as the more muscular BK method.)

4) The Pose principle of landing under the centre of gravity (COG) is actually impossible to achieve while remaining upright, except in the presence of a substantial head wind, because if the foot is only grounded when beneath or behind the COG, the body will acquire an increasing amount of angular momentum in a forwards and face-down direction on every stride and a face-down crash within a few strides is inevitable. Nonetheless, trying to achieve the impossible goal of landing under the COG might in practice be helpful as it does discourage over-striding (reaching forwards with leg immediately before footfall, which is undoubtedly inefficient and injurious).

5) The available evidence indicates that in the short and medium term, Pose results in a decrease in running efficiency; that is, it requires more energy to maintain a given speed (See http://www.sportsscientists.com/2007/10/pose-running-reduces-running-economythe.html). Although many elite athletes have experimented with Pose, as far as I can establish very few have substantially improved their performance after taking up Pose. The British triathlete, Tim Don is sometimes quoted as an example of a Pose success because his running performances improved during Romanov’s limited tenure with the British Triathlon team, but apparently Don no longer persists with orthodox Pose technique. In contrast, Debbie Savage (Australian 800m runner) continues to be enthusiastic about Pose and is a Pose coach.

6) Nicholas Romanov’s claim that the same technique can be applied irrespective of pace is misleading. When sprinting (or for that matter when running a 10K in less than 27 minutes) it is probably best to land on the forefoot without grounding the heel, but for a moderate standard marathon runner who takes more than 32,000 steps while running a marathon in 3 hours, it might be better to allow the heel to touch ground during each step to avoid repetitive strain injury to the Achilles tendon.

So, on balance, I would only recommend Pose if you can find a coach who understands its positive points, but is also aware of its potential pitfalls. But best of all would be a coach with an intelligent grasp of the strengths and weaknesses of all of these approaches to efficient running.

He could pass for a 62…

..in the dusk with the light behind him (with apologies to Angelina from Gilbert and Sullivan’s Trial by Jury, for the minor adjustment of age and sex).

It has been a year in which I have become increasingly aware of my age. The minor infirmities that were a mild nuisance in my youth have emerged from the shadows like drab spoil-sport harpies clawing at me and attempting to either suffocate me or hobble me. I am grateful that I can still run and have even enjoyed a few sublime running moments during the year, but more often I have been struggling with my wheezy chest or the fragile aching connective tissues that barely hold my frame together. So I was quite amused by a trivial incident during my run this morning.

I had set out with no particular plan other than to run as the mood took me. The northerly air stream that has swept over Britain during the Christmas period had abated to a mild breeze and swung from north to east bringing air from Siberia rather than the North Pole. Nonetheless, it was still quite bracing, and despite my recent debilitating episode of flu, I felt reasonably frisky. After crossing to the opposite bank of the Trent and heading southwards to Beeston, I decided that I would continue onwards to Attenborough Nature Reserve, a gaggle of lakes formed from old gravel pits and laced with a network of delightful paths. The point where the riverside path enters the Reserve is about 8 Km from home, so I was committed to a run of around 20 Km even if I only did one of the shorter lakeside loops. I was still feeling quite lively as I approached a man of about my own age pushing a bicycle. I called out hello and he responded: ‘Great weather for a run, kid’. I am not sure whether the ‘kid’ was ironic, or merely an indication of his failing eyesight, but I decided to take it as a compliment, and continued on my way with renewed friskiness.

Here is a picture taken during the Hardrock Challenge a few months ago. It was taken about a kilometre from the finish; at the point where I had pushed myself into the anaerobic zone to break free from the pack with whom I had been running in the mid-stages of the race. It is unclear whether the etched lines on my face are the furrows of effort or merely the wrinkles of old age. That race was probably the high point of my running year. The challenge for next year will be to train hard enough to improve without injuring myself or becoming ill.

A Puzzle and a Tribute

The puzzle

The proposed third section of my series on Dancing with the Devil will deal with the mental state necessary to allow us to achieve the movements required by the principles of biomechanics to achieve efficient running – the psychodynamics of running. However, I am delaying tackling the psychodynamics because there is one large question of the biomechanics of running that still puzzles me. The problem is deciding on the most efficient muscle action to achieve an adequately long stride when running at fairly high speed.

