UNDERSTANDING THE FACTORS INFLUENCING FUNCTIONAL TASKS FOR THE ASSESSMENT OF MUSCULOSKELETAL INJURY-RELATED BIOMECHANICS

Background: The evaluation of lower limb biomechanics during functional tasks is extremely common and relevant in the current sports and exercise medicine literature. The choice of which task to use, which variation to adopt and which metric to extract is dependent on the research question and on the population investigated. However, each of those factors (in combination with many others) may affect the findings obtained by functional task, which, in turn, may lead to inadequate planning of rehabilitation and injury prevention protocols in clinical and sports practice. Aims: To evaluate how distinct factors influence biomechanical assessment during functional tasks using different tasks, metrics, and populations. Thesis structure: Four experimental studies were conducted in order to address five specific aims that will contribute to the current knowledge on the use of functional tasks. Study 1: This study compared kinematics when executing three squat-based tasks (single-leg squat, anterior step-down, and lateral step-down) at three different speeds (slow, fast and self-selected. The study found that both task type and movement speed can influence several metrics commonly used to assess movement kinematics, albeit with small absolute difference in degrees. Study 2: This study investigated if there were relationships between two metrics of muscle activation of lower limb and core muscles during single-leg squats and anterior step-downs. The findings show that, although present, this relationship is muscle, metric and task dependent. Study 3: This study compared the differences between people with different running experience levels on linear and angular stiffness during running gait, finding that these metrics were not different between groups, suggesting that the increased injury rate in less-experienced runners is likely not explained by different gait patterns. Study 4: This study measured the test-retest reliability of force measurements during the execution of functional tasks with progressive difficulty in a healthy and pathological population. The results show that these metrics is dependent on the task, the metric and the participants’ injury status and that several metrics were not sufficiently reliable. Conclusion: The thesis findings support the idea that results are highly dependent on many components that need to be taken into account when using functional tasks for the evaluation of healthy and clinical populations. Furthermore, it supports the necessity for the sports and exercise medicine literature to provide as many details as possible when describing these tasks and that care should be taken when comparing research findings with other studies that might have used different task variations, metrics and populations.