In the 21st Century, it’s easy to be lazy. You can sit to work, to travel and to be entertained. This comfort comes at a cost though – your body won’t get the exercise it needs to be healthy.
But some of us don’t have the time, or the interest, to join a gym or go for a run.
However, you can improve your fitness in just four weeks, following High Intensity Interval Training (HIIT).
Find out more about how HIIT works at the BBC