Therapeutic Photobiomodulation Before Strenuous Exercise Attenuates Shoulder Muscle Fatigue

Context: Photobiomodulation therapy (PBMT) applied as a preconditioning treatment before exercise has been shown to attenuate fatigue and improve skeletal muscle contractile function during high-intensity resistance exercise. Practical implications for preconditioning muscles with PBMT before fatiguing exercise include a safe and noninvasive means to enhance performance and reduce the risk of musculoskeletal injury. Objective: To examine the muscle fatigue–attenuating effects of PBMT on performance of the shoulder external-rotator muscle group when applied as a preconditioning treatment before high-intensity, high-volume resistance exercise. Design: Sham-controlled, crossover design. Setting: Laboratory. Patients or Other Participants: Twenty healthy men (n ¼ 8) and women (n ¼ 12) between the ages of 18 and 30 years. Intervention(s): Photobiomodulation therapy was administered using a near-infrared laser (k ¼ 810/980 N·m, 1.8 W/cm², treatment area ¼ 80–120 cm²) to the shoulder external-rotator muscles at a radiant exposure of 10 J/cm². Participants performed 12 sets of isokinetic shoulder exercise. Each set consisted of 21 concentric contractions of internal and external rotation at 608/s. The sets were subdivided into 3 blocks of exercise (block 1: sets 1–4; block 2: sets 5–8; block 3: sets 9–12). Main Outcome Measure(s): Normalized peak torque (N·m/kg), average peak torque (N·m), total work (N·m), and average power (W). Results: During the last block of exercise (sets 9–12), all performance measures for the active PBMT condition were 6.2% to 10% greater than the sham PBMT values (P, .02 to P, .001). Conclusions: Photobiomodulation therapy attenuated fatigue and improved muscular performance of the shoulder external rotators in the latter stages of strenuous resistance exercise.