Control of the lower limb during a fatiguing dynamic task

Human locomotion often requires the performance of submaximal, repeated and rhythmical efforts over an extended period of time. The ability to maintain consistent performance for extended periods is likely due to multiple adaptive mechanisms and may be affected by the progression of fatigue. However, it remains unclear whether changes in movement strategies are due to fatigue, changes in task performance or the repetitive nature of the task. Further, it is unknown if there are differences in movement strategies between the sexes during extended and fatiguing locomotive tasks. The aims of this thesis were to investigate the influence of fatigue and the effect of sex on neuromechanical characteristics during a repetitive and rapid lower limb loading task while performance output was maintained. To address these aims, a series of experimental investigations were completed. The findings of these studies demonstrated a relationship between increased muscle activity and variability between adjoining lower limb segments as fatigue progressed. Further, men and women demonstrated differential changes as the level of fatigue increased. Women demonstrated a greater increase in joint coupling variability than men, which may have been associated with the greater relative dependence on the knee extensor muscle as the task progressed. These results extend the understanding of how there is an optimisation of variability in the neuromechanical system during the performance of repetitive tasks to fatigue in a healthy recreationally active population. Importantly, these results provide insight into what compensatory strategy may be utilised when motor performance was stereotypical