Inter-limb neuromuscular activity of the gastrocnemius muscle during unilateral and bilateral explosive jumps and relationship with jump performance

Understanding the neuromuscular demands of explosive tasks is essential for enhancing performance and reducing injury risk. This study analyzed inter-limb activation of the medial and lateral gastrocnemius during take-off and landing phases of bilateral and unilateral countermovement jumps (CMJ) and horizontal jumps (HJ), examining its relationship with inter-limb asymmetry and performance. Twenty-six physically active participants performed CMJ and HJ tasks while bilateral surface electromyography was recorded from both gastrocnemius heads. Jump performance was evaluated using flight time (CMJ) and distance (HJ), and asymmetry indices were computed between dominant and non-dominant limbs. Results showed significantly greater muscle activity during take-off than landing across all conditions (p < 0.05). During CMJ landings, the medial gastrocnemius was more active than the lateral, with no activation differences found between unilateral and bilateral jumps. A moderate positive correlation was observed between CMJ performance and bilateral take-off asymmetry (r = 0.43, p = 0.02). Conversely, greater activation in the non-dominant gastrocnemius was negatively associated with performance in both CMJ and HJ (r = -0.39 to -0.48, p < 0.05). In conclusion, gastrocnemius muscles display phase-specific activation patterns. Moderate asymmetry during take-off may benefit performance, while excessive activation in the non-dominant limb may reflect compensatory strategies detrimental to jump efficiency.