The effect of fatigue on phase specific countermovement jump asymmetries in ACL-R and non-injured rugby union players

Return to play (RTP) criteria and analysis of neuromuscular asymmetries should be evaluated and monitored to prevent high re-rupture rates in individuals that have undergone ACL reconstruction (ACL-R). This study investigated asymmetries between two groups of male rugby players (ACL-R and non-injured) in bilateral and unilateral countermovement jump (CMJ) performance pre and post-match play. Three countermovement jumps (CMJs) were performed pre, post 30 min and 48 h post game play. Force plates assessed vertical ground reaction forces and kinetic CMJ metrics, whilst sagittal lower limb kinematics were recorded. Global position systems were used to measure match-running variables to quantify workload. No significant difference existed in CMJ phase specific asymmetries between groups with no time and jump interaction (P > 0.05). Significant time effect changes occurred in ankle, knee, and hip flexion angles, highlighting an altered movement strategy. A significant difference (P = 0.004) in total distance covered was observed between the population groups (non-injured 6260.1 ± 524.2 m and ACL-R 4919.6 ± 771.7 m). No significant group differences existed between athletes that have previously undergone ACL-R and non-injured individuals for neuromuscular asymmetry values. This highlights the importance of individualized testing and tailored RTP criteria due to different positional and physiological demands.