School of Physiotherapy and Exercise Science, Gold Coast campus, Griffith University, Southport, QLD 4215, Australia.
Eur J Appl Physiol. 2010 May;109(2):287-95. doi: 10.1007/s00421-009-1351-8. Epub 2010 Jan 16.
The purpose of this study was to determine if improved supramaximal exercise performance in trained cyclists following caffeine ingestion was associated with enhanced O(2) uptake (VO2 kinetics), increased anaerobic energy provision (accumulated O(2)-AO(2)-deficit), or a reduction in the accumulation of metabolites (for example, K(+)) associated with muscular fatigue. Six highly trained male cyclists (VO2peak 68 +/- 8 mL kg(-1) min(-1)) performed supramaximal (120% VO2peak) exercise bouts to exhaustion on an electronically braked cycle ergometer, following double-blind and randomized ingestion of caffeine/placebo (5 mg kg(-1)). Time to exhaustion (TE), VO2 kinetics, AO(2) deficit, blood lactate (La(-)), plasma potassium (K(+)), caffeine and paraxanthine concentrations were measured. Caffeine ingestion elicited significant increases in TE (14.8%, p < 0.01) and AO(2) deficit (6.5%, p < 0.05). In contrast, no changes were observed in AO(2) deficit at isotime, VO2 kinetics, blood [La(-)] at exhaustion or peak [K(+)] following caffeine ingestion. However, [K(+)] was significantly reduced (13.4%, p < 0.01) during warm-up cycling immediately prior to the onset of the supramaximal bout for the caffeine trials, compared with placebo. It appears that caffeine ingestion is beneficial to supramaximal cycling performance in highly trained men. The reduced plasma [K(+)] during submaximal warm-up cycling may prolong the time taken to reach critical [K(+)] at exhaustion, thus delaying fatigue. Considering caffeine ingestion did not change VO2 kinetics or isotime AO(2) deficit, increases in absolute AO(2) deficit may be a consequence of prolonged TE, rather than causal.
本研究旨在确定摄入咖啡因是否会提高训练有素的自行车运动员的最大超量运动表现，从而与增强 O(2)摄取（VO2 动力学）、增加无氧能量供应（累积 O(2)-AO(2)-亏缺）或减少与肌肉疲劳相关的代谢物积累（例如 K(+)）有关。六名高训练水平的男性自行车运动员（VO2peak 为 68 ± 8 mL kg(-1) min(-1)) 在电子制动自行车测力计上进行超量（120% VO2peak）运动至力竭，之前进行了双盲和随机摄入咖啡因/安慰剂（5 mg kg(-1))。测试了运动时间（TE）、VO2 动力学、AO(2)亏缺、血乳酸（La(-)）、血浆钾（K(+)）、咖啡因和茶碱浓度。摄入咖啡因可显著增加 TE（14.8%，p < 0.01）和 AO(2)亏缺（6.5%，p < 0.05）。相比之下，在摄入咖啡因后，等时的 AO(2)亏缺、VO2 动力学、运动至力竭时的血 [La(-)]或峰值 [K(+)] 没有观察到变化。然而，在咖啡因试验中，与安慰剂相比，在开始超量运动前的预热自行车阶段，[K(+)]显著降低（13.4%，p < 0.01）。摄入咖啡因似乎对高训练水平男性的超量自行车运动表现有益。亚最大预热自行车期间的血浆 [K(+)]降低可能会延长达到疲劳时临界 [K(+)]所需的时间，从而延迟疲劳。考虑到摄入咖啡因不会改变 VO2 动力学或等时 AO(2)亏缺，绝对 AO(2)亏缺的增加可能是 TE 延长的结果，而不是因果关系。
