The Effects of Concurrent Training Versus Aerobic or Resistance Training Alone on Body Composition in Middle-Aged and Older Adults: A Systematic Review and Meta-Analysis

Introduction and Aim: The beneficial effects of aerobic training (AT) on preventing excess fat mass, and of resistance training (RT) on skeletal muscle adaptation, are well established. However, the effects of concurrent training (CT) compared to AT or RT alone on body composition in middle-aged and older adults are less understood, and therefore, the focus of this meta-analysis. Methods: Three databases, including PubMed, Web of Science, and Scopus, were searched from inception to March 2024. Randomized trials were included if they compared CT versus either AT or RT, and included body composition measures such as fat mass, body fat percentage, waist circumference, visceral fat mass, lean body mass (LBM), muscle mass/volume, or muscle or muscle fiber cross-sectional area (CSA), in middle-aged (50 to <65 years) and older adults (>= 65 years). Weighted mean differences (WMD) or standardized mean differences (SMD) and 95% confidence intervals (CIs) were calculated using random effects models. Results: A total of 53 studies involving 2873 participants were included. Overall, CT increased body weight and LBM significantly more, trending toward significantly larger increases in muscle mass and CSA, compared with AT alone. However, there were no significant differences between CT and RT alone, for body weight, BMI, body fat percentage, fat mass, waist circumference, or visceral fat mass. Conclusions: CT is as effective as AT for decreasing body fat measures and as effective as RT for increasing muscle mass in middle-aged and older adults, and it should be recommended accordingly.