Published in:
01-07-2021 | Original Research Article
Developing a New Curvilinear Allometric Model to Improve the Fit and Validity of the 20-m Shuttle Run Test as a Predictor of Cardiorespiratory Fitness in Adults and Youth
Published in: Sports Medicine | Issue 7/2021
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Background and Objectives
Doubts have been raised concerning the validity of the 20-m shuttle-run test (20 mSRT) as a predictor of cardiorespiratory fitness (CRF) in youth based on Léger’s equation/model. An alternative allometric model has been published recently that is thought to provide, not only a superior fit (criterion validity) but also a more biologically and physiologically interpretable model (construct validity). The purposes of this study were to explore whether allometry can provide a more valid predictor of CRF using 20 mSRT compared with Léger’s equation/model.
Methods
We fitted and compared Léger’s original model and an alternative allometric model using two cross-sectional datasets (youth, n = 306; adult n = 105) that contained measurements of CRF (\(\dot{V}{\text{O}}_{{2{\text{peak}}}}\)/\(\dot{V}{\text{O}}_{{{\text{2max}}}}\)) and 20 mSRT performance. Quality-of-fit was assessed using explained variance (R2) and Bland and Altman’s limits of agreement.
Results
The allometric models provided superior fits for the youth (explained variance R2 = 71.9%) and adult (R2 = 77.7%) datasets compared with Léger’s equation using their original fixed (R2 = 35.2%) or re-estimated parameter models (R2 = 65.9%), confirming that the allometric models demonstrate acceptable criterion validity. However, the allometric models also identified a non-linear “J-shaped” increase in energy cost (\(\dot{V}{\text{O}}_{{2{\text{peak}}}}\)/\(\dot{V}{\text{O}}_{{{\text{2max}}}}\)) with faster final shuttle-run speeds (fitted speed exponent = 1.52; 95% CI 1.38–1.65).
Conclusion
Not only do allometric models provide more accurate predictions of CRF (\(\dot{V}{\text{O}}_{{2{\text{peak}}}}\)/\(\dot{V}{\text{O}}_{{{\text{2max}}}}\); ml kg−1 min−1) for both youth and adults (evidence of criterion validity), the “J-shaped” rise in energy demand with increasing final shuttle-run speed also provides the evidence of construct validity, resulting in a more plausible, physiologically sound, and interpretable model.