Pre-Exercise Infrared Photobiomodulation Therapy (810 nm) in Skeletal Muscle Performance and Postexercise Recovery in Humans: What Is the Optimal Power Output?

BACKGROUND: Photobiomodulation therapy (PBMT) has recently been used to alleviate postexercise muscle fatigue and enhance recovery, demonstrating positive results. A previous study by our research group demonstrated the optimal dose for an infrared wavelength (810 nm), but the outcomes could be optimized further with the determination of the optimal output power. OBJECTIVE: The aim of the present study was to evaluate the effects of PBMT (through low-level laser therapy) on postexercise skeletal muscle recovery and identify the best output power. MATERIALS AND METHODS: A randomized, placebo-controlled double-blind clinical trial was conducted with the participation of 28 high-level soccer players. PBMT was applied before the eccentric contraction protocol with a cluster with five diodes, 810 nm, dose of 10 J, and output power of 100, 200, 400 mW per diode or placebo at six sites of knee extensors. Maximum isometric voluntary contraction (MIVC), delayed onset muscle soreness (DOMS) and biochemical markers related to muscle damage (creatine kinase and lactate dehydrogenase), inflammation (IL-1ß, IL-6, and TNF-α), and oxidative stress (catalase, superoxide dismutase, carbonylated proteins, and thiobarbituric acid) were evaluated before isokinetic exercise, as well as at 1 min and at 1, 24, 48, 72, and 96 h, after the eccentric contraction protocol. RESULTS: PBMT increased MIVC and decreased DOMS and levels of biochemical markers (p < 0.05) with the power output of 100 and 200 mW, with better results for the power output of 100 mW. CONCLUSIONS: PBMT with 100 mW power output per diode (500 mW total) before exercise achieves best outcomes in enhancing muscular performance and postexercise recovery. Another time it has been demonstrated that more power output is not necessarily better.

Reference Equation for the Incremental Shuttle Walk Test in Children and Adolescents.

OBJECTIVE: To determine a prediction equation for distance walked of incremental shuttle walk test (ISWT) and test its reliability in children and adolescents. STUDY DESIGN: Cross-sectional study, which included 108 healthy volunteers between 6 and 18 years old. Those who had an abnormal spirometry or had a history of chronic disease were excluded. Two ISWT were performed. Heart rate and peripheral capillary oxygen saturation (SpO2) were continuously measured during the test. Dyspnea and lower limb fatigue were assessed by Borg scale before and after the tests. RESULTS: Boys walked longer distances compared with girls (1066.4 ± 254.1 m vs 889.7 ± 159.6 m, respectively, P < .0001). Except for dyspnea, there were no significant differences in the other outcomes measured (heart rate, lower limb fatigue, SpO2, and distance walked) at the peak of the two ISWT. The variables included in the predicted equation were age, body mass index, and sex. The predicted equation is: ISWTpred = 845.559 + (sex * 193.265) + (age * 47.850) - (body mass index * 26.179). The distance walked had an excellent reliability between the two ISWT, 0.98 (95% CI 0.97-0.99). The Bland-Altman plot shows agreement between tests (range from -40 to 45 m). CONCLUSIONS: We established a prediction equation for ISWT. It can be used as a reference to evaluate exercise capacity for children and adolescents. ISWT has excellent repeatability and it is a maximal-effort field test for this age group.