When you’re going to do any faster running, such as Hills, Threshold Runs, Intervals or a race, it’s important to warm up gradually. A 10-15 minute jog allows your muscles to gradually warm up and improve their range of movement. It also allows your cardiovascular system to prepare for the harder work to be carried out.
A period of at least 10-15 minutes easy jogging and light stretching allows your body to adjust back to a steady state. Cooling down stops blood pooling in your legs and helps remove some of the waste products from the muscle cells, which helps to avoid undue muscle soreness.