Bibliographic Details
Title: |
Control of hyperpnoea and pulmonary gas exchange during prolonged exercise: The role of group III/IV muscle afferent feedback. |
Authors: |
Iannetta, Danilo, Weavil, Joshua C., Laginestra, Fabio Giuseppe, Thurston, Taylor S., Broxterman, Ryan M., Jenkinson, Robert H., Curtis, Michelle C., Chang, Jen, Wan, Hsuan‐Yu, Amann, Markus |
Source: |
Journal of Physiology; Oct2024, Vol. 602 Issue 20, p5375-5389, 15p |
Subject Terms: |
PULMONARY gas exchange, RESPIRATION, LOCOMOTOR ataxia, FENTANYL, ANALGESICS |
Abstract: |
It remains unclear whether feedback from group III/IV muscle afferents is of continuous significance for regulating the pulmonary response during prolonged (>5 min), steady‐state exercise. To elucidate the influence of these sensory neurons on hyperpnoea, gas exchange efficiency, arterial oxygenation and acid–base balance during prolonged locomotor exercise, 13 healthy participants (4 females; 21 (3) years, V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{max}}}}$: 46 (8) ml/kg/min) performed consecutive constant‐load cycling bouts at ∼50% (20 min), ∼75% (20 min) and ∼100% (5 min) of V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{max}}}}$ with intact (CTRL) and pharmacologically attenuated (lumbar intrathecal fentanyl; FENT) group III/IV muscle afferent feedback from the legs. Pulmonary responses were continuously recorded and arterial blood (radial catheter) periodically collected throughout the exercise. Pulmonary gas exchange efficiency was evaluated using the alveolar‐arterial PO2${{P}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ difference (A−aDO2${\mathrm{A - a}}{{D}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$). There were no differences in any of the variables of interest between conditions before the start of the exercise. Pulmonary ventilation was up to 20% lower across all intensities during FENT compared to CTRL exercise (P < 0.001) and this hypoventilation was accompanied by an up to 10% lower arterial PO2${{P}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ and a 2–4 mmHg higher PCO2${{P}_{{\mathrm{C}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$ (both P < 0.001). The exercise‐induced widening of A−aDO2${\mathrm{A - a}}{{D}_{{{{\mathrm{O}}}_{\mathrm{2}}}}}$ was up to 25% larger during FENT compared to CTRL (P < 0.001). Importantly, the differences developed within the first minute of each stage and persisted, or further increased, throughout the remainder of each bout. These findings reflect a critical and time‐independent significance of feedback from group III/IV leg muscle afferents for continuously regulating the ventilatory response, gas exchange efficiency, arterial oxygenation and acid–base balance during human locomotion. Key points: Feedback from group III/IV leg muscle afferents reflexly contributes to hyperpnoea during short duration (i.e. <5 min) locomotor exercise.Whether continuous feedback from these sensory neurons is obligatory to ensure adequate pulmonary responses during steady‐state exercise of longer duration remains unknown.Lumbar intrathecal fentanyl was used to attenuate the central projection of group III/IV leg muscle afferents during prolonged locomotor exercise (i.e. 45 min) at intensities ranging from 50% to 100% of V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_{\mathrm{2}}}{\mathrm{max}}}}$.Without affecting the metabolic rate, afferent blockade compromised pulmonary ventilation and gas exchange efficiency, consistently impairing arterial oxygenation and facilitating respiratory acidosis throughout exercise.These findings reflect the time‐independent significance of feedback from group III/IV muscle afferents for regulating exercise hyperpnoea and gas exchange efficiency, and thus for optimizing arterial oxygenation and acid–base balance, during prolonged human locomotion. [ABSTRACT FROM AUTHOR] |
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Database: |
Complementary Index |