Playing Surface Impacts Yo-Yo Intermittent Recovery Test (Level 1) Performance and Validity of Indirect VO2max Estimation.

This study compared performance on the Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) and the agility t-test between two playing surfaces, artificial turf and natural grass. This study also assessed agreement between estimated VO2max from the YYIR1 on artificial turf and natural grass with laboratory measured VO2max. Male collegiate soccer players completed three experimental sessions on separate days: YYIR1 and t-test on artificial turf, YYIR1 and t-test on natural grass, and a laboratory VO2max test. The validated Bangsbo et al. equation was used to estimate VO2max from YYIR1 distance. Participants covered more distance (2370 ± 662 vs. 1441 ± 463 m, p < .001) and reached higher maximal aerobic speed (17.29 ± 0.99 vs. 15.76 ± 0.78 km/h, p < .001) on natural grass. Agility t-test was faster on grass (8.75 ± 0.53 vs. 9.43 ± 0.73 s, p < .001). Grass estimated VO2max was higher than laboratory VO2max and turf estimated VO2max (58.0 ± 4.5 vs. 54.2 ± 3.4 vs. 49.8 ± 3.4 mL/kg/min, p < .001). Grass estimated VO2max was positively correlated with turf estimated VO2max (r = 0.91, p < .001). Bland-Altman analysis indicated that grass estimated VO2max overestimated laboratory VO2max and turf estimated VO2max underestimated laboratory VO2max (p < .001). Findings indicate playing surface is a critical factor in the performance outcome and accuracy of field-based aerobic fitness assessment. Findings emphasize the importance of considering environmental and contextual variables when administering and interpreting assessment data.