PURPOSE: The OPTIMA-Ex (Osteoporosis Prevention Through Impact and Muscle-loading Approaches to Exercise) trial aims to compare bone responses to two known osteogenic stimuli - impact exercise and resistance training in young women with lower than average bone mass.

METHODS: The trial is a three-arm, single-blind, single-centre, randomised controlled exercise intervention targeting healthy but sedentary women aged 18-30 years with lower than average bone mass (T-score ≤ 0). Participants were randomised to a 10 month, twice-weekly, either supervised high intensity impact training (IT), high intensity resistance training (RT) or home-based low intensity exercise (active control) (CON). Preliminary DXA (Medix DR) outcomes for lumbar spine (LS), dominant (D) and non-dominant (ND) femoral neck (FN); D and ND distal 1/3 radius (RAD) areal bone mineral density (aBMD) have been examined per-protocol, using repeated-measures ANCOVA adjusted for compliance, age, height, weight, total lifetime physical activity, dietary calcium and baseline values. DXA results are reported as mean difference ± SE, statistical significance set at p ≤ 0.05.

RESULTS: A total of 51 women (age=22.2±3.6 years; height=1.64±0.62 m; weight=58.1±8.7 kg) have been randomised (IT=17, RT=17, CON=17) with no between-group differences at baseline. Follow-up data is available for 22 participants (IT=6, RT=8, CON=8). Compliance currently differs between groups (IT=66.5±17.2%, RT=67.3±12.3%, CON=87.5±13.7%; p=0.011). There are no between-group differences in aBMD at any site. However, there are significant within-group differences in our primary outcome of LS aBMD for both IT (0.046±0.020 g/cm2; p=0.044) and RT (0.049±0.018 g/cm2; p=0.019). Additional within-group differences are present for ND FN (0.031±0.012 g/cm2; p=0.027) and ND RAD (0.047±0.020 g/cm2; p=0.036) aBMD for RT. A significant within-group difference is evident for ND (0.057±0.023 g/cm2; p=0.027) and D (0.061±0.024 g/cm2; p=0.029) RAD aBMD for CON.

CONCLUSIONS: Although minimal statistical power limits the conclusions that can be drawn from these preliminary data, results indicate both RT and IT improve spine bone mass, while RT may provide a broader osteogenic stimulus in young adult women with lower than average bone mass. Data collection is ongoing.