Effect of hyperhydration on bone mineralization in physically healthy subjects after prolonged restriction of motor activity

The objective of this investigation was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on bone mineralization in physically healthy male volunteers after exposure to hypokinesia (decreased number of steps taken/day) over a period of 364 days. The studies were performed after exposure to 364 days of hypokinesia (HK) on 18 physically healthy male volunteers who had an average VO2max of 65 ml/kg/min and were aged between 19 and 24 years. For the simulation of the hypokinetic effect the volunteers were kept under an average of 1000 steps/day. The subjects were divided into three equal groups of 6: 6 underwent a normal ambulatory life (control group), 6 were placed under HK (hypokinetic group) and the remaining 6 were subjected to HK and consumed a daily FSS (water 26 ml/kg body wt and NaCl 0.10 mg/kg body wt) (hyperhydrated group). The density of the ulnar, radius, tibia, fibular, lumbar vertebrae and calcenous was measured. Calcium and phosphorus changes, plasma volume, blood pressure and body weight were determined. Calcium content in the examined skeletal bones decreased more in the hypokinetic subjects than in the hyperhydrated subjects. Urinary calcium and phosphorus losses were more pronounced in hypokinetic than hyperhydrated subjects. Plasma volume and body weight increased in hyperhydrated subjects, while it decreased in hypokinetic subjects. It was concluded that a daily intake of FSS may be used to neutralize bone demineralization in physically healthy subjects during prolonged restriction of motor activity.