Hot yoga refers to yoga exercises performed under hot and humid conditions.
From the 1970s through approximately 2010, Bikram Yoga - the only major yoga tradition at that time to add heat and humidity - was known as "hot yoga". However, from approximately 2012 onward, many unrelated yoga-inspired exercise and fitness trends also began labelling themselves "hot yoga". Although traditionally associated with the style devised by Bikram Choudhury, "hot yoga" is now used to describe any number of yoga or yoga-inspired fitness styles that use heat.
The heat in Bikram Yoga is used to increase the "tourniquet effect", to train the mind, and to improve circulation to the joints. The heat in other types of hot yoga is used for various purposes.
- Bikram Yoga is the original hot yoga and was first instructed in North America in 1972. Bikram Yoga is a specific, unchanging, 26-posture sequence in the Calcutta lineage of Bishu Ghosh. It was synthesized by Bishnu Ghosh and Bikram Choudhury from traditional hatha yoga techniques and is practiced in a room heated to 40 °C (104 °F) and 40% humidity.
- Forrest Yoga combines yoga asana with Native American spirituality to create a "yoga sweat lodge" in a heated room.
- Power Yoga is derived from Ashtanga Vinyasa Yoga and uses heat to replicate environmental conditions in Mysore.
- TriBalance Yoga another form of hot yoga, performed in slightly warmer but less humid conditions than Bikram Yoga.
The original form of hot yoga - Bikram Yoga - was developed by Bikram Choudhury in the late 1960s and early 1970s. From a young age, Choudhury was raised and coached in Calcutta, India, by Paramahansa Yogananda's brother, Bishnu Ghosh. For many years he assisted in the clinic of Ghosh's College of Physical Education and learned how specific postures were prescribed for specific medical conditions. In the late 1960s, he was sent by Bishnu Ghosh to teach yoga in Japan and shortly thereafter was brought to the United States. His techniques were synthesized into Bikram's Beginning Yoga Class, a therapeutic hatha yoga class made up of 26 beginner postures and 2 breathing exercises.
Choudhury began teaching in Los Angeles in 1972 and started training teachers in the mid 1990s. From the late 1990s through 2012, hundreds of Bikram Yoga schools around the world were independently opened by teachers trained and authorized to teach by Bikram Choudhury. Largely due to the success and health benefits of Bikram Yoga, many unrelated yoga styles and fitness practices began adding heat and humidity to their practice environments. However, although these yoga styles do not share the teaching lineage of yoga, the practice and teaching methods, the repeated posture sequence, or the scientifically-tested effects of Bikram Yoga, proponents of "hot yoga" usually claim the same benefits as Bikram Yoga.
In 2012-2013, around the time Bikram Choudhury began getting increased media attention for his personal behavior, "hot yoga" studios popped up around the country, claiming the benefits of Bikram Yoga. At the same time, many former Bikram Yoga schools began removing the name "Bikram" from their name and changing their names to "hot yoga".
At present, "hot yoga" may either refer to 1) the 26-posture sequence taught by a Bikram method teacher, or to 2) an unrelated yoga, yoga-inspired fitness, or stretching class.
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Hatha is a broad term encompassing all types of yoga. Hatha is Sanskrit for “forceful”, the ancient Indian language, where most yoga terminology comes from. Modern Hatha classes are slower paced, with less flow between poses. This allows for time to focus on relaxation and the Pranayama breathing techniques, taught during these classes.
Bikram Yoga was the first style of hot yoga, taught and practiced in Japan since the late 1960s and the United States since the early 1970s. It was created by Bikram Choudhury from the Ghosh lineage of therapeutic hatha yoga. It is practiced in a room at 105 °F (41 °C) with 40% humidity. The class consists of the same 26 postures with 2 different breathing techniques and lasts for 90 minutes. It is taught by teachers trained personally by Bikram Choudhury or one of his senior teachers.
From a young age, Choudhury was raised and coached in Calcutta, India, by Paramahansa Yogananda's brother, Bishnu Ghosh. For many years Mr. Choudhury assisted in the clinic of Ghosh's College of Physical Education and learned how specific postures were prescribed for specific medical conditions. In the late 1960s, he was sent by Bishnu Ghosh to teach yoga in Japan and shortly thereafter was brought to the United States. His techniques were synthesized into Bikram's Beginning Yoga Class, a therapeutic hatha yoga class made up of 26 beginner postures and 2 breathing exercises.
Choudhury began teaching in Los Angeles in 1972 and - with the assistance of Rajashree Choudhury and Emmy Cleaves - began training teachers in the mid 1990s. Bikram Yoga continues to be instructed in its original form at yoga schools independently owned by lineage-trained teachers around the world. Numerous research studies on Bikram Yoga have demonstrated its health benefits - including improved insulin resistance, healthier cholesterol levels, and reductions in depression and anxiety.
Forrest Yoga is a modern style developed by Ana T. Forrest, from hatha Yoga. This specific style focuses on holding poses for a longer duration of time. The repetition of 20 specific poses accentuates the stretch equally on each side of the body. This yoga emphasizes the connection between your emotions and your physical being. Being practiced in a hot environment helps deepen the stretch without causing trauma to the body.
Power Yoga focuses on a fitness based Vinyasa styling. This encompasses the benefits of both Ashtanga and Vinyasa, including the building of internal heat, increase of stamina and flexibility, as well as reducing your body’s stress. This class is more personalized by teachers, for they will design their own sequence of postures. Students use this time to synchronize their breathing and movements.
Since hot yoga's rise to fame, it has become a popular way to stay in shape and increase flexibility, however, it is not for everyone. Some schools of thought believe that pregnant women in particular should avoid practicing yoga in extremely warm or humid conditions, unborn babies don't have the ability to sweat, allowing them to cool down. Overheating could jeopardize the health of a growing baby. 
However, findings in the field of exercise physiology do not lead to a necessary prohibition against yoga or exercise in heat. The only known problems with fetal development occur when pregnant women have prolonged high fever during the first trimester. Heat-acclimated women do not generally experience this rise in body temperature and can usually continue their pre-pregnancy level of activity, with mindfulness and attention to body temperature and exertion.
Rajashree's Pregnancy Yoga. a specific prenatal sequence developed in conjunction with medical professionals and recommended by physicians - has been practiced by pregnant women around the world since the 1980s. Pregnant women with at least 6 months of a near-daily Bikram Yoga practice are advised to practice the pregnancy series outside of the heated room during the first trimester, as a risk of neural tube defects is increased when pregnant women have repeated and prolonged high body temperature. However, for the 2nd and 3rd trimesters, those with a pre-pregnancy Bikram yoga practice of at least 6 months may generally return to the hot room for Rajashree's Pregnancy Yoga, taking care to rest when necessary and have access to cool air if necessary.
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