A Reappraisal of Ventilatory Thresholds in Wheelchair Athletes With a Spinal Cord Injury: Do They Really Exist?
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...
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Published in | Frontiers in physiology Vol. 12; p. 719341 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Switzerland
Frontiers Media S.A
26.11.2021
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Subjects | |
Online Access | Get full text |
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Summary: | 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 R
, and blocked bootstrapping was used to derive estimates of a median and 95% confidence intervals (CI). V̇O
-V̇CO
and V̇E/V̇O
-time data were assessed for the determination of the VT, and V̇CO
-V̇E and V̇E/V̇CO
-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 R
median ± 95% CI between the breakpoint and the no-breakpoint models for determining the VT (V̇O
-V̇CO
: 0.991 ± 0.003 vs. 0.990 ± 0.003; V̇E/V̇O
-time: 0.792 ± 0.101 vs. 0.782 ± 0.104, respectively) and RCP (V̇E-V̇CO
: 0.984 ± 0.004 vs. 0.984 ± 0.004; V̇E/V̇CO
-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 R
between the investigated breakpoint and no-breakpoint models; (2) breakpoints do not exist, as has been argued previously. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Reviewed by: Gino Panza, Wayne State University, United States; Isabelle Vivodtzev, INSERM U1158 Neurophysiologie Respiratoire Expérimentale et Clinique, France This article was submitted to Exercise Physiology, a section of the journal Frontiers in Physiology Edited by: Stuart Goodall, Northumbria University, United Kingdom |
ISSN: | 1664-042X 1664-042X |
DOI: | 10.3389/fphys.2021.719341 |