Remember to stretch before and after the workout.

Heart-rate based: Intervals will be based on your heart rate, so you'll need to wear a heart rate monitor.

First, find your max heart rate (you can use the Karvonen Formula here).

Start intervals by running as fast as you can to drive the heart rate to its max.

When max is reached, recover by walking at a slow-to-moderate speed (around 3.8) until heart rate reaches 30 beats below your max.

Repeat cycle for 20 minutes.

Perceived exertion: This is a time-based interval workout, so be sure to monitor the clock.

Start by running as fast as you can. Do 30 seconds if you're just starting to exercise, or a full minute if you're fit.

Recover for 2 minutes at a slow-to-moderate walking speed (about 3.8).

Repeat 30-second run/2-minute recovery or 1-minute run/2-minute recovery for 20 minutes.

Perform this 20-minute workout 2-3 times per week.

You can also perform this interval workout on the elliptical: use lower resistance and drive up your heart rate by increasing your revolutions per minute. To perform this workout outdoors, run as fast as you can to the first lamppost, then walk to the next two and repeat for 20 minutes.

Source: Technogym fitness consultant Marcus Eave