Muscle Glycogen and Electrolytes Following Exercise and Thermal Dehydration

Abstract

It is well established that a decrease in body weight of more than 2% by heat and/or exercise induced sweating causes an impairment in physical work capacity [1, 7, 17]. Studies have indicated that after a given sweat loss due to prolonged exercise the physical work capacity is more reduced than when sweating is stimulated by environmental heat stress. KozLowsxl and SALTIN [14] have demonstrated a marked difference in the distribution of body water when men reduced body weight (4%) by either exercise or thermally induced sweating. During exercise dehydration the major part of the sweating was achieved at the expense of intracellular water losses (−8,4%), whereas a similar degree of weight loss brought aboilt by inactive exposure to a hot, dry environment resulted in a significantly smaller loss of water from the intracellular compartment (−4,7%). Calculations of total body and plasma sodium, potassium and chloride changes suggested that during thermal dehydration there was a larger loss of sodium and chloride and a smaller loss of potassium from the extracellular space than during exercise dehydration. It seems possible that these variations in muscle water and electrolytes may alter the muscular excitability, thereby affecting the functional capacity of muscle.

This research was supported by grants from the American Heart Association, Northeast Indiana Chapter, Inc., a Chapter of the Indiana Heart Association, Inc.; the Royal Crown Cola Company; and the Swedish Medical Research Council (40x-2203).