Elsevier

Cardiology Clinics

Volume 19, Issue 3, 1 August 2001, Pages 369-387
Cardiology Clinics

EXERCISE AND AUTONOMIC FUNCTION IN HEALTH AND CARDIOVASCULAR DISEASE

https://doi.org/10.1016/S0733-8651(05)70223-XGet rights and content

Increasing attention is being focused on the role of the autonomic nervous system in health and disease. The complex interplay between sympathetic and parasympathetic components establishes and maintains a dynamic adaptive state, permitting the organism to withstand innumerable perturbations and allowing both short- and long-term adjustments to the ever-changing environment. During rest and exercise, the autonomic nervous system mediates changes in arterial blood pressure, heart rate, and peripheral vascular tone to facilitate regional and systemic circulatory regulation. Recent investigations have been directed at improving our understanding of how the autonomic nervous system regulates exercise and recovery, as well as how the autonomic nervous system changes in response to long-term endurance training.

This article begins with a brief discussion of the measurement of autonomic function followed by a description of the autonomic dysfunction that occurs in cardiovascular disease and its prognostic significance. We then review the dynamic changes in autonomic function that occur during exercise and recovery from exercise. The effect of endurance training on resting heart rate, on the heart rate response to exercise, and on the pattern of heart rate recovery is then discussed with an emphasis on the autonomic mechanisms responsible for these changes. Finally, we discuss the beneficial effects of endurance training in patients with cardiovascular disease. Exercise training can be thought of as a therapeutic intervention that can restore healthy autonomic dynamics in patients with autonomic dysfunction. We conclude with some speculation on a potential mechanism by which exercise training may improve mortality in patients with cardiovascular disease and discuss the paradoxical observation that acute exercise confers increased risk of sudden cardiac death in susceptible individuals, while chronic exercise may be cardioprotective.

Section snippets

Parasympathetic Nervous System

Efferent vagal outflow to the heart cannot be measured directly in conscious humans or laboratory animals. However, parasympathetic nerve activity can be inferred from the rise in heart rate observed after the administration of atropine, which inhibits the vagally mediated slowing of heart rate by competing with acetylcholine for available muscarinic receptors. Recently, various techniques have been developed to evaluate parasympathetic activity by quantifying beat-to-beat variations in R-R

AUTONOMIC FUNCTION IN CARDIOVASCULAR DISEASE

Three decades ago, dysfunction of the autonomic nervous system was reported in a number of cardiovascular diseases.36 Since then, a variety of measurements of autonomic function have demonstrated that patients after myocardial infarction (MI)12, 41, 70, 71 and patients with chronic heart failure26, 92, 93, 114 exhibit attenuated parasympathetic and increased sympathetic activity. In addition, the pattern of heart rate recovery after exercise is a new marker of autonomic dysfunction that has

AUTONOMIC FUNCTION DURING EXERCISE AND RECOVERY IN HEALTHY INDIVIDUALS

In order to understand how autonomic function is affected by exercise, it is necessary to distinguish the acute and chronic effects of exercise on autonomic function. In this section, we describe how autonomic function changes during an acute episode of exercise and during immediate recovery from exercise. Following this discussion, we examine how autonomic function changes in response to long-term exercise training.

EFFECT OF ENDURANCE TRAINING ON AUTONOMIC FUNCTION IN HEALTHY INDIVIDUALS

Long-term, or chronic, endurance training has a number of important effects on autonomic function. These effects can be understood by examining changes in the resting heart rate, changes in the heart rate response to exercise, and changes in the pattern of heart rate recovery immediately following exercise.

EXERCISE TRAINING, AUTONOMIC FUNCTION, AND CARDIOVASCULAR DISEASE

Two lines of inquiry led to the hypothesis that exercise training could be used therapeutically to restore autonomic nervous system function toward normal and thus contribute to an improvement in outcome. First, we have already reviewed the data demonstrating that cardiovascular disease is associated with autonomic dysfunction and that more severe autonomic dysfunction is associated with a poor outcome. Second, a number of investigators have shown that endurance training has the potential to

CARDIOPROTECTIVE EFFECTS OF EXERCISE: ACUTE RISKS OF EXERCISE VERSUS CHRONIC BENEFITS OF EXERCISE TRAINING

Sudden death during exercise occurs infrequently and has been associated with some of the sequelae of an acute bout of exercise: myocardial ischemia, hypokalemia, lactic acidosis, increased sympathetic tone, and decreased vagal tone.126 This is consistent with the observation that sudden cardiac death (SCD) often follows periods of increased sympathetic activation and high heart rates. While exercise training has well-known effects on resting autonomic tone, its most important benefit may be

SUMMARY

Autonomic nervous system activity contributes to the regulation of cardiac output during rest, exercise, and cardiovascular disease. Measurement of HRV has been particularly useful in assessing parasympathetic activity, while its utility for assessing sympathetic function and overall sympathovagal balance remains controversial. Studies have revealed that parasympathetic tone dominates the resting state, while exercise is associated with prompt withdrawal of vagal tone and subsequent sympathetic

ACKNOWLEDGMENT

The authors would like to acknowledge the thoughtful comments of Ary Goldberger, MD.

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    Address reprint requests to Rochelle L. Goldsmith, EdD, Division of Circulatory Physiology, Columbia University College of Physicians and Surgeons, 630 W 168th Street, New York, NY 10032, e-mail: [email protected]

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