Effects of a 16-Week Recruit Training Program on Bone Turnover Markers and Bone Mineral Density

Abstract

Military recruits exhibit a high rate of stress fracture (SF) during training. SF susceptibility during strenuous training may result from changes in bone turnover that favor bone resorption. This may compromise bone strength at fracture prone sites through transient changes in bone mineral density (BMD). PURPOSE: To monitor changes and gender disparity in markers of bone turnover and BMD during a 16-wk recruit training program. METHODS: Healthy men (n=26) and women (n=61) (19.2±0.7 yr) entering a 16-wk gender integrated basic training program in the Israeli Defense Forces volunteered for this study. Serum bone formation (BAP and PINP) and resorption (CTx and TRAP5b) markers were assessed at baseline, 8-wks, and 16-wks. Total body (TB) and lower extremity (LE) BMD were analyzed by DXA at 0 and 16-wks. A repeated measures ANOVA was used to analyze changes over time and between genders. Post hoc analyses were used to analyze significant main effects and interactions. RESULTS: Data (mean±SD) are presented in the following table:Table: † = main effect of gender across time, p<0.05; * = main effect of time for both genders, p<0.05Bone turnover markers were higher in men than women (p<0.01). Bone formation markers increased over time for men and women (p<0.01), while bone resorption markers were unchanged. TB BMD did not differ between genders, however LE BMD was greater in men (p=0.03). There was a slight gain in TB BMD over 16-wks in men (2%) and women (1%). LE BMD increased in males (1%) (p<.05), not in females. CONCLUSION: 16-wks of military training resulted in an increase in serum bone formation markers that was accompanied by a small increase in BMD in men and women, suggesting strenuous exercise results in overall changes that favor bone formation.