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Scaling the Oxygen Uptake Efficiency Slope for Body Size in Cystic Fibrosis

TOMLINSON, OWEN WILLIAM1,2; BARKER, ALAN ROBERT1; OADES, PATRICK JOHN2; WILLIAMS, CRAIG ANTHONY1,2

Medicine & Science in Sports & Exercise: October 2017 - Volume 49 - Issue 10 - p 1980–1986
doi: 10.1249/MSS.0000000000001314
Clinical Sciences

Purpose: The aim of this study was to describe the relationship between body size and oxygen uptake efficiency slope (OUES) in pediatric patients with cystic fibrosis (CF) and healthy controls (CON), to identify appropriate scaling procedures to adjust the influence of body size upon OUES.

Methods: The OUES was derived using maximal and submaximal points from cardiopulmonary exercise testing in 72 children (36 CF and 36 CON). OUES was subsequently scaled for stature, body mass (BM), and body surface area (BSA) using ratio-standard (Y/X) and allometric (Y/Xb) methods. Pearson’s correlation coefficients were used to determine the relationship between body size and OUES.

Results: When scaled using the ratio-standard method, OUES had a significant positive relationship with stature (r = 0.54, P < 0.001) and BSA (r = 0.25, P = 0.031) and significant negative relationship with BM (r = −0.38, P = 0.016) in the CF group. Combined allometric exponents (b) for CF and CON were stature 3.00, BM 0.86, and BSA 1.40. A significant negative correlation was found between OUES and stature in the CF group when scaled allometrically (r = −0.37, P = 0.027). Nonsignificant (P > 0.05) correlations for the whole group were found between OUES and allometrically scaled BM (CF r = −0.25, CON, r = 0.15) and BSA (CF r = −0.27, CON r = 0.13).

Conclusions: Only allometric scaling of either BM or BSA, and not ratio-standard scaling, successfully eliminates the influence of body size upon OUES. Therefore, this enables a more direct comparison of the OUES between patients with CF and healthy controls.

1Children’s Health and Exercise Research Centre, Sport and Health Sciences, University of Exeter, Exeter, UNITED KINGDOM; and 2Royal Devon and Exeter NHS Foundation Trust Hospital, Exeter, UNITED KINGDOM

Address for correspondence: Craig A. Williams, Ph.D., Children’s Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, St Luke’s Campus, Exeter, EX1 2LU, United Kingdom; E-mail: c.a.williams@exeter.ac.uk.

Submitted for publication March 2017.

Accepted for publication May 2017.

© 2017 American College of Sports Medicine