Abs Exercises: RUNNING MAN SIT-UP
It’s a bit like if the bicycle crunch got together with a standard sit-up. HOW TO DO IT: Lie flat on the floor with your hands behind your head. Exhale as you curl up, twisting your torso and bending your right knee so that you left elbow crosses over your right knee. Drop all the way back down to the start before repeating on the other side.
Abs Exercises: REVERSE CRUNCH PULSE

Begin lying on your back with your legs up in the air, perpendicular to the floor. Keep your arms down along your side with your palms facing down. Squeeze your lower abs and raise your butt and lower back off the floor with quick pulses. Try not to rely on momentum, but focus on only using your lower abs. You can do it either with legs straight up or legs bent at the knees with shins parallel to the floor.
Abs Exercises: RUSSIAN TWIST
Grab a medicine ball, dumbbell, or weight plate and sit on the floor with your hips and knees bent 90 degrees. Hold the weight straight out in front of you and keep your back straight, your torso should be at about 45 degrees to the floor.
Explosively twist your torso as far as you can to the left, and then reverse the motion, twisting as far as you can to the right. The strength you need to paddle a raft is generated in your core, not your arms or shoulders. This is great for your obliques as well as six pack abs.
Abs Exercises: PLANK

The Plank helps you to build strength in your core, upper and lower body so it is a good full body work out. You do not need any equipment to perform this exercise all you need is a bit of space, and it really helps improve flexibility by stretching muscles and will improve posture if performed regularly.
Abs Exercises: T-CROSS SIT UP
Begin lying on the floor with your legs straight and arms out wide to the sides, making a T with your body. In a slow and controlled motion, sit up, lifting your right leg and twisting to the right to bring your left hand to your right toes. Hold this position for a moment, pulling your abs toward your spine. Slowly roll down to return to the starting position to complete one rep. Repeat on the other side.

image sources
- the-best-abs-workouts: Photo courtesy of CrossFit Inc.