Are tibial angles measured with inertial sensors useful surrogates for frontal plane projection angles measured using 2-dimensional video analysis during single leg squat tasks? A reliability and agreement study in elite football (soccer) players

Tom Hughes,Richard K Jones,Chelsea Starbuck,Jonathan Picot,Jamie C Sergeant,Michael J Callaghan

doi:10.1016/j.jelekin.2018.11.005

Abstract

During single leg squats (SLS), tibial angle (TA) quantification using inertial measurement units (IMU) may offer a practical alternative to frontal plane projection angle (FPPA) measurement using 2-dimensional (2D) video analysis. This study determined: (i) the reliability of IMUs and 2D video analysis for TA measurement, and 2D video analysis for FPPA measurement; (ii) the agreement between IMU TA and both 2D video TA and FPPA measurements during single leg squats in elite footballers. 18 players were tested on consecutive days. Absolute TA (ATA) and relative TA (RTA) were measured with IMUs. ATA and FPPA were measured concurrently using 2D video analysis. Within-session reliability for all measurements varied across days (intraclass correlation coefficient (ICC) range = 0.27–0.83, standard error of measurement (SEM) range = 2.12–6.23°, minimal detectable change (MDC) range = 5.87–17.26°). Between-sessions, ATA reliability was good for both systems (ICCs = 0.70–0.74, SEMs = 1.64–7.53°, MDCs = 4.55–7.01°), while IMU RTA and 2D FPPA reliability ranged from poor to good (ICCs = 0.39–0.72, SEMs = 2.60–5.99°, MDCs = 7.20–16.61°). All limits of agreement exceeded a 5° acceptability threshold. Both systems were reliable for between-session ATA, although agreement was poor. IMU RTA and 2D video FPPA reliability was variable. For SLS assessment, IMU derived TAs are not useful surrogates for 2D video FPPA measures in this population.

Highlights

In professional football, periodic health examination (PHE) is commonly used to obtain performance or rehabilitation benchmarks and to assess potential prognostic factors associated with future injuries (Hughes et al, 2018)
Orthotics were used in the training shoes of 6 participants for both testing sessions, as they had been previously prescribed by a podiatrist
This study demonstrates the reliability limitations of an inertial measurement units (IMU) and 2D video analysis system for single leg squats (SLS) kinematic assessment in elite football players, especially during within-session analyses

Summary

Introduction

In professional football (soccer), periodic health examination (PHE) is commonly used to obtain performance or rehabilitation benchmarks and to assess potential prognostic factors (predictors) associated with future injuries (Hughes et al, 2018). Typical abnormal kinematics include increased hip medial rotation and adduction, medial tibial rotation and increased foot pronation (Hollman et al, 2009). These movements increase the knee abduction moment and result in medial knee displacement, known as dynamic valgus (Bell et al, 2008, Petersen et al, 2017) or medial collapse (Powers, 2003). Such kinematics are implicated in non-contact anterior cruciate ligament injury (Koga et al, 2011, Krosshaug et al, 2007, Walden et al, 2015) and in patellofemoral joint dysfunction (Herrington, 2014, Levinger et al, 2007, Nakagawa et al, 2012, Willson and Davis, 2008, Willy et al, 2012).

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