ABSTRACT
Objectives: This study aims to develop generic velocity thresholds for the analysis of external load data collected in international women’s football matches.
Methods: Doppler-derived recordings of instantaneous velocity and acceleration were collected (10 Hz GPS) from 27 international female football players during 52 international matches between 2012 and 2015. Data were examined with k-means, Gaussian mixture model (GMM), and Spectral Clustering methods to identify four velocity zones, in each completed half of match-play (277 observations). Spectral Clustering was also performed with 4 different smoothing parameters ( values of 0, 0.001, 0.01, and 0.1). Linear-mixed modelling was used to determine generic squad thresholds, accounting for the within-subject variation.
Results: k-means and GMM generated low transition velocities, which had limited logical validity and deemed not fit for purpose. Spectral Clustering with a value of 0.1 derived thresholds that differed from the various methods adopted in existing literature and industry practice, yet providing a rigorous, acceptable, and feasible determination of velocity thresholds.
Conclusion: Velocities of 3.46 (12.5 km h−1), 5.29 (19.0 km h−1), and 6.26 m s−1 (22.5 km h−1) are recommended as entry criteria into high, very-high velocity, and sprinting locomotor categories, respectively, for the purpose of external load assessments in elite women’s football.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary Material
Supplementary can be accessed here.