Neuromuscular markers of non-contact anterior cruciate ligament injury during dynamic tasks

This thesis explores the added value of neuromuscular markers of non-contact ACL injury risk. First, a systematic review was conducted to establish the existing evidence from the literature. The outcome of this review served to select candidate neuromuscular observations to be included in a large-scale prospective study. The two main risk factors that were found to be supported with some evidence were the (i) hamstrings to quadriceps ratio (HQR) and (ii) a unique neuromuscular activation pattern during side cutting. These parameters were included in a prospective cohort study to establish injury risk factors. After two years of data collection we still had not seen any non-contact ACL injuries in our study sample. As a fall back plan, the collected database was explored in search of evidence that can help support previous findings. First, we showed that quadriceps strength meaningfully affects HQRs (as quadriceps gets stronger, HQR value gets lower), introducing bias when profiling individuals for injury risk. We demonstrated how through an allometric approach this bias can be removed for future investigation into HQR as a risk factor for injury. Second, we evaluated whether HQR explains neuromuscular activations of the knee musculature during the execution a dynamic task. We found that variations between individuals in muscle (co-)activations were not explained by differences in muscle strength or HQR. Overall, through this work we have obtained a clear overview on the limited evidence on neuromuscular risk factors of non-contact ACL injury, provided in-depth insights into HQR as a measure of muscular capacity, and demonstrated how one should be careful in linking observations of muscular capacity with observations of muscular activation and vice versa