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New perspectives concerning feedback influences on cardiorespiratory control during rhythmic exercise and on exercise
1John Rankin Laboratory of Pulmonary Medicine, University of Wisconsin - Madison, 1300 University Ave, Room 4245 MSC, Madison, WI 53706-1532, USA. jdempsey@wisc.edu
The Journal of Physiology
|July 25, 2012
Summary
Exercise responses are driven by central command and feedback from muscle and respiratory afferents. These reflexes preserve oxygen transport and influence motor output to limit fatigue.
Area of Science:
- Physiology
- Exercise Science
- Cardiorespiratory Regulation
Background:
- The role of central command in exercise responses is well-established.
- Contributions of locomotor muscle afferents to the pressor response are recognized.
- The specific roles of feedback afferents in cardiorespiratory control during exercise require further elucidation.
Discussion:
- Transient inhibition of carotid chemoreceptors reduced muscle sympathetic nerve activity and increased limb blood flow.
- Reducing respiratory muscle work enhanced limb vascular conductance and blood flow.
- These effects were modulated by ganglionic blockade, chronic heart failure, and hypoxia.
Key Insights:
- Blockade of opioid-sensitive muscle afferents reduced blood pressure, heart rate, and ventilation during exercise.
- This blockade also impaired oxygen transport, increased central motor output, exacerbated muscle fatigue, and reduced endurance.
- Three afferent reflexes, potentially acting with central command, are crucial for maintaining oxygen delivery and performance.
Outlook:
- Further research can explore the interplay between these afferent systems and central command.
- Understanding these mechanisms may reveal new therapeutic targets for exercise intolerance.
- Investigating the metabolic feedback from muscle afferents could offer insights into fatigue management.
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