Critical Speed failure in a 2 Hour Marathon ‘Time Trial’

I would be interested to see EXACTLY what the Nike 2 hour marathon runners used to get tantalizingly close to the 2 hour marathon mark. For example they obviously used ‘special’ Nike shoes and Beet-It claim they used their beetroot product (likely). However, much of the gain from going below the world record was probably from pacing and wind shielding from the ‘pace car’ aka ‘draft car’. There are also things they could have tried such as along the lines of Gatlin’s existing 100m ‘record’ (Google it 😉 .. no it’s not Bolt) They could have also introduced fresh pacers at the half way stage.

Anyway here is some expert comment from another angle by Dr Mark Burnley on this ‘unique and surprisingly exciting’ time trial coming at the analysis from a ‘critical pace’ perspective.

Commenting on the attempt by 3 runners to break the 2-hour barrier for running a marathon, Dr Mark Burnley, a senior Physiology lecturer, says that he wouldn’t usually watch the first half of a marathon because it’s when almost nothing happens.

But on Saturday 6 May 2017, he made an exception as he saw Kenyan Eliud Kipchoge complete the 26.2 miles in a blistering 2:00:25, by 2.5 minutes the fastest a human has ever run the distance.

‘At 25 km, he was on schedule, but in the last 10 km he lost time, and lost about 15-20 s in the last 5 km alone. Why could he not hold that pace in spite of all of the assistance from the arrowhead of pacers (or the car)? To understand that, I think we need to look at what it takes, physiologically, to run a marathon.

‘The under 2 hour attempt “Breaking2” was a sportswear sponsored event at the Monza Formula One track in Milan, Italy.

‘A 2 hour marathon effort requires a running speed that is necessarily below the critical speed, because above this point, the slow component of oxygen uptake cannot be stabilised, leading rapidly to the attainment of maximal oxygen uptake and inevitably to task failure. But the sustainable pace for a marathon run this fast must have been very close to the critical speed. Thus, Kipchoge’s task was to run as close to his critical speed as possible, and stay there. For the most part, he succeeded.

‘We mere mortals cannot get close to critical speed during a marathon lasting 2:30-4:00 hours, but there is good reason to suppose elite athletes can. One reason for that is an apparent “domain compression” in which the Lacatate Threshold and critical speed both occur at a very high fraction of maximal oxygen uptake. Another is that elite runners have phenomenal fatigue resistance, in part due to the high percentage of type I (slow twitch) fibres in their muscles.

‘The above considerations provide a reason for Kipchoge’s basic speed, but not for his slowing down. Obviously, the distance itself places a severe strain on fuel stores, but he was still running exceptionally quickly towards the end, albeit grimacing. He didn’t look like he blew catastrophically.

‘He lost some of the advantaged of drafting as the “arrow” collapsed and the car gapped all of the runners, but again this would probably have a minor influence since this only happened in the last few laps. The effect of heat and dehydration were also probably minimal as it wasn’t hot and he was regularly drinking. That leaves few possibilities for his slowing down. Undoubtedly there would have been some muscle damage at this stage, and we know that progressive, slowly-developing fatigue occurs in the heavy domain. However, the slowing in running pace was not progressive, which leads me to conclude that his critical speed itself may have decreased.

‘The above idea seems at odds with what we have seen experimentally: fatiguing exercise and glycogen depletion does not seem to alter the critical power in cycling, but these experiments are nothing like prolonged exercise performance in elite athletes. I have heard anecdotal reports of a diminished critical power at the end of cycle stage races or long-duration time trials. If true, it would explain the fall-off in pace without catastrophic failure. What makes the 2 hour marathon such a challenge is that it is close to the limit of what we think humans can sustain, and the effort itself likely reduces that sustainable pace in the last 10-15 km.

‘Kipchoge is the first to treat the marathon like a 2 hour time trial and hold it together for most of the distance. If he can find a way of holding it together for the full duration, an athlete of Kipchoge’s talent really could break 2.’

Dr Mark Burnley, is a Senior lecturer in Physiology in the School of Sport and Exercise Sciences at the University of Kent and has expertise in the kinetics of oxygen uptake and the physiology of high-intensity exercise tolerance.
News releases can also be found at http://www.kent.ac.uk/news