Dosage Matters.

Background and Purpose- For stroke rehabilitation, task-specific training in animal models and human rehabilitation trials is considered important to modulate neuroplasticity, promote motor learning, and functional recovery. Little is known about what constitutes an effective dosage of therapy. Methods- This is a parallel group, 4 arms, single-blind, phase IIb, randomized controlled trial of 4 dosages of arm therapy delivered in an outpatient setting chronically after stroke. Participants were randomized into groups that varied in duration of scheduled therapy (ie, 0, 15, 30, or 60 hours). Forty-one participants completed the study. Planned primary analyses used linear mixed effects regression to model changes from baseline to postintervention in the Motor Activity Log-Quality of Movement rating and the Wolf Motor Function Test time score over 3 weeks of training as a function of therapy dosage. Results- We observed a dose response for the Motor Activity Log-Quality of Movement: the model that included dose and dose by week interaction significantly better fit the data than the model that included week only (log-likelihood test, P=0.0026). In addition, the greater the dosage of training, the greater the change in Motor Activity Log-Quality of Movement, with the dose by week interaction parameter equal to 0.0045 ( P=0.0016; 95% CI, 0.0018-0.0071). Over the 3 weeks of therapy, there was a gain of 0.92 in Motor Activity Log-Quality of Movement for the 60-hour group compared to the 0-hour group. There was no dose response for the Wolf Motor Function Test. Conclusions- For mild-to-moderately impaired stroke survivors, the dosage of patient-centered, task-specific practice systematically influences the gain in quality of arm use but not functional capacity. We caution that we may have been underpowered for the functional capacity outcome. These findings highlight the importance of recovery outcomes that capture arm use in the natural environment. Clinical Trial Registration- URL: https://www.clinicaltrials.gov . Unique identifier: NCT01749358.