The Effect of Bikram Yoga on Arterial Stiffness and Endothelial Function in Middle-Aged Adults

Bikram yoga is a trademarked form of yoga in which a series of 26 yoga postures are performed in a heated (41ºC), humidified environment over a 90-minute period. Bikram yoga has rapidly gained popularity with approximately 300 studios currently operating in the U.S. The 90-minute session consists of pranayama (breathing), and standing, balancing, strengthening, and stretching asanas (postures) all performed in a sauna-like environment. Although this highly controlled style of yoga provides an optimal choice for interventional research studies, few studies have attempted to elucidate the health benefits associated with Bikram yoga. Subjects will be randomly assigned to one of three groups: heated Bikram yoga (41ºC), room temperature Bikram yoga (22ºC), or control in which the participants will be instructed not to alter physical activity patterns. Collected data from this interventional study will be analyzed by ANOVA and/or ANCOVA with repeated measures. Pearson correlation coefficients will be used to examine associations between variables of interest. A significance level of p\<0.05 will be employed to determine statistical significance. A total of 80 sedentary (\<2 days of physical activity weekly) male and female adults between the ages of 40 and 60 years will be recruited and studied. Twenty subjects in each group will complete 12 weeks of Bikram yoga at room temperature (22ºC), Bikram yoga in a heated environment (41ºC), or a control period during which participants will be instructed not to alter physical activity levels. Based on a previous study competed by the investigators which employed Bikram yoga as an intervention, a dropout rate of 25% is anticipated. Therefore, as the goal of the investigators is to have a minimum of 60 subjects (20 per group) complete the 12-week intervention, the investigators will recruit and enroll 80 subjects. Once participants report to the laboratory, height and weight will be measured and a finger prick will be performed. Body composition will then be measured via dual energy x-ray absorptiometry scan. Endothelial function will be measured non-invasively via flow-mediated dilation. This technique involves ultrasound imaging of the upper arm to obtain an image of the brachial artery. Once baseline images are acquired, a cuff placed around the forearm will be inflated for 5 minutes. More images will be acquired after the cuff is deflated and the images will be analyzed to determine the percent change in arterial diameter from baseline. Arterial stiffness will be measured using pulse wave velocity. Tonometric sensors will be placed on the carotid and femoral pulse sites and blood pressure cuffs placed on the arms and ankles to determine brachial and tibial arterial blood pressure. The distance between the carotid and femoral pulse sites will be measured and pulse wave velocity will be determined as distance traveled divided by the time between the initiation of the carotid and femoral pulses.