Effects of Exercise Types on Muscle Strength and Body Composition in Men and Women: A Systematic Review and Meta-analysis

The aging of the population and lack of physical activity are major public health problems occurring worldwide. Further accelerating aging and lack of physical activity cause sarcopenia and obesity and affect the development of numerous related diseases. Physical activity plays a very important role in preventing and improving problems such as decreased physical ability, sarcopenia, and sarcopenic obesity. Although numerous types of exercises have been developed, endurance training (ET) and resistance training (RT) continue to receive sustained attention due to their exceptional exercise benefits. ET has various positive effects on the human body, including weight management, fat loss, bone health, and improvement of renal vascular function. RT strongly stimulates protein metabolism and muscle protein synthesis, promoting increases in muscle strength and muscle mass. Concurrent training (CT), which combined both ET and RT, can produce greater improvements in muscle strength and body composition compared to either intervention alone, provided that the appropriate exercise intensity and methods are applied. However, excessive exercise or inappropriate exercise programs may interfere or inhibit nerve adaptation and physical fitness improvement. In addition, the human body's response after exercise intervention varies depending on individual characteristics such as age, gender, and race. In particular, it has been proven that there are differences in body composition distribution, hormones, and energy metabolism depending on gender, and these are factors that can affect the human body's adaptation process after exercise. Therefore, the purpose of this study are to provide important information for the development and research of practical exercise programs according to sex by comparing the effects of exercise types on muscle strength and body composition in men and women through meta-analysis. In this study, a systematic literature search was conducted targeting articles published until April 30, 2024, utilizing the PubMed/Medline, Web of Science, CINAHL, and EBSCO databases. Keywords such as 'endurance training', 'resistance training', 'concurrent training', and 'muscle strength', 'body composition', and 'sex characteristics', and 'men and women' were combined and searched. Through systematic literature search, a total of 25 studies were finally included in the meta-analysis. Group-specific pre-post values were presented by exercise type and sex and standardized effect sizes were calculated using Hedges's g random-effects model. The standardized mean difference (SMD) calculated using the Hedges's g random effect model or fixed effect model were presented by classifying men and women and using the pre-post values in the group for each exercise type. The analysis results were presented through a forest plot with a 95% confidence interval (CI). According to the analysis results, the CT showed the greatest effect size on the increase in 'leg press' muscle strength in men (SMD, 2.33; 95% CIs, 1.40 to 3.25; p = .000), and the RT showed the greatest effect size in the women group (SMD, 3.38; 95% CIs, 1.04 to 5.71; p = .005). The CT group showed the greatest effect size in both men and women in increasing the 'Bench press' muscle strength (men: SMD, 2.25; 95% CIs, 0.77 to 3.74; p = .003, women: SMD, 2.89; 95% CIs, 0.25 to 5.54; p = .032). The RT group (men SMD, 0.21; 95% CIs, -0.01 to 0.43; p = .056, women: SMD, 0.22; 95% CIs, -0.03 to 0.74; p = .000) and the CT group (men: SMD, 0.22; 95% CIs, -0.04 to 0.48; p = 0.091, women: SMD, 0.24; 95% CIs, -0.06 to 0.55; p = .121) showed a small effect size of lean mass reduction in both men and women, and ET did not significantly affect the increase in lean mass in men and women (men: SMD, -0.12; 95% CIs, -0.45 to 0.20; p = .465, women: SMD, 0.10; 95% CIs, -0.29 to 0.50; p = .607). ET (SMD, -0.36; 95% CIs, -0.60 ∼ -0.12; p = .003) and CT (SMD, -0.28; 95% CIs, -0.53 ∼ -0.03; p = .029) significantly reduced fat mass in men. However, there were no significant changes in fat mass observed in any exercise type group among women. In conclusion, for men, CT is considered to be the most efficient type of exercise, as it is effective in both increasing upper and lower body muscle strength, increasing lean mass, and reducing fat mass. RT was most effective in increasing muscle strength in the women group, and ET was most effective in reducing fat mass. However, it is difficult to corroborate these results due to the lack of the number of study samples included in the analysis and the differences in exercise methods, subject age, and exercise duration. Therefore, it is considered that additional systematic literature review and meta-analysis considering these limitations are necessary in further studies.