This study analysed the reliability and validity of two intermittent running tests (the Yo-Yo IR1 test and the Andersen test) as tools for estimating VO2max in children under the age of 10. Two groups, aged 6-7 years (grade 0, n = 18) and 8-9 years (grade 2, n = 16), carried out two repetitions of a modified Yo-Yo IR1 test (2 x 16 m) and the Andersen test, as well as an incremental treadmill test, to directly determine the VO2max. No significant differences were observed in test-retest performance of the Yo-Yo IR1 test [693 +/- 418 (+/- SD) and 670 +/- 328 m, r(2) = 0.79, CV = 19%, p > 0.05, n = 32) and the Andersen test (988 +/- 77 and 989 +/- 87 m, r(2) = 0.86, CV = 3%, p > 0.05, n = 31). The Yo-Yo IR1 (r(2) = 0.47, n = 31, p < 0.002) and Andersen test performance (r(2) = 0.53, n = 32, p < 0.001) correlated with the VO2max. Yo-Yo IR1 performance correlated with Andersen test performance (r(2) = 0.74, n = 32, p < 0.0001). In conclusion, the Yo-Yo IR1 and the Andersen tests are reproducible and can be used as an indicator of aerobic fitness for 6- to 9-year-old children.
