There are 3 reasons. Stretching causes you to breathe deeply bringing oxygen to your brain, in effect waking you up. Secondly, stretching releases the physical form of stress that is stored in your muscles. Storing that tension takes constant work by your muscles. Relieving that work frees up energy. Lastly, stretching helps your body remove toxins from your tissues. When you breathe deeply and move your body your lymph system is activated, cleansing the body of pollutants. The end result. You feel great!
