James Rob S, Kohlsdorf Tiana, Cox Val M, Navas Carlos A
School of Science and the Environment, James Starley Building, Coventry University, Priory Street, Coventry CV1 5FB, UK.
Eur J Appl Physiol. 2005 Sep;95(1):74-82. doi: 10.1007/s00421-005-1396-2. Epub 2005 Jun 15.
Caffeine ingestion by human athletes has been found to improve endurance performance primarily acting via the central nervous system as an adenosine receptor antagonist. However, a few studies have implied that the resultant micromolar levels of caffeine in blood plasma (70 microM maximum for humans) may directly affect skeletal muscle causing enhanced force production. In the present study, the effects of 70 microM caffeine on force and power output in isolated mouse extensor digitorum longus muscle were investigated in vitro at 35 degrees C. Muscle preparations were subjected to cyclical sinusoidal length changes with electrical stimulation conditions optimised to produce maximal work. 70 microM caffeine caused a small but significant increase (2-3%) in peak force and net work produced during work loops (where net work represents the work input required to lengthen the muscle subtracted from the work produced during shortening). However, these micromolar caffeine levels did not affect the overall pattern of fatigue or the pattern of recovery from fatigue. Our results suggest that the plasma concentrations found when caffeine is used to enhance athletic performance in human athletes might directly enhance force and power during brief but not prolonged activities. These findings potentially confirm previous in vivo studies, using humans, which implied caffeine ingestion may cause acute improvements in muscle force and power output but would not enhance endurance.
已发现人类运动员摄入咖啡因主要通过作为腺苷受体拮抗剂作用于中枢神经系统来提高耐力表现。然而，一些研究表明，血浆中咖啡因产生的微摩尔水平（人类最高为70微摩尔）可能直接影响骨骼肌，导致力量产生增强。在本研究中，于35摄氏度体外研究了70微摩尔咖啡因对分离的小鼠趾长伸肌力量和功率输出的影响。对肌肉标本施加周期性正弦长度变化，同时优化电刺激条件以产生最大功。70微摩尔咖啡因使工作循环期间产生的峰值力量和净功出现小幅但显著的增加（2%-3%）（其中净功表示拉长肌肉所需的功输入减去缩短过程中产生的功）。然而，这些微摩尔咖啡因水平并未影响整体疲劳模式或从疲劳中恢复的模式。我们的结果表明，当咖啡因用于提高人类运动员运动表现时所发现的血浆浓度，可能在短暂而非长时间活动期间直接增强力量和功率。这些发现可能证实了先前使用人类进行的体内研究，这些研究表明摄入咖啡因可能会使肌肉力量和功率输出产生急性改善，但不会增强耐力。
