Is Deceleration the Key Element in Vertical Jump Performance to Return to Sport After Anterior Cruciate Ligament Reconstruction With Hamstring Graft? A Preliminary Study

Background/Purpose Anterior cruciate ligament reconstruction (ACLR) often leads to persistent neuromuscular deficits, complicating return-to-sport decisions. Reliable functional assessments are needed to guide RTS after ACLR. The main objective was to examine countermovement jump (CMJ) measures to identify which parameters can best distinguish between ACLR and control participants. The secondary objective was to determine whether performance alterations between operated and non-operated limb exist during CMJ after ACLR. Design Non-randomized, single blinded, cross-sectional study Methods Limb symmetry index (LSI) was calculated for vertical ground reaction force (vGRF), maximal power (MP), and eccentric rate of force development (RFDe) during countermovement jumps (CMJ) performed on force plates by an ACLR group (n=64) and a control group (n=47). First analysis compared LSI vGRF, LSI MP and LSI RFDe between groups. Secondary analysis compared vGRF, MP and RFDe between the operated/non-operated limb in the ACLR group and dominant/non-dominant limb in the control group. Between-group comparisons were made using Mann-Whitney tests due to non-normal data distribution. Effect sizes were calculated to assess the magnitude of differences. Results Participants included 64 ACLR patients (mean age 26.5 ± 5.0 years; 33 females) and 47 controls (mean age 23.6 ± 2.1 years; 24 females). CMJ measures in the ACLR group were significantly reduced for LSI vGRF (p < 0.001), LSI MP (p < 0.001) and LSI RFDe (p < 0.001). The ACLR group exhibited significant differences between both limbs in terms of vGRF (p < 0.001), MP ( p < 0.001), and RFDe (p < 0.01). No significant limb differences were found in the control group. Conclusion Measures of deceleration from the CMJ are altered after ACLR and should be considered throughout rehabilitation.