Comparing critical speed modelling approaches and exploring relationships with match-play variables in elite male youth soccer players

Abstract

Background: A novel bi-exponential method has emerged to estimate critical speed (CS) and D-prime (D′) from a 3-min allout test (3MT).
Objectives: To compare CS analysis methods to determine whether parameter estimations were interchangeable. Reference values and relationships  with key soccer matchplay variables were explored.
Methods: Thirteen elite male youth (14-15 years old) players completed a 30 m shuttle run 3MT to estimate CS, D′, rate of speed decline time constant,  maximal speed (S_max), time to S_max (t_max), and fatigue index (FI), using the traditional method and bi-exponential model on average (Bi-Exp_Average)  and max speed settings (Bi-Exp_Max-Speed). High-speed running (HSR) and sprinting distances and counts, and the number of accelerations were  collected from two matches. Magnitude based inferences (p < 0.05) with smallest worthwhile change of 0.2 effect sizes were used to analyse differences. Pearson’s and Spearman’s correlation coefficients were used to measure associations between CS model variables and match-play parameters.
Results: There were significant differences between the traditional method and both bi-exponential models for CS and D′, as well as between the bi-  exponential models for all variables except t_max. Using the Bi-Exp_Average model, strong correlations (r = 0.70-0.73; p < 0.05) were observed for D′ and FI  with the number of standardised and individualised HSRs, respectively. With the Bi-Exp_Max-Speed model, there were strong correlations (r/ρ = 0.64-0.68;  p < 0.05) between D′ and the number of standardised HSRs and sprints, and the number of individualised sprints.
Conclusion: There is a lack of interchangeability between analysis methods. It appears that D′ and FI from the biexponential models could be associated  with high-intensity actions in soccer match-play.