Effect of Tai Chi exercise with the same frequency and different exercise duration on the bone mineral density of older women

BACKGROUND: This study compared the effect of Tai Chi with the same frequency and different session duration on the bone mineral density (BMD) of older women. METHODS: Healthy older women aged 55-70 years were randomly divided into the short-time group (N.=17), long-time group (N.=18), and control group (N.=17). The BMD of L2-4 and the proximal femur were measured at baseline and after 48 weeks of intervention. RESULTS: From 0 to 48 weeks, the respective BMD values of L2-4 and the femoral neck in the short-time and long-time groups increased by 8.8% and 7.5% (P<0.01) and 8.8% and 12.7% (P<0.01), while the BMD of the greater trochanter in the control group decreased by 3.0% (P<0.05). After 48 weeks, the BMD of L2-4 and the femoral neck was greater in the short-time and long-time groups than the control group (P<0.001). CONCLUSIONS: Tai Chi for 30 or 60 minutes five times weekly for 48 weeks improves the BMD of L2-4 and the femoral neck in older women but does not affect the BMD of the greater trochanter and Ward's triangle. Increasing the exercise duration does not increase the effect of Tai Chi on BMD.