Daniels J W, Molé P A, Shaffrath J D, Stebbins C L
Human Performance Laboratory, Department of Exercise Science, University of California, Davis, California 95616, USA.
J Appl Physiol (1985). 1998 Jul;85(1):154-9. doi: 10.1152/jappl.1998.85.1.154.
This study examined the acute effects of caffeine on the cardiovascular system during dynamic leg exercise. Ten trained, caffeine-naive cyclists (7 women and 3 men) were studied at rest and during bicycle ergometry before and after the ingestion of 6 mg/kg caffeine or 6 mg/kg fructose (placebo) with 250 ml of water. After consumption of caffeine or placebo, subjects either rested for 100 min (rest protocol) or rested for 45 min followed by 55 min of cycle ergometry at 65% of maximal oxygen consumption (exercise protocol). Measurement of mean arterial pressure (MAP), forearm blood flow (FBF), heart rate, skin temperature, and rectal temperature and calculation of forearm vascular conductance (FVC) were made at baseline and at 20-min intervals. Plasma ANG II was measured at baseline and at 60 min postingestion in the two exercise protocols. Before exercise, caffeine increased both systolic blood pressure (17%) and MAP (11%) without affecting FBF or FVC. During dynamic exercise, caffeine attenuated the increase in FBF (53%) and FVC (50%) and accentuated exercise-induced increases in ANG II (44%). Systolic blood pressure and MAP were also higher during exercise plus caffeine; however, these increases were secondary to the effects of caffeine on resting blood pressure. No significant differences were observed in heart rate, skin temperature, or rectal temperature. These findings indicate that caffeine can alter the cardiovascular response to dynamic exercise in a manner that may modify regional blood flow and conductance.
本研究检测了咖啡因在动态腿部运动期间对心血管系统的急性影响。选取了10名训练有素、未摄入过咖啡因的自行车运动员（7名女性和3名男性），在其静息状态下以及摄入6毫克/千克咖啡因或6毫克/千克果糖（安慰剂）加250毫升水前后进行自行车测力计测试。摄入咖啡因或安慰剂后，受试者要么休息100分钟（静息方案），要么休息45分钟，随后以最大耗氧量的65%进行55分钟的自行车测力计测试（运动方案）。在基线以及每隔20分钟测量平均动脉压（MAP）、前臂血流量（FBF）、心率、皮肤温度和直肠温度，并计算前臂血管传导率（FVC）。在两种运动方案中，于基线和摄入后60分钟测量血浆血管紧张素II（ANG II）。运动前，咖啡因使收缩压升高了17%，MAP升高了11%，而未影响FBF或FVC。在动态运动期间，咖啡因减弱了FBF（53%）和FVC（50%）的升高，并加剧了运动诱导的ANG II升高（44%）。运动加咖啡因期间，收缩压和MAP也更高；然而，这些升高是咖啡因对静息血压影响的继发结果。在心率、皮肤温度或直肠温度方面未观察到显著差异。这些发现表明，咖啡因可以改变对动态运动的心血管反应，其方式可能会改变局部血流和传导。
