Hot yoga is a vigorous form of yoga performed in a studio that is heated to 105 F (40 C) and has a humidity of 40 percent. The formal name for hot yoga is "Bikram yoga. " Bikram yoga is a 90-minute program that consists of a series of 26 postures. The postures require lengthy, forceful and well-controlled contractions of all major muscle groups. The demanding nature of the poses and the heat are designed to raise your heart rate and tire your muscles. Because of its intensity and potential to cause heat-related illness, hot yoga isn't for everyone. Be sure you check with your doctor before trying hot yoga if you have any health concerns. If you have heart disease, problems with dehydration or heat intolerance, or have had heat-related illness (such as heatstroke) in the past, it is probably best to skip hot yoga. Pregnant women should also pass on this type of yoga. If you have no health concerns and you want to try a hot yoga class, be sure to drink plenty of water, and stop if you feel dizzy, lightheaded or sick in any way.