Exercising muscle oxygen delivery:demand matching impacts sustainable exercise tolerance. At the exercising muscle “macrovascular” level, the increase in total muscle blood flow resulting from vasodilation of resistance vessels with additional contributions from increasing arterial blood pressure at higher exercise intensities determines total oxygen delivery. At the microvascular level, spatial distribution of blood flow in relation to spatial heterogeneity of muscle fibre activation within a muscle reflects vasoregulatory and structural characteristics of the microcirculation that ultimately determine the diffusion of the oxygen to the mitochondrial site of demand. The spatially distributed magnitude of vasodilation reflects the balance of local vasodilator mechanisms, sympathetic vasoconstrictor activity, and factors blunting that vasoconstrictor activity (functional sympatholysis). This does not occur in isolation, as exercising skeletal muscle resistance vessel tone can be altered for the purpose of systemic cardiovascular arterial blood pressure regulation, and pressure elevation for the purpose of flow improvement in other exercising muscles.
Numerous exercising muscle vasodilator mechanisms have been well-characterized. However, their integration and link to muscle oxygen levels and oxygen demand remains poorly understood. Spatial matching of oxygen diffusion into activated skeletal muscle fibres is the ultimate delivery:demand matching. Yet understanding the structural “fit” of muscle contractile oxygen demand units and microvascular oxygen delivery units and the determinants of oxygen diffusion amongst them remains elusive. Furthermore, local exercising muscle oxygen delivery:demand matching needs to be understood in the context of other simultaneous systemic demands on the circulatory system such as arterial blood pressure regulation and thermoregulation which bring in to play peripheral sympathetic vasoconstriction and the hydraulic coupling of peripheral blood flows with cardiac output. While exercising muscle experiences increases in sympathetic vasoconstrictor activity and has local mechanisms that can blunt this activity, cardiac-vascular hydraulic coupling characteristics have not been adequately considered in obtaining a true understanding of the purpose of exercising muscle sympathetic vasoconstriction. Furthermore, if and when sympathetic vasoconstriction affects oxygen delivery:demand matching in the context of these systemic considerations remains unclear. The purpose of this Research Topic is to stimulate and accumulate research that takes the next step towards improving our understanding of exercising muscle oxygen delivery:demand matching.
We welcome original research or reviews addressing the following overarching questions:
• Is exercising muscle oxygen delivery:demand matching adequate (oxygen delivery supports the required oxygen uptake but increasing it improves muscle contractile and metabolic function) or optimal (no impact of an increase in oxygen delivery)?
• How do local vasodilator mechanisms interact and link to oxygenation of contracting muscle fibres?
• What is the spatial matching of oxygenation and oxygen diffusion to metabolic demand and what are the factors that determine it?
• Are there oxygen sensing mechanisms in skeletal muscle? How do they contribute to oxygen delivery:demand matching?
• What is the purpose of sympathetic vasoconstrictor activity in contracting skeletal muscle? Does it affect oxygen delivery:demand matching?
• What is the nature of the hydraulic coupling of peripheral blood flows to cardiac output? How does this coupling determine the dynamic balancing of cardiac output with exercising muscle blood flow?
• How is the microvascular network coordinating to match blood flow to metabolic demand?
Exercising muscle oxygen delivery:demand matching impacts sustainable exercise tolerance. At the exercising muscle “macrovascular” level, the increase in total muscle blood flow resulting from vasodilation of resistance vessels with additional contributions from increasing arterial blood pressure at higher exercise intensities determines total oxygen delivery. At the microvascular level, spatial distribution of blood flow in relation to spatial heterogeneity of muscle fibre activation within a muscle reflects vasoregulatory and structural characteristics of the microcirculation that ultimately determine the diffusion of the oxygen to the mitochondrial site of demand. The spatially distributed magnitude of vasodilation reflects the balance of local vasodilator mechanisms, sympathetic vasoconstrictor activity, and factors blunting that vasoconstrictor activity (functional sympatholysis). This does not occur in isolation, as exercising skeletal muscle resistance vessel tone can be altered for the purpose of systemic cardiovascular arterial blood pressure regulation, and pressure elevation for the purpose of flow improvement in other exercising muscles.
Numerous exercising muscle vasodilator mechanisms have been well-characterized. However, their integration and link to muscle oxygen levels and oxygen demand remains poorly understood. Spatial matching of oxygen diffusion into activated skeletal muscle fibres is the ultimate delivery:demand matching. Yet understanding the structural “fit” of muscle contractile oxygen demand units and microvascular oxygen delivery units and the determinants of oxygen diffusion amongst them remains elusive. Furthermore, local exercising muscle oxygen delivery:demand matching needs to be understood in the context of other simultaneous systemic demands on the circulatory system such as arterial blood pressure regulation and thermoregulation which bring in to play peripheral sympathetic vasoconstriction and the hydraulic coupling of peripheral blood flows with cardiac output. While exercising muscle experiences increases in sympathetic vasoconstrictor activity and has local mechanisms that can blunt this activity, cardiac-vascular hydraulic coupling characteristics have not been adequately considered in obtaining a true understanding of the purpose of exercising muscle sympathetic vasoconstriction. Furthermore, if and when sympathetic vasoconstriction affects oxygen delivery:demand matching in the context of these systemic considerations remains unclear. The purpose of this Research Topic is to stimulate and accumulate research that takes the next step towards improving our understanding of exercising muscle oxygen delivery:demand matching.
We welcome original research or reviews addressing the following overarching questions:
• Is exercising muscle oxygen delivery:demand matching adequate (oxygen delivery supports the required oxygen uptake but increasing it improves muscle contractile and metabolic function) or optimal (no impact of an increase in oxygen delivery)?
• How do local vasodilator mechanisms interact and link to oxygenation of contracting muscle fibres?
• What is the spatial matching of oxygenation and oxygen diffusion to metabolic demand and what are the factors that determine it?
• Are there oxygen sensing mechanisms in skeletal muscle? How do they contribute to oxygen delivery:demand matching?
• What is the purpose of sympathetic vasoconstrictor activity in contracting skeletal muscle? Does it affect oxygen delivery:demand matching?
• What is the nature of the hydraulic coupling of peripheral blood flows to cardiac output? How does this coupling determine the dynamic balancing of cardiac output with exercising muscle blood flow?
• How is the microvascular network coordinating to match blood flow to metabolic demand?