Regional changes in indices of bone strength of upper and lower limbs in response to high-intensity impact loading or high-intensity resistance training

Abstract

It is well known that the bone response to physical activity is highly dependent on the nature of the loads imposed. Despite this, few direct comparisons of the effect of impact-style loading and resistance training on bone have been made. We therefore aimed to compare the effects of 10-month, twice-weekly, high-impact loading and 10-month, twice-weekly, high-intensity resistance training on indices of bone strength of both the upper and lower limbs of young adult women. Physically inactive, otherwise healthy, young adult women (18-30years) with below average bone mass (T-score≤0) were recruited as part of the OPTIMA-Ex trial. Testing included DXA- and pQCT-derived measures of bone mass and indices of bone strength and QUS-derived measures of bone quality of the dominant (D) and non-dominant (ND) upper (radius) and lower limbs (femoral neck, tibia, calcaneus). The present study examined those participants who completed the impact training (IT; n=10) and resistance training (RT; n=12) arms of the trial. Age differed between groups at baseline (IT=23.2±3.8years, RT=20.5±1.8years; p=0.042). Compliance with the training programs did not differ (IT=61.4±15.1%, RT=66.4±11.2%, p=0.381). Age and baseline differences in bone outcomes served as covariates for repeated measures and univariate ANCOVA conducted for dependent variables and percent change respectively. IT improved distal pQCT-derived bone mineral density (BMD) of the upper limb (ND radius: total BMD=8.55±2.26% versus 1.50±2.04%, p=0.040 and trabecular BMD=1.86±0.90% versus -1.30±0.81%, p=0.029) and lower limb (ND tibia trabecular BMD=1.22±0.55% versus -0.82±0.50%, p=0.017), more than RT. IT also improved upper limb bone strength index (BSI) (ND radius total BSI=15.35±2.83% versus 2.67±2.55, p=0.005) and lower limb BSI (D tibia total BSI=5.16±1.13% versus 0.37±1.02%, p=0.008; D tibia trabecular BSI=3.93±1.76% versus -2.84±1.59, p=0.014, ND tibia trabecular BSI=3.57±1.63% versus -3.15±1.48%, p=0.009) more than RT. Conversely, RT improved DXA-derived cortical volumetric BMD at the femoral neck more than IT (3.68±1.99% versus -4.14±2.20%, p=0.021). Results suggest that IT and RT provide differing site-specific effects in both the upper and lower limbs, with superior bone responses observed at the distal segment from IT, while RT appeared to have greater effect on the shaft of the bone, on indices of bone-strength in young adult women.