Reliability and Validity of the 30-15 Intermittent Field Test With and Without a Soccer Ball

Objective: The purpose of this study was to examine the reliability and validity of the 30-15 Intermittent Field Test (30-15_IFT) with and without a ball. Methods: Twenty-four collegiate female soccer players (19.46 ± 1.22 years; 167.01 ± 7.23 cm; 60.95 ± 7.84 kg) performed 1 trial of the Yo-Yo Intermittent Recovery (YYIR) test, 3 trials of the 30-15_IFT, and 3 trials of the 30-15_IFT with a ball (30-15_IFT-B), separated by a minimum 48 hours. Maximal intermittent running velocity (V_IFT), heart rate at exhaustion (HR_peak), and rating of perceived exertion (RPE) were collected. Results: Intraclass correlation coefficients (ICCs) between trials demonstrated good reliability during the 30-15_IFT in V_IFT (ICC = 0.88) and HR_peak (ICC = 0.89), in addition to the 30-15_IFT-B V_IFT (ICC = 0.83) and HR_peak (ICC = 0.87). V_IFT was significantly reduced in 30-15_IFT-B (15.82 km h^-1) compared to 30-15_IFT (17.52 km h^-1; p < .001), regardless of trial. HR and RPE were significantly greater in 30-15_IFT compared to 30-15_IFT-B (p < .05). Estimated maximal oxygen consumption (VO₂max) YYIR and estimated VO₂max of 30-15_IFT and 30-15_IFT-B was very strongly (r = 0.82) and strongly (r = 0.68) correlated. Conclusion: The 30-15_IFT is considered valid and reliable and the 30-15_IFT-B was reliable in female soccer players.