Background In female athletes, bilateral aysmmetry in peak landing forces during the drop jump is associated with anterior cruciate ligament (ACL) injury risk and is proposed as a marker of rehabilitation progression following ACL rupture. Less is known regarding the value of the assessment of these asymmetry in jump tasks in relation to recovery from other lower extremity injuries, particularly in male athletes.

Objective To evaluate the association between previous injury and bilateral limb asymmetry in peak ground reaction forces during a countermovement jump (CMJ) and a drop jump (DJ).

Design Retrospective study.

Setting Professional football club.

Participants 24 first team players.

Risk factor assessment CMJ and DJ performed on two force platforms placed side by side with one foot on each platform.

Main outcome measurements Asymmetry in peak force during the take-off and landing phases of a CMJ countermovement jump in healthy players who either had (INJ) or had not (N-INJ) sustained a non-contact lower extremity injury in the preceding season.

Results Compared to N-INJ, P-INJ mean asymmetry in P-INJ was CMJ takeoff force was 8% higher (CMT-a), in landing force (CML-a) 57% higher, in DJ first landing (DJ1-a) and second landing (DJ2-a) 11% and 31% higher, respectively. None of these differences were significant, but based on Cohen's d, the difference between INJ and N-INJ in CML-a was large (d=0.65), in DJ2-a was moderate (d=0.39) and in CMT-a and DJ1-a was small (d=0.13 and d=0.28, respectively).

Conclusions Our findings suggest that in pro footballers jump landing force asymmetry both in CMJ and DJ may be a marker of residual deficits associated with previous lower extremity injury. Larger studies are needed to confirm these findings and to determine whether these asymmetries may also be a marker of future injury risk.