Effects of vibration and exercise training on bone mineral density and muscle strength in post-menopausal women

The purpose of this study was to compare the effects of a specific vibration programme with those of combined aerobic and resistance exercise training on bone mineral density (BMD), body composition, and muscular strength in post-menopausal women, over a period of 6 months. Thirty-two healthy, inactive post-menopausal women aged 46-62 years were divided into exercise (n = 10), vibration (n = 13), and control (n = 9) groups. The exercise group participated in a supervised programme of strength training at 70% of one-repetition maximum (1-RM) 2 days a week, and aerobic exercise at 70-85% of maximum heart rate one day a week. The vibration group performed vibration training 3 days a week (9 sets x 45-80 s per session, 35-40 Hz, peak-to-peak amplitude of vertical vibration = 1.5 mm) on a vibration platform (NemesTM LCB, Bosco System). The BMD of the lumbar spine (L2-L4) was assessed using dual-energy X-ray absorptiometry, and muscle strength with the 1-RM method at baseline and after 6 months of intervention. The BMD of L2-L4 increased in the exercise group (P < 0.05), remained steady in the vibration group, and decreased in the control group (P < 0.05). Muscular strength of leg-extension and leg-curl exercise improved by 28% and 25.5% (P < 0.01) in the exercise group and by 13% (P < 0.01) and 20.5% (P < 0.001) in the vibration group, respectively. The results indicate that conventional training contributed to the increase in BMD of L2-L4, while the vibration programme helped to maintain BMD in post-menopausal women. Both training programmes were efficient in improving muscle strength.