The influence of hand dominance, object distance, and size on reach-to-grasp coordination in a virtual environment.

Hand dominance influences motor control, yet the nature of asymmetries in reach-to-grasp coordination remains unclear. We used an immersive, haptic-free virtual environment to examine how hand dominance, object size, and distance shape kinematics and muscle activity during reach-to-grasp actions. Twelve right-handed participants performed unilateral movements with both hands toward virtual objects varying in size and distance. Kinematic and electromyographic data were collected from transport- and grasp-related muscles. A 2 (Hand: dominant, non-dominant) × 3 (Distance: near, middle, far) × 3 (Size: small, medium, large) repeated-measures ANOVA evaluated effects on movement parameters. Transport with the non-dominant hand showed higher peak velocities and accelerations and greater variability in 3-D position compared with the dominant hand. These differences were accompanied by increased triceps brachii activation during late transport, likely reflecting compensatory deceleration and stabilization before grasp. In contrast, grasp kinematics and grasp-related electromyographic activity did not differ significantly between hands. Task parameters modulated both transport and grasp, but object distance more strongly influenced transport, whereas object size more consistently affected grasp. Reach-to-grasp coordination in virtual reality revealed functional specialization between the hands, with asymmetries evident in transport but not grasp. These findings support models proposing a proximal-distal division of motor function between limbs. The results also demonstrate the utility of haptic-free VR as a methodological tool for investigating and potentially training limb-specific motor strategies in healthy individuals.