Estimating VO2max in children aged 5–6 years through the preschool-adapted 20-m shuttle-run test (PREFIT)

(1) To examine the comparability, i.e., discriminatory power, in a preschooler test (PREFIT 20-m shuttle-run test) and the 20mSRT-Original in 5–6-year-olds; (2) to provide an equation to estimate VO2max from the 20mSRT-PREFIT. 138 participants aged 5–6 years performed the 20mSRT-PREFIT and the 20mSRT-Original in a counterbalanced order. Total test duration, completed stages, maximum speed and maximum heart rate were registered. Participants finished stages from 2–10 in the 20mSRT-PREFIT, whereas stages 1–5 were completed in the 20mSRT-Original and a null was registered, showing the original version a lower discriminatory power. We also observed that the higher the cardiorespiratory fitness level the more comparable were the tests, i.e., − 0.04 km h−1 difference between tests in the fittest participants (i.e., maximum speed ≥ 9.5 km h−1). Using the original equation proposed by Leger and colleagues in 1988 and based on the estimation regression of maximum speed in the 20mSRT-Original from the PREFIT version, we computed a new equation to estimate VO2max from the 20mSRT-PREFIT: Y = 44.657 + 1.795X 1 − 2.601X 2 + 0.0852X 1 X 2 (r = 0.77; r 2 = 0.59; SEE = 1.25 ml kg−1 min−1 or 2.59% of estimated mean VO2max = 48.38 ml kg−1 min−1), where X 1 is the 20mSRT-PREFIT maximum speed (km h−1) and X 2 is the age of participants. The 20mSRT-PREFIT resulted in a significantly higher maximum heart rate than the 20mSRT-Original. The 20mSRT-PREFIT has higher discriminatory power than the 20mSRT-Original. Our study provides for the first time an opportunity to estimate VO2max in preschoolers and children based on the 20mSRT-PREFIT maximum speed and the age of participants.