Fluid-electrolyte metabolism and renal function in men under hypokinesia and physical exercise

It has been suggested that hypokinesia (diminished muscular activity) induces significant changes in fluid-electrolyte metabolism and renal function in physically conditioned men. Thus, the aim of this study was to investigate fluid-electrolyte metabolism and ionoregulatory renal function during 16 days of hypokinesia (HK) and 15 days of readaptation period (RP) in 12 physically conditioned male volunteers aged 19–23 years. They were divided into two equal groups. Group 1 was subjected to HK and intensive physical exercise (PE) and group 2 was submitted to pure HK, that is, without the use of any preventive measures. For the simulation of the hypokinetic effect all of the men were kept under a rigorous bed rest regime. Sodium, potassium, calcium and magnesium, creatinine, urea and osmotic concentration were calculated in blood serum and urine samples. Renal excretion of fluid, osmotically active substances and electrolytes was insignificantly different in the two groups. The level and period of water and electrolyte retention were different with respect to the duration of HK. The basic physiological mechanisms of changes in fluid-electrolyte metabolism were consistent with a reduction of the glomerular filtration rate and a change in water and ion transport of renal tubules. It was concluded that HK induced marked changes in fluid-electrolyte metabolism and renal function in physically conditioned men regard-less of their involvement in intensive physical exercise. Experimental studies of hypokinetic physiology are generally based on the assumption that diminished muscular activity (progressive reduction of number of steps per day) is hostile to animal and human organism, since the entire animal kingdom had been formed in a high motor activity environment that left its imprint on the evolution, structure, function and behaviour of animals and man. The impossibility of the body tissues to retain optimum amount of fluid and electrolytes is the dominant hypokinetic effect.