Aerobic fitness is considered to be an important health marker. In adults, strong independent associations have been reported between aerobic fitness and cardiovascular disease mortality1 and risk status.2 In children and adolescents, weak-to-moderate associations have been reported between aerobic fitness and cardiovascular disease risk status,3 with some studies (but not all) showing that these relationships persist even after controlling for fatness.4 Furthermore, aerobic fitness and cardiovascular disease risk factors track moderately well from childhood and adolescence into adulthood.5 From a public health perspective, this evidence highlights the need for aerobic fitness testing to be included as part of health screening and monitoring systems, but it also begs the question—is there a threshold level of aerobic fitness associated with low cardiovascular disease risk in children and adolescents? At present, there are no agreed threshold levels for aerobic fitness. However, by using a large pooled dataset of children and adolescents from four European countries, the linked study by Adegboye and colleagues (see pp 00)6 proposes age and sex-specific threshold levels for aerobic fitness associated with a clustering of cardiometabolic risk factors. …