What Is Energy?
Energy is the capacity or ability to do work. Energy is produced by the breakdown of a very special molecule known as adenosine triphosphate (ATP). Which of the energy systems that will get used during physical activity depends on the intensity and duration of the activity. The intensity is measured by heart rate, 220bp/m – age. There are three energy systems. The creatine phosphate and lactic acid energy systems are anaerobic methods of resynthesising ATP whereas the oxygen system uses food fuels in the presence of oxygen to resynthesis ATP and is therefore aerobic. The aerobic system is used at 70-80% of the person’s maximum heart rate and the anaerobic is used at 85-100% [2].