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 Millions of people worldwide practice Bikram yoga, typically in
90-minute sessions that involve breathing exercises and holding
poses for up to one minute or longer in a humid studio heated to
around 105 degrees Fahrenheit (40.5 degrees Celsius). Previous
research has linked Bikram yoga to improvements in the elasticity of
blood vessels, which can help lower blood pressure and reduce the
potential for arteries to harden and cause heart attacks.
For the current study, researchers randomly assigned 52 middle-aged
adults who were sedentary but otherwise healthy to remain inactive
or to do three Bikram yoga classes a week for three months, either
in a hot studio or a normal, 73-degree (23-degree C) room.
By the end of the experiment, people in both yoga groups experienced
similar improvements in blood vessel flexibility. But there were no
meaningful changes for people who remained sedentary.
“Given previous research showing some improvements in heart disease
risk factors with sauna therapy, we thought that the heated
environment in Bikram yoga might have augmented the changes in
vascular health and possibly other outcomes as well,” said lead
study author Stacy Hunter, a researcher at Texas State University in
San Marcos.
“We were certainly surprised to find no additional effect of the
heat,” Hunter said by email.
Some people are drawn to Bikram yoga because they think sweating in
a hot room during their practice may help them lose weight and
improve strength and flexibility, and some previous research
suggests they may be on to something. It’s not for everyone,
however, and it can cause dangerous side effects like severe
dizziness and dehydration.
People with a variety of health conditions that might make it unwise
to spend 90 minutes in an extremely hot room were excluded from the
study, including pregnant women and individuals with a history of
heart or lung problems.
When they joined the experiment, people had been generally
sedentary, getting moderate-intensity physical activity less than
two days a week.
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Although the Bikram yoga program appeared to benefit blood vessels
equally when it was done with added heat or without, the researchers
did find that only the hot-yoga group experienced statistically
meaningful decreases in body fat measurements, and notable declines
in LDL (“bad”) cholesterol.
One limitation of the study is that researchers only used one test
of blood vessel health known as brachial artery flow-mediated
dilation, and additional tests might provide a more complete picture
of any changes associated with yoga, the authors note.
Because the study only focused on Bikram yoga, and didn’t include
other forms of yoga or other exercises, it’s also not clear whether
the blood vessel changes in the study might be limited to Bikram
yoga or occur with other activities, said David Shannahoff-Khalsa of
the Center for Integrative Medicine at the University of California,
San Diego.
“We do not know if walking alone or playing for the same amount of
time would lead to the same result,” Shannahoff-Khalsa, who wasn’t
involved in the study, said by email.
There isn’t a clear rationale for why practicing physically
demanding yoga exercises in a heated room would be beneficial for
the heart, said Holger Cramer of the department of internal and
integrative medicine at Kliniken Essen-Mitte and the University of
Duisburg-Essen in Germany.
“Yoga, especially yogic breathing and meditation exercises, can
positively influence our nervous system, reduce the stress reaction
and balance certain stress-associated mediators in the brain,”
Cramer, who wasn’t involved in the study, said by email. “This
stress-reducing effect most likely is the active part in yoga’s
effects on heart health, and there is no reason why this should be
increased by increased heat.”
SOURCE: http://bit.ly/2EsuBQI Experimental Physiology, online
January 18, 2018.
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