Evidence strongly suggests that once cadence reaches 200 steps per minutes, further increases in cadence would require a rate of muscle contraction that becomes increasingly inefficient. Therefore, efficient increase in speed required an increase in stride length. A longer stride length at fixed cadence requires a faster average speed of the leg as it moves forwards from stance to stance to support the body, because the distance from footfall to footfall is greater but the duration of the stride is unchanged.

One way to achieve a higher average speed of the leg is to use more vigorous hip flexion in early swing. However, this action will tend to bring the foot forwards rather than upwards at lift-off, resulting in the foot being carried at the end of a longer lever arm In contrast, if lift-off is largely via hamstring contraction with minimal hip flexion, the knee flexes more, the foot rises behind the line for point of lift-off to hip, the lever arm is shorter, and hence the leg naturally swings faster under the influence of gravity while the other leg is on stance.

In fact the swing is a power assisted pendulum rather than a simple pendulum driven by gravity. To the extent that we use muscle power rather than gravity to drive the swing, it makes sense to drive the foot along the shortest path from lift-off to foot fall. The shortest trajectory is a low arch in which the highest point of the foot trajectory is achieved at approximately mid-swing, rather than the pear-shaped trajectory that includes the initial high upward loop to a position behind the buttocks.

So to resolve the issue, we need either a complex mechanical model which is impractical, or alternatively, we need to examine the evidence from observation of elite runners. Many elite runners, such as Haile Gebrselassie, do lift the heel quite high behind the buttocks, so that the foot trajectory is not a simple symmetrical curve, but it does nonetheless appear that the foot is pulled forwards at lift off as well as upwards. So the answer appears to be a compromise.

While I have a fairly clear mental image that promotes a strong hamstring contraction and a different mental image that promotes hip flexion, I have not yet been able to decide on the mental image that promotes the optimum compromise. So for the immediate future, I am postponing part three of ‘’Dancing with the Devil’ until I have had a greater opportunity to try different mental images.

The tribute

The tribute is to the ‘Efficient Running’ thread on the Fetcheveryone website (http://www.fetcheveryone.com ). This thread was started on 20^th August 2007 with a question about heel striking, and reached its 10,000^th entry a few days ago. That reflects an average of about 50 entries a day, so keeping up with the torrent of material has been enough to leave one breathless, or maybe just sleepless. The entries have included many thought provoking ideas about efficient running, in addition to much social chit-chat.

At times people have complained that very little is ever decided on the thread because too many individuals are fixed in their thinking and unprepared to change. My own view is that most people hold fairly strong opinions largely because a particular way of running ‘feels right’ and/or is based on concepts which appear to make a great deal of sense: concepts such as the notion that it is best to land with the foot under the centre of gravity (COG). This seems to make sense because it minimizes the inevitable braking effect when the point of support is in front of the COG. However, as discussed previously in this blog, unless the foot lands in front of the COG, the body must continually accelerate or suffer a face down crash after a few strides. It is impossible to land under the COG when running at constant speed on a level surface in the absence of wind resistance

Despite some skepticism regarding the laws of physics, illustrated by the statement of one Pose coach that arguments based on physics ‘matter diddly squat’, the discussions on the thread have often sparkled and have challenged me to examine carefully what I am doing when I run, and also to think deeply about biomechanics. I hope this has led to some useful conclusions.

Looking back, I think that the Fetcheveryone thread has been the second strongest influence (after Gordon Pirie’s book ‘Running Fast and Injury Free’) on my thinking about efficient running. The scene was set by an entry by Cabletow, posted 5 hours after the initiation of the thread, which provided a succinct summary of the five principles espoused by modern schools of thought about efficient running. In his words, the principles are:

‘increase cadence to 90 per leg
Land under your cog with a bent knee to release plyometric energy
Land with a rearward moving foot and relaxed ankle
Do not push off but lean forward into the run
Limit arm movement, bend the elbows and do not reach too far forward.’

These principles have exerted a huge influence on much of the discussion on the thread. I think they are excellent principles, though I would take issue with two features. As already discussed, landing under the COG is impossible when running at constant velocity on a level surface in the absence of wind resistance. The other issue is the recommendation to lean forward. This is a confusing and sometimes confused issue. At times, people take it to mean a forward inclination of the long axis that passes through point of support, hips and shoulders at mid-stance, as illustrated in the spectacular picture of a muscular young man running on a beach in the PoseTech advertising literature. At other times, as emphasized by Cabletow himself in recent posts, it is taken to mean the forward lean of the line from point of support to COG that occurs as a result of hip extension in the second half of stance.

