Dose-Response Relationships between Training Load Measures and Physical Fitness in Professional Soccer Players

The aim of this cohort study was two-fold: (i) to analyze within-group changes of final velocity in a 30-15 intermittent fitness test (V_IFT), final velocity in a Vameval test (V_vameval), 20-m sprint and countermovement jump (CMJ); (ii) to explore the relationships between V_IFT and Vvameval outcomes and their changes with internal and external loads. Twenty-two professional soccer players (mean ± SD; age 27.2 ± 3.4 years, height 174.2 ± 3.6 cm, body mass 69.1 ± 6.4 kg, and body fat 10.4 ± 4.1%, 3.1 ± 1.5 years in the club) participated in this study. External and internal loads were obtained using global positioning system, heart rate and rate of perceived effort (sRPE) after each training session. Players were assessed in CMJ, 20-m sprint, Vameval and 30-15 intermittent fitness test, before and after the observed period. Very large relationships were observed between V_IFT and Vameval for pre- (r = 0.76), post (r = 0.80) and pooled-data (r = 0.81). V_vameval showed less sensitivity (-22.4%, [-45.0 to 9.4]), ES -0.45 [-1.05 to 0.16]) than V_IFT. ∆V_IFT had unclear associations with all sRPE, but had moderate correlations with objective internal and external measures, while, ∆V_vameval varied between large and very large relationships with all sRPE, but had unclear associations with all other selected training loads. Objective internal and external loads may be used to track aerobic power related changes from V_IFT.