Purpose: Using elite youth soccer players' maximal sprinting speeds collected from a criterion and non- criterion measure, we demonstrate how expert practitioner opinion can be used to determine mea- surement validity. Methods: Expert soccer practitioners (n = 50) from around the world were surveyed on issues relating to the measurement of maximal sprinting speed and 12 elite youth soccer players performed two maximal 40 m sprints, measured by 10-Hz GPS units (non-criterion) and a 100-Hz Laser (criterion). Setting Statistical equivalence bounds as practitioner opinion of the practically acceptable amount of measurement error for maximal sprinting speed, we assessed agreement between GPS and Laser. Results: Survey respondents reported a combination of methods for deriving maximal sprinting speed (tests, training, match) but most did not assess System validity. Median value of the practically acceptable amount of measurement error for maximal sprinting speed was 0.20 m/s. Maximal sprinting speed was 8.79 ± 0.33 m/s (Laser) and 8.75 ± 0.32 m/s (GPS), and the mean difference was 0.04 (90% confidence interval -0.03 to 0.11) m/s. Using the median acceptable amount of measurement error, we set our lower and upper equivalence bounds to -0.10 m/s and +0.10 m/s, respectively. Equivalence testing showed Laser and GPS as likely equivalent measures (probability 93.7%). Condusion: Using expert-informed equivalence thresholds represents a novel way to assess validity in sports performance research.
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