Fatigue is a complex thing

I have been pre-occupied with fatigue in recent weeks, but I think that is now behind me.  For me, the most interesting thing as been the fairly clear evidence from my heart rate recordings that my non-conscious brain imposed a limit (mediated by the parasympathetic nervous system) on how much work my heart was able to do.   While I think that limit was initially based on a non-conscious but sensible protection strategy, it eventually because over-protective.   Furthermore, I think it is likely that my conscious strategy of graded exercise to teach the non-conscious part of my brain that regulates the autonomic nervous system, that it was safe to relax the limit, allowed me to recover fairly rapidly.

Ironically the final test of my recovery strategy was at the price of thrashing my legs beyond their current ability to cope in the Robin Hood half marathon.  So I am now nursing strained hip adductors.  However they are recovering. The bruising that tracked down the medial aspect of my thigh from near the point where adductor longus attaches to the femur has now turned yellowish-purple. In the past two days I have done very gentle runs of around 6Km without any sign of fresh bruising.  However it has been noteworthy that my legs are still tired, confirming that the adductor strain was merely a crunch that might have easily struck in any of the other major leg muscles.  In some ways I am pleased it was the adductors because shortening my stride allowed me to continue with relatively little further damage.  Maybe a tear of the hamstrings or quads would have stopped me from doing any further damage, but on balance, I am really pleased that I was able to finish.    For the next week or so, it will be gentle exercise to promote recovery while trying to avoid tearing the healing fibres apart.


Fatigue is a complex thing

While it appears that the parasympathetic action of the heart was the mechanism of my recent fatigue, I suspect that many instances of the more transient fatigue that sets in during long races are mediated by other mechanisms, especially by mechanisms that act directly on the leg muscles. 

One of the great things about the blogs by amateur runners is the insight they provide into what goes on in the mind and body during a long race.  I am cautious about expressing my thoughts about other people’s blogs in my own blog, but overall, I consider that what people have freely put into the public domain is legitimate material for comment.  I am therefore inclined to put down my speculations about the report on the Dingle marathon a week ago, by Thomas (Diary of a Rubbish Marathon Runner, http://rubbishrunner.blogspot.com/) though I should start with the caveat that my speculations  say more about me than about Thomas.  Nonetheless I will let Thomas know that I have written about him so he can correct any mis-perceptions on my part.

Thomas’ experience is especially informative because he is one of the most determined and motivated of those runners whose blogs I follow. Therefore I think it can be taken for granted that a far as conscious determination goes, few runners would approach a race with more dedication and determination than Thomas approached the Dingle marathon.  As the event unfolded, I think he ran an excellent race; his time and placing are, beyond doubt, great achievements.  He did not achieve a personal best, and one does not need to look far for the obvious explanations: an unseasonably warm day, and a brutal hill in the final few Km of the race. 

However, if one approaches the evidence with a mental bent towards understanding how it was that these two circumstances influenced Thomas’ race, several more intriguing thoughts arise.  


But first we need to look at the background.  Thomas achieved 3:05:37 in the Dublin marathon last year and has trained very hard and very effectively since then.  He ran a creditable 3:10:36 in Boston under difficult conditions in April this year.  As he approached Dingle, his training paces demonstrated that he had the potential for a sub- 3 hour marathon under favorable circumstances.

At Dingle, circumstances were not favorable.  After miserable weather through July and August, Saturday 12th September proved to be one of the most glorious days of summer for anyone except a marathon runner.  The temperature in Dingle was 22 degrees C (72 degrees Fahrenheit). 

Acclimatization to warm weather

There is no doubt that humans acclimatize to warm weather, though having spent my childhood in Adelaide, South Australia, I have often wondered about the mechanism of acclimatization.  Adelaide has cool winters and warm summers.  In early spring, when the temperatures first exceed 75 degrees Fahrenheit (we used the old units in those days) it felt great, but almost too hot for comfort.  A few months later,  we considered that we were being cheated of our summer if the temperature was not regularly in the upper 80’s or low 90’s,  and as children, we even took a perverse delight in times when the daily maximum temperature exceeded 100 degrees for several days on end.  I often trained in temperature well above 90 degrees and thought nothing of running a 5000m race on a mid-summer afternoon.