Both forms of lean result in a gravitational torque that tend to rotate the body in a face forwards and downwards direction. More confusing is the notion that lean promotes forward propulsion by means of this gravitational torque. This is a concept that arises from the questionable biomechanics proposed by Dr Nicholas Romanov in the theoretical underpinning of the Pose Method. It is a concept that ignores the law of conservation of angular momentum. If a face forwards and downwards torque is applied at some point in the gait cycle, it must be counteracted by an oppositely directed torque at some other point in the gait cycle if a face down crash is to be avoided. Nonetheless, the concept that gravitational torque provides useful forward propulsion continues to exert a strong influence on the discussions on the Fetcheveryone thread.

In relation to my personal priorities, the main limitation of the five principles proposed by Cabletow are that they do not adequately address the question of how to run with maximal mechanical efficiency, in the sense of using the minimum amount of energy per unit distance at a fixed speed. The five principles encourage a safe running style that minimises risk of injury. Minimising risk of injury is crucial to promoting good performance, but it leaves unanswered the question of the most efficient way to get the legs forward quickly enough to allow running at a constant high speed.

In my opinion, three of the modern schools of efficient running do make a coherent attempt to address the issue of how to run efficiently at high speed. These are Evolution Running developed by Ken Mierke (http://www.evolutionrunning.com); Stride Mechanics developed by Jack Cady (http://www.stridemechanics.com ); and the BK method developed by Frans Bosch and Ronald Klomp (http://www.runningdvd.com/content/en/). The concepts of Stride Mechanics have been presented occasionally on the Fetcheveryone thread by Jack Cady himself. However, as far as I can discern, neither Evolution Running nor BK method have been presented so far by individuals who are experts in those schools of efficient running, and I hope that they might be at some time in the future.

This tribute has not been a eulogy to a departed friend, but an account that reflects my own personal priorities, and includes an expression for hope for a broader perspective in the future. The Fetcheveryone Efficient Running thread has been a major source of inspiration to me. Thank-you to all who have contributed.

The Dance with the Devil: putting the steps together

Preamble

In the last three posts, I have attempted to describe what happens in the various stages of the gait cycle. However, the cycle is one integrated sequence, so this post will focus on how it all fits together, and including some detail about the torso and arms

Torso

Gordon Pirie recommends upright torso; Pose recommends a forward lean maintaining a straight-line from point of support via hips to shoulders, at mid-stance. The theory behind the Pose lean is based on what I believe to be false biomechanics. The proposal by Dr Romanov that gravitational torque can generate forward propulsion even when running at constant velocity is tempting, but violates the law of conservation of angular momentum. Subjectively, the lean can feel helpful – but I think that is a misleading perception based on the experience of starting from a stationary position. There is no doubt that a lean promotes acceleration that is helpful for a sprinter driving from the blocks, but acceleration is only a very minor part of longer distance running. So whose advice is more helpful: Pirie or Romanov? In a previous post I came down favouring Romanov, but that was after a session running into a strong wind. Maybe lean helps when you need continuing reinforcement of the horizontal drive on account of wind, but I am now inclined to think that Pirie’s advice is best on a level surface when the wind is not too strong.

The reason I think an upright torso is best is that it promotes a greater eccentric stretch of the hip flexors during late stance, and this will facilitate hip flexion after lift off, thereby bringing the leg forwards to overtake the torso by mid-swing. Upright torso also likely to promote effective deceleration of the leg by hamstrings and gluteus maximus in late stance, and good coordination of hamstrings and quads to achieve the required flexion of hips and knee at footfall. Both the quads and hamstrings cross hip and knee, and appear to have evolved so that despite being mutual antagonists, simultaneous contraction of both can produce well coordinated movements at both joints when the torso is upright.

Similarly, keeping the hips forward (i.e. avoiding ‘sitting in the bucket’) promotes more efficient hip flexor stretch in late stance which helps get the legs forward quickly; and promotes good coordination of the hip and knee at footfall.

