Emerging evidence has demonstrated the strong link between cardiorespiratory fitness and multiple aspects of health (i.e., physiological, physical, psychosocial, cognitive), independent of physical activity, among school-aged children and youth. Cardiorespiratory fitness is a trait that does not vary substantially from day-to-day, and provides an indication of recent physical activity levels, making it an important possible indicator of population health. Thus, the objective of this dissertation was to investigate the utility of cardiorespiratory fitness, measured using the 20-m shuttle run test, as a broad, holistic health indicator for population health surveillance among children and youth. To achieve this objective we completed 7 manuscripts, all prepared for submission to peer-reviewed, scientific journals: (1) Systematic review of the relationship between 20-m shuttle run performance and health indicators among children and youth. (2) Review of criterion-referenced standards for cardiorespiratory fitness: what percentage of 1 142 026 international children and youth are apparently healthy? (3) Cardiorespiratory fitness is associated with physical literacy in a large sample of Canadian children aged 8 to 12 years. (4) International variability in 20-m shuttle run performance in children and youth: Who are the fittest from a 50-country comparison? A systematic review with pooling of aggregate results. (5) Making a case for cardiorespiratory fitness surveillance among children and youth. (6) International normative 20-m shuttle run values from 1 142 026 children and youth representing 50 countries. (7) Temporal trends in the cardiorespiratory fitness of children and adolescents representing 19 high-income and upper middle-income countries between 1981 and 2014. Combined, this dissertation provides support for the importance of cardiorespiratory fitness for health surveillance among school-aged children and youth. Results from the international analysis highlighted the variability across countries, with countries in north-central Europe and Africa having the highest cardiorespiratory fitness, and countries in South America having the lowest cardiorespiratory fitness. The results indicated that declines in cardiorespiratory fitness may have stabilized in recent years in some high- and middle-income countries. This dissertation also identified 2 methods (criterion- and normative-referenced standards) to interpret cardiorespiratory fitness levels among children and youth, methods that could be used to inform future consensus, surveillance, and cardiorespiratory fitness guidelines.
