Can photobiomodulation improve quadriceps strength and endurance outcomes in asymptomatic adults? A double-blind randomized controlled trial.

AIM: To explore the effect of photobiomodulation on quadriceps strength and endurance torques in asymptomatic adults. METHODS: Twenty-eight asymptomatic adults were randomized to one of two interventions: photobiomodulation (n = 14) or sham (n = 14). Quadriceps strength was evaluated by maximum voluntary isometric contraction test (60°) and endurance by an elastic resistance in multiple-set knee extension/flexion repetitions using a traction dynamometer. The outcomes were measured at three time points: pre-baseline; baseline and; final assessment. The photobiomodulation was applied to the quadriceps and triceps surae muscles of each participant's dominant lower limb, using a cluster with 1 infrared laser diode and 3 led amber of 170 mW for 240 s over four consecutive days. The sham group went through the same procedures, but the equipment was off, and patients and assessors were blinded to the intervention. Reliability and minimal detectable change of the measures were obtained from the pre-baseline and baseline time points. Differences between interventions were tested by an analysis of covariance. RESULTS AND DISCUSSION: There was no difference between photobiomodulation compared to sham in maximum isometric torque (mean difference (95% CI) = 0.008 (-0.29 to 0.31) and endurance torques (mean difference (95% CI) = 0.04 (-0.03 to 0.12). The mean difference was lower than the minimal detectable change for the maximum isometric torque (1.02 Nm.kg-1) and endurance torque (0.49 Nm.kg-1). CONCLUSION: Photobiomodulation does not improve quadriceps strength and endurance outcomes in asymptomatic adults.

Using a single dose of photobiomodulation (laser + LED) to improve performance of lower limbs in functional test: Randomized clinical trial.

BACKGROUND: Photobiomodulation (PBM) improves motor performance despite doubts whether it occurs immediately or late after a single dose. We evaluated the effect of a cluster PMB (laser + LED) single dose on muscle fatigue recovery in young sedentary adults, both immediately and in the short term (period between 24 and 48 h) after the fatiguing event. METHODS: Randomized clinical trial with 60 volunteers randomized in 5 groups (n = 12 in each): control/(CG); placebo/(SG); PBM in knee extensor/(KE_G); plantar-flexor/(PF_G); knee extensor + plantar-flexor/(KE + FP_G). Before the intervention (pre) a fatiguing event (FE) was applied, which consisted in going up and down one step until exhaustion. Repetition number (RN) and time to exhaustion (TTE) were recorded. Then each group received its respective intervention and immediately after that, the FE was performed again (immediate post). In the period between 24 and 48 h after irradiation, a new FE was performed (late post). In addition to the comparative statistics, complementary metrics (if the mean difference [Diff] between the comparison pairs was higher or lower than minimum detectable change [MDC] and effect size [ES]) were calculated. RESULTS: Through the integrated analysis of inferential statistics and complementary metrics, it was observed that although there was no time of evaluation effect, there was a group effect. PBM improved performance in KE + FP_G (p-value<0.05; Diff>MDC; ES = moderate) and PF_G (p-value>0.05; but Diff > MDC; ES = moderate) regarding CG for both RN and TTE. CONCLUSION: A PBM single dose irradiation may improve motor performance and there is specificity of the irradiated muscle group, although it does not depend on the moment.