Foster, C., Schrager, M., Snyder, A. C., & Thompson, N. N. (1994). Pacing strategy and athletic performance. Sports Medicine, 17(2), 77-85.

The literature on pacing in athletic performances as well as the types of pacing exhibited in several sports (e.g., running, cycling, speed skating) at Olympic Games competitions were reviewed.

That a relatively even pace is the best way to distribute an effort in events lasting more than a couple of minutes has been based on limited data that existed over 50 years ago. However, pacing is complicated by different physiological mechanisms:

1. in short events metabolite accumulation is the primary limitation, and
2. in longer events it is substrate depletion which is limiting.

Pacing is different for two forms of events. In short duration events, those that are primarily anaerobically energized, it is best to go out fast and come home slower. Winners are usually differentiated on the latter part of the race in that a higher velocity can be maintained. Thus, for events in swimming, particularly 100 m and shorter, the performance should require setting a very fast pace and then seeing how well it can be maintained. As fatigue occurs in the second half of these "sprint" events, particular attention should be paid to maintaining cycle rate and propelling efficiency. Champions in these shorter events are usually able to release more energy than lesser performers (see Troup, 1991).

The effect of pacing errors on performance is more drastic in water and heavily resisted events than in air-resisted events where coasting (recovery) can be effected without too great a cost.

In short events, even though it is advocated that going out fast is the best and most popular strategy, the speed of the first half of the event should be a controlled maximum pace (most mechanically efficient) rather than one that possibly expends more energy but decreases in mechanical advantage because of its recruitment of extra muscles and changes in skill. This controlled all-out model predicts 500 and 1,000 m skating and 1,000 m cycling events quite well.

Studies have found that muscle ATP decreases only moderately (20-40%) after heavy exercise although CP is reduced more (50-95%). This remaining presence of ATP argues against substrate depletion as a primary cause of the decrease in power output and hence, against the necessity for pacing. On the other hand, muscle lactate accumulation may be one of the primary factors in creating the need to pace exercise of more than a few seconds duration. Exhaustion during heavy exercise is related to achieving critically low muscle pH.

Through training, athletes learn how to sense low pH values and adjust paces accordingly. In a race, the low pH values should occur as the finish is reached. Timing that sensitivity should be learned by extensive practice with different pacing strategies.

In middle distance and longer races, that is, those with aerobic dominance, even pacing is preferable. The pace that is held should promote the greatest mechanical/propelling efficiency as well as maintain supportive anaerobic metabolism at the maximum lactate steady state level. If an aerobic event is started too fast and fatigue occurs too early, it is known that fatigue interferes with skill efficiency. This is something of greater importance than the energizing of the performance. Unless movement economy is maintained, pacing according to an energy-only model will be too aggressive.

Implications. There are two distinct models for pacing different length events. As always, there will be considerable individual variation in how this is interpreted and used. There is likely to be a "mixed" model where "short" becomes a "long" event. In swimming, a 200 m crawl stroke race may be performed best by someone who is a distance swimmer by going out fast and coming home slower. To that person, the 200 m race is a "sprint." On the other hand, for someone who has an aptitude for 50 and 100 m racing, the 200 m event will seem like a middle distance event and should be paced evenly.

In general though, 50 and 100 m swimming events should have the first half much faster than the second. A value of 5 to 10% drop-off is not an unreasonable expectation. For races longer than 200 m, the pacing should be even with pace in the very final stages of the race being maintained by the final utilization of anaerobic energy sources so that muscle pH levels are lowest at the finish.

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