The reliability and validity of the measurement of lateral trunk motion in two-dimensional video analysis during unipodal functional screening tests in elite female athletes

Abstract

ObjectiveTo investigate the reliability and validity of the measurement of lateral trunk motion (LTM) in two-dimensional (2D) video analysis of unipodal functional screening tests. DesignObservational study. SettingResearch laboratory. ParticipantsForty-three injury-free female athletes. Main outcome measuresKnee valgus (KV) and lateral trunk motion (LTM) angles were measured with a standard digital camera during the single leg squat and the single leg drop vertical jump (SLDVJ). Three-dimensional motion analysis was used during the SLDVJ to measure peak external knee abduction moment (pKAM). Intraclass correlation coefficients were calculated to assess the intra- and intertester reliability of the LTM angle. Correlations between 2D angles and pKAM were calculated for the SLDVJ. ResultsExcellent intraclass correlation coefficients for the LTM angle were found within (0.99–1.00) and between testers (0.98–0.99). The sum of KV and LTM was significantly correlated with the pKAM during the SLDVJ for the dominant (r = −0.36; p = 0.017) and non-dominant leg (r = −0.32; p = 0.034), while either angle alone was not. ConclusionsLTM can be measured with excellent intra- and intertester reliability. The combination of KV and LTM was moderately associated with pKAM and thus including LTM may aid assessment of movement quality and injury risk.