What had changed between the first days of spring and mid-summer only three months later?   There might have been changes in the function of our kidneys or sweat glands, but I suspect that the main change had been a change in what our brains accepted as normal. 

Jim Peters and Il Topolino

So what happens when we race on hot days?  Probably the winner of a long race on a hot day is the runner who is best acclimatized, but what does acclimatization entail?  Jim Peters’ collapse only yards from the line in the Vancouver marathon in 1954, while miles ahead of his rivals, suggests that the reason he was so far ahead was not due to a greater ability of his body to withstand heat, but rather an ability to over-ride his brain’s attempts to keep his body temperature within safe limits.

Don Thompson’s gold medal in the 50K walk in Rome in 1960 provides another thought provoking illustration.  Thompson, who was nick-named Il Topolino (‘mighty mouse’) by the Italian crowds, was diminutive in stature but mighty in his spirit.  He had trained for Rome in an improvised hothouse in the bathroom of his mother’s house in Middlesex.  He installed a stove in the room and put on a kettle to boil; closed the door and window; and switched on the electric wall heater to augment the effect of the steaming kettle.  Years later, when asked how Paula Radcliffe should prepare for the marathon in Athens in 2004 his reply was: ‘I trained in the bathroom about three times a week, from May to September, but I didn’t stay in there long each time and I think it was more about a boost to my confidence.’  Maybe Il Topolino had trained his brain to believe that keeping up the pace when the temperature was above 80 degrees F was possible, rather than adjusting the function of his kidneys or sweat glands.

The scientific evidence

Scientific studies confirm athletes tend respond to hot weather by slowing down to minimize the rise in core temperature; rather than by slowing down once core temperature has already risen.  In a comparison of African and Caucasian runners during self-paced 8K treadmill runs performed under cool and warm conditions, Marino and colleagues found that both groups ran at similar pace in the cool conditions.  The Caucasians ran more slowly under warm conditions, but sweated more profusely and maintained similar body temperature.  Marino concluded that the observation that the African runners ran faster only in the heat despite similar thermoregulatory responses to those of the Caucasian runners suggests that the larger Caucasians reduced their running speed to ensure an optimal rate of heat storage without developing dangerous hyperthermia (Marino et al., J Appl Physiol, 96: 124-130, 2004).

The diminutive Il Topolino demonstrated in Rome that it is possible to train the brain to over-ride this mechanism, but the case of Jim Peters in Vancouver perhaps illustrates that it can be difficult to get the balance right.  Fortunately, Peters recovered quite rapidly after re-hydration.

Back to Dingle

So what happened to Thomas at Dingle?  The temperature was warm by Irish standards, but in fact not really all that hot, at least by Australian standards. However, Thomas had been training in cold and windy weather around the shore of Caragh Lake in Kerry.  To both his conscious and non-conscious brain it seemed hot.  Nonetheless, he started with a first mile of 6:51, almost exactly in line with his 3 hour target pace and he reports that first few miles went very, very well. He was running  easily, feeling relaxed and happy.  For much of the first half, the race continued to go very well.  He was holding a pace of around  7:05 pace per mile which would have given him a finishing time near to his PB of 3:05:37.  However, it is of interest to note from the traces he presents in his blog that has pace tended to slow slightly throughout the first half, and his heart rate to fall very slightly from a mean around 168 bpm between miles 1 and 3 to a mean around 166 bpm from miles 10 to 13, despite greater undulations in the course after 6 miles.   Was his brain, either consciously or unconsciously, protecting him from undue exertion?   He reported that at 10 miles he started to feel some signs of fatigue.  Nonetheless he was still running well until mile 19, when the pace record shows he ‘lost it.’ He slowed from a pace of 7:10 per mile around mile 18 to slower than 7:30 per mile around mile 20.  The undulations in the road make the precise figure irrelevant but there was a definite trend towards slowing despite a net fall in altitude of approximately 50 feet between mile 18 and mile 21. 

Something else was looming on the horizon.  He reports that as he approached the drinks station at mile 21 he ‘could see the mountain looming ahead. It reminded me very much of Connemara’s “Hell off the West”, and I was in no illusion about the task ahead. This was going to be tough’    Starting in the 22nd mile the road ascended 300 feet, at times with an incline of 13%.  He struggled gamely to the top, but shortly after the summit he was pole-axed by cramp.  His blog provides a graphic description of the pain in his calf muscles.  After a few protracted and excruciating moments he managed to apply a counter-tension that relieved the cramp, and he finished with an exultant wave to the crowd in 12th place in a time of  3:12:44.   

