The L-Seat
Gymnasts perform this move on the parallel bars and rings. “It’s an isometric exercise that challenges the strength and stamina of your rectus abdominus (six-pack muscles), hip flexors, lats, and triceps,” says Speer.
If you can hold the position for 20 to 30 seconds, you are the owner of a seriously strong torso.
Do it: Sit in between parallel bars or parallets, holding on to the bars. (If you don’t have access to either piece of equipment, you can use a pair of hexagonal dumbbells on the floor instead.) Straighten your arms, pulling your shoulders down away from your ears as if you’re doing a reverse shrug. Bend your knees toward your chest, and lift your legs and glutes off the floor until your feet are even with your hips. Hold this for 30 seconds. Then lower back down to the starting position.
Once you can hold the tucked position for 30 seconds, extend your legs straight out in front of you and hold.