Introduction: The OPTIMA-Ex (Osteoporosis Prevention Through Impact and Muscle-loading Approaches to Exercise) trial was designed to determine the most effective training method to improve indices of bone strength in young adult women with lower than average bone mass, through the comparison of two known osteogenic stimuli – targeted impact exercise and resistance training.
Methods: Healthy but sedentary women aged 18-30 years with lower than average bone mass (T-score≤0) were recruited and randomised to a 10 month, twice-weekly, supervised high intensity impact training (IT) or high intensity resistance training (RT), or unsupervised home-based very low intensity exercise (active control) (CON). DXA-derived (Medix DR, Medilink, France) lumbar spine (LS) aBMD served as the primary outcome measure, while secondary measures included dominant (DOM) and non-dominant (ND) femoral neck (FN) aBMD; DOM and ND distal third radius (RAD) aBMD. We present per protocol analyses, using repeated-measures ANCOVA (Bonferroni-adjusted) with change in height and change in extrinsic physical activity as covariates. Results are reported as adjusted mean differences ± SE, with statistical significance set at p≤0.05.
Results: A total of 51 women (age=22.2±3.6 years; height=1.64±0.62m; weight=58.1±8.7kg) were randomised (IT=17, RT=17, CON=17). No differences in bone outcomes were evident at baseline. Of the 51 that commenced, 32 participants completed the trial (IT=10, RT=12, CON=10). No between group effects were observed for any aBMD measure. Significant within-group differences in the primary outcome of LS aBMD were evident for both IT (0.041±0.011g/cm2; p=0.001) and RT groups (0.038±0.011g/cm2; p=0.001). Only the RT group exhibited an improvement in DOM FN aBMD (0.037±0.011g/cm2; p=0.003), with a non-significant trend evident for the ND FN (0.028±0.014g/cm2; p=0.058). All groups increased DOM RAD aBMD (IT=0.029±0.014, p=0.044; RT=0.039±0.013, p=0.005; CON=0.032±0.014, p=0.034). Compliance did not differ between groups (IT=61.36±15.1%; RT=66.38±11.2%; CON=78.8± 24.1%, p=0.085).
Conclusion: Although the conclusions that can be drawn from the study are constrained by limited statistical power, DXA observations suggest that RT may provide a more potent osteogenic stimulus than IT in young adult women with lower than average bone mass.