Chronic kidney disease (CKD) consists of kidney damage and progressive and irreversible loss of kidney function. The aim of this study is to evaluate the acute effect of different doses of photobiomodulation therapy on quadriceps isometric muscle strength, pain and muscle fatigue of lower limbs and to establish the ideal dose for patients with CKD on hemodialysis. Patients will be submitted to application of photobiomodulation therapy in the quadriceps muscle. Immediately after, the maximum isometric strength test of the quadriceps will be performed.

Chronic kidney disease (CKD) consists of kidney damage and progressive and irreversible loss of kidney function. In the most advanced stage of the disease the patients require hemodialysis (HD) and present alterations such as: sarcopenia, cardiovascular disorders, increased systemic inflammation, muscle weakness and fatigue. These factors negatively affect the individual's functionality, impacting the increase in hospitalization and mortality rates. Photobiomodulation (FBM) has shown positive results in different populations on improving performance during exercise, reducing fatigue and markers of muscle damage. The aim of this study is to evaluate the acute effect of FBM therapy on quadriceps muscle strength, pain and muscle fatigue in patients with CKD on HD and to establish the ideal therapeutic dose. Patients will be submitted to application of four applications with different doses of FBM (30J, 60J, 90J and placebo) in the quadriceps muscle, in random order and one week interval between them for washout. Patients and evaluators will be blinded to the intervention protocol. The following assessments will be performed prior to FBM: subjective perception of exertion (by modified Borg scale), muscle fatigue (by analysis of blood lactate) and pain perception (by numeric pain scale). After the FBM application, the maximum isometric strength test of the quadriceps will be performed by dynamometry. Immediately after performing the strength test, all assessments will be repeated.

Inclusion Criteria:

• Patients with CKD on HD for a period ≥ 3 months;
• Age between 18-80 years old;
• Patients of both sexes;
• Dialysis with a weekly frequency of 3 times/week;
• Adequate urea clearance rate (Kt/V ≥ 1.2 or URR ≥65%).

Exclusion Criteria:

• Cognitive dysfunction that prevents the performance of the assessments, as well as inability to understand and sign the informed consent form;
• Epidermal lesions at the site of application of photobiomodulation therapy;
• Patients with recent stroke sequelae (three months);
• Recent acute myocardial infarction (two months);
• Uncontrolled hypertension (SBP>230 mmHg and DBP>120 mmHg);
• HF grade IV according to the New York Heart Association or decompensated;
• Unstable angina;
• Peripheral vascular changes in lower limbs such as deep venous thrombosis;
• Disabling osteoarticular or musculoskeletal disease;
• Uncontrolled diabetes (blood glucose > 300mg/dL);
• Febrile state and/or infectious disease;
• Systemic lupus erythematosus;
• Patients undergoing cancer treatment.