Effects of inspiratory or respiratory muscle training on respiratory function, perceived exertion, and exercise or functional performance in team-sport athletes: a systematic review and meta-analysis

Inspiratory muscle training (IMT) and respiratory muscle training (RMT) target respiratory muscle function in sport. This review evaluated effects on respiratory function, perceived exertion, and exercise or functional performance in team-sport athletes. This PROSPERO-registered review followed PRISMA 2020. PubMed, Embase, CENTRAL, SPORTDiscus, Web of Science, and Scopus were searched from inception through May 2026. Controlled studies comparing IMT/RMT or inspiratory muscle loading with usual training, sham/placebo, active training, or no additional respiratory training were included. Random-effects models used mean differences (MDs) for same-unit outcomes and standardized mean differences (SMDs) for heterogeneous outcomes. Sensitivity analyses, comparator subgroup analysis, RoB 2/ROBINS-I, and GRADE were applied. Ten studies were included. Main analyses yielded suggestive favourable estimates for inspiratory muscle strength (MD = 25.91 cmH2O, 95% CI 8.46 to 43.36), expiratory muscle strength (MD = 19.61 cmH2O, 95% CI 1.14 to 38.07), and exercise or functional performance (SMD = 0.85, 95% CI 0.19 to 1.52). Heterogeneity was considerable (I2 = 94%, 89%, and 75%, respectively). Small main-analysis differences were observed for FVC (MD = 0.21 L, 95% CI 0.02 to 0.39) and FEV1 (MD = 0.16 L, 95% CI 0.06 to 0.25), but FVC, FEV1, and expiratory muscle strength were no longer significant after excluding the paediatric non-randomized study. The exploratory performance estimate remained significant after excluding Konca et al. and Nunes Júnior et al. (SMD = 0.57, 95% CI 0.17 to 0.96; I2 = 0%), although the tests were conceptually distinct. Perceived exertion or dyspnea-related outcomes showed no clear effect (SMD = -0.20, 95% CI -0.80 to 0.41). Low- to very-low-certainty evidence suggests possible favourable effects on inspiratory muscle strength and selected performance outcomes. These signals are exploratory because of small samples, risk of bias, heterogeneity, measurement differences, and sensitivity to influential studies. Spirometric and expiratory muscle strength findings were not robust, and performance should not be interpreted as a unified construct. PROSPERO CRD420261400072.