The role of muscle mechano and metaboreflexes in the control of ventilation: breathless with (over) excitement?

Abstract

Mechanically and metabolically sensitive thin fibre (group III and IV) muscle afferents are activated during exercise, causing reflex cardiovascular responses that are essential to normal cardiovascular control. Impaired exercise performance in some disease states can be linked to abnormal muscle mechanoreflex and muscle metaboreflex activity. A role for this same afferent feedback in contributing to the How to cite this article: White M, Bruce R. The role of muscle mechano and metaboreflexes in the control of ventilation:

Understanding mechanoreflex and metaboreflex interactions – a great challenge

“…[27,28] On the other hand, EPR is impaired in these conditions which probably raises cardiovascular risk, decreases exercise capacity, and contributes to progression of muscle fatigue and dyspnea. [2,7,8,[29][30][31][32][33][34] The deterioration of EPR is characterized partially by hyperactivity of mechanoreflex [1,2,[7][8][9]23,31,[35][36][37][38][39][40][41][42][43][44] and partially by alteration in metaboreflex activity. The character of the latter in heart failure is controversial -some experiments show abnormally high response of metaboreflex, [7,8,23,31,[37][38][39][40][41]45,46] whereas other studies report diminished activation.…”

Control of breathing during exercise: Who is the leader?

“…It is also accepted that a variety of peripheral signals are capable of regulating breathing during exercise.However, the exact contributions of multiple concomitant mechanisms to exercise hyperpnoea are contested. This is evident in a recent Exchange of Views on feedback control of ventilation during exercise (Haouzi, 2020;White & Bruce, 2020). Furthermore, although not the focus of the Exchange of Views, another contributor that we think deserves consideration is afferent input originating from pulmonary vascular baroreceptors.Almost 50 years ago, Wasserman, Whipp, and Castagna (1974) suggested a feedforward, cardiodynamic component to exercise hyperpnoea; that is, the increase in breathing during exercise might be linked mechanistically to the increase in cardiac output for efficient ventilation-perfusion matching.…”

“…However, the exact contributions of multiple concomitant mechanisms to exercise hyperpnoea are contested. This is evident in a recent Exchange of Views on feedback control of ventilation during exercise (Haouzi, 2020;White & Bruce, 2020). Furthermore, although not the focus of the Exchange of Views, another contributor that we think deserves consideration is afferent input originating from pulmonary vascular baroreceptors.…”

Editorial to accompany exchange of views: Role of exercise pressor reflex in control of ventilation during exercise

“…In this regard, although the ventilatory response to exercise has been well described, a complete understanding of the regulatory mechanisms controlling ventilation during exercise in health and disease remains less clear. However, as noted by White & Bruce (2020), there are many studies in humans and animals that support a role for muscle mechanoreflex and metaboreflex involvement in the ventilatory response to exercise (Fisher et al., 2015; Kaufman & Forster, 1996; Mueller et al., 2017; Smith et al., 2006). Furthermore, a synergistic interaction has been reported between the exercise pressor reflex and the central chemoreflex during exercise (Lam, Greenhough, Nazari, White, & Bruce, 2019; Wan et al., 2020; White & Bruce, 2020).…”

“…In the Exchange of Views presented by White & Bruce (2020) and Haouzi (2020), the role of the muscle metaboreflex in contributing to exercise hyperpnoea is debated. The technical aspects of experimental design are discussed, and contributions in isolation versus the integrative response during exercise are deliberated.…”