Fluid electrolyte and hormonal changes in conditioned and unconditioned men under hypokinesia.

It has been suggested that hypokinesia (diminished muscular activity) may induce more changes in fluid electrolyte metabolism and hormonal concentration of blood plasma in conditioned than unconditioned men. Thus, the objective of this investigation was to determine the effect of 7 days of hypokinesis (HK) on fluid-electrolyte excretion and hormonal content of blood in 12 physically healthy men aged 19-23 years. They were divided into two equal groups according to their physical conditioning. For the simulation of the hypokinetic effect the men were kept under a rigorous bed rest regime. During the background period (BGP), that is prior to the exposure to HK, and under HK, the rate of elimination of fluid, sodium and potassium, and the content of blood plasma aldosterone and cortisol was measured. The amount of excretion of fluid and electrolytes increased while blood plasma aldosterone content decreased. In the conditioned men, a greater excretion of fluid and electrolytes and a greater reduction of plasma aldosterone concentration was observed. It was concluded that hypokinesia induced substantial changes in fluid-electrolyte excretion and hormonal content of blood plasma in both conditioned and unconditioned men.