It was a great performance, and I think it is unlikely that Thomas could have done any better on the day.  It is probable that some physiological process such as electrolyte imbalance was the coup that pole-axed him on the final hill, but his prospects of a PB were gone by 21 miles.  At that stage his heart rate had already fallen below 165.  We do not know how much his body temperature had risen, but Marino’s study suggests it unlikely that it had risen to dangerous levels.  More likely, his brain was protecting him from the heat and from the mountain ahead.  Some non-conscious part of that brain was probably also aware of his electrolyte status, and integrated this information with the message from his conscious brain that things were about to get very tough.  

While it is unlikely that there was anything Thomas could have done to have overcome the sensible response of his non-conscious brain at that time, no matter how determined he was, I suspect that if he had trained in an improvised hot-house, as Il Topolino had done almost 50 years previously, his brain might have allowed him to sustain a faster pace between 3 and 21 miles.  But whatever the physiological limit proved to be – electrolyte disturbance, core temperature or something else, it is probably just as well that his brain did not allow him to run himself to a state of exhaustion in Dingle.  That wasn’t the right day or place for a PB.  His more recent blogs indicate that he is recovering rapidly, and after a two week recovery phase, he is about to begin his preparation for the Dublin Marathon in 5 weeks time.  I think there is a very good chance he will record a PB in Dublin, and if the weather is good, his goal of a sub-3 hour marathon is within reach.

12 Responses to “Fatigue is a complex thing”

  1. Pilates And Winsor Pilates | Aerobics Says:

    […] Fatigue is a complex thing « Canute's Efficient Running Site […]

  2. Thomas Says:

    Hi. I don’t mind at all you dissecting my race. As you said yourself “what people have freely put into the public domain is legitimate material for comment”, and I agree with this.

    My conclusions are very much in line with yours, but with one caveat. I wasn’t feeling as exhausted as I normally would have after a marathon, demonstrating that my fatigue levels weren’t particularly high (well … that’s relative, of course!).

    The higher temperatures definitely slowed me down though. As you said, it may not have been excessively warm, but it was a lot warmer than during my training runs. The fact that I always train early in the morning magnified that difference. But, while temperatures did reach 22C later during the day, it wasn’t quite as warm by the time I finished shortly after noon. I did feel sorry for the slower runners. The longer you took an that day the worse the temperatures got.

    Btw, do you think a lack of certain electrolytes caused the cramps?

  3. TrailClown Says:

    I think another relevant factor in Thomas’ “failure” to go sub-3 (or at least better his PR) is his mind’s “knowledge” that “everything has to go just right” to reach the milestone. On a day when the temps are a bit high, there’s a mountain or two, a few undulations, etc., then Thomas’ mind probably accepts that sub-3 will not happen. Granted, Thomas had already stated before the race that sub-3 was probably out of reach, but it warrants saying nonetheless, because I think it is a big factor in many runners not reaching ultimate goals…the feeling that things need to be just right. In fact, if you look at elite runners, they are usually not as affected by heat/rain/wind/course as non-elite runners, because their bodies are well-trained enough, and their inner goals and motivation high enough, that their minds do not cause a drop-off in final performance.

  4. canute1 Says:

    Thomas, Thanks for your response. I am interested to hear that you did not feel as exhausted as you usually do after a marathon. I think that fits with the idea that non-conscious processes in your brain acted in anticipation to protect you from exhaustion. Maybe my use of the word fatigue was misleading. I agree that you did not suffer fatigue in the sense of utter exhaustion; rather I was raising the possibility that you experienced anticipatory fatigue around mile 19 that actually protected you from exhaustion. The question that intrigues me is how we might train our non-conscious brains to find the right balance between self-protection and stretching ourselves to the limit. I believe Il Topolino found the right balance in Rome, while Peters stretched himself a bit too far in Vancouver.
    As for the cause of the cramp you suffered, I do not think it is possible to give a definite answer, as many factors can contribute to cramp. However, on balance I think electrolyte disturbance (probably low concentration of sodium and/or magnesium ) was quite likely a significant contributor in your case simply because you were probably losing more electrolytes than usual in sweat but you were only drinking water.
    TC, I agree that the belief that one cannot achieve ones best unless circumstances are ideal can have an insidious destructive effect. The confidence that one can surmount obstacles is a crucial part of stretching oneself to the limit.

