Ready to take your ab training up a level? This advanced ab HIIT workout  combines challenging leg lift and V-up variations that demand serious control and strength. If you’ve mastered the basics, this is your next step. The Workout Format: 40 seconds per move 20 seconds rest between moves 3 rounds total Rest 1 minute between rounds Moves: Single Leg V-Up Straddle Leg Lift Hip Raises Benefits of This Advanced Ab HIIT Workout Single Leg V-Up:  Targets abs with extra balance ch