Yoga thins the blood which can decrease the risk of heart attack and stroke, as they are often caused by blood clots. Twisting poses wring out venous blood from internal organs and allow oxygenated blood to flow in when the twist is released. Inverted poses encourage venous blood flow from the legs and pelvis back to the heart and then pumped through the lungs where it becomes freshly oxygenated. Yoga increases blood flow and levels of hemoglobin and red blood cells which allows for more oxygen to reach the body cells, enhancing their function.
If you practice hot yoga, it’s important to be well-hydrated – for a variety of reasons. One being: hot yoga will only thin the blood in hydrated individuals. In dehydrated individuals, hot yoga increases blood viscosity, increases muscle fatigue and prevents muscle growth.
(sources: Timothy McCall, M.D and Wendy Shubin, Certified Yoga Therapist)