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Abstract

Disturbed mental status (DMS) is the most obvious sign of exertional heatstroke in humans, and is one of the main complications of severe exercise heat-stress (SHS). The cause of exertional heat-stroke has been attributed to many factors such as thermoregulatory failure or impairment of muscular function. This investigation was designed to assess muscle energy metabolism in two groups of rats running at 34 °C. One group (n = 17) stopped because of DMS (SHS rats), while the other group (n = 21) stopped because of mild or moderate exercise heat-stress (MHS rats). SHS rats ran longer and had a higher final rectal temperature (T_re): 66.5 ± 4.2 °C vs 47.3 ± 3.8 °C, p <0.05 and 42.7 ± 0.12 °C vs42.2 ± 0.15 °C, p < 0.05, respectively. SHS rats also had a slower rate of change of T_re (0.054 ± 0.007 °C min⁻¹ vs 0.072 ± 0.008 °C min⁻¹) and a lower mean rate of dehydration: 0.065 ± 0.006 vs 0.084 ± 0.005% bodyweight min⁻¹, p < 0.05. There were no significant differences between the two groups for skeletal muscle concentration of high energy phosphates and glycogen, but lactate was higher in SHS than in MHS rats: 25.0 ± 6.7 vs 11.8 ± 1.6 μmoles per mg protein respectively, p <0.05. These data suggest that DMS may be linked to T_re and that there is muscular functional impairment caused by SHS.

Keywords

exercise heat-exhaustion disturbed mental status

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Exercise heat stress in rats: performance and biochemical effects

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