Effects of 18 months of multicomponent exercise training on body composition, bone parameters, and muscle strength in healthy young men with normal-to-high baseline bone mineral density

Abstract

This single-arm prospective longitudinal study examined the effects of 18 months of supervised multicomponent exercise training on body composition, bone mineral density (BMD), and isokinetic muscle strength in healthy young men with normal-to-high baseline bone mineral density (mean Z-score = –0.05 ± 0.46). Sixty young men (mean age 18.68 ± 0.85 years) completed the 18-month program, which included aerobic, resistance, flexibility, and impact/power training sessions. Whole-body dual-energy X-ray absorptiometry (DXA) was used to assess body composition and bone parameters before and after the intervention. Isokinetic muscle strength was measured in a subgroup of 15 participants using a Biodex System 4 Pro dynamometer at 60°/s. Training led to significant increases in BMD at multiple sites, including the upper limbs, pelvis, thoracic spine, and whole body (all p  < 0.01 or p  < 0.001). Regional lean mass and isokinetic muscle strength also improved, particularly at the shoulder, wrist, and knee joints. However, these positive musculoskeletal changes were accompanied by significant increases in whole-body fat mass, fat percentage, and central adiposity indices (including fat mass index, waist-to-hip ratio, and trunk-to-limb fat ratio, all p  < 0.05). Muscle-to-bone ratios decreased across several regions. In healthy young men with normal-to-high baseline BMD, 18 months of multicomponent exercise training was associated with improvements in bone mineral density and muscle strength. However, these benefits were accompanied by increases in fat mass and central adiposity. Nutritional monitoring may be important to optimize the overall body composition response to such training. Further randomized controlled trials are needed to confirm these observations.