Handgrip Strength Related to Long-Term Electromyography: Application for Assessing Functional Decline in Parkinson Disease.

Abstract

To determine which clinical measures of physical function (ie, gait, balance, and grip strength) best represent long-term electromyography in persons with Parkinson disease (PD) compared with those without PD. Cross-sectional study. Local community. A sample (N=37) of men and women with PD (n=23) and those without PD (n=14), living independently at home, older than 50 years of age, from the local community. Not applicable. Measures of gait, balance, and grip strength were completed, and electromyography was examined in biceps brachii, triceps brachii, vastus lateralis, and biceps femoris during a 6.5-hour day. Muscle activity was quantified through burst in electromyography (>2% of the normalized maximum voluntary exertion with a continuous activity period of >0.1s). Stepwise multiple regression models were used to determine the proportion of variance in burst characteristics explained by clinical measures of physical function in PD. Grip strength was the best predictor of muscle activity in persons with PD (R²=.17-.33; P<.04), whereas gait characteristics explained muscle activity in healthy controls (R²=.40-.82; P<.04). Grip strength could serve as an effective clinical assessment tool to determine changes in muscle activity, which is a precursor to functional loss in persons with PD.