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. 2021 Oct 29;18(21):11390.
doi: 10.3390/ijerph182111390.

Cross-Validation of Predictive Equation for Cardiorespiratory Fitness by Modified Shuttle Walk Test in Adults with Schizophrenia: A Secondary Analysis of the CORTEX-SP Study

Mikel Tous-Espelosin  1   2 , Sonia Ruiz de Azua  3 , Nagore Iriarte-Yoller  4 , Pedro M Sanchez  4   5 , Edorta Elizagarate  4 , Agurne Sampedro  6 , Sara Maldonado-Martín  1   2
Affiliations

Cross-Validation of Predictive Equation for Cardiorespiratory Fitness by Modified Shuttle Walk Test in Adults with Schizophrenia: A Secondary Analysis of the CORTEX-SP Study

Mikel Tous-Espelosin et al. Int J Environ Res Public Health. .

Abstract

Cardiorespiratory fitness (CRF) can be direct or estimated from different field tests. The Modified Shuttle Walk Test (MSWT) is suitable for all levels of function, allowing a peak response to be elicited. Therefore, we aimed (1) to validate the equation presented in the original study by Singh et al. for evaluating the relationship between MSWT with peak oxygen uptake (VO2peak) in adults with schizophrenia (SZ), (2) to develop a new equation for the MSWT to predict VO2peak, and (3) to validate the new equation. Participants (N = 144, 41.3 ± 10.2 years old) with SZ performed a direct measurement of VO2peak through a cardiopulmonary exercise test and the MSWT. A new equation incorporating resting heart rate, body mass index, and distance from MSWT (R2 = 0.617; adjusted R2 = 0.60; p < 0.001) performs better than the Singh et al. equation (R2 = 0.57; adjusted R2 = 0.57; p < 0.001) to estimate VO2peak for the studied population. The posteriori cross-validation method confirmed the model's stability (R2 = 0.617 vs. 0.626). The findings of the current study support the validity of the new regression equation incorporating resting heart rate, body mass index, and distance from MSWT to predict VO2peak for assessment of CRF in people with SZ.

Keywords: assessment; equation for estimation; field test; peak oxygen uptake; validation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Relationship between measured VO2peak and VO2peak values from the predicted equation generated in the present study. The central line represents the linear regression line, and the flanking lines represent the 95% individual prediction intervals. CPET, cardiopulmonary exercise test; VO2peak, peak oxygen uptake.
Figure 2
Figure 2
Bland and Altman plot. Intraindividual difference in VO2peak (mL·kg−1·min−1) between two exercise tests (MSWT vs. CPET) plotted against intraindividual mean values of the exercise tests (MSWT and CPET). The central line represents the mean of the intraindividual differences, and the flanking lines represent the 95% limits of agreement.
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