muffintop-less:

Numerous studies have shown that HIIT cardio is extremely effective for fat loss. It revs up your metabolism (unlike steady-state cardio) and keeps it elevated for hours after you finish. Give it a try!:

Warm up at a comfortable intensity for 5 minutes.
Then, give your maximum effort for 15 to 30 seconds, followed by a 2-minute recovery.
You can walk during the recovery or you can just take it down to a very light jog, depending on your current level of fitness. More than likely, though, you will be going so hard that you will need to walk during the recovery.
Perform between 6 and 10 of these intervals, and finish with a cooldown.

Just did this! I love it. I’m going to start doing this twice a week (Tuesdays and Thursdays).