The Exercise Pressor Reflex

Abstract

The exercise pressor reflex is believed to play a role in causing the cardiovascular and ventilatory responses to exercise. This review will discuss the evidence that the reflex is active in both humans and animals. In addition, this review will discuss the nature of the mechanical and metabolic stimuli that evoke the exercise pressor reflex. Particular attention will be paid to the discharge properties of the thin fiber sensory nerves (i. e., group III and IV muscle afferents) whose activation by these mechanical and metabolic stimuli is responsible for evoking the reflex. Finally, some current findings and controversies will be discussed.

Why Not to Use the Handgrip Test in the Assessment of Cardiovascular Autonomic Neuropathy Among Patients with Diabetes Mellitus?

“…Static (isometric) exercise causes heart rate-dependent increases in cardiac output accompanied by increased or unchanged peripheral vascular resistance resulting in substantially elevated BP [19,20]. There is emerging evidence that hypertension is associated with excessive pressor responses during muscle contraction; both mechanically (mechanoreflex) and metabolically (metaboreflex) driven components of the pressor reflex are suggested being involved [21,22].…”

Muscle sympathetic nerve activity and ventilation during exercise in subjects with and without chronic heart failure

“…Previous work from our laboratory (13) has focused on the efferent sympathoneural limb of this somatic pressor reflex. When the afferent nerve endings in skeletal muscle that are responsive to metabolic products of work (metaboreceptors, primarily type IV fibres) [14]) are stimulated by isometric or isotonic exercise, the reflex increase in MSNA is elicited at a lower workload in HF CLINICAL STUDIES ©2008 Pulsus Group Inc. All rights reserved KKA Witte, CF Notarius, J Ivanov, JS Floras. Muscle sympathetic nerve activity and ventilation during exercise in subjects with and without chronic heart failure.…”

“…HF patients with the lowest pVO2 exhibit the highest reflex sympathoneural responses to these stimuli (13). Similarly, if passive exercise is used to stimulate the afferent nerve endings that are responsive to stretch (mechanoreceptors, primarily type III fibres [14]) and remove the confounding influence of central command, MSNA increases reflexively in HF patients, but not in control subjects (15). Augmentation of these exercise pressor reflexes in HF could act as a peripheral neurogenic constraint to exercise in this condition.…”

Physiological Responses Underlying the Perception of Effort during Moderate and Heavy Intensity Cycle Ergometry

“…More recently, Cochrane et al [6] reported dissociations among RPE, O2, HR, , and respiratory exchange ratio (RER) during cycle ergometry at a constant RPE, 20% below the GET (within the moderate domain). To explain these patterns of fatigue-related responses, Cochrane et al [6] made some hypotheses regarding the applicability of fatigue models [11][12][13][14][15]. It was hypothesized [6] that small nerve afferents associated with respiratory muscles responsible for mediating were the likely mediators of the perception of effort during constant RPE cycle ergometry within the moderate domain.…”

“…It has been theorized [16,17] that there is some level of brain involvement in the perception and manifestation of fatigue, with some theories suggesting the brain is responsible for conscious and unconscious integration of feedback from the working muscles and external stimuli (environment and time) [15], those that suggest the brain performs regulation without peripheral feedback [13], and others advocating a greater influence of unconscious "reflexes" on responses during exercise [11,12,14]. However, there is still debate regarding which, if any, of these theories best explains pacing and the onset of fatigue during dynamic exercise.…”