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

Objective: To investigate the reliability and validity of the measurement of lateral trunk motion (LTM) in two-dimensional (2D) video analysis of unipodal functional screening tests. Design: Observational study. Setting: Research laboratory. Participants: Forty-three injury-free female athletes. Main outcome measures: Knee 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. Results: Excellent 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. Conclusions: LTM can be measured with excellent intra- and intertester reliability. The combination of IN and LTM was moderately associated with pKAM and thus including LTM may aid assessment of movement quality and injury risk. (C) 2013 Elsevier Ltd. All rights reserved.