Effects of physical activity and menopausal hormone replacement therapy on postural stability in postmenopausal women--a cross-sectional study.

Objectives: Poor postural stability and muscular strength in postmenopausal women are associated with increased risk of falls and fractures. This study examined whether these risk factors for falls differed according to habitual physical activity and menopausal hormone replacement therapy (HRT) use.

Methods: Subjects were 117 postmenopausal women (mean age 65.3+/-6.0 years); of whom 70 had taken HRT for at least 5 years (42 tibolone and 28 transdermal oestradiol), whilst 47 had not received HRT. Duration of physical activity was assessed with monitors worn on a waist belt. Subjects were grouped into low (LPA; < or = 15 min day(-1)) or high (HPA; >15 min day(-1)) physical activity. Postural stability was assessed using a swaymeter which measured displacement at the waist. Maximal isometric strength of knee flexors was determined in 23 of the tibolone group, 26 of the oestrogen group and 12 of the no therapy group.

Results: Stature and body mass did not differ according to physical activity participation or HRT use, although the more active women were on average 2.5 years younger than the less active women. Body sway was lower in more physically active women in three of the four measurement conditions (P<0.05) and this effect persisted after inclusion of age as covariate. Body sway tended to be highest in the no therapy group, although not significantly so. Mean knee extensor strength was higher in women taking tibolone and oestrogen than in those not on therapy (115.3 (5.2), 118.2 (7.2) and 97.6 (9.3) Nm, respectively), although again this difference was not statistically significant.

Conclusions: The more physically active postmenopausal women had significantly better postural stability than less active women, whilst HRT had no significant effect. Physical activity might thus have a role in reducing the risk of fracture through reducing the risk of falling.