Lots of studies now show that you don’t have to exercise for very long, and long as you push it, and HIIT can improve your aerobic fitness more that longer less intense exercise.

Often called HIIT (high intensity interval training)—it definitely hits you.

Here are some HIIT routines from Women’s Health or from Huffington Post that can burn fat and get you fit!

OK,  it’s tough to do a workout of of 30- or 60-second intervals so strenuous you moan, followed by one to four minutes of  recovery, and repeat for total of four times (or intervals). But then you are DONE! Do this twice a week, and then let your third outing be a more leisurely and longer exercise routine.

Keep at it! Most people find that after a couple of weeks of HIIT, it becomes much easier and more fun. So stick with it for a few weeks before deciding if it’s for you.

Still not convinced? Here are the latest scientific studies: one from Canada and one from Norway.