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346 The placebo effect, a favorable outcome from belief that one has received a beneficial treatment, may be an important phenomenon in athletic performance. We have therefore investigated the placebo effect of a sports drink on performance of a 40-km cycling time trial by 50 subelite endurance cyclists (4 females, 46 males; peak oxygen consumption 63 ± 10 ml.min-1.kg-1, mean ± SD). The cyclists performed two trials with their own bikes on an air-braked ergometer. In the first trial they ingested water to establish baseline performance (61 ± 6 min). For the second trial 6-8 d later the cyclists were randomized to two groups: one group ingested 16 ml.kg-1 of a drink containing 7.6 g of carbohydrate per 100 ml; the other group ingested a drink containing a non-caloric sweetener. Cyclists in each group were further randomized to three subgroups according to what they were told was in the drink: carbohydrate, sweetener, or either (not told). The cyclists told carbohydrate was in the drink showed an enhancement of performance of 2.7% (95%CI = 5.8 to -0.5%) relative to those told sweetener; the enhancement was less relative to the cyclists not told(0.7%, 95%CI = 3.9 to -2.4%). Reliability of performance controlled for group effects was not high (retest r = 0.84, coefficient of variation = 3.2%). These findings need to be confirmed with reliable elite athletes and for other potentially ergogenic treatments; meanwhile it can be assumed that the placebo effect inflates endurance performance by several percent in unblinded trials or reports of personal experience.
Clark et al. (Fri,) studied this question.