How do athletes in Olympic level endurance competition do it?
To evaluate the physiologic strain during competitions ranging from 5-100 km, we evaluated heart rate (HR) records of competitive runners (n = 211). We found evidence that:
1) physiologic strain (% of maximum HR (%HRmax)) increased in proportional manner relative to distance completed, and was regulated by variations in running pace;
2) the %HRmax achieved decreased with relative distance;
3) slower runners had similar %HRmax response within a racing distance compared to faster runners, and despite differences in pace, the profile of %HRmax during a race was very similar in runners of differing ability; and
4) in cases where there was a discontinuity in the running performance, there was evidence that physiologic effort was maintained for some time even after the pace had decreased.
During a race, the runners' heart rate increases in a very controlled way apparently scaled to the distance of the race. So, the the runner's body, anticipates future stresses. It would seem that athletes actively manage the level of strain on their body with an ongoing assessment of fatigue levels in relation to expectations.
Surprisingly, elite runners did not run proportionally harder than the run of the mill athletes and all the athletes had about the same heart rate responses despite a great deal of variation among them. This suggests that elite runners such as Paula Radcliffe are so good because of their basic physiological capacity, not because of the level of effort they expend. Apparently, training and innate ability both matter!
The study also looked at the phenomenon of "hitting the wall." This is when athlete's glycogen stores have nearly run out, so the body starts to convert (at a high rate) fat into energy. This leads to fatigue and is potentially dangerous from a medical perspective. The research suggests that this sort of catastrophic outcome occurs frequently during endurance competition because athletes either can not or simply do not slow down their heart rate.
Jonathan Esteve-Lanao, Alejandro Lucia, Jos J. deKoning, Carl Foster, Conrad P. Earnest (2008). How Do Humans Control Physiological Strain during Strenuous Endurance Exercise? PLoS ONE, 3 (8) DOI: 10.1371/journal.pone.0002943
When I run marathons, I just run (I run about 4 hour marathons). I am not progressed enough in training to even pretend to know how to pace (I just like running long distances). I run very negative splits. in my last marathon, I ran my fastest 10K, 10M and 13.2 mile splits ever (even compared to my fastest 10K training run or 10K race), now the second half of the marathon was slower (by a good bit) but I did not feel like it was any harder (other than a hamstring cramp at mile 21 that took couple of miles to work its way out).
It is funny, when I am training, I find 5 mile days to be as hard as 10 mile days. For me it feel like it is all mental, but maybe my body is responding to expected distances (anticipating the end of the run), my perception of "hardness" of the run does not depend on pace or distance, but rather what my initial expection of the distance will be. Now the day after a run, the pain is proportional to the distance/speed of the previous day's run.
"Surprisingly, elite runners did not run proportionally harder than the run of the mill athletes and all the athletes had about the same heart rate responses despite a great deal of variation among them."
How is this surprising? What matters is how much oxygen is transported out to the various cells per heartbeat, i.e. minute volume. That's what makes the difference. And this can be trained, quite easily, in fact (in fact, the ability to transport oxygen seems to be THE variable in endurancebased sports - minute volume, hemoglobin level, capillary network; all factors contributing to the oxygen flow). If you measure level of effort by some (any kind of) HR profile, you won't find any difference between the top runners and the rest; that's well-known to be the only constant in this business. max heart rate cannot be trained, and individual variations actually doesn't seem to matter to the minute volume. And well-trained athletes WILL attain more or less the same % of max HR in a given race; the differences in performance is due to all the other factors influencing the oxygen transportation. But this has been known for at least 50 years. No surprise there.
The "hitting the wall" phenomenon is also a thoroughly well-known and exhaustively described phenomenon (unless they find anything that substantially departs from your summary).
In general, from the abstract and your description of the results of this study, it study seems to fail to provide anything that hasn't been common knowledge for at least 50 years, probably much longer.
(I hope any physiologist will pardon any non-idiomatic formulations here; I am not a native English speaker, and I have no background in these matters other than as an coach myself).
I'm not surprised by this at all.
Over a marathon distance your body's limits are very significant, and if you push beyond what your body can maintain it will get you every time. It's really only the last few kilometers where effort can play a factor as you don't have to worry about wearing yourself out for later at that point.