Bone Density and Physical Function in Postmenopausal Women After a 12-Month Water Exercise Intervention

Abstract

2015 Exercise may be the most effective strategy to reduce osteoporotic fractures in older adults because of its potential to reduce bone loss and fall risk. It is unclear whether water exercise is an effective strategy to reduce fracture risk in postmenopausal women. PURPOSE: To examine the effects of a 12-month shallow water exercise program on bone mineral density (BMD) and physical function in postmenopausal women. METHODS: We recruited 59 women (≥5 years past menopause; 27 exercisers and 32 controls) and evaluated subject characteristics (weight and age), BMD (anterior-posterior spine, total hip, femoral neck) by dual energy x-ray absorptiometry, and physical function (leg power, arm endurance, cardiorespiratory fitness, flexibility) at baseline and 12 months. The exercise group participated in a 45-minute shallow water exercise class 3 times per week for 12 months, while the control group was asked to maintain initial activity levels. RESULTS: Using ANCOVA (covariates: initial BMD and weight) BMD difference scores at the spine, total hip, and femoral neck were similar between exercisers and controls after the 12-month intervention (p = 0.14–0.31). However, one-sample t-tests revealed that over the 12-months, femoral neck BMD decreased 3.0% in controls (p<0.01) but did not change in exercisers (p = 0.98). Using ANCOVA to evaluate difference scores in physical function, (covariates: baseline weight and age), leg power, arm endurance, and flexibility were not different between the groups, whereas exercisers exhibited greater cardiorespiratory fitness after 12-months of water exercise than controls (p = 0.03). One-sample t-tests revealed that exercisers increased leg power (+14.1%, p = 0.01) and flexibility (+11.4%, p<0.01), while controls did not change. CONCLUSION: Maintenance of BMD in exercisers at the femoral neck, a clinically relevant fracture location, provides preliminary evidence that shallow water exercise may be an effective alternative to land-based exercise programs. Furthermore, we conclude that shallow water exercise is an effective means of maintaining and improving physical function as women age. Funded by the John C. Erkkila, M.D. Endowment for Health and Human Performance, the Aquatic Exercise Association, and the BRL Clinical Program.