Effects of 12-week combined resistance and aerobic training on body composition and functional capacity in middle-aged adults

Purpose: This study investigated the effects of a 12-week combined resistance and aerobic training programme on body composition, muscle strength, and aerobic capacity in sedentary middle-aged adults. Additionally, it evaluated whether changes in phase angle, a non-invasive marker of cellular health, were associated with improvements in functional outcomes. Methods: Sixty-four sedentary adults (32 males and 32 females; age 51.3 ± 6.2 years) were enrolled in a 12-week, supervised combined training intervention. Sessions were held 3 times per week and comprised resistance and aerobic components with progressively increasing volume and intensity. Assessments of body composition (fat mass, fat-free mass, phase angle), handgrip strength, and aerobic capacity (estimated VO2max) were performed at baseline, 6, and 12 weeks. Pearson’s correlations and regression analyses were used to explore associations between changes in body composition and functional measures. Results: The combined training resulted in significant reductions in body mass (- 2.3 ± 0.9 kg) and fat mass (- 3.6 ± 1.1 kg), alongside increases in fat-free mass (+ 1.8 ± 0.7 kg) and phase angle (+ 0.6 ± 0.2°, p<0.001). Handgrip strength improved by + 4.2 ± 1.3 kg in males and + 3.1 ± 1.1 kg in females (p<0.001), while estimated VO2max rose by + 4.6 ± 1.5 ml/kg/min. Changes in phase angle were strongly positively correlated with improvements in handgrip strength (r = 0.68) and VO2max (r = 0.57). Regression models identified phase angle and fat-free mass as independent predictors. Conclusions: A 12-week combined resistance and aerobic training programme effectively improved body composition, muscle strength, and aerobic capacity in sedentary middle-aged adults. Furthermore, increases in phase angle were strongly associated with functional improvements, suggesting it may serve as a valuable biomarker to track the effects of multicomponent training.