A critical analysis of two popular field-based movement screens

The Functional Movement Screen (FMS) and the Landing Error Scoring System (LESS) are two of the most commonly used field-based movement screens in the practical setting. The FMS is a series of seven tests that examine movement patterns of the body through assessing an overhead squat, an inline lunge, a hurdle step, two tests of core stability and upper and lower body mobility tests. The LESS is a dynamic drop jump where the landing is assessed and scored. The key purpose of both screens is to identify those who move poorly and may be at increased risk of injury. Theoretically, the premise behind movement screening as a tool to identify those at increased risk of injury is sound. There is a large body of evidence highlighting that aberrant movements during dynamic tasks, as identified through 3D motion analysis, are associated with increased chance of injury. Therefore, if field-based screens could distinguish similar poor mechanics it may identify those at increased risk of injury. Despite the theoretical justification and practical use of the FMS and LESS, several topics related to the two screening protocols require investigation. First, there is a lack of evidence examining the relationship between the FMS and LESS. It is unknown whether the FMS and LESS provide similar information to each other or whether they measure different movement variables. Second, there have been no studies investigating the association of injury with the FMS and LESS in the same cohort. Finally, there is a lack of empirical evidence examining the relationship between 3D kinematics during a dynamic task and FMS and LESS scores. To address these gaps in the literature a series of progressive studies were conducted. First, FMS and LESS scores of 98 participants were correlated against each other. A significant moderate correlation (rho 100 and 21 point = -0.528; -0.487; p< .001) but poor shared variance (r² 100 and 21 point FMS=0.26 and 0.24 respectively) was reported in this study highlighting that the FMS and LESS measure different movement variables. The results of this first study highlighted that the FMS and LESS should not be used as a substitute for each other. However, the results could not determine which screen had a greater association with injury. Therefore, a prospective injury study was conducted with 132 military participants undertaking an intensive 16 week fitness regimen. Injury data was recorded daily with this cohort. The results identified that a total FMS score was not a significant predictor of injury. LESS scores of > 5 or having a score of 1 on any FMS test were significantly associated with injury. LESS scores had greater relative risk, sensitivity and specificity (2.2 (95% CI= 1.48-3.34); 71% and 87% respectively) compared to scores of 1 on the FMS (relative risk = 1.32 (95% CI= 1.0-1.7); sensitivity =50% and specificity = 76%). The final study of this research examined LESS and FMS scores of 52 participants against 3D lower limb kinematics during a drop jump. The results demonstrated that LESS scores could differentiate between poor and acceptable groups at initial contact and maximal displacement for hip flexion, hip adduction, knee valgus and knee rotation. These variables have been associated with injury in previous large prospective and retrospective studies. FMS scores could differentiate maximal hip flexion and knee valgus with a moderate to small effect size (ES= 0.71 and 0.74 respectively) but could not differentiate any other kinematic variables in the sagittal, frontal or transverse plane at the hip or knee at initial contact or maximal displacement. These results highlighted a limited ability of FMS scores to identify those who would perform a drop jump with kinematics associated with increased chance of injury. The results of this programme of research highlight that the LESS and FMS are reliable screening tools. The two screening tools do not provide the same information and should not be used as a substitute for one another. The LESS has a stronger association with injury compared to the FMS, most likely due to its greater association with aberrant 3D kinematics during dynamic tasks. This research highlights limitations in using the FMS as a standalone screening assessment due to its limited ability to assess dynamic movements. Given the findings presented in this thesis practitioners should incorporate an additional dynamic screen, such as the LESS if using the FMS as their sole assessment of movement ability in order to get a more comprehensive assessment of movement quality and injury risk.