This study aimed to investigate the effects of respiratory muscle strength training on respiratory function and cardiorespiratory endurance in adults participating in aerobic exercise, and to provide foundational data for the advancement of community-based physical activity programs. The study subjects were 20 adults, regardless of gender, aged 19-29 years, who participated in a running club and exercised regularly at least twice a week. They used a resistance-based respiratory muscle exercise machine provided by the researcher to perform maximal effortful expiration and inhalation. The group that performed respiratory muscle strength training in conjunction with aerobic exercise showed greater improvements in respiratory function (FEV₁/FVC) than the group that performed aerobic exercise only. The group that performed respiratory muscle strength training in conjunction with aerobic exercise showed greater improvements in cardiorespiratory endurance (20 m shuttle run) than the group that performed aerobic exercise only. Respiratory muscle strength training performed alongside aerobic exercise significantly improved respiratory function (FEV₁/FVC). Respiratory muscle strength training performed alongside aerobic exercise significantly improved cardiorespiratory endurance (20 m shuttle run). These findings suggest that incorporating respiratory muscle strength training into aerobic exercise programs can significantly enhance respiratory muscle function and cardiorespiratory endurance. Therefore, it is recommended that such training be adopted as a supplementary intervention to improve overall physical fitness and exercise performance among adults engaged in aerobic activity.