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Identifying Dosage Effect of Light-Emitting Diode Therapy on Muscular Fatigue in Quadriceps

Hemmings, Thomas J.; Kendall, Kristina L.; Dobson, John L.

The Journal of Strength & Conditioning Research: February 2017 - Volume 31 - Issue 2 - p 395–402
doi: 10.1519/JSC.0000000000001523
Original Research

Hemmings, TJ, Kendall, KL, and Dobson, JL. Identifying dosage effect of light-emitting diode therapy on muscular fatigue in quadriceps. J Strength Cond Res 31(2): 395–402, 2017—The purpose of this study was to compare the effects of various dosages of light-emitting diode therapy (LEDT) on muscle fatigue while performing a single-leg extension to exhaustion. A total of 34 recreationally resistance-trained athletes between the ages of 18 and 26 participated in 4 trials. Each trial included pre-exercise/postexercise blood lactate measurements and 2 sets of 3 maximal voluntary isometric contractions (MVICs), followed by LEDT on 6 points across the superficial quadriceps. Each randomized trial consisted of a placebo, 30, 60, or 120 seconds on each point on the quadriceps. Three minutes after LEDT, the participants performed an eccentric leg extension with 120% of MVIC until fatigue. There was significant increase in the number of repetitions performed between the placebo treatment and 60 seconds (p = 0.023), as well as placebo and 120 seconds (p = 0.004) of irradiation on each point. There were no significant differences in blood lactate levels between any of the 4 trials. In conclusion, LEDT had a positive effect on performance when irradiating 6 points on the superficial quadriceps for 60 and 120 seconds before an eccentric leg extension.

Department of Health and Kinesiology, Georgia Southern University, Statesboro, Georgia

Address correspondence to Thomas J. Hemmings,

Copyright © 2017 by the National Strength & Conditioning Association.