Response

Dear Editor-in-Chief: Our response is a plausible conversation between two sport scientists at a future ACSM meeting. Kim: Hey, I hear you've switched to times to exhaustion with your endurance athletes. How come? Jeukendrup and Currell reckon those tests are unrealistic and unreliable (4). Kylie: Yeah, we used to do time trials, but we suspected the athletes were just remembering their usual race pace, or even something more comfortable, from trial to trial. After all, they usually pick up the pace toward the end of a time trial (e.g., 6), so they could have gone faster earlier Kim: That change of pace in time trials is a worry. A more even pace may be optimal for longer endurance (1). So athletes don't usually do their best in time trials? Kylie: Exactly¡ And it's probably worse when you do something that changes their ability to produce power. How well do athletes set their pace early in a time trial to suit their new state? Who knows? With constant-power and incremental tests to maximum effort, athletes don't have to set the right pace—they just have to keep going as long as possible. Kim: But isn't winning races all about pacing? Kylie: Pacing can be important, and we'll use time trials when we want to study self-selected pacing. But usually an athlete tries to hang in with the front runners. Either way, the more power the athlete can sustain, the better—and that's why just about everything we try with athletes is aimed at increasing power output. So when we test athletes, we want to measure their change in power output accurately. Allowing athletes to pace themselves adds noise. It also makes enhancements and impairments of maximum sustainable power look smaller than they really are, but that's another story. Kim: How many times to exhaustion? Jeukendrup and Currell said there was no point in doing several when one time trial will do. Kylie: Well, you need two to get around the problem of individual differences in the power-duration curve, and we're checking that two work properly with log-log modeling for longer tests, as Hinckson and Hopkins suggested (2). But we used to do two time trials anyway, because we wanted to track endurance capability over short and long durations. What's better for that: two time trials or two times to exhaustion? Kim: Time trials, surely, because times to exhaustion are unreliable? Kylie: Look, Hopkins and colleagues (3) had already shown that times to exhaustion are reliable over everything from minutes to hours. Hinckson and Hopkins put it on a solid theoretical and experimental footing with tests lasting 1–10 min. Jeukendrup and Currell's failure to recognize that was disappointing. They could have written something like this: “We admit Jeukendrup and colleagues (5) were wrong in 1996. Hinckson and Hopkins have explained clearly how it's all a matter of signal to noise arising from the shape of the power-duration curve. And their use of calculus with modeling shows a commendable level of scholarship. However…” Erica A. Hinckson, Ph.D. Will G. Hopkins, Ph.D.