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Abstract
Muscle activation during landing is paramount to stabilise lower limb joints and avoid abnormal movement patterns. Delayed muscle activity onset measured by electromyography (EMG) has been suggested to be associated with anterior cruciate ligament (ACL) injury. Therefore, the aim of this systematic review and meta-analysis was to test the hypothesis if ACL-injured patients display different results for muscle onset timing during standard deceleration tasks compared to healthy control participants. PubMed, Embase, Scopus and ScienceDirect databases were systematically searched over the period from January 1980 to February 2015, yielding a total of 1461 citations. Six studies meeting inclusion criteria underwent quality assessment, data extraction and re-computing procedures for the meta-analysis. The quality was rated “moderate” for 2 studies and “poor” for 4. Patients included and procedures used were highly heterogeneous. The tasks investigated were single leg hopping, decelerating from running or walking, tested on a total of 102 ACL-injured participants and 86 controls. EMG analyses of the muscles vastus lateralis, vastus medialis, lateral and medial hamstrings revealed trivial and non-significant standardised mean differences (SMD<0.20; p>0.05) between patients and control participants. Furthermore, no differences were found between the contralateral leg of patients and controls for muscle activity onset of the medial and lateral gastrocnemius (SMD<0.20; p>0.05). Based on 3 studies, the involved legs of ACL-injured patients showed overall earlier muscle activity onset compared to control participants for the medial gastrocnemius (SMD = 0.5; p = 0.05). Similar results were found for the lateral gastrocnemius (SMD = 2.1; p<0.001), with a greater effect size but based only on a single study. We conclude that there are no differences between leg muscles of ACL-injured patients and healthy controls regarding the muscle activity onset during landing. However, current evidence is scarce and weak, which highlights the need for further research in this area.
Highlights
Non-contact anterior cruciate ligament (ACL) injuries commonly occur in a sport context, during abrupt deceleration movements associated with sudden changes of direction, such as cutting, pivoting or landing movements
Negative standardized mean difference (SMD) values indicate that the muscles of ACL-deficient or -reconstructed patients have lower onset values compared to the control group, reflecting later onset of muscle activity prior to contact with the ground
Based on the results available for the present systematic review and meta-analysis, we were not able to conclude on any differences in the muscle activity onset timings between leg muscles of ACL-injured patients and healthy controls
Summary
Non-contact anterior cruciate ligament (ACL) injuries commonly occur in a sport context, during abrupt deceleration movements associated with sudden changes of direction, such as cutting, pivoting or landing movements. These manoeuvres challenge balance control and can lead to abnormal loading and injury of the ACL [1]. The restoration of function to a comparable level as prior to injury depends critically on the rehabilitation process and requires a strong focus on muscle strength, balance training and proprioception exercises [7, 8]
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