Timing of Muscle Activation Is Altered During Single-Leg Landing Tasks After Anterior Cruciate Ligament Reconstruction at the Time of Return to Sport

Abstract

Patients and intervention: Fifteen male athletes following ACL-R using patellar tendon and 11 using hamstrings autograft at the time of return to sport were recruited. Fifteen healthy athletes served as control group. Participants performed 4 different single-leg landing tasks arriving onto a force plate. Main outcome measures: Electromyographic (EMG) activity of knee extensors and flexors, normalized vertical ground reaction force and knee angular displacement were recorded. Results: In all the tasks pre-impact EMG duration was longer in ACL-R (112±28 ms in the knee extensors; 200±34 ms in the knee flexors) compared to healthy participants (74±19 ms in the knee extensors; 153±29 ms in the knee flexors; P<0.05). Initial Contact and Maximum Post-Impact knee angle were lower in ACL-R (9±7 degrees at Initial Contact; 39±12 degrees at maximum flexion) compared to healthy participants (17±9 degrees at Initial Contact; 52±15 degrees at maximum flexion; P<0.05). Normalized vertical GRF was higher in ACL-R compared to healthy participants (3.4±0.5 and 2.7±0.6; P<0.05). Conclusion: At the time of return to sport ACL-R subjects showed altered motor control strategies of single-leg landings. These alterations may lead to uncoordinated movement, hence increasing the risk of re-injury.

Quadriceps muscle compensatory activations are delayed following anterior cruciate ligament reconstruction using hamstring tendon graft

“…The longer duration of anticipatory activity before surgery is in accordance with previous literature [10] and might represent a safety strategy adopted by patients to ensure minimization of postural disturbances and maintain functional joint stability [9]. Similar results have been found in case of joint instability when the ACL is broken during more complex tasks, as for example landing from a jump [8,35], and when sudden decelerations occur while running [36]. During the postoperative measurements, no differences in anticipatory postural adjustments were found between ACL patients and healthy participants.…”

“…However, the preoperative assessments were conducted within 1 month following injury, which is probably too short a time frame in which to create adaptations, thus explaining the earlier anticipatory response in ACL-injured patients, whereas there was enough time to 're-create' a normal anticipatory activation in ACL-reconstructed patients 2 and 6 months after surgery. Abnormal anticipatory activation of lower limb muscles has also been reported by previous studies [7,8,26]. Altered timing and magnitude of muscle activation have been observed during dynamic tasks, such as landing from a jump [7,26].…”

“…Abnormal responses, such as an earlier activity of both knee extensor and flexor muscles, have been found in late stages of the rehabilitation during weight-bearing tasks, such as stepping [6], squatting [7] or landing [8], following ACL reconstruction in comparison with uninjured subjects. In addition, it has been recently shown that delayed compensatory muscle activations occur following ACL injury and early after surgery in response to unexpected perturbations during an unweighted single knee joint task, in which ACL individuals were asked to suddenly stabilize the knee [9,10].…”

Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction

“…ACLR was performed by the same surgeon within 30 days from a non‐contact ACL injury, using either an ipsilateral bone‐patellar tendon‐bone (BPTB) or a semitendinosus and gracilis tendon (STGR) graft. The same standardized rehabilitation protocol was followed by all patients 21 . Those with previous knee joint injury or multi‐ligament knee surgery, as well as those reporting anterior knee pain during open kinetic chain exercises, were excluded.…”

Innovative rehabilitative bracing with applied resistance improves walking pattern recovery in the early stages of rehabilitation after ACL reconstruction: a preliminary investigation

“…After ACL rupture, patients develop peculiar strategies of neuromuscular activation to prevent joint instability according to the motor task performed [12,13]. In the midand long-term perspective, this is often associated with persistent thigh muscles weakness in the operated limb, thereby leading to a side-to-side asymmetry that alters normal knee and lower limb mechanics during daily motion [14,15].…”