The body has three primary energy systems:
- Alactic anaerobic
Which energy system used is determined by the intensity and duration of the exercise. Each system has a range of intensity (low to high) and duration (short to long). This is what the body responds to, time (duration) and intensity. Generally, the shorter the time, the higher the intensity should be and the longer the recovery needs to be. The exception is when you do a lower intensity for a short time and you keep the recovery short.