Effects of a Comprehensive Exercise Training Regimen and KMgCit on Bone Elasticity as an Indicator of Bone Quality after 5 Weeks of Bedrest

Abstract

We investigated the effects of a multi‐load exercise program and KMgCit supplementation on the preservation of bone quality following 5 weeks of bedrest as measured by ultrasound critical‐angle reflectometry (UCR). The bone elasticity of 35 subjects (26 M, 9 F, 35 ± 10 yrs) was studied before and after bedrest. The subjects were divided into 4 groups: sedentary with no drug (n=12); sedentary with KMgCit (n=11); exercise (n=11); and exercise with KMgCit (n=4). The exercise group underwent intense multi‐joint rowing ergometry (30–45 min/d, 6 d/wk) and resistive strength training (2 d/wk). Subjects receiving the study drug were given 42:21:63 mEq KMgCit a day. Bone elasticity, a correlate of bone strength, was assessed by UCR on the tibia and calcaneus at multiple angles. In the sedentary group, prolonged bedrest resulted in a small decrease in bone elasticity, most notable in the more responsive trabecular bone (2.5%, 2779±140, 2709±92 m/s, p=0.06). KMgCit increased trabecular elasticity (4.2%, 2705±125, 2814±140 m/s, p<0.05), while exercise showed a similar trend (3.5%, 2701±121, 2798 ±100 m/s, p=0.08). Treatment with both exercise and KMgCit demonstrated a 1.9% increase, but included only 4 subjects. These findings suggest that KMgCit and exercise training are effective countermeasures against trabecular bone quality loss during prolonged periods in microgravity. Supported by NSBRI.