While the popularity of yoga practice in suffocating rooms is booming worldwide, researchers say the benefits to blood vessels are the same whether the movements are performed with or without heat.
Bikram yoga was founded by the controversial instructor Bikram Choudhury and involves 26 poses and two breathing exercises performed in a room heated to just over 40 ° C (104 ° F).
After having taken off in the 1970s, Bikram yoga classes are now widespread, and some research suggests that they could offer health benefits, such as improving the function of the inner lining of blood vessels, problems that are related to an increased risk of fatty plaques building inside the arteries.
But now researchers say that the potential vascular benefits of Bikram are not due to heat.
"Postures and breathing exercises are sufficient in the absence of the heated environment to elicit some beneficial adaptations that could reduce the risk of heart disease," said Dr. Stacey Hunter, co-author of the Texas Inquiry State University and research director of yoga advocacy organization Pure Action Inc, which funded the study.
It is not the first time that yoga is related to health benefits, and previous studies suggest that it could be as good as riding a bicycle or walking at a rapid pace to reduce the risk of cardiovascular disease. r disease, for example.
However, little work has been done to discover the impact of different types of yoga, some of which are more intense than others, or how much yoga is needed to see the benefits.  In an article published in the journal Experimental Physiology, Hunter and his colleagues describe how they randomly assigned healthy but sedentary middle-aged adults to one of three groups. While 19 participants continued as usual, 14 performed 12 weeks of three Bikram classes of 90 minutes at room temperature and 19 participants performed Bikram classes at 40.5 C.
A series of measurements were taken as part of the study , including weight and cholesterol levels, blood pressure and the ability of the main artery in the forearm to dilate in response to increased blood flow, a measure of the function of the inner lining of blood vessels.
The results reveal that both yoga groups showed improvements in the function of their arterial lining, the size of the benefits was the same regardless of the temperature of the classes. Those who did not do yoga showed no improvement.
No significant effects on blood pressure, cholesterol, blood lipids, weight or blood glucose were observed in any of the groups, but the team points out that those who performed hot yoga showed a small drop of water. body fat, possibly due to the extra energy that is used.
Paulus Kirchhof, professor of cardiovascular medicine at the University of Birmingham, said that in general, the impact of yoga on health was not yet clear.  "Yoga, similar to other behaviors, can help improve vascular health.If yoga per se is particularly effective in reducing blood pressure or if yoga has effects similar to regular physical exercise [for example] it is less clear "He said, adding that he would advise people to do the recommended 30-45 minutes of moderate activity. five times a week, with yoga as an optional addition.
Julie Ward, senior cardiac nurse at the British Heart Foundation, said that previous studies had shown some improvements in measures that include blood pressure and cholesterol, but that high temperatures could be dangerous for those with conditions underlying cardiac
"This study, although interesting, is a very small study and has significant limitations, so more research would be needed to confirm the findings," he told The Guardian.
But that does not mean that people have to roll up their mats. "The benefits of yoga in emotional health are well established and any physical activity that can help reduce the risk of a fatal myocardial infarction or stroke should be encouraged," Ward said.