OBJECTIVE: The aim of this study was to evaluate the acute effects of low-level laser therapy (LLLT) on the functional capacity to exercise tested by incremental shuttle walking test (ISWT) after coronary artery bypass graft (CABG) surgery. METHODS: Fifteen male patients (60 +/- 9 years) were crossed over during the experiment, to compare the outcomes after active LLLT and placebo LLLT treatments. LLLT (850 nm, 200 mW, 30 J to each point, resulting in a total of 240 J per quadriceps muscle), using a multidiode cluster (five spots; 6 J/spot) in eight points per leg was performed 3 min before the ISWT. We analyzed distance walked, Borg scale of perceived exertion, heart rate, and brachial arterial blood pressure. Markers of tissue damage (lactate dehydrogenase (LDH)) and oxidative stress (lipid peroxidation, total thiol levels, and antioxidant enzyme activity of superoxide dismutase (SOD) and catalase (CAT)) were also measured in peripheral blood. RESULTS: Comparison of the distances walked revealed no significant differences between the LLLT and placebo LLLT groups (p = 0.779). Regarding the Borg scale (p = 0.567), heart rate (p = 0.506) as well as systolic and diastolic blood pressure (p = 0.164 and p = 0.140, respectively), no differences were observed between LLLT and placebo LLLT groups. Application of LLLT was not able to change levels of LDH (p = 0.214), oxidative lipid damage (p = 0.733), total thiol levels (p = 0.925), SOD (p = 0.202), and CAT (p = 0.825) enzyme activities. CONCLUSIONS: Acute LLLT improved neither functional capacity to exercise nor the markers of oxidation after CABG. TRIAL REGISTRATION: Registered as a clinical trial (NCT02688426).

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