Fluid electrolyte changes in physically healthy subjects during prolonged restriction of motor activity and daily...

The aim of this report was to present some of our results, in a compressed form, obtained from our previous studies on the effect of 364-d hypokinesia (decreased number of steps taken per day by the volunteers) on the following: (1) regulation of fluid volume and osmosis, (2) regulation of electrolytes, and (3) functional condition of the kidneys and its role in the fluid-electrolyte homeostasis on 30 physically healthy male volunteers aged 22-26 years. Prior to their exposure to hypokinesia all subjects were on 13.8 km/day (10,000 running steps/day) and were all well conditioned, with (oxygen uptake capacities (VO2 max 68 ml/kg-min). During the hypokinetic period of 364 days, the 1st group was subjected to pure hypokinesia (HK), that is without the use of physical exercise (PE), the 2nd group was subjected to a set of intensive PE (energy expenditure of 700 kcal/h) and the 3rd group submitted to a set of moderate PE (energy expenditure of 400 kcal/h). All volunteers consumed daily fluid and salt supplementation (FSS) aimed at increasing body hydration level during the hypokinetic period. For the simulation of the hypokinetic effect all volunteers were kept on 2.7 km/day (3000 walking steps per day). All volunteers were on a diet of freshly prepared food, with a daily intake of 2500-2700 kcal, 3340 ml water, 1500 mgs calcium, 500 mgs magnesium, 1200 mgs potassium, 1500 mgs phosphorus, 8.5 gms sodium and 9.8 gms chloride. The amount of fluid and electrolytes consumed and eliminated in urine, as well as their concentrations in the urine and blood plasma were determined. There were also measured urinary volume, osmolality, creatine, and urea changes in urine. During HK the amount of fluid and electrolytes consumed daily decreased while the rate of excretion increased significantly. During post HK the fluid and electrolytes concentrations in urine decreased significantly. The urinary urea, osmolality and creatinine increased significantly during HK. It was concluded that prolonged restriction of motor activity induced significant changes in fluid, excretion and concentration of electrolytes in plasma, as well as in the rate of their excretion by the kidneys.