Velocity and target location influence the upper limb reaching movements: Three-dimensional motion analysis combined with surface electromyograph

BACKGROUND: Three-dimensional (3D) motion analysis system combined with electromyograph cannot only objectively analyze movement function of the upper limb, but also exert an important role in exploring the exercise-related factors and the underlying mechanism. OBJECTIVE: To explore the influence of movement velocity and target location on kinematics and muscle activity in upper limb reaching. METHODS: Twelve healthy young adults reached for three different location targets (frontal, ipsilateral and contralateral) at self-selected and fast speeds to with the dominant right hand, respectively. Kinematic parameters and muscle activity were recorded by Vicon 3D motion analysis system and Noraxon wireless electromyograph, synchronously. RESULTS AND CONCLUSION: Reach path ratio became smaller when moving faster (P < 0. 001), while mean velocity, peak velocity and the time percentage of peak velocity increased (P < 0. 001). Posterior deltoid, biceps brachii and triceps brachii activation was higher during fast speed movement (P < 0. 001). Muscle activation of anterior deltoid was lower in ipsitralateral reaching than contralateral (P=0. 001) and frontal reaching (P < 0. 001), and posterior deltoid was higher than contralateral reaching (P=0. 019). Biceps brachii (P=0. 039) and triceps brachii (P < 0. 001) activation was also higher in ipsitralateral reaching than frontal reaching. These results suggest that moving fast can contribute to more muscle activation, high velocity, smooth trajectory and increased movement quality. Posterior deltoid, elbow extension and flexion muscle activation are high in ipsitralateral reaching, while high anterior deltoid activation in contralateral reaching; therefore, target location result in muscle synergies.