EFFECT OF DIFFERENT DOSES OF CAFFEINE ON PHYSIOLOGICAL RESPONSES TO SUBMAXIMAL E

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. It is estimated that 30 million United States children participate in organized sports. Further, it has been reported that up to 86% of 6-11 year old children consume caffeine. Yet, only two studies, which used relatively high doses of caffeine (4 and 5 mg/kg body mass), have investigated the acute effect of caffeine during exercise in children. Thus, this research aims to: 1) determine the acute effect of low (1 mg/kg body mass) and moderate (3 mg/kg body mass) doses of caffeine on physiological responses to exercise in children; 2) determine if there is a threshold level of caffeine below which physiological responses to exercise in children are not affected; and 3) determine if there is a dose response effect of caffeine on physiological responses to exercise in children. To achieve these objectives 7-9 year old children (20 boys and 20 girls) will participate in a counter balanced, double blind study. Children will visit the laboratory five times. During visit one consents and activity questionnaires will be completed, and body composition and maximal oxygen consumption will be determined. On visits 2-5 one of four treatment trials will be randomly performed in a counter balanced design. Treatment trails are: 0 mg/kg (placebo); 1 mg/kg; 3 mg/kg; and 5 mg/kg of caffeine. The treatment consists of sprite mixed in cherry syrup, and the appropriate treatment. Following a 60-minute wash-in period resting physiological measures will be taken. The subjects will then ride a stationary cycle ergometer for two consecutive eight-minute stages at 25 W and then 60% VO2max. During this time oxygen consumption, ventilation, and heart rate will be monitored continuously while blood pressure will be measured every two minutes. Each treatment will be conducted at least 48 hours apart and within a 2-3 week period. To control for diurnal variation each test will be conducted within 1-2 hours of the same time of day.