Effects of Wrist Weights on Kinematic and Myographic Movement Characteristics During a Reaching Task in Individuals With Parkinson Disease

Objective: To investigate the kinematic and myographic effects of weighted wrist cuffs on individuals with Parkinson disease (PD) during a reaching task. Design: Cross-sectional study. Setting: Biomechanics research laboratory. Participants: Individuals (N=39) with PD (n=19) and healthy age-matched control subjects (n=20). Interventions: Participants were instructed to reach and grasp a can at a distance of 80% of their arm length without a wrist cuff, while wearing separate 0.5- and 1.0-kg wrist cuffs, and subsequently without a wrist cuff. Main Outcome Measures: Movement time, kinematic, and electromyographic data were recorded during all reach and grasp movements. Four end point coordinate strategy variables, 3 joint recruitment variables, and 2 co-contraction indices were derived from the raw data for analysis. Results: Significant interaction effects were found in the trunk and index finger movement time as the weight of the cuff increased from 0.5 to 1.0kg. The group of individuals with PD showed decreased movement times in both instances, whereas the control group showed increased movement times as the weight of the wrist cuff increased from baseline to 0.5 and 1.0kg. No group difference was observed in the co-contraction index of the upper arm and forearm. Conclusions: Adoption of weighted wrist cuffs in the clinic should be cautiously undertaken because compensatory movements may be induced in the trunk of individuals with PD.