Minimal Number of Events Required for Acceleration-Speed Profiling in Elite Women's Soccer.

Abstract

To determine the minimum number of events (training or matches) for producing valid acceleration-speed (AS) profiles from global navigation satellite system (GNSS) data. Nine elite female soccer players participated in a 4-week training camp consisting of 19 events. AS profile metrics calculated from different combinations of athlete events were compared to force-velocity (FV) profile metrics from 2 × 40-m stand-alone sprint effort trials, using the same GNSS 10-Hz technology. Force-velocity profiles were calculated, from which AS profiles were obtained. AS profiles from training and matches were generated by plotting acceleration and speed points and performing a regression through the maximal points to obtain the AS metrics (theoretical maximal speed, x-intercept [in meters per second], theoretical maximal acceleration, y-intercept [in meters per second squared], and the slope per second). A linear mixed model was performed with the AS metrics as the outcome variables, the number of events as a fixed effect, and the participant identifier as a mixed effect. Dunnett post hoc multiple comparisons were used to compare the means of each number of event grouping (1-19 events) to those estimated from the dedicated sprint test. Theoretical maximal speed and theoretical maximal acceleration means were no longer significantly different from the isolated sprint reference with 9 to 19 (small to trivial differences = -0.31 to -0.04m·s-1, P = .12-.99) and 6 to 19 (small differences = -0.4 to -0.28m·s-2, P = .06-.79) events, and the slopes were no longer different with 1 to 19 events (trivial differences = 0.06-0.03s-1, P = .35-.99). AS profiles can be estimated from a minimum of 9days of tracking data. Future research should investigate methodology resulting in AS profiles estimated from fewer events.