The Effects Of Exercise Training Mode On Biochemical Indices Of Bone Turnover And Bone Density In Untrained, Young Women

Abstract

PURPOSE The study was designed to examine the efficacy of either step aerobics or resistance exercise to induce positive changes in bone density in previously untrained, young women. METHODS Sixty-nine women between 20–35 years of age completed the first six months of a year long study investigating the effects of exercise mode or non-intervention (control) on changes in bone mineral density (BMD) and biochemical markers of bone turn-over. Those who completed the six month assessments were distributed as follows: step aerobics (SA) n=27; resistance training (RT) n=22; control (CON) n=20. Assessments for bone density (DEXA and Pixi scan) and biochemical markers of bone turnover (calcitonin, osteocalcin, NTx, PTH) were made at baseline and following six months of group assignment. Supervised exercise session were held three days/week for RT and SA. RESULTS There were no significant group differences at baseline for BMD. Unadjusted changes in BMD were significantly greater for heel BMD in SA than RT and CON (p<0.01). Lumbar 3 BMD and left leg BMD increased in SA more than in RT (p<0.05 for both). However, hip BMD was reduced in SA compared to RT (p<0.05). ANOVA revealed a significant time effect (p=0.042) but no interaction or group effect for calcitonin and a significant group effect for osteocalcin (p=0.50) with SA being significantly higher than RT. CONCLUSIONS Based on the results of this study, six months of SA or RT appear to produce positive but different effects on bone remodeling and BMD with minor changes in biochemical markers of bone turn-over. Supported by NIH grant #5 806 GM053933-06 and NASA grant #SAA2-401535