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 muscle with PBMT prior to fatiguing exercise include a safe and non-invasive 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, cross-over design.

Setting:

Laboratory.

Participants:

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

Intervention:

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].

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 < 0.02 to 0.001).

Conclusions:

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]