Background: To determine whether prolonged (24 weeks) intradialytic progressive resistance training (PRT) could counteract muscle wasting more effectively than short-duration training (12 weeks) in patients with end-stage renal disease.
Study design: Randomized controlled trial.
Setting & participants: 49 patients (age, 62.6 +/- 14.2 years; 0.3 to 16.7 years on hemodialysis therapy) were randomly assigned to PRT plus usual care for 24 weeks (24WK group) or a crossover control group that received usual care for the first 12 weeks, then PRT plus usual care for the latter 12 weeks (12WK group).
Intervention: Two sets of 10 free-weight PRT exercises were performed at a high intensity during routine thrice-weekly hemodialysis treatment under direct supervision.
Outcomes & measurements: Primary outcomes include thigh muscle cross-sectional area by means of computed tomography and intramuscular lipid content estimated through attenuation. Secondary outcomes include muscular strength, exercise capacity, and C-reactive protein level.
Results: The 24WK group increased muscle cross-sectional area (+1.82 +/- 3.25 cm(2)) compared with losses in the 12WK group (-1.37 +/- 6.87 cm(2); relative effect size, 0.59; 95% confidence interval [CI], -0.27 to 6.65; P = 0.04). However, this outcome did not achieve the level of statistical significance required (P = 0.025) after Bonferroni correction for multiple primary outcomes. There was no significant change in intramuscular lipid content between groups (+0.19 +/- 1.32 versus +0.16 +/- 1.69 Hounsfield units in the 24WK and 12WK groups, respectively; P = 0.31). Log C-reactive protein level tended to decrease in the 24WK group compared with the 12WK group (relative effect size, -0.63; 95% CI, -0.27 [-0.54 to 0.00]; P = 0.05). The 24WK group improved muscular strength measures and exercise capacity throughout the trial.
Limitations: Single geographic site used; no control group without exercise exposure; unblinded assessment of some secondary outcome measures.
Conclusions: Prolonged intradialytic PRT did not significantly improve muscle cross-sectional area or intramuscular lipid content compared with a shorter duration of exercise. Future trials are required to more thoroughly investigate the clinical importance and magnitude of myogenic adaptations to PRT in this cohort.