Rapid, deep breaths increase blood flow to the muscles, causing them to grow stronger and more powerful. This is why athletes often practice "deep breathing" exercises - so they can gain strength and stamina during competition. The more blood that flows to the muscles, the more oxygen they receive and the more energy they have for intense activity. Hyperventilating causes the blood pH level to become acidic. This helps rid the body of harmful toxins. The kidneys are able to remove more toxins this way, too. Hyperventilation also increases levels of carbon dioxide in the blood.