Arms

When the neurosurgeon Wilder Penfield used electrodes applied directly to the brain to stimulate muscle contraction, as part of pre-surgical exploration of brain function in patients needing surgery for epilepsy at the Montreal Neurological Institute in the 1930’s, he demonstrated that a much larger area of the motor cortex in the brain is devoted to controlling the upper limb than the lower limb. This fits with the observation that most people are more dextrous with their hands than their feet. However, the upper and lower limbs automatically work in synchrony when running. So it is plausible that conscious focus on what we do with the upper limb will be more effective than focussing on the legs and feet. In particular, focus on the backward movement of the arm on the side of the leg that is beginning to swing in early swing phase is likely to help bring the leg forward in the optimum direction at the beginning of swing. Even more importantly, making sure that the subsequent forward swing of that arm does not go too far forward will promote the required (non-conscious) braking of the swing leg in late swing and minimize risk of over-striding. The harness proposed by Jack Cady of Stride Mechanics achieves this. This arm swing should be purposeful and controlled but not too tense to avoid wasteful isometric contraction in the shoulders. I find it helpful to form a lightly held ring-shape by resting the index finger of each hand against the adjacent thumb. I think this fairly delicate action encourages a controlled but relaxed arm. This recommendation for hand posture is attributed to Emil Zatopek, the great distance runner of 1950’s, who was famous for his contorted neck and facial features while running, but nonetheless, managed to maintain remarkable relaxation of his limbs (see Wikipedia entry for Emil Zatopek).

Rotation about the long axis of the body

As the hip extends in late stance, the hip rotates externally, thereby producing eccentric stretching of the internal rotators. At lift off, the hip rotates internally bring the leg around and forwards, thereby lengthening the stride and ensuring that the foot is in the midline by foot-fall. This rotation is facilitated by a balancing rotation of the upper torso produced by arm swing.

Integration

Assembling the main features from the previous postings, together with these principles regarding the upper body leads to the following integrated picture:

1) Cadence should be high (e.g. in the range 180-200 strides per minute) to minimise work required to overcome gravity in the airborne phase.

2) Time on stance should be short, though there is a balance between peak mechanical efficiency achieved with a time on stance around 50-60 milliseconds) and minimization of risk of tissue damage (maybe best achieved at around 100-120 milliseconds on stance. Short time on stance minimizes braking in early stance

3) Torso should be held near to upright, with perhaps a slight forward lean if needed to counter wind resistance.

4) Arms should swing in a relaxed but controlled manner, avoiding swinging too far forwards.

5) At foot fall, the hip and knee should be slightly flexed and the ankle near neutral, but with very sight plantar flexion to that the initial point of contact is on the outside edge just forward of mid-sole. As speed increases, the degree of flexion of the hip and knee should decrease making the leg stiffer, leading to a more rapid recoil and shorter time on stance. However, this will increase stress on musculo-skeletal tissues. It should be noted that many elite athletes actually land on the heel. This will result in an even stiffer leg, which may enhance mechanical efficiency, but the risks of over-striding and of musculo-skeletal damage are likely to be higher.

6) In mid-stance, contraction of the hip abductors prevents the hip dropping on the unsupported side, allowing the leg to swing freely and avoiding sideways slanting of the torso.

7) In late stance, recoil aided by contraction of the quadriceps will generate the vertical Ground Reaction Force that provides the impulse required to lift the body. Extension of the hip will preload the hip flexors.

8 ) A conscious pull using hamstring promotes a well-timed lift-off, and an associated concentric contraction of hip flexors in early swing brings the leg forwards to overtake the torso by the time the other leg is at mid-stance.

9) Rotation about the vertical axis of the body, produced by synchronised concentric contraction of the hip rotators with arm swing, will help open up the stride, and ensure that the support foot lands on the midline.

10) In late swing, gluteus maximus and hamstrings decelerate the leg so that horizontal velocity relative to the ground is near zero at footfall.

The next section of the Dance with the Devil will tackle the issue of the perceptions that allow us to achieve these actions effectively, and the mental state that prepares us for peak performance.

