BONE HISTOMORPHOMETRIC CHANGES IN TRAINED SUBJECTS DURING PROLONGED RESTRICTION OF MUSCULAR-ACTIVITY AND CHRONIC HYPERHYDRATION

Background. The purpose of this study was to determine whether histomo rphometric changes, which are developed during prolonged hypokinesia ( decreased number of km/day) could be prevented or minimized with a dai ly intake of fluid and salt supplementation (FSS). Methods. The studie s on hypokinesia (HK) were performed for 364 days on thirty endurance trained male volunteers (ETV) in the age of 19 to 25 years, with an av erage peak oxygen uptake (POU), of 65 mL/kg(-1).min(-1). All volunteer s were divided into three equal groups: ten volunteers were placed on a continuous regime of exercise of 13.8 km/day and served as control s ubjects. Ten volunteers were subjected to continuous HK without FSS an d were considered as the unsupplemented hypokinetic subjects (UHS). Th e remaining volunteers were under continuous HK and FSS and were consi dered as the supplemented hypokinetic subjects (SHS). For the simulati on of the hypokinetic effect, the SHS and UHS groups were kept continu ously under an average of 2.7 km/day for the duration of the experimen t. Prior to exposure to HK, all volunteers were on the same exercise r egime as the control subjects. During the 60 day pre-HK period and dur ing the experimental period, the following parameter were determined: sodium and calcium in urine and plasma, hemoglobin (Db), hematocrit (H ct), plasma osmolality, plasma protein concentration, plasma renin act ivity, aldosterone and parathyroid hormone (PTH) concentration. Result s. In the UHS iliac crest cancellous bone volume and PTH content decre ased, urinary and plasma electrolytes, plasma renin activity, aldoster one, plasma osmolality, protein content, Hb and Hct increased signific antly. In the SHS iliac crest cancellous bone volume and PTH content i ncreased, while electrolytes in urine and plasma Hb, Hct, osmolality, protein, aldosterone and plasma renin activity decreased. Conclusions. It was concluded that daily intake of PSS may be used to minimize or prevent histomorphometric changes in endurance trained volunteers duri ng exposure to prolonged HK.