Time and magnitude of torque generation is impaired in both arms following stroke

Muscle strength, usually measured as the peak torque during maximal contraction, is impaired in persons with stroke. Time-dependent properties of muscle contraction may also be altered but have not been quantified. We quantified both magnitude (peak torque) and time-dependent parameters (times to develop and reduce torque) in eight different isometric joint actions. Parameters were compared among the more and less affected arms of 20 persons with chronic stroke and the nondominant arms of 10 similarly aged healthy persons. Torque-generation parameters were independent from one another (i.e., low correlations) and highly reliable between trials and days. All parameters were impaired in the more affected arm, whereas peak torque and time to develop torque were impaired in the less affected arm. Following stroke, torque-generation impairments include both magnitude and time-dependent properties and exist not only in the more affected but also in the less affected arm. Clinicians attempting to improve upper-extremity function should employ therapeutic exercises that challenge patients to improve both their strength and speed of muscle contraction.