Effects of bone-specific physical activity on body composition, bone mineral density, and health-related physical fitness in middle-aged women

[Purpose] The study aimed to determine the effects of bone-specific physical activity on body composition, bone mineral density (BMD), and health-related physical fitness in middle-aged women. [Methods] One hundred eighty-six middle-aged women aged 31-49 years participated in this study. The subjects were divided into tertile groups according to the level of physical activity (low-score group, n=62; middle-score group, n=62; high-score group, n=62). Bone-specific physical activity participation was assessed using the bone-specific physical activity questionnaire. Body composition and BMD were measured using dual-energy X-ray absorptiometry. Health-related physical fitness test included isometric muscle strength (grip strength), muscular endurance (sit-ups), flexibility (sit and reach), and cardiorespiratory fitness (maximal oxygen uptake [VO_2max]). [Results] The high-score group had a significantly higher fat-free mass (p=.045, partial eta-squared value[η_p²]=.033) than the middle- and low-score groups, whereas the high-score group had significantly lower percent body fat (p=.005, η_p²=.056) than the other two groups. Whole-body BMD (p=.034, η_p²=.036) and lumbar BMD (p=.003, η_p²=.060) were significantly higher in the high-score group than in the low-score group. The high-score group performed significantly better for grip strength (p=.0001, η_p²=.101), sit-ups (p=.0001, η_p²=.108), and VO_2max (p=.0001, η_p²=.092) than the other two groups. [Conclusion] The present study suggests that bone-specific physical activity could be useful in improving body composition, BMD, and health-related physical fitness in middle-aged women, significantly enhancing their BMD and health conditions.