The role of thin fibre muscle afferent feedback, and its modification by exercise training, in human ventilatory control

Alghaith, Jassim Mohammed (2019). The role of thin fibre muscle afferent feedback, and its modification by exercise training, in human ventilatory control. University of Birmingham. Ph.D.

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Abstract

Historically it was believed that activation of the muscle metaboreflex alone by post exercise circulatory occlusion (PECO) does not result in hyperpnea. Recently, studies have shown that activation of the muscle metaboreflex combined with stimulation of the ventilatory chemoreflex (by concurrent hypercapnia) resulted in an increased ventilatory response, suggesting a potential interaction between these neural inputs. This thesis investigated the nature of this interaction by manipulating one of these neural inputs at a time. Firstly, it was observed that the magnitude of the additional ventilatory response to a standardised level of muscle metaboreflex activation (PECO) rose progressively with the level of concurrent hypercapnia, indicating a linear relationship [V̇\(_E\) (l.min\(^-\)\(^1\)) = 0.85 x P\(_E\)\(_T\)CO\(_2\) (mmHg) + 0.80 (l.min\(^-\)\(^1\))] (R=0.78 range, 0.39-0.99). Secondly, the ventilatory chemoreflex was constantly stimulated (constant level of hypercapnia), but inputs from muscle metaboreceptive afferents were altered by local muscle training. Exercise training of one leg for 6 weeks attenuated the muscle metaboreflex and resulted in decreases in ventilatory (V̇\(_E\): from 17.5 ± 2 to 9.8 ± 2.1 L.min\(^-\)\(^1\), p ≤ 0.05) and cardiovascular (MAP: from 16.1± 2.3 to 14.1 ± 2.1 mmHg, p ≤ 0.05) responses to PECO under the hypercapnia condition but only in the trained leg. Overall these findings support the concept of a synergistic interaction between the neural inputs, and the findings from the training study provide evidence that has promising clinical implication for patients with exercise intolerance and dyspnoea.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):