There’s a longstanding debate about whether even pacing is always best in long (i.e. more than about four minutes) races. Physiologically, it makes sense – but when you look at the actual pacing patterns of world records, they almost universally tend to form an inverted-U shape: slightly quicker start, steady in the middle, then speeding up again at the end.
A really neat new study, published in the European Journal of Applied Physiology by researchers from Northumbria University (and other places), UK, takes an interesting approach to the even pacing question. They had 15 well-trained cyclists each complete a series of 20km time trials. First, they did self-paced time trials, where the goal was simply to complete the distance as fast as possible. Then they did two even-paced time trials.
In the first even-paced trial, the power output of the stationary bikes was set at the average power they’d maintained during their best self-paced trial. The goal was simply to keep going as long as they could. If they lasted longer than 20km, that would suggest that the even pacing was more efficient; if they lasted less than 20km, that would suggest that their self-paced strategy was more efficient.
The second even-paced trial was slightly different in that the power of the bikes was free to vary, so they had to expend some mental effort maintaining their power output at the goal pace. Basically it just served as a check to make sure the results in the other even-paced strategy weren’t a one-off fluke.
The results? Nine of the cyclists gave up before getting to 20km (they gave up between 10.3 and 15.3km), while six made it past 20km (they made it between 20 and 27.4 km). Here’s where it gets interesting: the researchers went back and analysed the self-paced performances of the group that didn’t finish versus the group that did. Here’s their respective pacing profiles from the self-paced trial:
What jumps out is that the DNF group started faster than the pace they eventually maintained, gradually slowed in the middle, then finished hard – just like the world record patterns. To reiterate, this was a successful strategy: they rode so fast that they weren’t able to replicate the performance when they tried again with even pacing.
The other group, on the other hand, started out more conservatively, stayed relatively even in the middle, then sped up. This was not an optimal approach, because they were able to beat that performance when they tried even pacing.
The lesson? Well, there are a lot of subtleties in the paper’s discussion section. Certainly no one disputes that relatively even pacing is the best approach. But subtle deviations – in this case, starting out just 1-2% faster for the first 6 km of the trial – seem to translate into better performances. To explain this, the researchers note recent suggestions that peripheral fatigue (i.e. muscles) dominates in the first half of extended exercise bouts, while central fatigue (i.e. brain) dominates in the second half. As muscles become fatigued during the middle of the race, it’s perhaps more efficient to allow a bit decceleration than to tell the brain to start recruiting more muscle, which would drive up fatigue prematurely.
This is a debate that isn’t likely to be settled anytime soon, and it’s certainly not a license to sprint the start of your next race. There’s a reasonable body of literature showing that elite athletes stay closer to even pace than less-experienced athletes – it’s only once you’re very close to even that these subtleties come into play.
