Is Drafting a Placebo?

Most runners prefer to run behind a pacer rather than forging ahead on their own. There are a number of possible reasons for this, like the energy saved by sheltering from air resistance and the saved mental effort when you don’t have to worry about pace. But a new study by French and Tunisian researchers, recently published in the International Journal of Sports Physiology and Performance, suggests a third possibility – that it’s all a placebo effect. (The journal article is actually titled “Drafting Improves 3000m Running Performance in Elite Athletes: Is it a Placebo Effect?”)

The study involved 10 members of the Tunisian national track team, each of whom ran a pair of 3000-metre time trials. In one trial, they drafted behind two pacers for the first 2000 metres; in the other, they ran on their own. In both trials, they were instructed to run at a steady pace corresponding to 95 to 100 per cent of maximal aerobic speed for the first 2000 metres, then finish as fast as they could. In the unpaced trial, timekeepers located every 100 metres told them whether they were on pace or needed to speed up or slow down.

If the primary effect of drafting is physiological due to air resistance, you’d expect that the drafting runners would have used less energy during the first 2000 metres. Instead, oxygen consumption (as measured by portable analysers) wasn’t significantly different between the two trials. Still, the runners were able to finish the drafting trials much faster (9:04 versus 9:13), with lower perceived effort (16.1 versus 13.1 on a 20-point scale) and (confusingly) lower lactate levels.

So what’s going on? As I mentioned above, the researchers conclude that the benefits are psychological rather than physiological, since they didn’t see differences in oxygen consumption. I’m not 100 per cent convinced that drafting benefits wouldn’t have shown up with a closer look (e.g. more subjects), but I can believe that the bigger effects are unrelated to air resistance. That doesn’t necessarily mean it’s a placebo, though. It takes mental effort to set, monitor, and maintain a challenging pace; saving that mental effort so that you can expend it toward the end of the race should help you go faster. Subjectively, I’ve always felt that was the biggest benefit of running behind a pacer or in a pack, except on windy days when the air resistance is a bigger deal.

There’s an important difference between calling the benefits of drafting a “placebo” (or saying they’re “psychological”) and attributing the benefits to avoiding mental fatigue. In the former case, all it takes is a change of mindset to make frontrunning just as efficient as following. In the latter case, mental fatigue itself is a real “physiological” phenomenon that confers an unavoidable* disadvantage on frontrunners compared to followers. This experiment isn’t able to distinguish between the two possibilities – but my guess is that mental fatigue does play a role.

(* Well, maybe the disadvantage isn’t “unavoidable.” There may be situations where running in front can produce less mental fatigue. For example, steeplechasers like to run in front so they can see the barriers coming; running in a pack during a steeplechase may produce higher mental fatigue because of the constant focus and jostling required to see and clear each barrier. The same may even be true in flat races when the pack is tightly bunched and jostling. And frontrunners also have the advantage of knowing what’s about to happen, so if they insert surges and slowdowns that keep the pace changing, that may be mentally fatiguing for athletes who are trying to follow them and have to keep reacting to sudden changes of unknown duration. But in the classic case of two evenly matched runners running at a relatively steady pace, the one behind should be able to relax and conserve some mental resources.)


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