Muscle calcium metabolic effects of hypokinesia in physically healthy subjects.

The incompleteness of electrolyte deposition during hypokinesia (HK; diminished movement) is the defining factor of electrolyte metabolic changes, yet the effect of prolonged HK upon electrolyte deposition is poorly understood. The objective of this investigation was to determine the effect of muscle calcium (Ca(++)) changes upon Ca(++) losses during prolonged HK. Studies were conducted on 20 physically healthy male volunteers during a pre-experimental period of 30 days and an experimental period of 364 days. Subjects were equally divided in two groups: control subjects (CS) and experimental subjects (ES). The CS group ran average distances of 9.2 ± 1.2 km day(-l), and the ES group walked average distances of 2.3 ± 0.2 km day(-l). Muscle Ca(++) contents, plasma Ca(++) concentrations, and Ca(++) losses in urine and feces were measured in the experimental and control groups of subjects. The muscle Ca(++) contents decreased (p < 0.05), and plasma Ca(++) levels and Ca(++) losses in the urine and feces increased (p < 0.05) in the ES group compared with their pre-experimental levels and the values in their respective CS group. Muscle Ca(++) contents and plasma Ca(++) levels and urinary and fecal Ca(++) losses did not change in the CS group compared to their pre-experimental levels. It is concluded that prolonged HK increase plasma Ca(++) concentrations and Ca(++) losses in Ca(++) deficient muscle indicating decreased Ca(++) deposition.