Yo-Yo intermittent tests are a valid tool for aerobic fitness assessment in recreational football

Purpose: To examine the suitability of three versions and two levels of the Yo-Yo intermittent tests for assessing and tracking aerobic fitness status development in male recreational football players. Sixty-six untrained participants (age 39 ± 6 years, VO_2max 41.2 ± 6.2 ml kg⁻¹ min⁻¹, body mass 81.9 ± 10.8 kg, height 173.2 ± 6.4 cm) partook in a 12-week recreational football training program. They were evaluated during the Yo-Yo intermittent endurance level 1 (YYIE1) and 2 (YYIE2) tests and the Yo-Yo intermittent recovery level 1 test (YYIR1), and during a treadmill test for VO_2max assessment, at baseline. Thirty-two out of these 66 participants replicated all these tests at post-intervention. An additional group of 30 male age-matched recreational football players that afterwards started the 12-week recreational football program (age 39 ± 6 years, VO_2max 45.3 ± 5.8 ml kg⁻¹ min⁻¹, body mass 82.5 ± 7.8 kg, height 172.8 ± 5.4 cm) was evaluated at baseline to test cross-validation. Results: The Yo-Yo tests showed very large associations with VO_2max at baseline (r = 0.75–0.77; P < 0.0001) and at post-intervention (r = 0.76–0.82; P < 0.0005). Post-training, very large associations were found between YYIE2 performance and VO_2max (r = 0.65, P < 0.0001). Cross-validation revealed small to large differences between the observed and estimated VO_2max values (1.5–2.96 ml kg⁻¹ min⁻¹) with moderate typical error of estimation (7.9–8.7%) across the tests. Performance in the YYIE1, YYIE2 and YYIR1 tests of ≥ 1760, 480 and 600 m, respectively, indicated good to excellent VO_2max values. Conclusions: The Yo-Yo tests considered here showed robust and consistent criterion validity. The YYIE2 could be a more accurate option to track aerobic fitness development in recreational football players.