Department of Kinesiology, California State University-San Marcos, San Marcos, CA, USA.
Nutr Res. 2012 Feb;32(2):78-84. doi: 10.1016/j.nutres.2011.12.001.
The primary aim of this study was to determine the repeatability of caffeine's ergogenic effects on cycling performance. It was hypothesized that improvements in performance would be similar when caffeine was ingested on 2 separate days. Nine endurance-trained men and women (mean age and maximal oxygen uptake, 27.4 ± 5.9 years and 57.5 ± 3.9 mL kg⁻¹ min⁻¹) initially completed 2 familiarization trials. During 3 subsequent sessions separated by at least 48 hours, the subjects completed a 10-km cycling time trial preceded by ingestion of a drink containing caffeine (5 mg/kg) or placebo. Treatments were ingested using a randomized, single-blind, crossover design, and the subjects were deceived as to the specific content of all drinks. During exercise, heart rate, rating of perceived exertion, and time were recorded every 1.6 km. Repeated-measures analysis of variance was used to compare the differences in variables across distance and treatment. In both caffeine trials, caffeine increased (P = .02) cycling performance by 1.6% and 1.9% vs placebo (16.98 ± 0.96 and 16.92 ± 0.97 minutes with caffeine vs 17.25 ± 0.96 minutes in placebo), and 7 of 9 subjects revealed improved performance. The mean performance improvement in the caffeine trials was similar (P = .35; -0.27 and -0.32 minutes, respectively) across days. Heart rate during exercise was higher (P b .001) with caffeine vs placebo, although the rating of perceived exertion was similar (P = .65). Data reveal that caffeine's ergogenic effects on cycling performance are repeatable across days, yet some individuals did not exhibit improved performance with caffeine.
本研究的主要目的是确定咖啡因对自行车运动表现的重复作用。假设在 2 天分别摄入咖啡因时，表现的改善将相似。9 名耐力训练的男性和女性（平均年龄和最大摄氧量分别为 27.4 ± 5.9 岁和 57.5 ± 3.9 mL kg⁻¹ min⁻¹）最初完成了 2 次熟悉试验。在至少相隔 48 小时的 3 次随后的试验中，受试者完成了 10 公里自行车计时赛，在这之前摄入了含有咖啡因（5mg/kg）或安慰剂的饮料。处理方法采用随机、单盲、交叉设计，受试者被欺骗以为所有饮料的具体内容。在运动过程中，每 1.6 公里记录心率、感知用力程度和时间。使用重复测量方差分析比较距离和处理之间变量的差异。在咖啡因试验中，咖啡因分别提高（P =.02）了自行车运动表现 1.6%和 1.9%，而安慰剂为 16.98 ± 0.96 和 16.92 ± 0.97 分钟（分别为 17.25 ± 0.96 分钟），7 名受试者中 9 名显示出了运动表现的改善。咖啡因试验中的平均表现改善在两天之间相似（P =.35；分别为 -0.27 和 -0.32 分钟）。运动时的心率（P b.001）更高，但感知用力程度相似（P =.65）。数据显示，咖啡因对自行车运动表现的增强作用是可重复的，但是有些个体没有表现出咖啡因的改善作用。
