Normative Yo-Yo Intermittent Recovery Level 1 and Yo-Yo Intermittent Endurance Level 1 test values of boys aged 9–16 years

ObjectivesTo provide age- and sex-specific reference values of Yo-Yo tests in children and adolescents.DesignSystematic review.MethodsA literature search for articles on Yo-Yo Intermittent (YYI) tests was performed in MEDLINE, SPORTDiscus, Web of Science and Google Scholar. Original reports on healthy children/adolescents 6–16years of age were eligible. For each test, age- and sex-related reference values were calculated using global means and percentiles.ResultsNinety-two studies (7398 participants) fulfilled the eligibility criteria. The YYI tests most frequently used were the Yo-Yo Intermittent Recovery Level 1 test (YYIR1, 57.8%), Yo-Yo Intermittent Endurance Level 1 test (YYIE1, 14.7%), Yo-Yo Intermittent Recovery Level 1 Children’s test (YYIR1C, 12.7%), Yo-Yo Intermittent Endurance Level 2 test (YYIE2, 8.8%) and the Yo-Yo Intermittent Recovery Level 2 test (YYIR2, 5.9%). Of these, 71.6% reported test results of boys, 17.6% reported mixed test results and 10.8% reported test results of girls. Smoothed centile curves for the YYIR1 and YYIE1 over the entire age range were generated for boys, revealing constantly increasing performance with increasing age.ConclusionsYYI tests values differ with respect to age and sex. In boys, development of YYIR1 and YYIE1 test values (6–16years of age) was different, suggesting better applicability of the YYIR1 test for boys >13years of age. The results may be used to rate YYI test performance for continuous screening and to identify children with low physical fitness. Since limited data was available of females, further research on YYI tests is needed with respect to sex-specific results.