Serum, urinary, and fecal calcium changes in trained and untrained subjects during prolonged hypokinetic and ambulatory conditions

Electrolyte metabolism undergoes significant changes in trained subjects, b ut it is unknown if it undergoes significant changes in untrained subjects during hypokinesia (decreased movement). The aim of this study was to measu re calcium (Ca) changes in trained and untrained subjects during prolonged hypokinesia (HK). Studies were done during 30 d of a pre-HK period and 364 d of a HK period. Forty male trained and untrained volunteers aged 23-25 yr were chosen as su bjects. All subjects were equally divided into four groups: trained ambulat ory control subjects (TACS), trained hypokinetic subjects (THKS), untrained hypokinetic subjects (UHKS), and untrained ambulatory control subjects (UA CS). The THKS and UHKS groups were kept under an average running distance o f 0.7 km/d. Fecal Ca excretion, urinary Ca and magnesium (Mg) excretion, serum ionized calcium (Ca-I), Ca, Mg, intact parathyroid hormone (iPTH) acid 1,25 dihydro xyvitamin D [1,25 (OH)2 D] concentration, body weight, and peak oxygen upta ke were measured. Fecal Ca loss, urinary Ca and Mg excretion, and serum Ca- I, Mg, and Ca increased significantly (p less than or equal to 0.01), where as serum iPTH and 1,25 (OH)2 D concentration body weight and peak oxygen up take decreased significantly (p less than or equal to 0.01) in the THKS and UHKS groups when compared with the TACS and UACS groups. The measured para meters were much greater and much faster in the THKS group than in the UHKS group. By contrast, the corresponding parameters did not change significan tly in the TACS and UACS groups when compared with the baseline control val ues. It was concluded that prolonged HK induces significant focal, urinary, and serum Ca changes in the hypokinetic subjects when compared with control sub jects. However, fecal, urinary, and serum Ca changes were much greater and appeared much faster in the THKS group than the UHKS group.