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Examining blood pressure responses to yoga

This is an excerpt from Physiology of Sport and Exercise 6th Edition With Web Study Guide by W. Larry Kenney,Jack Wilmore & David Costill.

Research Perspective 8.2

Blood Pressure Responses to Yoga

Yoga is an increasingly popular form of exercise that is designed to increase flexibility, muscular strength, and overall health. Over half of yoga practitioners surveyed by Yoga Magazine in 2012 said that they started practicing yoga to improve their overall health. Yoga is a unique form of exercise in that it involves whole-body isometric muscle contraction, stretching, relaxation techniques, and breathing exercises and is purported to have beneficial effects on mental and physical health, stress and anxiety, blood pressure control, and even glucose tolerance.

A recent study conducted at the University of Texas examined the acute effects of practicing one session of hatha yoga on blood pressure and cardiovascular responses.⁸ The researchers were further interested in determining whether regular practitioners of yoga had blunted responses compared to those who were practicing yoga for the first time. On the basis of the known cardiovascular and sympathetic nervous system responses to isometric exercise, they hypothesized that blood pressure would increase markedly during yoga, more so in novice exercisers compared to people who regularly practice yoga.

Subjects in both groups participated in a standardized yoga session consisting of 23 different yoga postures including standing, floor, and inverse poses. A video was used to instruct the subjects. Before the yoga practice session, the investigators measured each subject's trunk and lumbar flexibility, along with a measurement of central arterial stiffness. To measure arterial stiffness, they examined the transit time for a single pulse to travel between two different sensors placed on the carotid and femoral arteries, a value termed carotid - femoral pulse wave velocity (cfPWV). The longer it takes for the pulse to travel between sensors, the more distensible the arteries are, whereas a faster cfPWV is indicative of stiffer arteries. (Arterial stiffness occurs as a consequence of age and arteriosclerosis and is associated with an increased risk of cardiovascular events.) Additionally, using a cuff placed around the finger, beat-by-beat blood pressures were measured and adjusted for changes in hydrostatic pressures as postures changed during the yoga practice. Cardiac output and SV were also calculated.

During the yoga session, mean arterial pressure (MAP) increased by up to 30 mmHg, especially during the standing poses. The increases in blood pressure were primarily due to an increase in cardiac output as opposed to an increase in peripheral vascular resistance. Further, there were no differences in the blood pressure responses between the subjects who regularly practiced yoga and the novice subjects. However, there was an inverse relation between cfPWV and lumbar flexibility (see figure), such that subjects who had been practicing yoga regularly had greater lumbar flexibility and a slower cfPWV, that is, decreased central artery stiffness.

The results of this recent study demonstrate two important phenomena. First, individuals who have recently experienced a cardiovascular event and those who are at high risk due to uncontrolled hypertension may need to avoid or modify standing yoga postures to prevent such transient increases in blood pressure. Second, regular yoga practice may help to attenuate central artery stiffening.

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The association between lumbar flexion and carotid - femoral pulse wave velocity.

Reprinted, by permission, from S.C. Miles et al., 2013, "Arterial blood pressure and cardiovascular responses to yoga practice," Alternative Therapies in Health and Medicine 19(1): 38-45.

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