Robin Hood half marathon

I awoke a few minutes before the alarm to a perfect blue sky framed by the skylight. After several days of Indian summer that have almost allowed us to forget how miserable the second half of summer has been, it looked as if it might actually be warm for the Robin Hood marathon and half marathon today. Yesterday had been glorious for any outdoor activity apart from marathon running.  Would today be the same?  

However the weather was not really my main concern.  I was more interested to know whether or not the ‘post-illness’ fatigue that had held me back in recent weeks had really resolved.  For the previous two days, the orthostatic increase in my heart rate on standing had been 14 bpm, a marked contrast to the values in the range -1 to 2 bpm during the fatigue and associated parasympathetic over-activity, which I have suffered in recent weeks.   This morning the orthostatic rise was down to 6 bpm – a little disconcerting but probably not a significant reason for concern. 

My illness in June, and the fatigue that followed, had greatly curtailed my training and it was clear that the goal of 99 min that I had set 5 months previously was no longer feasible.  Now the major goal was to confirm that the low volume, graded intensity sessions of the previous three weeks had overcome the fatigue.  It appeared that the best way to do this was to set the goal of maintaining a heart rate in the range 134-137 for the full 13.1 miles.  A few weeks ago, pushing my heart rate much above this level for even a few minutes was crushingly difficult.

While the primary challenge was proving that my cardiovascular system could cope, I was aware that the truncation of my training had prevented me from preparing my legs for the task of racing a half-marathon.  An additional issue was the fact that I had been woken by severe leg muscle cramps several times in the past week, and after yesterday’s hot weather, I was a little concerned about the risk of cramp while running today.  Thomas’ graphic report of his calf muscle cramp in the final stages of the Dingle marathon in yesterday’s heat raised my concern a few notches higher, so before going to bed last night I had mixed myself several litres of an isotonic drink containing 1 gm of salt per litre (roughly the concentration of salt in sweat) in addition to about 80 gm/litre of sugar and some lemon squash.  I had drunk almost a litre before bed and planned to finish the remaining 1 ½ litres this morning before the race. 

By the time I had finished breakfast, sporadic clouds had appeared.  The combination of accumulating cloud cover, glimpses of sunshine, and the light north easterly breeze promised perfect weather for running, but nonetheless I was happy with my precautions and consumed the remainder of my drink as I walked along the embankment beside the river Trent to the starting area.

Because my primary goal was demonstrating that I had overcome the limitations provided by excessive parasympathetic activity, I had decided on the strategy of setting my pace according to heart rate.  In normal circumstances, the main problem with this strategy is that the excitement of the race might increase sympathetic output and lead to misleadingly high heart rate.  As I stood in the start corral, surrounded by milling, anxious athletes, in the few minutes between the cheer that accompanied the start of the wheelchair race, and hooter that would set the  marathon & half-marathon runners on their way, I noted that my pulse was 58.  I suspect that not too many other runners in the corral had a pulse below 60 at that moment.  It was clear that I did not need to worry about spurious sympathetic drive; on the contrary it looked as if my parasympathetic system was still overactive.  Nonetheless, I decided to stick to my strategy of aiming for a heart rate around 134-137. 

The hooter sounded and a mass of 12000 runners began to accumulate speed gradually as they moved towards and then over the starting mats.  No doubt each individual was in his or her own world, intent of what lay ahead, and mainly concerned at this stage to avoid being tripped-up in the melee.  However, to a distant observer, it must have appeared more like a single creature; perhaps some ponderous dragon awakening.  I had positioned myself with the 100-120 minute half-marathon group; and at first I let the human tide carry me forwards.  I reached the 1 mile marker in 7:45 with a heart rate of 135 and feeling relaxed.  Perfect.  

I could see the 105 minutes pace group leader a short distance ahead.  At first I thought that he had misjudged his pace, but then realized that he had probably crossed the starting mat about 15 seconds ahead of me.   His banner was an attractive target to focus on, but I knew that I should ignore it if it distracted me from my target heart rate.   As we ascended the steep climb to Nottingham Castle I allowed my heart rate to rise to 140, but set that as a definite upper limit.  I lost sight of the 105 minute pace leader.  Runners streamed by, many panting with the exertion of the climb.  Rounding the sharp corner beneath the Castle gate, I was delighted by the rousing rhythms of a jazz band.    

The 105 minute pace leader was again in sight and I settled back to cruise at 135-136 bpm.  In the melee of the first water station shortly after 3 miles, I again lost the 105 minute group.  By this stage I was able to select my own path on the road some of the time, but at corners or any other narrowings, we were still hemmed in like African wildebeests in a mass migration.   A short while later, after beginning the gradual ascent towards the ridge that dominates the north east corner of the university campus, I passed Mick and Phil.   Those unfamiliar with the UK running world might not be aware of this inspiring duo.   Mick pushes his severely disabled son in a wheelchair – not one of the whizzy racers but a barely modified ‘domestic’ wheelchair.  Last week they had completed the Wolverhampton marathon in 4:39, and, it appeared that they were moving somewhat faster today, though seeing Mick pushing Phil uphill with more than 22 miles still to go, one couldn’t help feeling humbled by their prodigious effort.

