Single leg drop jump performance identifies functional deficit in collegiate athletes who have returned to sports after ACL reconstruction: A case–control study

Despite its apparent functional importance, there is a general lack of data in explosive strength in individuals recovering from an anterior cruciate ligament reconstruction (ACLR). Hence, we wonder if single leg drop jump (SLDJ) can be an effective testing since drop jump is a commonly used testing which rely on adequate development of explosive strength and stretch shortening cycle function. The purpose of this study was to determine if SLDJ test can identify functional deficit in collegiate athletes who have returned to sports (RTS) after ACLR when comparing it with the common return to sport testing. Nine collegiate athletes who had undergone a unilateral ACLR and returned to their primary sport with at least 10 months post-surgery were recruited and assigned into the injured group and compared with 9 matched non-injured athletes as the control group. Both groups underwent an identical battery testing in 1 session with the sequence of first modified star excursion balance test (SEBT), second single hop and bound test, third SLDJ and lastly 1 repetition maximum (1RM) single leg press. A 2-way mixed model analysis of variance showed that there is no significant interaction effect on common RTS testing which include modified SEBT, single hop and bound tests, and 1RM single leg press, but significant interaction effect on SLDJ jump height (P = .03), reactive strength index (P = .03) and mean propulsion force (P = .03). For the injured group, ACLR leg jump height (10.35 ± 2.71 cm) was significantly lower than non-ACLR leg (12.86 ± 3.51 cm) with a mean difference of 2.51 (95% confidence interval [CI]: 0.55‐4.47). ACLR leg reactive strength index (0.29 ± 0.10 m/s) was significantly < non-ACLR leg (0.39 ± 0.16 m/s) with a mean difference of 0.1 (95% CI: 0.03‐0.17) and ACLR leg mean propulsion force (1087.49 ± 287.26 N) was significantly < non-ACLR leg (1157.40 ± 299.80 N) with a mean difference of 69.91 (95% CI: 16.04 to 123.78). SLDJ was able to identify jump height, reactive strength and propulsion force deficit in the involved limb of collegiate athletes who have returned to sports after ACLR.