Chronic obstructive pulmonary disease (COPD) is characterized by dyspnea, as well as musculoskeletal and systemic manifestations. Photobiomodulation therapy (PBMT) with use of low-level laser therapy (LLLT) and/or light emitting diode therapy (LEDT) is an electrophysical intervention that has been found to minimize or delay muscle fatigue. The aim of this study is to evaluate the acute effect of PBMT with combined use of lasers diodes, light emitting diodes (LEDs), on muscle performance, exercise tolerance and metabolic variables during the 6-minute stepper test (6MST) in patients with COPD. Twenty-one patients with COPD will completed the 6MST protocol over 2 weeks, with 1 session per week. PBMT or placebo (PL) will be performed before each 6MST (17 sites on each lower limb, with a dose of 30 J per site, using a cluster of 12 diodes: 4 × 905 nm super-pulsed laser diodes, 4 × 875 nm infrared LEDs, and 4 × 640 nm red LEDs; Multi Radiance Medical™, Solon - OH, USA). Patients will be randomized into two groups before the test according to the treatment they will receive. Assessments will be performed before the start of each protocol. The primary outcomes are oxygen uptake and number of steps, and the secondary outcome are perceived exertion (dyspnea and fatigue in the lower limbs).

All patients will have a diagnosis of COPD according to the global initiative for chronic obstructive lung disease (GOLD) criteria. The patients will be at a stable phase of the disease, indicated by a lack of change in medical therapy (including oral steroids) or an exacerbation of symptoms in the preceding 4 weeks. Patients with other known severe chronic diseases, including cardiac, neuromuscular, or orthopedic disorders, will be excluded.

Inclusion Criteria:

• COPD patients
• Patients are at a stable phase of the disease

Exclusion Criteria:

• Patients with cardiac diseases
• Neuromuscular diseases
• Orthopedic disorders

A participating researcher who programmed the PBMT device (Multi Radiance Medical™, Solon, OH) based on the randomization results performed the randomization. He will be instructed not to inform the participants or other researchers of the PBMT dose (active or placebo). Thus, the researcher who performed the PBMT will be blinded to the dose administered to the participants. To further maintain blinding, participants used opaque goggles to prevent them from seeing whether a light will be irradiated.