Acute effects of photobiomodulation therapy applied to respiratory muscles of chronic obstructive pulmonary disease patients: a double-blind, randomized, placebo-controlled crossover trial.

To investigate the effects of photobiomodulation applied to respiratory muscles on lung function, thoracoabdominal mobility, respiratory muscle strength, and functional capacity in COPD patients. This is a randomized double-blind crossover clinical trial. Twelve male COPD patients participated in the study. Participants were randomly allocated to receive two photobiomodulation sessions, 1 week apart: (1) an effective photobiomodulation session applied at the main respiratory muscles by means of a cluster with 69 light-emitting diodes (LEDs), containing 35 red (630 ± 10 nm; 10 mW; 0.2 cm2) and 34 near-infrared (830 ± 20 nm; 10 mW; 0.2 cm2) LEDs and (2) a sham photobiomodulation session, following the same procedures without emitting light. The primary outcomes were pulmonary function (spirometric indexes); thoracoabdominal mobility (cirtometry); respiratory muscle strength (maximal respiratory pressures), assessed at three moments: (1) baseline, (2) 1 h after intervention, and (3) 24 h after intervention; and the functional capacity, assessed by the 6-min walk test (6MWT) at baseline and 24 h after intervention. No significant interactions were found for spirometric variables, maximal respiratory pressures, and cirtometry. However, there was a Time × Condition interaction (F = 18.63; p = 0.001; η2p = 0.62) in the walked distance on the 6MWT, with a significant increase after photobiomodulation intervention (p < 0.01) compared with the baseline. Photobiomodulation applied to respiratory muscles was effective in improving acute functional capacity in COPD patients. To the best of our knowledge, this is the first study assessing the effects of photobiomodulation applied to respiratory muscles in patients with COPD.

Time-Response of Photobiomodulation Therapy by Light-Emitting Diodes on Muscle Torque and Fatigue Resistance in Young Men: Randomized, Double-Blind, Crossover and Placebo-Controlled Study.

Background: Photobiomodulation therapy (PBMT) by lasers or light-emitting diodes (LEDs) has been used in the last two decades to increase muscle performance in humans. The main findings of PBMT on muscle performance are increment in torque and number of muscle contractions, and fatigue resistance in high-intensity exercises. Although there are suggested light energies to be followed, the literature has also pointed out to a possible time-response of PBMT to increase exercise performance and recovery in humans. Objective: To investigate the possible time-response of PBMT by LEDs to increase muscle performance in young men regarding peak torque (PT), rate of torque development (RTD), fatigue resistance, and subjective perception of effort in maximal voluntary isometric contractions (MVIC) of elbow flexion. Methods: This randomized, double-blind, placebo-controlled, crossover trial with two arms enrolled 34 healthy and physically active young men, but 30 (21.10 ± 2.25 years old) completed all procedures. All volunteers were allocated into two equal arms (groups): PBMT (60 J; 1152 mW; 52 sec; and 166.75 cm2) applied on biceps brachii by a flexible array of LEDs, and placebo treatment. Each arm (n = 15) investigated the time-response (5 min, 1 h, 3 h, and 6 h) of PBMT in a randomized, double-blind, and crossover manner on the PT, RTD, fatigue resistance, and subjective perception of effort. Results: There were no significant results (p > 0.05) for all comparisons within and between groups regarding PT, RTD, fatigue resistance, and subjective perception of effort in MVIC of the elbow flexion in all time-response tested (5 min, 1 h, 3 h, and 6 h) before or after fatigue test. Only RTD did not decay significantly after fatigue test at all time-responses for PBMT group. Conclusions: PBMT was not effective to increase muscle performance and decrease fatigue to demonstrate the possible time-response in humans.