Peripheral Circulation

Abstract

Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine

“…Tissue perfusion is regulated by changes in diameter of the small arteries and arterioles of the vascular bed supplying the tissue. Myriad vasoactive factors, derived from neurohumoral systems, the endothelium and local metabolites interact to determine vascular tone and ensure adequate tissue perfusion 1,5,12,16 . Changes in systemic and pulmonary vascular resistance or the inverse, vascular conductance, can be calculated from the blood pressure and flow signals and interpreted in terms of changes in vasomotor tone in the systemic and pulmonary vasculature.…”

“…Adequate cardiopulmonary function is essential to supply the body with oxygen and nutrients, particularly during conditions of increased metabolic demand such as during exercise 1 . The cardiopulmonary response to exercise is characterized by a number of adaptations in cardiac function, i.e., an increase in heart rate, contractility and stroke volume, and microvascular function, i.e., vasodilation in the vascular beds supplying exercising muscles as well as in the pulmonary vasculature, and vasoconstriction in the vascular beds supplying the gastrointestinal system as well as inactive muscles 1 .…”

“…The cardiopulmonary response to exercise is characterized by a number of adaptations in cardiac function, i.e., an increase in heart rate, contractility and stroke volume, and microvascular function, i.e., vasodilation in the vascular beds supplying exercising muscles as well as in the pulmonary vasculature, and vasoconstriction in the vascular beds supplying the gastrointestinal system as well as inactive muscles 1 . Impaired exercise capacity is an early hallmark of cardiopulmonary dysfunction, and cardiopulmonary exercise testing is used as an effective method to delineate between cardiac dysfunction, vascular dysfunction and/ or pulmonary dysfunction in patients with impaired exercise capacity 1.…”

Phosphodiesterase-5 activity exerts a coronary vasoconstrictor influence in awake swine that is mediated in part via an increase in endothelin production

“…Regulation of coronary resistance vessel tone is the result of interplay of a myriad of not only vasodilator but also vasoconstrictor influences (10,26). Many of the coronary vascular control mechanisms are highly similar across species (26), but some interspecies differences exist, including a lack of significant ␣-adrenergic constriction of coronary resistance vessels in swine (20).…”

“…In conclusion, PDE5 activity exerts a vasoconstrictor influence on coronary resistance vessels that is mediated, in part, via an increase in endothelial ET production. PDE5 inhibition; ETA/ETB blockade; ET; Big ET; coronary vasomotor tone CORONARY BLOOD FLOW IS TIGHTLY coupled to myocardial oxygen demand to maintain a consistently high level of myocardial oxygen extraction (10,16,26). This tight coupling has been proposed to depend on a myriad of vasodilators and vasoconstrictors, including nitric oxide (NO) and endothelin-1 (ET).…”