Hypervolemia, thermoregulation, and exercise performance under severe heat stress
Date
2010-02-23T20:06:23Z
Authors
Nelson, Michael Douglas
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Abstract
The purpose of this study was to determine if the ingestion of sodium citrate (CIT), and the subsequent expansion of plasma volume, would have a direct effect on thermoregulation and physiological function during a simulated 1-hour time trial (TT) under sever heat stress. Eight subjects, aged 24.9 years (SD + 4.4), were studied under the following three conditions: (1) High Sodium Citrate (HCIT; 0.2 g/kg sodium citrate), (2) Low Sodium Citrate (LCIT; 0.1 g/kg sodium citrate), and (3) Control (Gatorade). Blood samples, taken before and during exercise, were analyzed for hematocrit (Het), haemoglobin (Hb), bicarbonate (HCO3-), base excess (BE), pH, sodium (Na), potassium (K), and glucose (GLU). Rectal temperature (Tr) and skin temperature (Tsk) was also recorded. Heart rate and psychophysical strain were also measured throughout each TT. Plasma volume significantly increased by 7.1% after ingesting the HCIT compared to the other two trials. There were no differences in mean body temperature, physiological strain, cardiovascular strain or psychophysical perception. The ingestion of HCIT appears to improve cycling performance despite no difference in physiological measurements. HCIT reduced split times, better maintained power output over the TT. and improved time total cycling time.
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Keywords
exercise, heat, physiological aspects