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Bone histomorphometric changes in trained subjects during prolonged restriction of muscular activity and chronic
Y G Zorbas1, Y N Yaroshenko, N K Kuznetsov
1Hypokinetic Physiology Laboratory, Odos Agias Sophias, Athens, Greece.
Background:
The purpose of this study was to determine whether histomorphometric changes, which are developed during prolonged hypokinesia (decreased number of km/day) could be prevented or minimized with a daily intake of fluid and salt supplementation (FSS).
Methods:
The studies 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 average peak oxygen uptake (POU), of 65 mL/kg-1.min-1. All volunteers 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 subjects. Ten volunteers were subjected to continuous HK without FSS and were considered as the unsupplemented hypokinetic subjects (UHS). The remaining volunteers were under continuous HK and FSS and were considered as the supplemented hypokinetic subjects (SHS). For the simulation of the hypokinetic effect, the SHS and UHS groups were kept continuously under an average of 2.7 km/day for the duration of the experiment. Prior to exposure to HK, all volunteers were on the same exercise regime as the control subjects. During the 60 day pre-HK period and during the experimental period, the following parameter were determined: sodium and calcium in urine and plasma, hemoglobin (Hb), hematocrit (Hct), plasma osmolality, plasma protein concentration, plasma renin activity, aldosterone and parathyroid hormone (PTH) concentration.
Results:
In the UHS iliac crest cancellous bone volume and PTH content decreased, urinary and plasma electrolytes, plasma renin activity, aldosterone, plasma osmolality, protein content, Hb and Hct increased significantly. In the SHS iliac crest cancellous bone volume and PTH content increased, while electrolytes in urine and plasma Hb, Hct, osmolality, protein, aldosterone and plasma renin activity decreased.
Conclusions:
It was concluded that daily intake of FSS may be used to minimize or prevent histomorphometric changes in endurance trained volunteers during exposure to prolonged HK.