If your goal is to improve your times

Energy may be generated rapidly through working at high intensities, but the total amount of work and power that the body can generate is limited.

In addition to aerobic training (70 - 80%), training anaerobically (80-100%) can improve performance, by increasing both speed and tolerance for the build up of lactic acid (lactate).

Anaerobic exercise is only sustainable for short periods.

To work over the duration necessary to gain benefit from this form of exercise, these intensive bursts should be followed by low intensity periods of recovery. You can achieve this type of exercise with interval training which is discussed later.

• Prolonged anaerobic exercise reduces the effect of weight reduction and aerobic training.

• Short bursts of anaerobic exercise should be followed by low intensity periods of recovery.