The 20 m shuttle run is not a valid test of cardiorespiratory fitness in boys aged 11–14 years

OBJECTIVES: The 20 m shuttle run test (20mSRT) is used to estimate cardiorespiratory fitness (CRF) through the prediction of peak oxygen uptake ([Formula: see text]), but its validity as a measure of CRF during childhood and adolescence is questionable. This study examined the validity of the 20mSRT to predict peak [Formula: see text] . METHODS: Peak [Formula: see text] was measured during treadmill running. Log-linear regression was used to correct peak [Formula: see text] for body mass and sum of skinfolds plus age. Boys completed the 20mSRT under standardised conditions. Maximum speed (km/h) was used with age to predict peak [Formula: see text] using the equation developed by Léger et al. Validity was examined from linear regression methods and limits of agreement (LoA). Relationships between 20mSRT performance and allometrically adjusted peak [Formula: see text] , and predicted per cent fat were examined. RESULTS: The sample comprised 76 boys aged 11–14 years. Predicted and measured mass-related peak [Formula: see text] (mL/kg/min) shared common variance of 32%. LoA revealed that measured peak [Formula: see text] ranged from 15% below to 25% above predicted peak [Formula: see text] . There were no significant relationships (p>0.05) between predicted peak [Formula: see text] and measured peak [Formula: see text] adjusted for mass, age and skinfold thicknesses. Adjusted for body mass and age, peak [Formula: see text] was not significantly related (p>0.05) to 20mSRT final speed but a weak, statistically significant (r=0.24, p<0.05) relationship was found with peak [Formula: see text] adjusted for mass and fatness. Predicted per cent fat was negatively correlated with 20mSRT speed (r=−0.61, p<0.001). CONCLUSIONS: The 20mSRT reflects fatness rather than CRF and has poor validity grounded in its flawed estimation and interpretation of peak [Formula: see text] in mL/kg/min.