Beschreibung:
<jats:title>Abstract</jats:title>
<jats:p>Scott, TJ, Duthie, GM, Delaney, JA, Sanctuary, CE, Ballard, DA, Hickmans, JA, and Dascombe, BJ. The validity and contributing physiological factors to 30-15 intermittent fitness test performance in rugby league. <jats:italic toggle="yes">J Strength Cond Res</jats:italic> 31(9): 2409–2416, 2017—This study examined the validity of the 30-15 Intermittent Fitness Test (30-15<jats:sub>IFT</jats:sub>) within rugby league. Sixty-three Australian elite and junior-elite rugby league players (22.5 ± 4.5 years, 96.1 ± 9.5 kg, Σ7 skinfolds: 71.0 ± 18.7 mm) from a professional club participated in this study. Players were assessed for anthropometry (body mass, Σ7 skinfolds, lean mass index), prolonged high-intensity intermittent running (PHIR; measured by 30-15<jats:sub>IFT</jats:sub>), predicted aerobic capacity (MSFT) and power (AAS), speed (40 m sprint), repeated sprint, and change of direction (COD—505 agility test) ability before and after an 11-week preseason training period. Validity of the 30-15<jats:sub>IFT</jats:sub> was established using Pearson's coefficient correlations. Forward stepwise regression model identified the fewest variables that could predict individual final velocity (<jats:italic toggle="yes">V</jats:italic>
<jats:sub>IFT</jats:sub>) and change within 30-15<jats:sub>IFT</jats:sub> performance. Significant correlations between <jats:italic toggle="yes">V</jats:italic>
<jats:sub>IFT</jats:sub> and Σ7 skinfolds, repeated sprint decrement, V̇<jats:sc>o</jats:sc>
<jats:sub>2</jats:sub>max<jats:sub>MSFT</jats:sub>, and average aerobic speed were observed. A total of 71.8% of the adjusted variance in 30-15<jats:sub>IFT</jats:sub> performance was explained using a 4-step best fit model (V̇<jats:sc>o</jats:sc>
<jats:sub>2</jats:sub>max<jats:sub>MSFT</jats:sub>, 61.4%; average aerobic speed, 4.7%; maximal velocity, 4.1%; lean mass index, 1.6%). Across the training period, 25% of the variance was accounted by ΔV̇<jats:sc>o</jats:sc>
<jats:sub>2</jats:sub>max<jats:sub>MSFT</jats:sub> (<jats:italic toggle="yes">R</jats:italic>
<jats:sup>2</jats:sup> = 0.25). These relationships suggest that the 30-15<jats:sub>IFT</jats:sub> is a valid test of PHIR within rugby league. Poor correlations were observed with measures of acceleration, speed, and COD. These findings demonstrate that although the 30-15<jats:sub>IFT</jats:sub> is a valid measure of PHIR, it also simultaneously examines various physiological capacities that differ between sporting cohorts.</jats:p>