Test-retest Reliability Of The 40-yd Dash And Vertical Jump Assessments In Youth Athletes

Abstract

INTRODUCTION: Limited data exist on the reliability and sensitivity of the 40-yard dash (40-yd) and vertical jump (VJ) tests in youth athletes, which are popular combine performance assessments. PURPOSE: To examine the test-retest reliability for the 40-yd and VJ in youth athletes. METHODS: Seventy-seven 5-15 year-old athletes (mean height ± SD = 153.0 cm ± 14.9; weight = 45.8 kg ± 16.3) volunteered for the performance assessments during two visits separated by 24-72 hours. Athletes were divided into three age groups (5 - 9, 10 - 11, and 12 - 15 years old). The 40-yd was assessed in seconds (s) with a digital timing gate, and the VJ was assessed in centimeters (cm) with a vertec, both performed on indoor field turf. Intra-class correlation coefficients (ICC) with corresponding 95% confidence intervals, standard errors of measurement (SEM), coefficients of variation (CV), and minimum detectable changes (MDC) were calculated from the repeated measures analysis of variance (ANOVA) from test 1 to test 2 for both assessments. RESULTS: There were systematic decreases in 40-yd times from test 1 to test 2 for the 12 - 15 year-old group, but there was no other detectable systematic variability for any other variable. The ICCs ranged from 0.78 to 0.96, which were greater than zero. MDCs (calculated from SEMs) for the 5 - 9, 10 - 11, and 12 - 15 age groups were 0.49, 0.70, and 0.38 s for the 40-yd, and 6.7, 4.3, and 13.7 cm for the VJ, respectively. CONCLUSIONS: Twelve to fifteen year olds may need a familiarization trial (i.e., test run) for the 40-yd. Based on the age of the athlete, 0.4 - 0.7 s and 4 - 14 cm changes in the 40-yd and VJ, respectively, may be necessary for individual youth athletes to consider their improvements real beyond the errors of the measurements.