Asymmetry of arm-swing not related to handedness

This study systematically investigated the symmetry of arm-swing kinematics in 16 normal subjects (8 right-handed, 8 left-handed) during treadmill locomotion, including forward walking (2–6 km/h), running (8 km/h), and backward walking (4 km/h). Kinematic data of both sides were compared. Significant differences between the left and right amplitudes of arm-swing (p < 0.05) were detected in 47 of the 96 gait trials (16 subjects × 6 conditions). The mean magnitude of the side differences was 8.6 cm during forward walking (averaged across all subjects). The mean index of asymmetry of 12.5 ± 24.0 (±S.D.) indicated a trend towards left arm-swing preference. In 10 of the 16 subjects, the individual direction of the arm-swing asymmetry could be reproduced across different velocities and locomotor modes. The asymmetry was not related to handedness, nor was it related to asymmetrical leg movements. The first comprehensive normative data of arm-swing asymmetry during treadmill walking are provided. A certain degree of asymmetry is physiological.