The steps of the dance: 3. Swing Phase

SWING PHASE

The goal of early swing is to get airborne and accelerate the leg forwards on a trajectory that will allow it to overtake the torso by mid-swing. While it is essential that the foot should accelerate in early swing, it should be borne in mind that it must decelerate in late swing if it is to have zero horizontal velocity relative to the ground at foot-strike. It might seem at first sight that the need to match an energy consumptive acceleration with a deceleration that will also consume energy should encourage us to be conservative in the generation of acceleration. However, this would be a very misleading conclusion. Our ability to generate adequate forward acceleration of the foot in early swing determines our ability to maintain a particular target speed.

The crucial role of acceleration of the leg in early swing
To understand why forward acceleration of the leg in early swing is crucial, we need to return to basic biomechanical principles. In the earlier posts in this series in which we considered the implications of Newtonian physics we reached the conclusion that cadence should be high and time on stance should be short. Except at very slow speeds, cadence should be near the limit determined by the optimum speed of contraction of muscles. Observation of elite runners suggests the optimum is a cadence in the range 180-200 strides per minute. Elite athletes employ a cadence in this range for all except very slow paces.

Furthermore, time on stance should be as short as can be tolerated, after allowing for the fact that ground reaction forces and risk of tissue damage increase dramatically as time on stance becomes very short. Elite athletes tend to spend only about 50-100 milliseconds on stance, with the longer times being applicable in long events where protection of muscles from damage due to repetitive impacts in important. Apart from these relatively small variations, cadence and time on stance are fairly consistent over a range of paces extending from 1500K pace to marathon pace. Therefore, over this range of paces, the major variable that increases as pace increases is stride length.

As shown on the calculations page accessed via the side bar, the work that must be done against gravity (per unit of time) is determined by cadence, time on stance and body weight. The energy required to lift the body is not directly influenced by stride length. However, increase in stride length must be matched by an increase in the amount of acceleration required to bring the foot forward fast enough to support the body at foot fall. Thus, it is ability to accelerate the leg in early swing phase (and then decelerate it again in late swing phase), that is the main determinant of our ability to maintain a high pace. So how should we do this?

Breaking contact with the ground
In late stance the elastic recoil of quadriceps, augmented by concentric contraction, has imparted an upward impulse to raise the centre of gravity and hip extension has preloaded the hip flexors (e.g. psoas). As the body rises, an active contraction of hamstrings lifts the foot from the ground. Contraction of the hamstring alone, when the hip is already extended, will produce flexion at the knee, pulling the foot up wards behind the line from foot to hip. While this is the path of the foot observed in many athletes, if the main goal is to accelerate the leg forwards, the hamstring contraction should be accompanied by hip flexion.

Accelerating the leg
Fortunately, the preloading of the hip extensors (i.e stretching associated by eccentric contraction) during hip extension in late stance can be utilized to facilitate a powerful recoil associated with concentric contraction of the hip flexors that accelerates the leg forwards.

Deceleration of the leg
However, the price paid for this powerful forward acceleration is the need for a powerful deceleration in late swing, provided by an eccentric contraction of the hip extensors. This is stressful for the hamstrings, and suggest that exercises such as hip swings might play a useful role in conditioning the body during training.

As the hip extensors decelerate the leg, the lower leg and foot should be allowed to swing down to that the knee is only mildly flexed, in preparation for footfall. The combination of contraction of hip extensors and relaxed un-flexing of the knee present a challenge. Because the hamstrings cross both hip and knee joint, pure hamstring contraction to decelerate the leg would prevent the relaxed swinging of the knee. Therefore it is essential to use gluteus maximus to assist in the deceleration of the leg. In addition, some contraction of the quadriceps might also be used to un-flex the knee, but this should be done very sparingly, as vigorous contraction of quadriceps at this stage is likely to result in over-striding.

In summary

Contraction of the hamstrings will help break contact with the ground as the body rises under the influence of the upwards impulse generated by recoil and quadriceps contraction in late stance. However, the ability to accelerate the leg forwards in early swing phase (and then decelerate it again in late swing phase), is the main determinant of our ability to maintain a high pace. Rapid forward acceleration of the leg in early swing might be achieved by employing the preloading of the hip flexors (e.g. psoas) that occurred during late stance to facilitate a powerful contraction of the hip flexors. However, this must be matched by a deceleration produced by contraction of hamstrings and gluteus maximus in late swing, allowing the foot to drop to the ground with the knee slightly flexed and travelling with approximately zero horizontal velocity relative to the ground.