LAUSR

In their editorial, Armstrong and Welsman1 suggest that the 20 m shuttle run test (20mSRT) (mis)represents and (mis)interprets youth cardiorespiratory fitness (CRF), and potentially (mis)informs health promotion and clinical practice. Their main arguments are: (a) the 20mSRT only provides an estimate of CRF (ie, peak ![Formula][1] O2) and (b) estimates are ratio-scaled (ie, expressed relative to body mass). In this response we provide several reasons, rooted in evidence, which refute their interpretation of our work. CRF measures the body’s capacity to deliver and utilise oxygen for energy transfer to support muscle activity during physical activity.2 The 20mSRT provides a simple, single measure that assesses the integrated responses of the physiological systems’ ability to perform progressive aerobic exercise. Unfortunately, it does not provide specific information on the function or contribution of specific systems that can be obtained from a gas analysed peak ![Formula][2] O2 test. The 20mSRT is a good measure of functional exercise capacity that authentically imitates youth physical activities (eg, running, agility) in a natural setting. At the individual level, the 20mSRT is a true indicator of peak ![Formula][3] O2 (absolute or … [1]: /embed/mml-math-1.gif [2]: /embed/mml-math-2.gif [3]: /embed/mml-math-3.gif