Postural control is associated with muscle power in post-menopausal women with low bone mass

Older women with low bone mass are at higher risk of fracture and there is limited data on what is associated with risk of falls. We found explosive jumping to relate most strongly to postural control. It may be beneficial to include power or speed training into falls prevention programs.

INTRODUCTION

Post-menopausal women with low bone mass are at higher risk of bone fractures subsequent to falls. Understanding the correlates of postural control in this collective informs intervention design for falls prevention.

METHODS

We examined postural control in single-leg stance on stable and unstable surfaces in 63 community-dwelling post-menopausal women with osteopenia or osteoporosis but without diagnosed neuromuscular, vestibular or arthritic diseases. Postural measures were compared to countermovement jump performance (height, force and power), leg-press strength (10 repetition maximum), calf muscle area and density (via peripheral quantitative computed tomography), body mass, height and age.

RESULTS

On step-wise regression, peak countermovement jump power and jump height (p ≤ 0.014), but not jump force, leg-press strength or calf muscle size, were related to postural control in single-leg stance on, respectively, an unstable surface (eyes open) and standing on a stable surface (eyes open). None of the parameters measured were significantly related to the postural control parameters in single-leg stance on a stable surface with eyes closed. With testing on the stable surface, body mass was associated with slow mean centre of pressure movement speed (p ≤ 0.030).

CONCLUSIONS

Our findings show that, in post-menopausal women with low bone mass, neuromuscular power is a more important determinant of postural control than muscle strength or size. Our findings provide evidence to support the integration of power or speed training into falls prevention and balance training programs in post-menopausal women with osteopenia and osteoporosis.

Vibration or balance training on neuromuscular performance in osteopenic women

Maintaining neuromuscular function in older age is an important topic for aging societies, especially for older women with low bone density who may be at risk of falls and bone fracture. This randomized controlled trial investigated the effect of resistive exercise with either whole-body vibration training (VIB) or coordination/balance training (BAL) on neuromuscular function (countermovement jump, multiple 1-leg hopping, sit-to-stand test). 68 postmenopausal women with osteopenia or osteoporosis were recruited for the study. 57 subjects completed the 9-month, twice weekly, intervention period. All subjects conducted 30 min of resistance exercise each training day. The VIB-group performed additional training on the Galileo vibration exercise device. The BAL-group performed balance training. An "intent-to-treat" analysis showed greater improvement in the VIB-group for peak countermovement power (p=0.004). The mean [95% confidence interval] effect size for this parameter was a  + 0.9[0.3 to 1.5] W/kg greater change in VIB than BAL after 9 months. In multiple 1-leg hopping, a significantly better performance in the VIB-group after the intervention period was seen on a "per-protocol" analysis only. Both groups improved in the sit-to-stand test. The current study provides evidence that short-duration whole-body vibration exercise can have a greater impact on some aspects of neuromuscular function in post-menopausal women with low bone density than proprioceptive training.

Bone strength and density via pQCT in post-menopausal osteopenic women after 9 months resistive exercise with whole body vibration or proprioceptive exercise

OBJECTIVES

In order to better understand which training approaches are more effective for preventing bone loss in post-menopausal women with low bone mass, we examined the effect of a nine-month resistive exercise program with either an additional whole body vibration exercise (VIB) or balance training (BAL).

METHODS

68 post-menopausal women with osteopenia were recruited for the study and were randomised to either the VIB or BAL group. Two training sessions per week were performed. 57 subjects completed the study (VIB n=26; BAL n=31). Peripheral quantitative computed tomography (pQCT) measurements of the tibia, fibula, radius and ulna were performed at baseline and at the end of the intervention period at the epiphysis (4% site) and diaphysis (66% site). Analysis was done on an intent-to-treat approach.

RESULTS

Significant increases in bone density and strength were seen at a number of measurement sites after the intervention period. No significant differences were seen in the response of the two groups at the lower-leg.

CONCLUSIONS

This study provided evidence that a twice weekly resistive exercise program with either additional balance or vibration training could increase bone density at the distal tibia after a nine-month intervention period in post-menopausal women with low bone mass.