The hyperpnoea of exercise in health: Respiratory influences on neurovascular control

Abstract

It is known that the respiratory muscles have a significant increasing oxygen demand in line with hyperpnoea during whole-body endurance exercise and are susceptible to fatigue, in much the same way as locomotor muscles. The act of ventilation can itself be considered a form of exercise. The manipulation of respiratory load at near-maximal exercise alters leg blood flow significantly, demonstrating a competitive relationship between different skeletal muscle vascular beds to perfuse both sets of muscles adequately with a finite cardiac output. In recent years, the question has moved towards whether this effect exists during submaximal exercise, and the use of more direct measurements of respiratory muscle blood flow itself to confirm assumptions that uphold the concept. Evidence thus far has shown that there is a reciprocal effect on blood flow redistribution during ventilatory load manipulation observed at the respiratory muscles themselves and that the effect is observable during submaximal exercise, where active limb blood flow was reduced in conditions that simulated a high work of breathing. This has clinical applications for populations with respiratory disease and heart failure, where the work of breathing is remarkably high, even during submaximal efforts.

Breath Tools: A Synthesis of Evidence-Based Breathing Strategies to Enhance Human Running

“…The intercostals, parasternals, scalenes, and neck muscles contribute to ventilation at high intensities by moderating EILV and airway caliber (e.g., dilation and inflammation). Altogether, the diaphragm and associated ventilatory pump musculature are remarkably efficient [~3%–5% total O 2 consumption (VO 2 )] and fatigue-resistant at submaximal intensities ( Welch et al, 2019 ; Sheel et al, 2020 ).…”

“…Flow limitation could lead to “breath stacking,” a negative consequence when subsequent breaths have slightly larger inspiratory than expiratory flow ( Ward, 2007 ). Breath stacking causes EILV and EELV to progressively increase, leading to dynamic hyperinflation ( Figure 3 ; Sheel et al, 2020 ). At these higher LOV, the lungs are stiffer, less compliant, and require more muscle work to expand ( Sheel et al, 2020 ).…”

“…Breath stacking causes EILV and EELV to progressively increase, leading to dynamic hyperinflation ( Figure 3 ; Sheel et al, 2020 ). At these higher LOV, the lungs are stiffer, less compliant, and require more muscle work to expand ( Sheel et al, 2020 ). Unfortunately, dynamic hyperinflation places the diaphragm in a suboptimal length for expanding the lungs and managing intrathoracic pressures, further fatiguing the ventilatory musculature ( Aliverti, 2016 ).…”

Blood pressure and coeliac artery blood flow responses during increased inspiratory muscle work in healthy males

“…Furthermore, a series of studies revealed increased sympathetic vasomotor outflow and reduced resting limb blood flow in association with respiratory muscle work (Derchak et al, 2002;Sheel et al, 2001Sheel et al, , 2002St Croix et al, 2000). Based on these data, it is obvious that increased work of breathing leads to metabolite accumulation within the respiratory muscle (i.e., respiratory muscle-induced metaboreflex), which affects the distribution of limb blood flow (Dempsey et al, 2006;Sheel et al, 2020).…”

Respiratory influences on oxygen transport and exercise performance in health and disease

“…In their report, Sheel, Taylor, and Katayama (2020) emphasise recent findings in healthy humans that show a significant influence of sympathetic vasoconstrictor activity, mediated by both respiratory and locomotor muscle metaboreceptors during intense endurance exercise, on the constraint of blood flow and O 2 transport to both sets of muscles. Experimentally increasing the work of breathing was found to elicit reductions in blood flow to inactive and active limb muscles during submaximal exercise, but only if the work of breathing was of a sufficient magnitude.…”