Altered sagittal plane mechanics is associated with Functional Movement Screen deep squat score

Background: The Functional Movement Screen (FMS) assesses the quality of movements, including the deep squat (DS), which is used in sports settings. The validity of the individual item scores has yet to be established. Objectives: To investigate the validity of the FMS DS by comparing the sagittal plane kinematics of participants who achieve different observer scores. Method: Seventeen injury-free, adolescent male cricket bowlers were assessed. The movement was captured using the Optitrack((R)) motion capture system. Simultaneously, observers scored participants' execution of the DS according to the standard FMS scoring criteria. Participants were grouped into Group 1 (lowest score), Group 2 (altered movement mechanics) or Group 3 (perfect score) according to observer scores. Specific joint angles of each group were compared using the Kruskal-Wallis and Mann-Whitney U tests. Results: There were significant differences in the degree to which the femur passed the horizontal between Group 3 and Group 1 (p = 0.04, r = 0.61) and Group 2 and Group 1 (p = 0.03, r = 0.66) and the difference in the degree to which the torso was kept vertical between Group 3 and Group 1 (p = 0.02, r = 0.66) and Group 2 and Group 1 (p = 0.02; r = 0.72). Conclusion: Kinematic differences exist between participants who achieve different observer scores for the FMS DS. Clinical implications: While differences in sagittal plane kinematics have been observed in participants scoring high on the FMS DS and participants scoring low, further investigation into the validity of the frontal plane kinematics is warranted, as well as the concurrent validity of the individual scoring criteria.