Again I allowed my heart rate to rise to 140 on the ascent, and was pleased that there was no sign of the crushing fatigue that I had experienced around that effort level a few weeks ago.  Then there was the helter-skelter descent to the university lake.  I thought ruefully that it was unfair to have to toil steadily uphill for about a mile and then throw away the fruit of that effort in a few hundred yards of knee-jarring descent.  However I consoled myself with the thought that the two remaining substantial hills would each be followed by a gentle down-slope.

Along the shore of the lake I was still hemmed in, but really enjoying the run.  Then came the ascent back to the ridge top.  Again I limited my heart rate to 140, and a handful of runners moved past me, though by this stage, there were others prepared to let their pace drop on the ascents.   Although I was feeling comfortable as I approached the drink station at 6 miles and the weather had remained perfect with almost continuous cloud-cover, I decided to take the offered bottle of Lucozade.  Despite the somewhat sickly sweetness of isotonic drinks while running, I thought it was best to keep my salt level topped- up.  I sipped about half of the 300ml bottle over the next half mile before abandoning it.

By this stage I was descending past the halfway point and pondering whether or not to increase the pace a little.  The 105 minute pace leader was still in sight about 100 yds ahead.  It was now 51 minutes into the race and I was sure he was going a little too fast. I was also beginning to wonder if a time not much over 100 minutes might be within reach.  But then things went seriously wrong.  I had been aware of a tightening of the hip adductors in my left leg since the sharp turn though the gates out of the University campus, and as I increased stride length approaching the 7 mile marker, the pain became quite intense.   I was unsure whether or not to continue.  My legs were clearly not adequately conditioned for a hard half-marathon, and there was a risk of significant muscle damage.  In any case, unless I could do something to relieve the rapidly increasing tightening of my adductors, I would have no option but to slow to a painful limp.

As I turned the corner towards the entrance to Wollaton Park and began the long ascent to Wollaton Hall, I shortened my stride to about 60 cm and the pain in my adductors began to ease.  Despite a cadence of over 200 steps per minute, my pace was now about 8 min/Km (or 12 min per mile).   However, by the drink station at 8.5 miles, just beyond the summit, the pain was easing and I decided to carry on.  Instead of the hoped-for powerful surge down the gentle slope though the deer park in compensation for the slog up to the Hall, I was limited to a very tentative increase in speed. The 105 min pace leader was now out of sight.

Although the adductors continued to nag me, I gradually picked up speed and after leaving the Park, just beyond the nine mile marker, I saw the 105 minute pace leader ahead again.  I decided that fate had declared that he would be my lodestar today, and set out to close the gap.  I drew up to his shoulder at 10 ½ miles but had the feeling I could cope with a faster pace, so I passed him and began steadily working my way forward through the field.  Despite the continuing nagging of my adductors I was fairly comfortable maintaining a pace of around 7:55 per mile. 

Subsequent examination of my heart rate recording confirmed that I was minimally stressed.  Here is the trace of heart rate for a three minute segment at around 80 minutes and also the Poincare plot for the 10th and 11th miles.  The heart rate trace shows fluctuations at a rate of about 50 peaks per minute.  As I was breathing at a rate of one breath every four steps, and my cadence was still around 200, these fluctuations almost certainly matched my breathing rate and represent a healthy sinus arrhythmia – the parasympathetic driven fluctuations that ensure that cardiac filling is greatest when the level of oxygen in the lungs is at its highest.  

 

Heart rate trace and Poincare plot during the 10th and 11th miles of the half-marathon

Heart rate trace and Poincare plot during the 10th and 11th miles of the half-marathon

The wide spread of point across the 45 degree line in the Poincare plot confirms a strong parasympathetic drive.  The figure also shows the amount of power in the low frequency range (0.04-0.15 cycles per sec) and the high frequency range (0.15 to 0.4 cycles per sec) of the heart rate power spectrum.  The low frequency activity reflects sympathetic activity while the high frequency reflects parasympathetic activity (though it should be noted that the upper boundary of 0.4 cycles per sec agreed by an  international committee of cardiologists, is actually below the respiratory frequency when running at this pace, and therefore, the high frequency power does not include the respiratory fluctuations).  Nonetheless, there is still greater power even within the high frequency range truncated at 0.4 cycles per sec, providing strong evidence that the balance between sympathetic fight/flight and parasympathetic rest/recovery was tipped towards parasympathetic activity.  Normally one would expect an excess of sympathetic activity at this stage in a half marathon.  Overall, this data is evidence that my parasympathetic system is still being a bit over-protective, but unlike the situation a few weeks ago, I was able to maintain my heart rate near the intended level, without any feeling of fatigue. 

My main problem was my nagging adductor muscles.  As I had stepped-up the pace, the pain had increased again, so I eased back a little in the final mile or so to minimize damage, and crossed the finish line in 103:28 (chip time 103:17).  My average heart rate for the entire race was 137 bpm.  Ninety-two seconds later, the 105 minute pace leader crossed the line, on schedule to within a second.    

