What are the cardiovascular adjustment during exercise in human?

Answer 1

BY LORD AKERECONFI IntroductionTop

Abstract

Introduction

Methods

Results

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During exercise, cardiac output (CO) increases to provide the flow needed to serve the contracting skeletal muscles.1,2 Yet, by resetting the operating point for the arterial baroreceptors, vasodilatation is regulated to make blood pressure stable or to increase during exercise.3,4 Such a balance between CO and total peripheral resistance would be considered to be governed by an interplay between the autonomic influence on the heart, vasodilatory substances released from the working muscles, and sympathetic mediated vasoconstriction, including active skeletal muscles.2 The central nervous system (CNS),3,4 and especially neural feedback from contracting muscles,5-9 are important for the blood pressure response to exercise. Acceleration of the heart is governed by central command,10 whereas a blood-borne substance may contribute to the maintained elevation of heart rate (HR).11 Even in the absence of influence from CNS and neural feedback from working muscles, a tight coupling between CO and whole body oxygen uptake (O2) is maintained.12 We hypothesized that in the absence of not only motor control and neural feed back from contracting muscles5-9 but also sympathetic activity, at a level where it affects the heart, it would be difficult to maintain blood pressure during exercise. Individuals in whom neural transmission between the CNS and the contracting muscles was absent (spinal cord-injured individuals [SCI]) were studied at rest and during electrically induced contractions of their paralyzed legs after 1 year of similar electrically induced training.13 The results were compared with those established in able-bodied (control [CON]) individuals performing comparable voluntary exercise. By studying 2 groups of SCI, tetraplegic (TETRA) and paraplegic (PARA), the influence of sympathetic innervation to the heart on the cardiovascular responses to exercise was evaluated. Finally, to evaluate the influence of passive movement of the legs on cardiovascular variables while seated, the effect was compared with that established by contractile activity.