Trunk Muscle Strength is a Strong Predictor of Bone Loss in Postmenopausal Women

To clarify whether trunk muscle strength and self-reported exercise habits predict subsequent bone loss in healthy post- menopausal women, we examined 143 community-dwelling ambulatory postmenopausal Japanese women (age: 59.9 +/- 6.5 years) without any diseases affecting bone metabolism at baseline, and followed 109 of the 143 subjects for 4 years. Bone mineral density at baseline and at followup was measured at the spine by DEXA to determine the annual change in bone mineral density during the followup. Subjects who lost bone mineral density at an annual rate exceeding -1.78% (1 standard deviation below the mean rate) were defined as rapid bone losers. The isokinetic concentric and eccentric peak torques of the trunk flexors and extensors were measured at baseline. The exercise habits of the subjects were evaluated through detailed interviews. The eccentric trunk flexor and extensor torques were found to correlate with a positive dose-dependent effect on change in bone mineral density while exercise habits showed no correlation. The lower tertile group for the extensor torque showed a ten-fold greater risk for rapid bone loss compared with the upper tertile group. Postmenopausal women with decreased trunk muscle torque may be at increased risk for osteoporosis and should be a target group for preventive measures.Prognostic study, level II (prospective study). See the Guidelines for Authors for a complete description of the levels of evidence.