Core training is prevalent in injury prevention programmes and particularly in soccer. The anterior core muscles (i.e. muscles that flex the trunk) and posterior core muscles, particularly the lumbar extensors, possess mechanisms that increase anterior rotation of the pelvis whilst sprinting if they were weak, thus increasing hamstring injury risk. The literature indicates the lumbar extensors are more likely to be weak from soccer match play based on the demands of sprinting, which might be partly because the lumbar extensors are unable to be strengthened through typical resistance exercises. This thesis found lumbar extensor strength in soccer players is no different to resistance trained individuals and powerlifters. Further, the lumbar extensors were observed to experience a greater magnitude of fatigue compared to the trunk flexors after simulating 90 minutes of competitive soccer match play (median and interquartile range of -13% [5.5%] and -4.5% [29%] respectively), which was likely due to a local mechanism based on the observed reduction in hand grip strength (-6% [12.8%]). Therefore, it was investigated whether fatigue in the lumbar extensors equivalent to that induced from soccer match play could anteriorly tilt the pelvis whilst sprinting. The thesis established a protocol to replicate the lumbar extensor fatigue whilst avoiding fatigue in other muscles. Subsequently, this protocol was used to establish the effect of the lumbar extensor fatigue on the anterior pelvic tilt whilst running. In addition, it was investigated whether lumbar extensor fatigue can reduce hamstring torque by limiting the lumbar extensors capacity to oppose the pelvic rotation created by maximal hamstring actions. The principal findings showed the lumbar extensor fatigue significantly increased anterior pelvic tilt during the early and terminal swing phase of running, and reduced maximum hamstring torque up to -26 N·m ± 27 N·m. These findings are the first to show that weakness in a core muscle is capable of increasing anterior pelvic tilt whilst running, likely increasing the risk of hamstring strain injury. Likewise, it is the first to show evidence of proximal muscle fatigue affecting hamstring torque production. Nonetheless, the magnitude of the increase in anterior pelvic tilt (no greater than ~1.3 ± 2.0°) raises some concerns for the wider adoption of core muscle training for hamstring injury prevention.
|Date of Award||Jan 2020|