Best Practice Model for Pediatric Research

Dear Editor-in-Chief,

Cross-sectional relationships reported by Haapala et al. (1) provide welcome confirmation of previous studies of insulin resistance in young children, including the UK Early Bird (2) and the Australian LOOK studies (3), which among others have continued on with interventions (4) and longitudinal investigations (5). Haapala and colleagues supported revisiting cross-sectional relationships by asserting that previous studies measuring cardiorespiratory fitness may have elicited spurious relationships. Their rationale was that scaling fitness by body weight is not justified from a statistical or physiological perspective in children because it does not remove the effect of body size and composition (1).

Debate continues as to the best way of converting an absolute measure such as physical performance into a measure of physical fitness suitable for comparing children of different heights, weights, and body composition. The process is complicated in that allometric relationships change during growth, but also by the nature of the test. For example, in contrast to seated cycle ergometry, a running test involves both vertical and horizontal vectors of whole-body momentum, requiring different scaling approaches.