Rapid Grip Strength and Muscle Activity as Predictors of Reaction Time

INTRODUCTION: Reaction time may be broadly defined as the time between stimulus presentation and a response. Analysis of reaction time in terms of rate of force development (RFD), peak force, and surface electromyography (EMG) may help bridge the gaps in knowledge pertaining to the neuromuscular system\u27s role in reaction time. The purpose of the present study was to identify predictors of reaction time using digital hand grip dynamometry and EMG. It was hypothesized that RFD and rate of EMG rise (RER) at the onset of a contraction would correlate with reaction time. METHODS: For grip testing, participants were instructed to squeeze a handheld dynamometer with the right hand …as hard and fast as possible for 5 seconds upon hearing a beep from the computer. A total of 5 attempts were performed, with 1-minute rest periods. Bipolar surface EMG signals were detected from the right first dorsal interosseous (FDI) and flexor carpi radialis (FCR) muscles throughout grip testing. Bivariate correlations (Pearson r) were used to examine the statistical associations. The 95% confidence interval (CI) for each Pearson r was also computed. An alpha level of p ≤ 0.05 was used to reject the null hypothesis. RESULTS: Significant correlations were observed between reaction time and all other measures of grip force (r = -0.507 to -0.557, p= 0.016 to 0.042), except for time until peak force (r = 0.029, p = 0.915). As FDI EMG amplitude increased reaction time decreased (r = -0.664, p = .005). CONCLUSION: Many of the grip force variables were significantly associated with reaction time. Peak force and rapid force variables showed significant correlations with reaction time. While no significant correlations for any of the FDI RER or FCR variables were found, EMG amplitude from the FDI presented the strongest bivariate correlation. As FDI EMG amplitude, peak force, and rapid force variables increased reaction time decreased. These findings give some insight into the neuromuscular system\u27s role in hand grip tasks and help broaden the current understanding of variables that may be used to assess or improve reaction time in the clinical setting