Effect of soccer match-play on markers of anterior cruciate ligament injury risk

Non-contact anterior cruciate ligament (ACL) injuries have a high prevalence in soccer players, and this particularly during the latter stages of match-play. Gaining a better understanding of how match-play increases ACL injury risk will benefit the development of effective screening and injury prevention programmes. This thesis therefore aimed to investigate the effects of simulating soccer match-play on markers of ACL injury risk. First, 45 min treadmill versus overground match-play simulations were evaluated for external validity by observing physiological responses and key biomechanical and muscular strength related markers of ACL injury risk. Generally, overground simulations demonstrated physiological responses that were more similar to actual soccer match-play than treadmill simulations, and for some of the markers of ACL injury risk the expected detrimental effects were greater, albeit only in males. These markers were mostly related with reduced hamstrings eccentric peak torques. With this notion that overground simulations better represent actual match-play demands, the influence of a 90 min overground simulation on muscle strength markers, and on biomechanical markers during unanticipated side cutting manoeuvres were investigated. This confirmed the previous observations, whilst also showing more extended knee extension angles at initial contact, and an unexpected reduction in peak knee abduction moments over time. Overall though, sufficient evidence was gathered that certain impairments in muscle strength and altered knee and hip mechanics, particularly in the second playing half and even immediately following a passive half time rest, may induce increased ACL injury risk. Finally, the potential to reverse these impairments was investigated through an intervention involving re-warm up during half-time. The re-warm up intervention could not reverse the impairments, yet the outcome revealed some valuable practical implications. Overall, this work has helped gain a greater understanding for the development of better screening and injury prevention programmes.