Vol. 7, Issue 2, Part A (2025)

Electromyography (EMG) provides critical insights into neuromuscular function during explosive movements like vertical jumping. This study aimed to investigate the surface EMG activity of the Vastus Medialis (VM) and Vastus Lateralis (VL) muscles on both right and left sides during countermovement jumps (CMJ) with and without hand swing among trained national-level male long jumpers. Ten right-leg take-off athletes aged 18-25 years participated in the study. EMG data were collected using a wireless Trigno system and analyzed for muscle activation patterns and symmetry. Results revealed that the VM showed higher and more consistent activation than the VL across both conditions, indicating its primary role in knee extension and stabilization during vertical jumps. Greater overall muscle activation was observed in the hand-swing condition, suggesting the contribution of arm motion to improved jump performance. Paired sample t-tests revealed no statistically significant differences between right and left VM or VL, although the left VL showed a trend toward higher activation. These findings suggest that elite long jumpers demonstrate symmetrical lower limb muscle function with effective neuromuscular coordination. The data support the value of EMG analysis in optimizing jump training, detecting asymmetries, and guiding performance enhancement strategies.