- The human body has three main energy systems - ATP-CP, lactic acid, and oxidative - that provide fuel for physical activity through the production of ATP.
- The ATP-CP system provides immediate energy for bursts of intense activity lasting 10 seconds or less without using oxygen.
- The lactic acid system fuels slightly longer intense activity through glycogen breakdown, but produces lactic acid which can cause fatigue.
- The oxidative system is the most complex and provides sustained energy for longer duration moderate-intensity activities through aerobic pathways using oxygen.