Effects of Laser Therapy on Muscle Function in COPD Patients

Light-emitting diodes (LEDs) have been used to minimize muscle fatigue in athletes and healthy subjects. Patients with chronic obstructive pulmonary disease (COPD) are susceptible to early muscle fatigue. The objective of this study is to assess the acute effects of LEDs on muscle function, exercise capacity, and cardiorespiratory responses during isometric and dynamic exercise in patients with COPD. This study will assess 30 patients with moderate to severe obstruction (FEV1 ≤ 70% predicted). Isometric and dynamic protocols will be conducted in two visits each, for a total of four visits a week a part. First, a venous blood sample will be taken from the patients. The isometric protocol will start with the determination of the maximum voluntary isometric contraction (MIVC) to determine the workload (60% of MIVC) for the isometric endurance test (IET). Patients will be randomized to receive either the placebo or LED application. Immediately after finishing this procedure, the patients will carry out the IET until the limit of tolerance or until a 20% fall of strength is observed. After the test, another blood sample will be taken. In the other visit (one week later), the same order of procedures will be performed, except with the opposite (LED or placebo). For the dynamic protocol, the same procedures described above will be followed except with the maximal incremental cycle ergometer test used instead of the IET. The electromyography will be recorded during the isometric and dynamic protocols. Differences in muscle function, exercise capacity, and cardiorespiratory responses between the LED and placebo applications will be analyzed. The therapeutic effects of LED could minimize muscle fatigue in patients with COPD by increasing exercise tolerance.