What happens during increase phsucal activity?

Aerobic heart beat increases, to circulate the oxygen in the blood to the muscles faster, and remove toxins from the cell faster. This increases the blood pressure. To get more oxygen into the bloodstream, and get toxins out, the breathing rate increases, and the lungs expand and contract more. Lactic acid is produced and will cause a burning sensation in the muscles. The body will try to get oxygen to the muscles as fast as it can, but it is not always able to give the muscles all the oxygen they need. When this happens, the muscles will shift to anaerobic respiration until they can get the oxygen they need. This usually happens during any aerobic workout, if the person is trying to push him or herself. When it does happen, the muscles will produce many toxins that are created during anaerobic respiration, and then the liver will try to cleanse those toxins as fast as it can. When the liver cannot remove the toxins as fast as they are created, they build up. When a person experiences pain in their muscles because of working out, it is usually because of lactic acid building up (unless the person has pulled a muscle or damaged something).