What is health-related fitness? Investigating the underlying factor structure of fitness in youth:

Health-related fitness (HRF) is theoretically defined as a multidimensional construct containing the components cardiorespiratory endurance, muscular strength, muscular endurance, flexibility and body composition. Given the range of field-based HRF tests available, health practitioners face a difficult task in selecting tests that best reflect the HRF construct as defined in the literature. This study aimed to investigate the underlying factor structure of the theoretical HRF construct with a view to identifying field-based tests representative of HRF in youth. Participants were 261 children (53% female, 47% male; mean age 12.22 +/- 0.48 years). Indicators of four fitness components (20m shuttle run, curl-ups, push-ups, horizontal jump, vertical jump, handgrip, and modified back-saver sit-and-reach) were measured. Confirmatory factor analysis of the four-component model revealed a low contribution of flexibility (.10) to the overall model, leading to its removal. The subsequent three-component model showed better fit across all fit statistics (NFI, TLI, CFI, RMSEA, SRMR). Analysis of indicator loadings led to the removal of handgrip (.37), further improving model fit. The reduced three-component model was re-specified as a first-order model containing five indicators, and showed the best fit (NFI, CFI, SRMR). These findings suggest that a fitness construct in youth is adequately represented by three HRF components included in the theoretical definition (cardiorespiratory endurance, muscular strength, muscular endurance). These components load onto the same construct and can be tested using five tests (20m shuttle run, curl-ups, push-ups, horizontal jump, vertical jump) suitable for field-based research.