Muscle Afferent Feedback during Exercise: Putting the Pressure on Flow

Jennifer C. Richards
Anne R. Crecelius, University of Dayton
Brett S. Kirby, Duke University Medical Center

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An examination of recent research: Following the original observations of an EPR, numerous studies have attempted to investigate the role that afferent signals originating from exercising muscle have on the cardiovascular response to exercise on both a systemic and local level. In humans, a variety of techniques have been employed; predominately limiting arterial inflow in order to augment metabolic afferent signalling, or administering local anesthetics to reduce afferent signalling to the CNS during voluntary contractions. Both methods are limited in that the former limits arterial inflow, complicating the assessment of vascular tone in response to the EPR and the latter augments central command. To date, these approaches have prevented the direct and continuous assessment of the exercise induced augmentation of mean arterial pressure (MAP) and its influence on skeletal muscle blood flow. As a result, it has been difficult to understand what contribution group III and IV skeletal muscle afferent feedback may have in regulating the cardiovascular response to exercise. Specifically, it remains unclear whether the blood pressure elevating reflex that occurs following stimulation of these muscle afferents serves to augment blood flow to muscle during exercise.