RESUMEN
OBJECTIVE: To evaluate the effects of neuromuscular electrical stimulation of high and low frequency and intensity, performed during hemodialysis, on physical function and inflammation markers in patients with chronic kidney disease (CKD). DESIGN: Randomized clinical trial. SETTING: Hemodialysis clinic. PARTICIPANTS: Patients with CKD (N=51) were randomized into blocks of 4 using opaque sealed envelopes. They were divided into a group of high frequency and intensity neuromuscular electrical stimulation and a group of low frequency and intensity neuromuscular electrical stimulation. INTERVENTIONS: The high frequency and intensity neuromuscular electrical stimulation group was submitted to neuromuscular electrical stimulation at a frequency of 50Hz and a medium intensity of 72.90mA, and the low frequency and intensity neuromuscular electrical stimulation group used a frequency of 5Hz and a medium intensity of 13.85mA, 3 times per week for 1 hour, during 12 sessions. MAIN OUTCOME MEASURES: Peripheral muscle strength, exercise capacity, levels of muscle trophism marker (insulin growth factor 1) and levels of proinflammatory (tumor necrosis factor α) and anti-inflammatory (interleukin 10) cytokines. RESULTS: The high frequency and intensity neuromuscular electrical stimulation group showed a significant increase in right peripheral muscle strength (155.35±65.32Nm initial vs 161.60±68.73Nm final; P=.01) and left peripheral muscle strength (156.60±66.51Nm initial vs 164.10±69.76Nm final; P=.02) after the training, which did not occur in the low frequency and intensity neuromuscular electrical stimulation group for both right muscle strength (109.40±32.08Nm initial vs 112.65±38.44Nm final; P=.50) and left muscle strength (113.65±37.79Nm initial vs 116.15±43.01Nm final; P=.61). The 6-minute walk test distance (6MWTD) increased in both groups: high frequency and intensity neuromuscular electrical stimulation group (435.55±95.81m initial vs 457.25±90.64m final; P=.02) and low frequency and intensity neuromuscular electrical stimulation group (403.80±90.56m initial vs 428.90±87.42m final; P=.007). The groups did not differ in peripheral muscle strength and 6MWTD after the training protocol. In the high frequency and intensity neuromuscular electrical stimulation group, a correlation was observed between the initial and final values of 6MWTD and muscle strength. In the low frequency and intensity neuromuscular electrical stimulation group, correlations occurred only between the 6MWTD and the initial muscle strength. Only the low frequency and intensity neuromuscular electrical stimulation group increased levels of insulin growth factor 1 (252.38±156.35pg/mL initial vs 336.97±207.34pg/mL final; P=.03), and only the high frequency and intensity neuromuscular electrical stimulation group reduced levels of interleukin 10 (7.26±1.81pg/mL vs 6.32±1.54pg/mL; P=.03). The groups showed no differences in tumor necrosis factor α levels. CONCLUSIONS: Patients with CKD on hemodialysis improve exercise capacity after peripheral neuromuscular electrical stimulation of high and low frequency and intensity. However, the benefits on muscle and inflammatory outcomes seem to be specific for the adopted electrical stimulation strategy.