There are so many types of hot yoga out there. But Bikram yoga is one of the best known and most popular. It is essentially a routine of 26 yoga poses practised within 90 minutes in a room heated to 40.5 degrees Celsius/105 Farenheit with 40% humidity. Sounds quite specific, doesn’t it? Once you are familiar with the sequence, flowing through the established series of poses in heat becomes second nature, helping you to stretch your whole body and relax your mind. Bikram yoga was invented in the 1970s by Bikram Choudhury. It aims to amplify the benefits of traditional yoga using heat, which helps your muscles to stretch more easily. The heat also makes you sweat, which is thought to help with flushing out toxins and losing weight. Unlike other forms of hot yoga, Bikram yoga has a set sequence of 26 poses that you move through repeatedly until the end of the session, which is usually 90 minutes long. No matter where you go for your Bikram yoga class, these same 26 yoga poses will be used and the class will last roughly the same amount of time. The sequence is designed to stretch your whole body, increase blood circulation, and bring more oxygen to your muscles, in addition to the standard benefits of yoga.
More info on Wikipedia