Motor control characteristics for simultaneous bilateral asymmetrical tasks performed by upper limbs

Abstract

This study aimed to investigate motor control characteristics of the upper limbs through bilateral simultaneous grading tasks. The participants included 18 healthy right-handed women. They were instructed to perform isometric elbow flexion tasks under unilateral and bilateral conditions. The grading tasks were aimed at increasing the maximum voluntary force (MVF) from 10% to 30% or 50%. In the unilateral condition, participants performed tasks with the right or left upper limb. In the bilateral condition, participants increased their force level to 30% MVF with the right limb and then to 50% MVF with the left limb, or they increased their force level to 50% MVF with the right limb and then to 30% MVF with the left limb. Participants were asked to perform tasks as rapidly and accurately as possible. We evaluated the rapidity, accuracy, and reproducibility. Regarding the rapidity, the reaction time at 30% MVF was longer than that at 50% MVF, while the adjustment time at 50% MVF was longer than that at 30% MVF. Regarding the total adjustment time, there was no difference between both limbs in both bilateral conditions. Accuracy and reproducibility were higher when the task was performed at 30% MVF. These results suggest that when different levels of force are exerted by both upper limbs, the movement time is drawn to the side that exerts larger force, and the accuracy of force exertion increases on the limb that exerts less force.

Keywords

• grading task
• isometric flexion
• entrainment
• maximum voluntary force
• motor control