earticle

영어

To determine proper hand load standards, we examined the influence of external load on the kinematics (head-neck and scapular angular displacements) and onset time of the neck muscles during shoulder forward flexion. Six adults (age, 21–25 years) performed shoulder forward flexion. The hand was loaded with 0kg, 1kg, or 5% of the participant’s body weight and the kinematic data and muscle onset time were obtained. The head-neck angular displacements were 11.06±5.4°(0kg), 11.9±3.3°(1kg), and 10.3±0.7° (5% of body weight), while the mean scapular rotations were 19.0±7.0°, 19.2±6.2°, and 17.0±6.5°, respectively. The average amounts of retraction and protraction were 16.7±8.4°, 16.2±9.8°, and 14.7±9.5°, while the mean scapular tilts were 32.2±8.7°, 34.9±10.0°, and 29.5±15.0°, respectively. The addition of an external load normalized to 5% of each participant’s body weight altered the head- neck and scapular kinematics as well as the superficial neck muscle onset time. Our findings suggest that the application of a hand load during shoulder flexion must be individualized according to neck and scapular motion as well as muscle onset time.