Quadriceps Function and Hamstrings Co-Activation After Anterior Cruciate Ligament Reconstruction

Abstract

Context: Individuals with anterior cruciate ligament reconstruction (ACLR) have quadriceps dysfunction that contributes to physical disability and posttraumatic knee osteoarthritis. Quadriceps function in the ACLR limb is commonly evaluated relative to the contralateral uninjured limb. Bilateral quadriceps dysfunction is common in individuals with ACLR, potentially biasing these evaluations.Objective: To compare quadriceps function between individuals with ACLR and uninjured control participants.Design: Cross-sectional study. Setting: Research laboratory.Patients or Other Participants: Twenty individuals with unilateral ACLR (age ¼ 21.1 6 1.7 years, mass ¼ 68.3 6 14.9 kg, time since ACLR ¼ 50.7 6 21.3 months; females ¼ 14; Tegner Score ¼ 7.1 6 0.3; 16 patellar tendon autografts, 3 hamstrings autografts, 1 allograft) matched to 20 control participants (age ¼ 21.2 6 1.2 years, mass ¼ 67.9 6 11.3 kg; females ¼ 14; Tegner Score ¼ 7.1 6 0.4) on age, sex, body mass index, and Tegner Activity Scale.Main Outcome Measure(s): Maximal voluntary isometric knee extension was performed on an isokinetic dynamometer. Peak torque (PT), rate of torque development (RTD), electromyographic (EMG) amplitude, central activation ratio (CAR), and hamstrings EMG amplitude were assessed during maximal voluntary isometric knee extension and compared between groups using independent-samples t tests. Relationships between hamstrings co-activation and quadriceps function were assessed using Pearson correlations.Results: Participants with anterior cruciate ligament reconstruction displayed lesser quadriceps PT (1.86 6 0.74 versus 2.56 6 0.37 Nm/kg, P ¼ .001), RTD (39.4 6 18.7 versus 52.9 6 16.4 Nm/s/kg, P ¼ .03), EMG amplitude (0.25 6 0.12 versus 0.37 6 0.26 mV, P ¼ .04), and CAR (83.3% 6 11.1% versus 93.7% 6 3.2%, P ¼ .002) and greater hamstrings co-activation (27.2% 6 12.8% versus 14.3% 6 3.7%, P , .001) compared with control participants. Correlations were found between hamstrings co-activation and PT (r ¼ À0.39, P ¼ .007), RTD (r ¼ À0.30, P ¼ .03), and EMG amplitude (r ¼ À0.30, P ¼ .03).Conclusions: Individuals with ACLR possessed deficits in PT, RTD, and CAR compared with control participants. Peak torque is the net result of all agonist and antagonist activity, and lesser PT in individuals with ACLR is partially attributable to greater hamstrings co-activation.

Quadriceps Strength and Volitional Activation After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

“…Based on the modified version of the Downs and Black checklist, 10 studies 5 , 13 , 18 , 25 , 28 , 40 , 41 , 52 , 55 , 56 of the 28 were classified as low quality, 8 studies 4 , 22 , 27 , 29 , 36 , 42 , 44 , 46 were classified as moderate quality, and 10 studies 9 , 12 , 17 , 23 , 30 - 32 , 35 , 37 , 50 were classified as high quality. Of the articles assessed, 12% were not representative of overall clinical populations, 40% had selection bias, 36% did not identify a comparison group, 100% did not blind the assessors, 61% did not describe potential confounding variables, 9% did not adjust for potential confounders, and 73% did not report the appropriate sample size to power the study.…”

Contractile rate of force development after anterior cruciate ligament reconstruction—a comprehensive review and meta‐analysis

“…The participant activity level may have contributed to these discrepant findings as Larsen et al 65 examined recreationally active individuals whereas Jordan et al 58 included elite-level alpine ski racers, who were presumably highly trained. As a 2-year post-surgical recovery period is expected after ACLR to restore normal/previous knee joint health and function, 108 the findings reported by Larsen et al 65 and Jordan et al 58 may be related to post-operative time periods of insufficient duration along with factors such as AMI, 16 chronic elevations in hamstring co-contraction, 86 and persistent atrophy of the knee extensors 82,91,94,[109][110][111] and knee flexors 82,88,89,94,[96][97][98]100 after ACLR.…”

“…Changes in the activation of cortical brain areas 74,79 and reduced excitability in descending corticospinal 76,[80][81][82][83] and spinal reflex pathways 81,[83][84][85] have been observed after ACL injury, contributing to a persistent depression in maximal knee extensor strength. 80 More specifically, increased hamstring co-activation, 86 gammaloop dysfunction, 17 and AMI 16 might explain the observed between-limb asymmetries and RFD deficits after ACLR. Pamukoff et al 86 described increased hamstring co-activation in ACLR knees (50.7 ± 21.3 months after ACLR) compared to healthy uninjured controls.…”

“…80 More specifically, increased hamstring co-activation, 86 gammaloop dysfunction, 17 and AMI 16 might explain the observed between-limb asymmetries and RFD deficits after ACLR. Pamukoff et al 86 described increased hamstring co-activation in ACLR knees (50.7 ± 21.3 months after ACLR) compared to healthy uninjured controls. Interestingly, increased hamstring co-activation was associated with reductions in knee extensor peak torque (r = −.39), Peak RTD (r = −.30), central activation ratio (CAR) (r = −.40), and electromyography (EMG) amplitude (r = −.30).…”

“…Interestingly, increased hamstring co-activation was associated with reductions in knee extensor peak torque (r = −.39), Peak RTD (r = −.30), central activation ratio (CAR) (r = −.40), and electromyography (EMG) amplitude (r = −.30). 86 Additionally, the ACL is known to have sensory functions. 17,87 Loss of afferent feedback from ACL rupture itself and surgical reconstruction may lead to gamma-loop dysfunction and impaired Ia afferent input to spinal motoneurons during the first 6 months after ACLR.…”