The Effect of Body Mass on the 30-15 Intermittent Fitness Test in Rugby Union Players.

Purpose: To evaluate the difference in performance of the 30-15 Intermittent Fitness Test (30-15_IFT) across 4 squads in a professional rugby union club in the UK and consider body mass in the interpretation of the end velocity of the 30-15_IFT (V_IFT). Methods: One hundred fourteen rugby union players completed the 3O-15_IFT midseason. Results: V_IFT demonstrated small and possibly lower (ES = -0.33; 4/29/67) values in the under 16s compared with the under 21s, with further comparisons unclear. With body mass included as a covariate, all differences were moderate to large and very likely to almost certainly lower in the squads with lower body mass, with the exception of comparisons between senior and under-21 squads. Conclusions: The data demonstrate that there appears to be a ceiling to the V_IFT attained in rugby union players that does not increase from under-16 to senior level. However, the associated increases in body mass with increased playing level suggest that the ability to perform high-intensity running increases with age, although not translating into greater V_IFT due to the detrimental effect of body mass on change of direction. Practitioners should be aware that V_IFT is unlikely to improve, but it needs to be monitored during periods where increases in body mass are evident. [ABSTRACT FROM AUTHOR]