When you are starting out or getting back into running, alternating between walking and running will help you build up your endurance to run for longer periods without stopping!
After 10 minutes of fitness walking, which will prepare your muscles for the physical effort, you'll alternate between 2 minutes of running and 1 minute of walking, for a total of 22 minutes.
You'll finish the session by walking slowly for 5 minutes to help your recovery.