Relationships and agreement between Yo-Yo intermittent recovery test level 1 performance and laboratory VO2max in adolescent male soccer players: roles of maturity status, playing position, and running economy

Abstract

Background: Accurate assessment of aerobic fitness is essential in youth soccer. The Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) provides a practical estimate of maximal oxygen uptake (VO2max), but its agreement with laboratory values across maturity stages remains uncertain. Aim: To examine the relationship and agreement between YYIR1 performance and laboratory-measured VO2max in adolescent male soccer players, and to assess whether biological maturation, playing position, and running economy (RE) affect estimation consistency. Subjects and methods: Twenty-three players (13.7 ± 0.5 years) completed YYIR1 and laboratory treadmill tests (LTT). VO2max was measured during LTT and estimated from YYIR1 performance. Effects of biological maturation [pre-, circa-, post-peak height velocity (PHV)], position, and RE were analysed. Results: YYIR1 underestimated VO2max by 5.2% versus LTT (p < 0.001) but showed strong correlation (r = 0.82). Bland–Altman analysis indicated acceptable agreement. Estimation consistency was higher in pre- and circa-PHV players, though subgroup sizes were small. Maturation, position, and RE had no significant effects. Conclusions: YYIR1 is strongly associated with laboratory VO2max but systematically underestimates it. Coaches may use YYIR1 distance to monitor intermittent endurance, while interpreting estimated VO2max with caution. Larger, maturity-balanced samples are needed to clarify subgroup differences and improve youth-specific prediction accuracy.