1) Why yoga make you feel relax?
Because it helps the body to release happy hormones includes Dopamine, Serotonin, Oxytocin, and Endorphin.
Yoga decreases Sympathetic Nervous System (SNS) arousal which also known as Stress Response and Fight/flight/freeze. Fight/flight/freeze means anger, anxiety and depression.
Most mental health problems relate to an over-stimulated SNS, which also affects physical health as a result. In the other hand, yoga increases Parasympathetic Nervous System (PNS) function which regulate relaxation response and help rest and digest.
2) Why Pranayama and Meditation is so important?
They have a positive effect on the parasympathetic system. It slows the heart rate, increases intestinal and gland activity.
3) Why yoga save body energy than others forms of exercise?
White muscle fibers are increased during aerobatic exercise. And hence, lead to fatigue muscle. On the other hand, yoga boosts red muscle fibers and results to less fatigue, and thus save energy than other exercise.