Chronic kidney disease is a renal injury and progressive and irreversible loss of kidney function and in its most advanced stage is called chronic renal failure. Although hemodialysis replace some kidney function, patients suffer some alterations characterized by "uremic syndrome" typically expressed by: motor neuropathy and/or autonomic neuropathy, cardiac or musculoskeletal myopathies, peripheral vascular changes, among others. Thus, the functional capacity and ability to exercise presents diminished these patients. The aim of this study is to verify the acute effect of low level laser therapy on the functional capacity of these individuals.

The research will be developed in the hemodialysis unit of the Santa Clara hospital of Santa Casa de Misericordia de Porto Alegre and the patients will be evaluated before and immediately after the application of laser therapy protocol. Before the protocol will be evaluated pain in the lower limbs, Borg scale, level of physical activity through the International Physical Activity Questionnaire (IPAQ) and blood collection will be held for later analysis parameters of biochemical oxidative stress and deoxyribonucleic acid (DNA) damage.

The laser therapy protocol will be applied in 6 points in quadriceps and 4 points in the gastrocnemius, bilaterally. After application, will be held the 6-minute walk test, effort subjective perception by Borg scale, assessment of pain in the lower limbs with visual analog scale and a new blood sample for further analysis. Patients will be randomized in two groups. The intervention group (IG), which will be held laser therapy and placebo group (PG), where the laser therapy will be placebo mode applied. The application will take place with the Chattanooga device, with the laser diode cluster probe from the same manufacturer consisting of five diodes 850 nanometers (nm) and power output of 200 milliwatts (mW). It is irradiated 6 points in quadriceps and 4 points in gastrocnemius, bilaterally.

Inclusion Criteria:

• Patients with chronic kidney disease on hemodialysis for more than 3 months;
• Clearance of urea during hemodialysis (Kt/V ≥ 1.2).

Exclusion Criteria:

• Cognitive impairment that prevents conducting evaluations, as well as inability to understand and sign the informed consent form;
• Epidermal lesions at the site of application and/or intolerance stimulator and/or skin sensitivity change;
• Patients with recent sequel of stroke;
• Disabling musculoskeletal disease;
• Uncontrolled hypertension (Systolic blood pressure > 230 mmHg and diastolic blood pressure > 120 mmHg);
• Grade IV heart failure (NYHA) or decompensated;
• Uncontrolled diabetes (blood glucose > 300 mg/dL);
• Unstable angina;
• Fever and/or infectious disease;
• Recent acute myocardial infarction (two months);
• Active smokers; Peripheral vascular disease in the lower limbs as deep vein thrombosis or obliterates thromboangiitis.