The goal of this clinical trial is to evaluate the effects of intradialytic aerobic exercise on muscle capacity, functionality and motivation of patients with chronic kidney disease undergoing hemodialysis.

The main question it aims to answer are:

• Is intradialytic aerobic exercise at moderate intensity effective in improving peripheral muscle function, functional status and motivation in patients with chronic kidney disease?

The progressive and irreversible advance of chronic kidney disease generates the systemic involvement of the organism and, consequently, the impairment of functionality and quality of life. Hemodialysis therapy is a strategy to increase survival and its long implementation time appears as a space for physiotherapeutic interventions in delaying functional impairment in these individuals. The objective will be to evaluate the effects of intradialytic aerobic exercise on muscle capacity, functionality and motivation of patients with chronic kidney disease undergoing hemodialysis. Patients with chronic kidney disease who undergo hemodialysis at TR São José - Clínica de hemodialysis LTDA (São José/SC) will be evaluated. Patients will be randomized, via a convenience sample, into two groups: intradialytic aerobic exercise group and control group. Interventions will take place within the first two hours of hemodialysis, using a portable cycle ergometer. Intensity will be controlled by heart rate and BORG Perceived Exertion Index. The training, for both groups, will be three times a week, for a period of three months. The aerobic exercise intensity will be moderate, in the percentage of maximum heart rate from 55 to 74% and BORG 4 to 6. A portable cycle ergometer will be used. The evaluations will be in the baseline period, after each complete month and after six months of the end. There will be three days of assessments at the hemodialysis clinic prior to renal replacement therapy and seven days using a home device, following the sequence: baseline blood sample collection, anthropometric assessment, vital signs, BORG, spirometry, mean quadriceps thickness, capacity functional status (six-minute step test), cognitive status (Montreal Cognitive Assessment-BR), quality of life (Kidney Disease And Quality-Of-Life Short Form), sleep quality (Pittsburgh Sleep Quality Index), state motivational (Behavior Regulation Exercise Questionnaire - BREQ3), muscle strength and endurance and daily physical activity. The sample calculation will be performed a posteriori, with Gpower software, based on the variables of the six-minute step test and muscle resistance value. Data will be systematized in the Statistical Package for Social Sciences version 20.0. Initially, descriptive statistics will be performed. To characterize the sample, the following variables will be considered: age, gender, anthropometric data, spirometric parameters, body composition, urea and creatinine clearance, cognitive status. Data distribution will be evaluated using the Shapiro-Wilk test or a non-parametric analogue. To compare the response of the outcome variables between the groups, the ANOVA two-way test of repeated measures, or a non-parametric analogue, will be used. To verify relationships between numeric variables, Pearson's correlation coefficient or non-parametric analogue will be used. The significance level adopted for the statistical treatment will be 5% (p < 0.05).

Inclusion Criteria:

• diagnosis of chronic kidney disease undergoing renal replacement therapy via hemodialysis
• aged 20 to 65 years
• low body mass index at overweight (21 kg/m2 to 29.9 kg/m2)
• regular renal replacement therapy via hemodialysis for 6 months, without acute complications related to the diagnosis and/or comorbidities for the period of 3 months prior to the evaluation and intervention.

Exclusion Criteria:

• patients who do not reach a score equal to or above 20 assessed by the Mini Mental State Examination
• severe heart failure according to the New York Heart Association classification
• musculoskeletal alteration that prevents the correct execution of the assessment activities
• who have participated in other exercise protocols in the last 6 months prior to the present study
• patients who show signs of clinical instability during the hemodialysis procedure or after training for two consecutive sessions will be excluded throughout the protocol.