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 muscle with PBMT prior to fatiguing exercise include a safe and non-invasive means to enhance performance and reduce the risk of musculoskeletal injury.


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.


Sham-controlled, cross-over design.




Twenty healthy men (n=8) and women (n=12) between the age of 18 and 30.


PBMT was administered using a near-infrared laser (λ=810/980nm, 1.8 W/cm2, treatment area = 80cm2-120 cm2) to the shoulder external rotator muscles at a radiant exposure of 10 J/cm2. Subjects performed 12 sets of isokinetic shoulder exercise. Each set consisted of 21 concentric contractions of internal and external rotation at 60°/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 Measures:

normalized peak torque [Nm/kg], average peak torque [Nm], total work [Nm], and average power [W].


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 < 0.02 to 0.001).


PBMT attenuated fatigue and improved muscular performance of the shoulder external rotators in the latter stages of strenuous resistance exercise.

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Author notes

Co-Author Title and Contact:

John W. Stauffer, Graduate Student. [email protected]

David Levine, Emeritus Professor and Walter M. Cline Chair of Excellence in Physical Therapy. [email protected]

R. Barry Dale, Professor and Chair. [email protected]

Paul Borsa, Associate Professor. [email protected]