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A reappraisal of ventilatory thresholds in wheelchair athletes with a spinal cord injury: do they really exist?

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posted on 2021-12-08, 14:27 authored by Julia Baumgart, Gertjan Ettema, Katy Griggs, Vicky Goosey-TolfreyVicky Goosey-Tolfrey, Christof LeichtChristof Leicht
The ventilatory threshold (VT) separates low- from moderate-intensity exercise, the respiratory compensation point (RCP) moderate- from high-intensity exercise. Both concepts assume breakpoints in respiratory data. However, the objective determination of the VT and RCP using breakpoint models during upper-body modality exercise in wheelchair athletes with spinal cord injury (SCI) has received little attention. Therefore, the aim of this study was to compare the fit of breakpoint models (i.e., two linear regression lines) with continuous no-breakpoint models (i.e., exponential curve/second-order polynomial) to respiratory data obtained during a graded wheelchair exercise test to exhaustion. These fits were compared employing adjusted R2, and blocked bootstrapping was used to derive estimates of a median and 95% confidence intervals (CI). V̇O2-V̇CO2 and V̇E/V̇O2-time data were assessed for the determination of the VT, and V̇CO2-V̇E and V̇E/V̇CO2-time data for the determination of the RCP. Data of 9 wheelchair athletes with tetraplegia and 8 with paraplegia were evaluated. On an overall group-level, there was an overlap in the adjusted R2 median ± 95% CI between the breakpoint and the no-breakpoint models for determining the VT (V̇O2-V̇CO2: 0.991 ± 0.003 vs. 0.990 ± 0.003; V̇E/V̇O2-time: 0.792 ± 0.101 vs. 0.782 ± 0.104, respectively) and RCP (V̇E-V̇CO2: 0.984 ± 0.004 vs. 0.984 ± 0.004; V̇E/V̇CO2-time: 0.729 ± 0.064 vs. 0.691 ± 0.063, respectively), indicating similar model fit. We offer two lines of reasoning: (1) breakpoints in these respiratory data exist but are too subtle to result in a significant difference in adjusted R2 between the investigated breakpoint and no-breakpoint models; (2) breakpoints do not exist, as has been argued previously.

Funding

Peter Harrison Centre for Disability Sport

History

School

  • Sport, Exercise and Health Sciences

Published in

Frontiers in Physiology

Volume

12

Publisher

Frontiers Media

Version

  • VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This is an Open Access Article. It is published by Frontiers Media under the Creative Commons Attribution 4.0 International Licence (CC BY 4.0). Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/

Acceptance date

2021-10-27

Publication date

2021-11-26

Copyright date

2021

ISSN

1664-042X

Language

  • en

Depositor

Dr Christof Leicht. Deposit date: 27 October 2021

Article number

719341

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