Fingertip force variability on the left and right hand during low-level sustained precision pinch

This study examined the fingertip force variability on the left and right hand during low-level sustained precision pinch with the thumb and index finger. Ten healthy, right-handed subjects were required to pinch a device with a stable force output at 5 N for 1 min. The pinch force was recorded for the right and left hand, separately. Visual feedback was provided for the first 30 s and removed for the second 30 s. Coefficient of variance (CV) and approximate entropy (ApEn) were used to quantify the amount and structure of fingertip force variability. Cross approximate entropy (X-ApEn) was applied to examine inter-digit force coordination. Results showed that the left nondominant hand had lower CV values than the right dominant hand, though it was only observable from the index finger. The force structure or force coordination showed no significant difference between the left and right hands, but an significant decrease after removing visual feedback. The force structure and coordination are reflected in a high-level control strategy that may not be influenced by the asymmetry between the dominant and non-dominant hand.