20 min abs and HIIT workout with no equipment required. For more workouts and programs, check out my app Greenland Voters Reject Trump in Favor of Independence Every Upcoming Sci-Fi Movie Sequel ...

For fitness enthusiasts who need a little cardio variety, HIIT (or high-intensity interval training) has long been a popular choice. According to a study in Biology of Sport, HIIT — which pairs short ...

HIIT workouts ... Each cycle will take just under four minutes, and you'll want to complete five cycles. In total, this workout will take about 20 minutes (although it's always a good idea ...