Effects of Unilateral Hand Contraction on the Persistence of Hemispheric Asymmetry of Cortical Activity

Athletes who squeezed a ball with their left hand immediately prior to execution of sports activities did not show performance deterioration under severe pressure (Beckmann, Gröpel, & Ehrlenspiel, 2013). This result has been explained by priming of the dominant right hemisphere. However, it remains unclear what variables have the greatest effect on asymmetrical brain activity (e.g., duration and strength of ball squeezing). We hypothesized that squeezing a ball harder for a longer period might lead to stronger asymmetrical activity because motor-related areas would have increased activation due to the more forceful movement. We used electroencephalograms (EEGs) to investigate the hemispheric asymmetry of brain activity produced by squeezing a ball with a unilateral hand. EEGs were assessed during a baseline period as well as in eight experimental conditions wherein the strength and duration of the ball squeeze were manipulated. Our results showed that right-hemispheric-dominant brain activation was maximized when participants squeezed with their left hand a ball that had an internal pressure of 100 hPa for 90 s or 20 hPa for 30 s. Moreover, squeezing the ball with 100 hPa internal pressure for 90 s created a prominent interhemispheric asymmetry of cortical activity. We suspect that squeezing a ball strongly for a long period might be helpful in dealing with "choking" under pressure by producing greater right-hemispheric activation. This result could help improve simple methods for competitive athletes to reduce the likelihood of exhibiting choking behavior that could be practiced with minimal effort, even during short breaks during a game.