Objective: Determine if asymmetry relative to the preferred kicking leg exists for the psoas and quadratus lumborum muscles among elite Australian Football League (AFL) players.
Design: AFL players were assessed at 3 time points from 2005-2007 (start of pre-season, end of season and end of pre-season training). Magnetic Resonance Imaging (MRI) was used to determine the cross-sectional areas (CSAs) of the psoas and quadratus lumborum (QL) muscles at the L4-5 vertebral level (psoas) and the L3-4 vertebral level (QL).
Setting: MRI was performed in a hospital setting.
Participants: 54 professional AFL players were eligible to participate in this study. The number of subjects at each of the 3 time points was 36 for Time 1 (T1 Nov 2005), 31 for Time 2 (T2 Aug 06) and 43 for Time 3 (T3 Feb/Mar 07).
Risk Factors: The repeated measures factor in the analyses was ‘asymmetry’, defined as ‘ipsilateral’ or ‘contralateral’ to preferred kicking leg. Number of injuries (coded as 0, 1, 2 or more) was also included as a risk factor.
Main Outcome Measurements: The dependent variables were the CSAs of the psoas and QL muscles.
Results: At all 3 time points, the CSA of the psoas muscle was significantly greater ipsilateral to the kicking leg, while the CSA of the QL muscle was significantly greater on the side contralateral to the kicking leg. Asymmetry in muscle size was not related to number of injuries.
Conclusions: Asymmetry of the psoas and the quadratus lumborum muscle exists in elite AFL players.