Comparison of Upper Extremity and Trunk Muscle Activation According to Movement Speed and Motion Type During Vibration-Based Upper Limb Exercise

Objective: This study aimed to examine the effects of movement speed and motion type on upper extremity and trunk muscle activation during vibration-based upper limb exercise and to clarify the role of movement speed as a practical exercise prescription variable.Design: Experimental repeated-measures study.Methods: Fourteen healthy adults performed four upper-limb motions (shoulder flexion, horizontal adduction, diagonal rotation, and vibration-focused movement) using a vibration-based exercise device at 40 and 60 beats/min.Surface electromyography (EMG) was recorded from the anterior deltoid, middle trapezius, erector spinae, and right internal oblique.Peak EMG during each vibration condition was normalized to values obtained during the corresponding motion performed with a dumbbell equal to 5% of body weight and expressed as EMG_%baseline.A 2 × 4 repeated-measures ANOVA and follow-up t-tests were conducted.Results: The anterior deltoid showed no significant effects.The middle trapezius showed a significant speed effect (p<0.05), with greater activation at 60 beats/min during shoulder flexion (p<0.05) and diagonal rotation (p<0.05).The erector spinae showed a significant motion effect (p<0.05) and greater activation at 60 beats/min during diagonal rotation (p<0.05).The right internal oblique showed significant speed, motion, and interaction effects (p<0.05), with greateractivation at 60 beats/min during diagonal rotation (p<0.05) and vibration-focused movement (p<0.05).Conclusions: Vibration-based upper limb exercise elicited muscle-specific activation patterns that varied with movement speed and motion type.These findings suggest that movement speed is not merely a repetition-rate parameter but an important variable for modulating exercise intensity and selectively activating trunk stabilization muscles to meet specific training objectives.