The 3d kinematics of the single leg flat and decline squat

THE 3D KINEMATICS OF THE SINGLE LEG FLAT AND DECLINE SQUAT Stephen Timms Bachelor of Applied Science (Human Movements Studies) Professor Keith Davids, Dr Anthony Shield, Dr Marc Portus Submitted in fulfilment of the requirements for the degree of Masters of Science (Research) School of Human Movements Faculty of Health Queensland University of Technology i Keywords Kinematics, biomechanics, single leg squat, physiotherapy screening protocols, lumbopelvic stability, intrinsic injury risk, malalignment, hip strength, ankle dorsiflexion The 3D kinematics of the single leg flat and decline squat i ii Abstract Background: Pre-participation screening is commonly used to measure and assess potential intrinsic injury risk The single leg squat is one such clinical screening measure used to assess lumbopelvic stability and associated intrinsic injury risk With the addition of a decline board, the single leg decline squat (SLDS) has been shown to reduce ankle dorsiflexion restrictions and allowed greater sagittal plane movement of the hip and knee On this basis, the SLDS has been employed in the Cricket Australia physiotherapy screening protocols as a measure of lumbopelvic control in the place of the more traditional single leg flat squat (SLFS) Previous research has failed to demonstrate which squatting technique allows for a more comprehensive assessment of lumbopelvic stability Tenuous links are drawn between kinematics and hip strength measures within the literature for the SLS Formal evaluation of subjective screening methods has also been suggested within the literature Purpose: This study had several focal points namely 1) to compare the kinematic differences between the two single leg squatting conditions, primarily the five key kinematic variables fundamental to subjectively assess lumbopelvic stability; 2) determine the effect of ankle dorsiflexion range of motion has on squat kinematics in the two squat techniques; 3) examine the association between key kinematics and subjective physiotherapists’ assessment; and finally 4) explore the association between key kinematics and hip strength Methods: Nineteen (n=19) subjects performed five SLDS and five SLFS on each leg while being filmed by an camera motion analysis system Four hip strength measures (internal/external rotation and abd/adduction) and ankle dorsiflexion range of motion were measured using a hand held dynamometer and a goniometer respectively on 16 of these subjects The same 16 participants were subjectively assessed by an experienced physiotherapist for lumbopelvic stability Paired samples t-tests were performed on the five predetermined kinematic variables to assess the differences between squat conditions A Bonferroni correction for multiple comparisons was used which adjusted the significance value to p = 0.005 for the paired t-tests Linear regressions were used to assess the relationship between kinematics, ankle range of motion and hip strength measures Bivariate correlations ii The 3D kinematics of the single leg flat and decline squat iii between hip strength measures and kinematics and pelvic obliquity were employed to investigate any possible relationships Results: 1) Significant kinematic differences between squats were observed in dominant (D) and non-dominant (ND) end of range hip external rotation (ND p =