Reliability of the 30-15 Intermittent Fitness Test in Semiprofessional Soccer Players

Purpose: The purpose of this investigation was to determine the reliability of the 30-15 Intermittent Fitness Test (30-15(IFT)) in semiprofessional soccer players. Methods: Fourteen male semiprofessional soccer players performed the 30-15(IFT) on 2 occasions separated by 7 d. Reliability was assessed by intraclass correlation coefficient (ICC), typical error of measurement expressed as a coefficient of variation (CV), and smallest worthwhile change (SWC) to determine any significant difference between testing sessions. Results: Maximal intermittent running velocity (V-IFT) demonstrated good reliability (ICC = .80) for between-sessions reliability. The CV was 2.5% for between-sessions reliability of the 30-15(IFT). As the SWC (0.70 km/h) falls within the range in which the individual's true score is likely to lie (1.0 km/h), the usefulness of the V-IFT was rated as marginal. Despite the usefulness of the 30-15(IFT) being deemed marginal, a change in performance as small as 1.0 km/h (2 stages) in V-IFT could be considered substantial or real. Conclusion: This study demonstrates that V-IFT in the 30-15(IFT) is reliable, resulting in a reliable assessment of team-sport-specific cardiorespiratory fitness, with changes as small as 1.0 km/h (2 stages) in V-IFT considered meaningful.