| The period of peak bone mass accretion presents a window of opportunity to enhance a young woman's bone mass prior to age- and hormone-related bone loss. Resistance training offers a non-pharmacologic intervention strategy to assist in the prevention of osteoporosis. Therefore, the purpose of this study was to determine the effect of eccentric progressive resistance training (PRT) on bone mass, biochemical markers of bone metabolism, muscular strength, lean mass, exercise-induced muscle damage markers, and endogenous sex hormone levels in young women. Thirty-seven female volunteers aged 24.4 +/- 2.2 years were randomized to one of 3 groups: low-intensity (75% of a concentric 1-RM) eccentric PRT (LRT group), high-intensity (125% of a concentric 1-RM) eccentric PRT (HRT group), or control. Those randomized to exercise trained six muscle groups twice per week on non-consecutive days for 16 weeks. Measures of bone mass by DXA, muscular strength by 1-RM, serum osteocalcin, androstenedione, creatine kinase (CK), Interleukin-6 (IL-6) and urin deoxypyridinoline and creatinine were assessed at baseline, and weeks 4, 8, 12, and 16 in the training groups and at baseline and week 16 in the control group. Data were analyzed by ANOVA and ANCOVA to determine between, within, and interaction effects for the dependent variables (p ≤ 0.05). Concentric strength increased 20--65% in both groups. Bone mineral content of the lumbar spine significantly increased in the LRT group (0.855 +/- 0.958 g/cm) which was the only increases in bone mass measured in any group. Lean mass significantly increased in both the LRT (0.7 +/- 0.6kg) and HRT (0.9 +/- 0.9kg) groups. Osteocalcin significantly increased in the LRT group (165 +/- 61%) and deoxypyridinoline significantly decreased in the HRT group (56 +/- 53%). Serum CK significantly increased in the LRT group (47 +/- 51%). Lastly, no significant changes in androstenedione and IL-6 were measured in any group. These findings suggest that low-intensity eccentric PRT is more influential on bone mass, bone formation, muscular strength, and markers of muscle damage than high-intensity eccentric PRT. |
