الفهرس 
Effect of different pre application time intervals of light emitting diode therapy on muscle fatigue
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Abstract
Background: Although Photobiomodulation therapy (PBMT) had shown its effectiveness as a muscular preconditioning modality to resist fatigue, the identification of the best point of time to irradiate muscle tissue is contradictory and needs further investigation. purpose: To detect the time of optimum response of PBMT by near-infrared (NIR) light emitting diode (LED) on muscle fatigue resistance of elbow flexor muscles. Design: A randomized, single blind, pre{u2013}test post-test, placebo-controlled crossover study. Participants: Forty-five healthy nonathletic participants of both sexes were randomly allocated to 3 equal groups: 5 minutes, 1-hour or 5-hours groups. Interventions: Each group (number=15) received either active(60J) or placebo(0J) (conditions) NIR-LED of 890 nm wavelength at the first session before fatigue inducing exercise; by 5 minutes, 1 hour, or 5 hours according to their random allocation within the groups and application condition, then after 7 days washout period, received the other condition of NIR-LED before exercise at the second session. Outcome measures: each session using isokinetic dynamometer, isometric peak torque (IMPT) and isokinetic peak torque (IKPT) were evaluated at base line and post exercise as well as assessing strength loss index (SLI) and number of repetitions to reach fatigue (NRRF) post exercise. Results: Pre NIR-LED application there was no statistically significant difference between groups and between conditions in IMPT and IKPT (p > 0.05). There was a statistically significant decrease in IMPT and IKPT post treatment compared with that pre-treatment (p < 0.01), but the 5 minutes group showed the least percent of decrease compared to other groups. There was a statistically significant decrease in SLI and statistically significant increase in NRRF in the 5 minutes group in active condition compared with that of 1 hour and 5 hours groups and compared to the placebo condition (p < 0.05)