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 AND 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 AND 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 cm2) compared with losses in the 12WK group (-1.37 +/- 6.87 cm2; 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.
With permission from the National Kidney Foundation.

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