Purpose: The purpose of this study was to examine core temperature (TC) and markers of dehydration during one-a-day (D1) practices compared to two-a-day (D2) practices. Methods: Twenty-five National Collegiate Athletic Association (NCAA) Division I Football Championship Subdivision (FCS) football players volunteered to participate in the study, with thirteen subjects providing data for all four practices. Each subject was measured prior to and following D1 and D2 practices and tested for body mass, core temperature, supine and standing blood pressure, and blood volume changes. Environmental temperature, humidity and barometric pressure were measured at the practice field during the last hour of each practice. Results: During moderate environmental temperatures and humidity, body mass was found to decrease following practice. Core temperature increased following both types of practice. Post practice plasma volume was 4% higher following D1 compared to D2 practice type. Conclusions/Recommendations: In this study, these NCAA Division I FCS football players remained well-hydrated during preseason practice training. The athletes’ plasma volume increased during practice, and even though core temperature increased, it remained lower than levels at which heat illness is indicated. In conclusion, the results of this study indicate that the risk of heat illness in NCAA Division I FCS football players is very low during fall football training practices in conditions of moderate heat and humidity. We recommend that this study should be repeated in various environments, including higher temperatures and/or percent relative humidity where the risk of heat illness may be greater.




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