  5. Ewen Says:

    Thanks Canute. A most interesting analysis of Thomas’ race. I’m in agreement that his non-conscious brain was protective of pushing himself to the point of collapse.

    There’s also the “time motivation” factor. Once a time-goal is definitely lost, the non-conscious brain becomes even more protective. This is more of a problem for recreational runners, who are racing for PBs, not so for elite runners, who are just racing the opposition.

    I wonder if there’s an “experience reinforcement” factor? The more one races, the more one’s brain knows what’s possible.

    Acclimatisation of the brain to heat is interesting. For example, last Sunday in Sydney, it was ‘warm’ 15-18C for me, and maybe up to mid-20s for the late finishing marathoners. I didn’t find it that warm though, as I’d raced the previous Sunday in much higher temperatures.

  6. canute1 Says:

    Ewen, there is little doubt that once one’s PB is no longer achievable, maintaining a ‘near PB’ pace is virtually impossible. I agree that experience reinforcement is a factor. I think there is quite a lot we can do to teach our brains about what is possible (and reasonably safe), though it is not simply a matter of telling ourselves to try harder – our non-conscious brain might not always get things right, but it is not a fool. It learns by experience, and is resistent to simply being told to try harder without being given evidence that it is reasonably safe.

  7. Paul Says:

    As many do, I too wonder about the brain’s impact on my running performance. In my case, I want to make sure it doesn’t hold me back. Typically (and thankfully for me) I tend to ‘race well’ despite often limited preparations. For this marathon in a few weeks I have been preparing myself to “enter a world of pain” and am hoping that this will help convince my brain that – on race day – I am not about to die and that it should just let me be!


    Thursday, September 24, 2009
    LINK: Mind Over Matter – We’ve all heard the old adage about running being 90% mental. Turns out it might be true! … as readers of this blog know, from your Humble Blogger’s recent post, “To Train in the Membrane”

  9. canute1 Says:

    Rick, Thanks for that link. The ‘Younger legs’ article contains a lot of food for thought


    I’ve noticed for a long time that I seem to perform very well on the second hard day of consecutive training, ie; a race followed by an interval session or two races in a weekend; often the second hard run feels much better than the first day!
    How can this be, it does not make sense, the muscles will be damaged from the first hard session, yet time after time I have performed well on the second hard day!
    Maybe it is the chemicals in the brain that are produced after the first hard day that make me feel good and let me push the barriers back on the second day!
    I’m sure we have all felt that buzz the day after a race only to feel tired and flat the day after that, maybe this is proof that it is indeed the brain that controls the body.
    And if this is so maybe we need to look differently at the training we do the day before a race to flood the brain with pain killing chemicals the day before the race, maybe we should replace the easy day with a mile at race pace to get us buzzing for race day! WHAT DO YOU THINK?

  11. canute1 Says:

    In my own experience, I don’t achieve my best on the day following a really hard session – at least not if the hard session included a substantial volume of running. However I have found that a short fast run is the best thing to do the day before before a race. So yes, I think that a km or maybe a mile at race pace is probably better than a jog on the day before a long race. On the day before a 5Km or 10 Km, I think some strides at race pace might be useful, though I have not tried this myself recently– I have not raced either of these distance in recent times.
    I do not know the mechanism of the benefit of a fast run the day before, though I can offer a few speculations. I do not think it due to endorphins, which are triggered by pain – if you are well prepared, a warm up followed by a short fast run is exhilarating rather than painful. It might be that a fast run creates the right muscle memory – and maybe it creates a state of excited anticipation. In terms of brain chemistry, it is probable that excited anticipation is associated with increased release of naturally produced dopamine in the brain – this is the brain chemical that is released by amphetamine (‘speed’), but it is safer to generate it through ‘natural’ excitement rather than a less predictable drug effect


    Thanks for reply, I’ve tried strides the day before a short race and it did not really work for me, maybe just a warm up followed by one 400m effort at 5-10 k pace the day before a short race might work well, in the past I’ve just tried a warm up followed by a mile at marathon- 1/2 marathon pace the day before a race which seems to work well!
    cheers RICK

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