FLUID-ELECTROLYTE SHIFTS AND THERMOREGULATION - REST AND WORK IN HEAT WITH HEAD COOLING

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 51  (8) , 747-753
Abstract
Plasma volume and thermoregulatory responses were measured, during head and neck cooling with a liquid-cooled neoprene headgear, in four men (21-43 yr old) during 60 min of rest, 60 min of ergometer exercise (45% .ovrhdot.VO2 max) and 30 min of recovery in the supine position at 40.1.degree. C DBT and 40% rh [relative humidity]. Compared with control (noncooling) responses, cooling decreased thigh sweating and increased mean skin temperature (.hivin.Tsk) at rest, and attenuated the increases in thigh sweating by 0.26 mg/min .cntdot. cm2 (-22.4%, P < 0.05), heart rate by 10 b[beats]/min (-8.5%, N.S.), rectal temperature (Tre) by 0.3.degree. C (N.S.) and ventilation by 12.5% (N.S.) during exercise. In recovery, cooling facilitated the decreases in thigh sweat rate, heart rate, Tre and forearm blood flow and enhanced the increase in .hivin.Tsk toward control levels. Cooling had no effect upon plasma protein, osmotic or electrolyte shifts during rest, exercise or recovery. Plasma volume (PV) loss during exercise was 11.2% without cooling and 10.9% with cooling. Cooling increased PV by 3% (P < 0.05) during rest. This differential was maintained throughout the exercise and recovery periods.