ATP-PCr system
The quickest, and most powerful source of energy for muscle movement. The phosphagen system is a form of anaerobic metabolism. It uses creatine phosphate to generate ATP (adenosine triphosphate, the chemical which provides energy for all body processes). Unfortunately, it will support activity for only about 10 seconds, just enough time for top-class runners to complete a 100 metre sprint. Although the phosphagen system produces only a little ATP, it generates energy very quickly. This provides the maximal power needed for short bursts of activity, such as when a sprinter explodes out of the blocks, or when a weight-lifter performs a clean-and-jerk. Creatine phosphate is stored in muscle and its depletion causes fatigue. Dietary supplements which increase creatine phosphate levels in muscles may delay fatigue and improve the explosive power of sprinters and other athletes. See also creatine.
