Dynamics of Body Composition Indices and of Some Biochemical Parameters in Participants of the Countermeasures-Free 21-day “Dry” Immersion
The article presents the results of a study of the temporal dynamics of the body composition and of the levels of hormones involved in the regulation of energy metabolism and eating behavior in healthy volunteers who were exposed to dry immersion (DI) conditions during 21 days without the use of countermeasures against negative effects of experimental conditions. The body composition of the test subjects was investigated using bioimpedance analysis (BIA). It was shown that the influence of the 21-day “dry” immersion factors on the body composition of 10 participants was expressed in a decrease in the proportion of lean mass with a simultaneous increase in the fat component. Two homogeneous groups consisting of equal number of participants with a reduced group variability of body composition and systemic regulation of energy metabolism parameters were identified using the cluster analysis. The impact of 21-day immersion factors was expressed by a significant decrease (p < 0.05) in the proportion of skeletal muscle mass (SMM%) of the body at a higher relative body fat mass, but at a lower fatless one, with a higher basal metabolic rate. It was indicated that the SMM% share was stable during the 21-day immersion with an increase in the SMM% index (p < 0.05) after completion of DI at a lower relative body fat mass, but at a higher fatless one, with a lower basal metabolic rate. This group showed a significant increase in blood insulin levels during DI. The concentrations of leptin, triglycerides differed between groups at different periods of the experiment.