Muscular torque variability in Parkinson's Disease with and without dopaminergic medication

We examined whether dopaminergic medication improves sustained muscular torque/force steadiness in Parkinson's disease (PD). Ten individuals with PD performed 40 second isometric ankle dorsiflexion contractions at 10%, 20%, and 30% maximum voluntary torque (MVT) in OFF- and ON-medication states. Torque variability was quantified using the coefficient of variation (CoV). In the OFF-medication state, torque CoV increased progressively over time, indicating reduced force steadiness during sustained contraction. Medication significantly reduced overall CoV. Higher contraction intensities were associated with lower variability, whereas age and disease duration were not significant predictors. These findings demonstrate that dopaminergic therapy enhances motor output stability in PD and reduces torque variability during sustained contractions. Torque/muscle force steadiness could potentially be a clinically meaningful marker of treatment response in PD.