Muscle activity patterns during drop vertical jump in young adults following anterior cruciate ligament reconstruction
ESSKA Academy. Meyer C. May 11, 2018; 218186; FP52-1657
Christophe Meyer
Christophe Meyer
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Objectives: Patients following anterior cruciate ligament reconstruction (ACLR) reportedly have abnormal knee landing biomechanics. Moreover, different neuromuscular activity of knee flexor and extensor muscles has been observed and suggested as ACL injury risk factors. Therefore, this study aimed at comparing knee biomechanics and electromyographical patterns of ACLR patients and controls during drop vertical jump (DVJ).

Methods: 3D motion analysis of the DVJ task was prospectively performed in a rehabilitated cohort of 16 patients with ACLR (age: 25±7 years, body mass index: 22.9±2.3 kg/m2, 9.0±1.3 months since surgery, 6 bone-patellar-tendon-bone/10 hamstring grafts) and in 20 healthy age/BMI-matched controls (24±7 years, BMI: 22.8±2.5 kg/m2). DVJ was performed on 2 separate force platforms and standardized from 0 to 100%, determined from landing to subsequent take-off. Landing and push-off phases were defined from initial contact to maximal knee flexion and from maximal knee flexion to take-off, respectively. Sagittal knee power was computed based on an inverse dynamics approach. Surface electromyographic (sEMG) signals were recorded from both legs for the vastii and the medial and lateral hamstrings. Linear envelopes of three trials per side, per participant and per muscle were obtained after applying a band-pass filter (10-500Hz), signal rectification and a low-pass filter (10Hz). Linear envelopes were amplitude-normalized based on maximal sEMG signals obtained during a separate, maximally executed countermovement jump. Per patient and muscle, ensemble-averages of linear envelopes of the operated and non-operated leg were computed. Per healthy participant, ensemble-averages of a randomly chosen leg were generated. For each muscle, separate statistical parametric mapping t-test or paired t-test analyses were performed to test for significant differences (p<0.05) in sagittal knee power and sEMG waveforms.

Results: In ACLR patients, knee power absorption and generation were decreased by 25% and 21%, respectively, at the operated leg compared to their non-operated one. Decreased knee power absorption (15%) was also observed in the operated leg of ACLR patients compared to controls. No difference was found in the vastii and biceps femoris sEMG activities, neither when comparing the two legs of the patients, nor when comparing ACLR patients and controls. However, semitendinosus sEMG activity was increased (+30%) during the push-off phase at the operated leg of ACLR patients compared to their non-operated one.

Conclusions: An unloading strategy was observed in the operated knee of ACLR patients during landing from a DVJ 9 months post-surgery. Loading asymmetry may be considered as a risk factor for early-onset knee osteoarthritis development. Previous reports showing decreased knee flexor and increased knee extensor activity during landing were not confirmed. However, increased semitendinosus activity during the push-off phase might be regarded as a compensation strategy.

Electromyography; Neuromuscular control; Knee injury; Anteriror cruciate ligament; Knee injury;
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