Jog for 10 minutes to warm up, then walk for 2 minutes.
From the bottom of a gentle incline, run up for 5 seconds, then walk back to the starting point.
Run up again for 7 seconds, then walk down.
Run for 10 seconds, walk down.
Shorten your stride and keep your feet low to the ground on the ascents.
Feeling strong? Repeat the sequence 3-5 times.