I sit here now with a painful thigh, unsure how much damage I have done, though I do not think it is very severe.  A time of 103:28 for a half marathon is not in itself a great achievement.  If my goal had been a fast time, it would have been foolish to have continued beyond the 7 mile point.   However, this summer various circumstances have conspired against me, and I had been forced to set aside the target time selected five months ago.  Although I had been undecided about starting the race until about two days ago, once it was clear that my fatigue was resolving, running the event with the target of maintaining a heart rate of 134-137 became as important a goal as running a half-marathon in 99 minutes had appeared to be in May.  It was potentially a stringent test of whether or not I have overcome the fatigue.   In the event, I achieved my target despite the adductor problem. 

It was especially pleasing to have been within 4 ½ minutes of my original target time despite seriously curtailed training.  It is tempting to think I might have even achieved the 99 minute target today if it had not been for the injured adductor, but this is very improbable.  The primary problem was that my legs had not been conditioned by an adequate number of tempo and long runs.  Although the overt limitation was provided by the adductors, in fact my legs could not have coped with a much faster pace.  Both legs felt like jelly afterwards, and I was wobbly on my feet for a few hours, quite apart from the limp.  My legs could not have carried me much faster, but it is encouraging to know that my heart appears to have coped well.

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5 Responses to “Robin Hood half marathon”

  1. Paul Wilson Says:

    Canute. OUTSTANDING effort. This has brought a big smile to my face; hopefully one for you too! Given all the challenges you had to face over the last few months this is a great result. Good stuff. Very motivating for me too. Cheers, Paul 🙂

  2. Ewen Says:

    Canute, that was an excellent experiment and a not too bad result all things considered. Your strategy to recover from the fatigue seems to have worked perfectly. The aerobic system is in good nick, but the muscular is not quite matching it at this stage. A bit of a shame about the adductor going – perhaps a couple of minutes there.

    I might try your HR strategy for my ‘training’ half in Sydney on Sunday – hold within a strict limit for the first half…

  3. RICKS RUNNING Says:

    Well done on finishing your 1/2 on limited training, I must say I’m glad I ditched my P.R. montior along time a go!
    I really think your much better off listening to your inner computer than a heart rate moniter, I ran all my best times after I got rid of the moniter and I bet you ran your super quick marathons without one!

  4. Andrew(AJH) Says:

    You say “A time of 103:28 for a half marathon is not in itself a great achievement.”, but given that it is 7 seconds inside my HM PB, I’d be happy with it!

    Seriously though, well done, a great effort, hope the thigh recovers quickly!

  5. canute1 Says:

    Paul, Thanks for the comment. Your recent progress is very impressive. Well done in persevering through the doldrums of a few weeks back. Good luck with the Melbourne marathon
    Ewen, I hope things go well with the Sydney half; it is a good opportunity to re-establish your confidence in your ability to finish a long race strongly. It is great to hit that sweet spot at the halfway point when you are running strongly but know that you still have something in reserve. The interesting challenge is how to hit the sweet spot. I think that when you are running well, the non-conscious brain can make amazingly accurate predictions of the optimum pace, but during phases when the brain is a bit bamboozled, the HRM can be helpful.
    Rick, My initial impulse is to agree with you that listening to the body is better than reading the HRM. It is true my fastest races were run without a HRM. However, there are circumstances were listening to the body can be misleading. The most trivial instance is during the first few Km of a marathon. In most circumstances the extra adrenaline makes a pace that had seemed difficult in training so easy that the conscious brain can scarcely believe it. (I understand that the adrenaline surge associated with running past Wellesley College in the Boston marathon provides an interesting illustration of a similar phenomenon.) Of course with experience, it is possible to learn to recognize the misleading feedback.
    However, there are even trickier situations where the body gives the wrong message. I think that this can occur in both the fatigue syndrome and in the parasympathetic phase of over-training. The body (or perhaps the non-conscious brain) says slow down – and that was my initial response about five weeks ago when the fatigue started to develop. It was only by careful inspection of the HR records that I realized that my non-conscious brain was being over-protective and I need re-train the non-conscious part of my brain that controls the autonomic nervous system to accept that I could safely run at a higher intensity. That was the basis of my moderate intensity low volume approach – and it seems to have worked. There might have been other ways to recover, but so far, I think I made the right decision.
    I would not use the HRM to set pace in a race where the goal was to win or to achieve a fast time. In the RH half-marathon those were not my goals. I wanted to consolidate the acceptance by that non-conscious part of my brain that I could safely maintain a moderate pace for 13 miles.
    Smart technology can be misleading, but the brain too can sometime be smart and sometimes wrong-headed. Maybe there is an art in getting the best of the capacities of both the intuitions of the body and the data derived via an HRM.
    Andrew, with the knee settling and your running mileage building up, it might not be too long before you are ready to knock a few minutes of that half marathon PB – but meanwhile you should savour the moments when your 14 year old training partner asks you to slow down.

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