When a short, intensive burst of activity occurs there is a temporary shortage of oxygen being delivered to the working muscles at first. The production of anaerobic energy creates a by-product; lactic acid. As mentioned above, lactic acid causes muscle fatigue, which is the reason the session cannot last long. However, after regular training the person's body becomes better equipped to handle lactic acid. After several practice sessions the body becomes better at getting rid of lactic acid - it also learns how to produce less of it. The body also produces buffers that postpone the onset of fatigue during an anaerobic session. Anaerobic exercises offer the following benefits: