Effects of resistance training with/without Photobiomodulation on muscle and respiratory function in difficult-to-control asthma: a randomized trial

Difficult-to-Control Asthma (DTCA) is characterized by persistent symptoms, frequent exacerbations, and reduced functional capacity despite optimized pharmacological therapy. Patients with DTCA commonly exhibit peripheral muscle dysfunction, making strategies that may potentiate the effects of resistance training clinically relevant. Photobiomodulation therapy (PBMT) has been investigated as a modality capable of improving muscle performance and exercise tolerance. The aim of this study was to determine whether combining resistance training with LED-based PBMT (RT+LEDT) results in greater improvements in peripheral muscle strength and functional exercise capacity compared with resistance training alone in adults with DTCA. This randomized, triple-blind controlled trial included 30 adults with DTCA who met predefined inclusion and exclusion criteria. Participants were allocated equally to an experimental group (RT+LEDT; n = 15) or a control group (RT; n = 15). Both groups completed supervised resistance training twice weekly for 12 weeks. The experimental group received active PBMT before each session, while the control group received placebo PBMT. The primary outcome was peripheral muscle strength assessed by one-repetition maximum (1RM). Secondary outcomes included cardiopulmonary exercise test variables, shuttle walk test performance, spirometry, physical activity level, and asthma control. Post-intervention group comparisons were performed using independent t-tests. Compared with RT alone, RT+LEDT produced greater post-treatment gains in 1RM strength across major muscle groups, along with significant improvements in oxygen consumption at the anaerobic threshold and shuttle walk test distance. No between-group differences were observed in pulmonary function or asthma control. PBMT combined with resistance training yielded clinically meaningful improvements in muscle strength and functional capacity, suggesting its potential as an adjunctive strategy in rehabilitation programs for DTCA.