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Patients receiving hemodialysis (HD) experience myopathy, muscle atrophy, or uremic neuropathy due to high serum levels of calcium, urea, acidosis, low levels of carnitine, secondary hyperparathyroidism, and atrophy due to sedentary lifestyle [1]. Thus, muscle weakness, and fatigue experienced in HD patients limits activities of daily living and may reduce balance and increase risk of falls. Due to the limited functional capacity and poor physical status in HD patients, intradialytic electrical stimulation (E-stim) could serve as a surrogate for exercise training to prevent muscle atrophy and reduce balance decline. The purpose of our study was to test the efficacy of a 12-week intradialytic plantar E-stim intervention in outpatients subjected to HD as a potential method to preserve balance decline.
Participants were allocated randomly into two groups: the intervention group (IG, n=45) and the control group (CG, n=48). Those in the IG received a one-hour plantar E-stim treatment concurrent with their regular tri-weekly HD sessions for a period of 12 weeks. The CG, on the other hand, had a visually identical but non-operational device applied for the same duration over a 12-week period. Balance was assessed using wearable technology (BalanSens™, BioSensics, MA, USA) consisting of three inertial sensors attached to the right and left shank and lower back. Participants completed two types of balance tests with their eyes closed: 1. Double stance, feet shoulder width apart for 30 seconds, 2. Semi-tandem, with the dominant foot placed on the back of the non-dominant foot in a straight line, for 20 seconds. Generalized linear models [2×2; Group (Control vs Intervention) × Visit (Baseline vs. Follow-up)] were used to test the differences in anteroposterior (AP) and mediolateral (ML) Reciprocal Compensatory Index (RCI) across groups and visits. RCI measures postural coordination strategy through the coordination of hip and ankle motion [2]. Near zero RCI values demonstrate good postural control strategy and better postural coordination (i.e., negative correlation between hip and ankle movements). This study was supported by the Qatar National Research Foundation (QNRF, Award #NPRP10-0208-170400I).
Ninety-three HD patients completed the study (IG (n=45): age= 53.09 ± 12.67 years; Body mass index=30.91 ± 7.21 kg/m2; Female= 44.44%; CG (n=48): age= 54.23 ± 12.04 years; Body mass index=31.17± 5.97 kg/m2; Female= 47.91%). Both groups did now show statistically significant differences in age, BMI, and sex. Although no statistical significance were seen between group*visit interaction effect in all outcome measures (Figure 1 & 2), a trend was found between group*visit interaction effects in AP RCI during eyes closed semi-tandem balance test (χ2 (DF=1) = 3.494, p = 0.062, partial η2 = 0.017, Observed Power= 0.419) (Figure 2). These findings demonstrate that although balance did not improve in the intervention group, it was preserved compared to the control group which showed deterioration in AP RCI after 12-weeks of no E-Stim therapy during a more challenging balance task (i.e., eyes closed semi-tandem).
This study highlights that a 12-week regimen of intradialytic plantar E-Sim could potentially preserve static balance decline in HD patients. Future research should focus on targeting specific HD patients that may benefit more from E-Stim to improve muscle strength and balance, such as those that are pre-frail or frail, as it was previously shown that E-Stim increased maximum voluntary contraction, muscular tendinous stiffness, and limit of stability in pre-frail older women [3].