Respiratory Muscle Training Combinations in Amateur Runners: A Randomized Trial of Pulmonary Function, Respiratory Muscle Strength, and Exercise Capacity

BACKGROUND: Amateur runners may benefit from combining respiratory muscle training (RMT) with resistance or aerobic modalities, but direct comparisons are scarce. This study compared different RMT-based combinations on pulmonary function, respiratory muscle strength, and whole-body exercise capacity. METHODS: In this randomized four-arm trial, 48 amateur runners were allocated equally to stand-alone RMT, RMT plus upper-limb resistance (RMT + ULRT), RMT plus lower-limb resistance (RMT + LLRT), or RMT plus aerobic exercise (RMT + AET). All groups completed supervised sessions three times per week for six weeks. Pulmonary function (forced vital capacity [FVC], forced expiratory volume in one second [FEV1], FEV1/FVC), respiratory muscle strength (maximal inspiratory and expiratory pressures, MIP and MEP), and cardiopulmonary exercise test indices (peak oxygen uptake [VO2peak], VE/VCO2 slope) were assessed before and after training using standardized spirometry, mouth-pressure measurements, and treadmill cardiopulmonary exercise testing (CPET). Pre-post changes within groups and the overall between-group differences were evaluated using standard parametric methods. RESULTS: All four interventions were associated with improvements in at least one respiratory or cardiopulmonary domain. FVC and FEV1 tended to improve more in the resistance-combination groups, whereas the FEV1/FVC ratio increased with RMT alone and when combined with resistance. MIP increased in the RMT, RMT + ULRT, and RMT + LLRT groups, and MEP increased across all groups. VO2peak rose in every group, while the VE/VCO2 slope improved only when RMT was combined with upper- or lower-limb resistance or aerobic exercise. Between-group differences in change scores were not statistically significant and did not clearly favor any single regimen. CONCLUSIONS: In amateur runners, six weeks of RMT-based programs are feasible and associated with domain-specific improvements in lung function, respiratory muscle strength, and exercise capacity. Because between-group differences in change scores were not statistically significant and the sample size was modest, these findings should be considered exploratory and may inform hypothesis generation regarding the use of different RMT combinations in future, larger trials.