Metabolic effects of physical countermeasures against deficient weight-bearing in an experiment with seven-day immersion

Abstract

Metabolic effects of physical countermeasures against deficient weight-bearing were studied in three groups of 21- to 30 year-old volunteers during seven-day dry immersion (DI). Blood serum was investigated for 38 biochemical parameters that characterize the myocardium, skeletal musculature, hepatobiliary system, kidney, pancreas, and gastrointestinal tract, as well as prostate, protein-nucleic, carbohydrate, electrolyte and mineral metabolisms. Seven-day DI without countermeasures (n = 5) increased the concentration of conjugated bilirubin, suppressed the activities of muscular (creatine phosphokinase CPK MM) and myocardial enzymes (CPK MB, OBDH), and caused an upward trend in cholesterol, its atherogenic LDP fraction and triglycerides. Mechanic foot stimulation (n = 6) intensified, within the physiologically normal limits, erythrocyte hemolysis, raising total bilirubin and potassium. Despite the stimulation, activity of muscle and myocardial enzymes decreased. Blood creatinine decreased to a lesser extent than in the immersed group without stimulation; however, lipid parameters did not rise. High-frequency stimulation of the lower leg and hip muscles in the course of immersion (n = 5) was found to heighten the activity of muscle enzymes and potassium level in blood beyond the physiologically normal range. Change in creatinine did not reach statistical significance, and lipid metabolism parameters were not different from baseline values. The use of these physical methods of counteracting weight-bearing deficiency did not interfere with redistribution of body liquids due to immersion. The parameters under study were mostly within the normal limits throughout the experimental exposure, suggesting the absence of pathological developments during DI or as a consequence of physical stimulation. Therefore, the reactions were obviously of normal adaptive nature.