Effects of Dietary Sodium on Muscle Water and Electrolytes during Heat Acclimatization.

In an effort to assess the influence of daily sodium intake on muscle water and electrolytes during eight, successive days of exercise and heat exposure 90minday 40.1 C 23.5 R.H. 44-50 Vo2 max, nine men were studied under two dietary sodium Na regimens 399 and 98 mEq Naday. Both the 399 mEq Na HI and 98 mEq Na LO diets contained 80 mEq potassium K per day. The LO treatment resulted in higher heart rates, higher rectal temperatures, and a smaller plasma volume expansion than during the HI regimen. Though plasma K concentration was unchanged throughout both treatments, the plasma K, Na and C1- content increased in proportion to the increase in plasma volume. Muscle water, Na, and C1- contents were significantly increased P.05 were found between the two Na diets. Muscle K, on the other hand, remained unaffected by either the days of heat-exercise stress or the HI-LO diets. Although the LO diet appeared to lessen the subjects acclimatization to the heat, neither diet affected the body K content, nor did they effect the excretion of K in urine or sweat.