Vertical jump impulse deficits persist from six to nine months after ACL reconstruction

Costley, Jill, Miles, Joshua, King, Enda and Daniels, Katherine AJ (2023) Vertical jump impulse deficits persist from six to nine months after ACL reconstruction. Sports Biomechanics, 22 (1). pp. 123-141. ISSN 1476-3141

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Abstract

Later-stage rehabilitation following ACL reconstruction (ACLR) provides a valuable opportunity to target performance deficits before return to sport. This study aimed to: 1) evaluate bilateral counter-movement jump (CMJ) phase-specific impulse and isokinetic strength inter-limb asymmetry progression from six to nine months post-ACLR; and 2) examine the extent to which individual changes in strength asymmetry could explain changes in impulse asymmetry. Male athletes (n=44) with a hamstring tendon or bone-patellar tendon-bone autograft were tested six and nine months post-ACLR. Two-way mixed-model ANOVAs were used to identify inter-session and inter-graft differences in CMJ phase-specific impulse asymmetries and knee isokinetic flexor and extensor strength asymmetries, as well as in absolute impulse and strength values of independent (ACLR/uninvolved) limbs. Linear regression models were used to assess the relationship between changes in impulse asymmetry and strength asymmetry. Reductions in strength asymmetry arose from improved ACLR-limb performance, whereas concentric impulse asymmetry reduced consequent to decreased uninvolved-limb performance and eccentric deceleration impulses decreased bilaterally. Graft type did not modulate findings. Changes in strength asymmetry had little or no ability to explain changes in impulse asymmetry. Consideration of approaches which may influence persisting deficits observed bi-laterally throughout vertical jumping performance post-ACLR may enhance rehabilitation practice.