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首页> 外文期刊>Journal of the International Society of Sports Nutrition >Low doses of caffeine reduce heart rate during submaximal cycle ergometry
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Low doses of caffeine reduce heart rate during submaximal cycle ergometry

机译：低剂量咖啡因降低了次最大周期测功时的心率

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Background The purpose of this study was to examine the cardiovascular effects of two low-levels of caffeine ingestion in non habitual caffeine users at various submaximal and maximal exercise intensities. Methods Nine male subjects (19–25 yr; 83.3 ± 3.1 kg; 184 ± 2 cm), underwent three testing sessions administered in a randomized and double-blind fashion. During each session, subjects were provided 4 oz of water and a gelatin capsule containing a placebo, 1.5 mg/kg caffeine, or 3.0 mg/kg caffeine. After thirty minutes of rest, a warm-up (30 Watts for 2 min) the pedal rate of 60 rpm was maintained at a steady-state output of 60 watts for five minutes; increased to 120 watts for five minutes and to 180 watts for five minutes. After a 2 min rest the workload was 180 watts for one minute and increased by 30 watts every minute until exhaustion. Heart rate (HR) was measured during the last 15-seconds of each minute of submaximal exercise. Systolic blood pressure (BP) was measured at rest and during each of the three sub-maximal steady state power outputs. Minute ventilation (VE), Tidal volume (VT), Breathing frequency (Bf), Rating of perceived exertion (RPE), Respiratory exchange ratio (RER), and Oxygen consumption (VO2) were measured at rest and during each minute of exercise. Results Caffeine at 1.5 and 3.0 mg/kg body weight significantly lowered (p < 0.05) HR during all three submaximal exercise intensities compared to placebo (range – 4 to 7 bpm lower) but not at rest or maximal exercise. BP was significantly higher (p < 0.05) at rest and after the 3 mg/kg caffeine vs placebo (116 ± 13 vs 123 ± 10 mm Hg). Neither dose of caffeine had any effect on BP during submaximal exercise. Caffeine had no effect on VE, VT, VO2, RPE, maximal power output or time to exhaustion. Conclusion In non habitual caffeine users it appears that consuming a caffeine pill (1.5 & 3.0 mg/kg) at a dose comparable to 1–3 cups of coffee lowers heart rate during submaximal exercise but not at near maximal and maximal exercise. In addition, this caffeine dose also only appears to affect systolic blood pressure at rest but not during cycling exercise.
机译：背景技术这项研究的目的是研究在不同的次最大运动强度和最大运动强度下，非习惯性咖啡因使用者摄入两种低水平咖啡因对心血管的影响。方法九名男性受试者（19–25岁; 83.3±3.1千克; 184±2厘米）以随机和双盲方式进行了三个测试。在每个疗程中，为受试者提供4盎司水和包含安慰剂，1.5 mg / kg咖啡因或3.0 mg / kg咖啡因的明胶胶囊。休息三十分钟后，以60 rpm的稳态输出进行预热（30瓦，持续2分钟），踏板速度为60 rpm，持续5分钟;在五分钟内升至120瓦，在五分钟内升至180瓦。休息2分钟后，工作量为180瓦，持续一分钟，每分钟增加30瓦，直到筋疲力尽。在次最大运动量的每分钟的最后15秒内测量心率（HR）。在三个次最大稳态功率输出中的每个静止和静止期间测量收缩压（BP）。在休息和运动的每分钟期间，测量分钟通气量（VE），潮气量（VT），呼吸频率（Bf），感知劳累力（RPE），呼吸交换率（RER）和耗氧量（VO2）。结果与安慰剂相比，在三种次最大运动强度下，咖啡因浓度分别为1.5和3.0 mg / kg时，HR显着降低（p <0.05）HR（范围降低– 4至7 bpm），但在静止或最大运动量下则不降低。咖啡因和3 mg / kg咖啡因后的血压显着高于安慰剂组（116±13 vs 123±10 mm Hg）（p <0.05）。在最大程度的运动期间，两种剂量的咖啡因都不会对血压产生任何影响。咖啡因对VE，VT，VO2，RPE，最大功率输出或衰竭时间没有影响。结论在非习惯性咖啡因使用者中，似乎以1-3杯咖啡的剂量食用咖啡因丸（1.5和3.0 mg / kg）可降低次最大运动量时的心率，但在接近最大运动量时却不会。此外，这种咖啡因的剂量似乎也只影响静止时的收缩压，而不会影响骑车运动时的收缩压。

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