Fig. 2
Comparison for Yo-Yo intermittent recovery test across playing standards for the two age-categories. The Yo-Yo IRT L1 test scores significantly improved with increasing playing standard among U16 s but failed to distinguish elite from sub-elite rugby players at U19 level. The sub-elite rugby players showed the largest mean differences between U19 and U16 athletes (p < 0.05; η2p = 0.26)