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Optimum frequency of exercise for bone health : randomised controlled trial of a high-impact unilateral intervention . INTRODUCTION Exercise can increase bone strength , but to be effective in reducing fracture risk , exercise must be feasible enough to be adopted into daily life and influence potentially vulnerable skeletal sites such as the superolateral cortex of the femoral neck , where thinning is associated with increased fracture risk . Brief , high-impact exercise increases femoral neck bone density but the optimal frequency of such exercise and the location of bone accrual is unknown . This study thus examined ( 1 ) the effectiveness of different weekly frequencies of exercise on femoral neck BMD and ( 2 ) whether BMD change differed between hip sites using a high-impact , unilateral intervention . METHODS Healthy premenopausal women were randomly assigned to exercise 0 , 2 , 4 , or 7 days/week for 6 months . The exercise intervention incorporated 50 multidirectional hops on one randomly selected leg . BMD was measured by DXA at baseline and after 6 months of exercise . Changes in the exercise leg were compared between groups using ANCOVA , with change in the control leg and baseline BMD as covariates . RM-MANOVA was conducted to determine whether bone changes from exercise differed between hip sites . RESULTS 61 women ( age 33.6+/-11.1 years ) completed the intervention . Compliance amongst exercisers was 86.7+/-10.6 % . Peak ground reaction forces during exercise increased from 2.5 to 2.8 times body weight . The change in femoral neck BMD in the exercise limb ( adjusted for change in the control limb and baseline BMD ) differed between groups ( p=0.015 ) , being -0.3 % ( -1.2 to 0.6 ) , 0.0 % ( -1.0 to 1.0 ) , 0.9 % ( -0.1 to 2.0 ) and 1.8 % ( 0.8 to 2.8 ) in those exercising 0 , 2 , 4 and 7 days per week , respectively . When BMD changes at upper neck , lower neck and trochanter were compared using RM-MANOVA , a significant exercise effect was observed ( p=0.048 ) , but this did not differ significantly between sites ( p=0.439 ) despite greatest mean increases at the upper femoral neck . CONCLUSIONS Brief , daily hopping exercises increased femoral neck BMD in premenopausal women but less frequent exercise was not effective . Brief high-impact exercise may have a role in reducing hip fragility , but may need to be performed frequently for optimal response .
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Intervention_Physical
exercise
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Intervention_Physical
Exercise
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Intervention_Physical
exercise
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Intervention_Physical
Brief , high-impact exercise
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Intervention_Physical
exercise
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Intervention_Physical
exercise intervention
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Intervention_Physical
exercise
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Intervention_Physical
exercise
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Intervention_Physical
exercises
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Intervention_Physical
Brief high-impact exercise
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Outcome_Physical
bone health
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Outcome_Physical
bone strength
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Outcome_Physical
femoral neck bone density
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Outcome_Physical
femoral neck BMD
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Outcome_Physical
whether BMD change differed between hip sites
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Outcome_Physical
BMD
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Outcome_Physical
bone changes
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Outcome_Physical
Peak ground reaction forces
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Outcome_Physical
change in femoral neck BMD
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Outcome_Physical
BMD changes at upper neck , lower neck and trochanter
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Outcome_Physical
femoral neck BMD
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Outcome_Physical
hip fragility
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Participant_Condition
premenopausal women