Measurements in calcium-supplemented athletes during and after hypokinetic and ambulatory conditions

Abstract

Study objective: Hypokinesia (diminished movement) induces significant calcium (Ca) changes, however, little is known about Ca deficiency during hypokinesia (HK). By using Ca supplements during and after HK, the aim of this study was to establish whether HK could contribute to Ca deficiency. Design and methods: Studies were done during the pre-HK period of 30 days, HK period of 364 days and post-HK period of 30 days. Forty male trained athletes aged, 25.0 ± 7.7 yr were chosen as subjects. They were equally divided into four groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented ambulatory control subjects (SACS), and supplemented hypokinetic subjects (SHKS). The SHKS and SACS groups took daily 55.0 mg elemental Ca per kg body weight. Hypokinetic subjects were limited to an average walking distance of 0.7 km/day, while the control subjects were running 11.6 km/day. Results: Fecal Ca, urinary Ca, and urinary phosphate (P) excretion, serum ionized calcium (Ca I), P and total Ca levels, intact parathyroid hormone (iPTH), 1,25 dihydroxyvitamin D (1,25 (OH) 2 D 3), fluid and food intakes, peak oxygen uptake, and physical characteristics were measured. During HK fecal Ca, urinary Ca, and urinary P excretion and serum P, Ca I, and Ca level increased significantly ( p ≤ 0.01), whereas during the initial days of post-HK decreased significantly ( p ≤ 0.01) in the SHKS and unsupplemented hypokinetic subjects groups when compared with the SACS and UACS groups, respectively. During HK serum 1,25 (OH) 2 D 3, iPTH levels, food and fluid intakes, body weight, body fat, and peak oxygen uptake decreased significantly ( p ≤ 0.01), while during the initial days of post-HK remained significantly ( p ≤ 0.01) depressed and fluid intakes increased significantly ( p ≤ 0.01) in the SHKS and unsupplemented hypokinetic subjects groups when compared with SACS and UACS groups, respectively. Serum, urinary and fecal Ca changed much more in the SHKS than UHKS. Serum, fecal, and urinary minerals, iPTH, 1,25 (OH) 2 D 3 levels, food and fluid intakes, body weight, body fat, and peak oxygen uptake did not change markedly in the SACS and UACS groups when compared with their baseline values. Conclusion: It was shown that serum Ca concentration, urinary, and fecal Ca excretion increased during HK and decreased significantly during post-HK. Oral Ca supplementation did not significantly affect serum Ca levels or urinary and fecal Ca loss. It was concluded that decreased urinary and fecal Ca loss during post-HK, may suggest the presence of Ca deficiency during prolonged HK.