Sports Science Unit, School of Medical Sciences, Universiti Sains Malaysia, 16150, Kubang Kerian, Kelantan Malaysia.
Indian J Med Res. 2010 Jul;132:36-41.
BACKGROUND & OBJECTIVES: Athletes in Malaysia need to perform in a hot and humid climate. Chronic supplementation of caffeine on endurance performance have been studied extensively in different populations. However, concurrent research on the effects of acute supplementation of caffeine on cardiorespiratory responses during endurance exercise in the Malaysian context especially in a hot and humid environment is unavailable.
Nine heat adapted recreational Malaysian male runners (aged: 25.4+/-6.9 yr) who were nonusers of caffeine (23.7+/-12.6 mg per day) were recruited in this placebo--controlled double--blind randomized study. Caffeine (5 mg per kg of body weight) or placebo was ingested in the form of a capsule one hour prior to the running exercise trial at 70 per cent of VO2max on a motorised treadmill in a heat-controlled laboratory (31 degrees C, 70% relative humidity). Subjects drank 3 ml of cool water per kg of body weight every 20 min during the running trials to avoid the adverse effects of dehydration. Heart rate, core body temperature and rate of perceived exertion (RPE) were recorded at intervals of 10 min, while oxygen consumption was measured at intervals of 20 min.
Running time to exhaustion was significantly (P<0.05) higher in the caffeine trial compared to the placebo trial. Heart rate, core body temperature, oxygen uptake and RPE did not show any significant variation between the trials but it increased significantly during exercise from their respective resting values in both trials (P<0.001).
INTERPRETATION & CONCLUSION: Our study showed that ingestion of 5 mg of caffeine per kg of body weight improved the endurance running performance but did not impose any significant effect on other individual cardiorespiratory parameters of heat-acclimated recreational runners in hot and humid conditions.
马来西亚的运动员需要在炎热潮湿的气候中进行比赛。在不同人群中，已广泛研究了慢性补充咖啡因对耐力表现的影响。然而，在马来西亚的炎热潮湿环境中，特别是在热环境中，关于急性补充咖啡因对耐力运动中心肺反应的影响的研究尚不多见。
本研究招募了 9 名适应热环境的马来西亚男性业余跑步者（年龄：25.4±6.9 岁），他们均不使用咖啡因（每天 23.7±12.6mg）。在热控实验室（31°C，70%相对湿度）的电动跑步机上，以 70%最大摄氧量（VO2max）进行跑步运动试验前一小时，以胶囊形式摄入咖啡因（5mg/kg 体重）或安慰剂。在跑步试验期间，受试者每 20 分钟每公斤体重饮用 3ml 冷水，以避免脱水的不利影响。每隔 10 分钟记录心率、核心体温和感知用力程度（RPE），每隔 20 分钟测量一次耗氧量。
与安慰剂试验相比，咖啡因试验的跑步至力竭时间明显（P<0.05）延长。心率、核心体温、摄氧量和 RPE 在两个试验之间没有显示出任何显著变化，但在两个试验中，它们在运动期间都从各自的静息值显著增加（P<0.001）。
我们的研究表明，摄入 5mg/kg 体重的咖啡因可提高耐力跑步表现，但对热适应的业余跑步者在炎热潮湿条件下的其他单个心肺参数没有产生任何显著影响。
