Abstract
Both convective oxygen (O2) transport to, and diffusive transport within, skeletal muscle are markedly diminished in patients with COPD. However, it is unknown how these determinants of peak muscle O2 uptake (V′mO2peak) respond to exercise training in patients with COPD. Therefore, the purpose of this study was to assess the plasticity of skeletal muscle O2 transport determinants of V′mO2peak in patients with COPD.
Adaptations to 8 weeks of single-leg knee-extensor exercise training were measured in eight patients with severe COPD (mean±sem forced expiratory volume in 1 s (FEV1) 0.9±0.1 L) and eight healthy, well-matched controls. Femoral arterial and venous blood samples, and thermodilution-assessed leg blood flow were used to determine muscle O2 transport and utilisation at maximal exercise pre- and post-training.
Training increased V′mO2peak in both COPD (by ∼26% from 271±29 to 342±35 mL·min−1) and controls (by ∼32% from 418±37 to 553±41 mL·min−1), restoring V′mO2peak in COPD to only ∼80% of pre-training control V′mO2peak. Muscle diffusive O2 transport increased similarly in both COPD (by ∼38% from 6.6±0.9 to 9.1±0.9 mL·min−1·mmHg−1) and controls (by ∼36% from 10.4±0.7 to 14.1±0.8 mL·min−1·mmHg−1), with the patients reaching ∼90% of pre-training control values. In contrast, muscle convective O2 transport increased significantly only in controls (by ∼26% from 688±57 to 865±69 mL·min−1), leaving patients with COPD (438±45 versus 491±51 mL·min−1) at ∼70% of pre-training control values.
While muscle diffusive O2 transport in COPD was largely restored by exercise training, V′mO2peak remained constrained by limited plasticity in muscle convective O2 transport.
Abstract
Patients with severe COPD exhibited attenuated plasticity in muscle convective oxygen transport, and therefore muscle V′O2peak, in response to exercise training that extended beyond simply disuse and would be expected to contribute to muscle dysfunction. https://bit.ly/38uAGfS
Footnotes
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Author contributions: Study design, data acquisition, data analysis, or data interpretation: all authors; drafting or revising the work for critically important intellectual content: all authors; approval of the work: all authors; agreement to be accountable for all aspects of the work: all authors.
Conflict of interest: R.M. Broxterman reports grants from National Heart, Lung, and Blood Institute, grants from US Department of Veterans Affairs, during the conduct of the study.
Conflict of interest: P.D. Wagner reports grants from National Heart, Lung, and Blood Institute, grants from US Department of Veterans Affairs, during the conduct of the study.
Conflict of interest: R.S. Richardson reports grants from National Heart, Lung, and Blood Institute, grants from US Department of Veterans Affairs, during the conduct of the study.
Support statement: This work was supported by National Heart, Lung, and Blood Institute grant number HL-091830, a Ruth L. Kirschtein National Research Service Award grant number 1T32HL139451, and the Veterans Administration Rehabilitation Research and Development Service grant numbers E6910-R, E1697-R, E3207-R, E9275-L, and E1572-P. Funding information for this article has been deposited with the Crossref Funder Registry.
- Received November 10, 2020.
- Accepted January 5, 2021.
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