The role of skeletal muscle afferent feedback in ventilator and cardiovascular control during human exercise

Bruce, Richard (2014). The role of skeletal muscle afferent feedback in ventilator and cardiovascular control during human exercise. University of Birmingham. Ph.D.

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Abstract

Stimulating muscle metaboreceptive afferents alone via post exercise circulatory occlusion (PECO) typically does not result in hyperpnea in healthy humans. However ventilatory responses have been observed if metabolite accumulation is great enough (e.g. in diseased states) or during a concurrent hypercapnia-induced chemoreflex, suggesting a possible synergistic interaction. This thesis investigated the ventilatory responses to interactions between muscle afferent feedback and potentially synergistic inputs. It was firstly observed that muscle metabo/mechanoreflex activation (via PECO and passive muscle stretch, respectively) increases ventilation but only during acute hypercapnia. Additional investigations suggested that these ventilatory responses were caused by a central interaction, possibly between the medullary input from muscle afferents and central chemoreceptors. Secondly, experimental augmentation of the muscle metaboreflex enhances the ventilatory response during exercise, but not during PECO, suggesting interactions between the metaboreflex and other inputs activated in exercise. Lastly, PECO caused increased ventilation in COPD patients but this was unrelated to chronic hypercapnia. Collectively these findings suggest that in health, muscle metabo/mechanoreflex stimulation induces ventilatory responses, but their effects only appear to be unmasked in combination with secondary synergistic inputs. However, when the metaboreflex is powerful enough, arguably such as in COPD, ventilatory responses to metaboreceptor stimulation alone can be observed.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):