Effects of Photobiomodulation Therapy on Muscle Strength and Muscle Endurance: A Systematic Review and Meta-Analysis.

OBJECTIVES: To investigate the effects of photobiomodulation therapy (PBMT) on muscle strength and muscle endurance and to explore potential sources of variation related to participant characteristics and intervention parameters. DATA SOURCES: A systematic search was conducted in PubMed, CENTRAL, Scopus, Medline, EBSCOhost, and Web of Science from inception to November 2025. STUDY SELECTION: Randomized controlled trials (RCTs) evaluating the effects of PBMT on muscle performance in healthy humans were selected. Two reviewers independently screened titles and abstracts. Studies were included if they compared PBMT to a placebo control using quantitative outcome measures. DATA EXTRACTION: Data regarding participant characteristics, intervention protocols, and outcomes were extracted independently by two investigators using a standardized form. Methodological quality was assessed using the Cochrane Risk of Bias 2 tool. DATA SYNTHESIS: Twenty-three RCTs were included and pooled using a random-effects model. PBMT showed small effects on muscle endurance (p = 0.02) and muscle strength (p = 0.04). Subgroup differences were mostly nonsignificant. Muscle endurance benefits were found in athletes (p = 0.05), but not in physically active individuals (p = 0.07). For muscle endurance, favorable parameters included ≤100 mW per diode (p = 0.03), 31-100 J (p = 0.05), a 1-3 min pre-exercise interval (p = 0.03), and ≤4 application sites (p = 0.007). Strength improved with 151-300 J (p = 0.05) and when the interval was over 3 min (p = 0.007). CONCLUSIONS: PBMT may modestly improve muscle endurance and muscle strength, particularly for endurance-related outcomes. However, subgroup findings remain exploratory, and current evidence is insufficient to define optimal protocols. Further high-quality trials are needed to standardize PBMT parameters for sports performance and rehabilitation.