Core/Abs

With the J20 workout concept you will be able to complete my Ab/Core workout in just 20 Minutes!

Hollow rock exercise:

hollow-rock

The hollow rock is a staple of gymnastics conditioning and one of the most functional exercises you can do for your core. Hollow rocks develop midline stability and teach you how to brace the spine, which in turn make you stronger (and safer) at squatting and overhead pressing as well as advanced bodyweight movements like headstands.
How to do it: Lie faceup on the floor with your arms extended and covering your ears and your legs straight and toes pointed. Round your lower back, and lift your feet and hands approximately 12 inches off the floor. You should be shaped like a banana and unable to slide a hand under your lower back. With your lower back acting as a fulcrum, rock your body so your toes dip toward the floor and your shoulders come farther off the ground. Then rock the other way so your feet rise and your torso tilts closer to the ground. Continue that back-and-forth motion for a full 30 seconds.
Sets and reps: 4 x 30 seconds
Tempo: Rock in a slow and controlled motion. The priority is to maintain the hollow-body position, so move as slowly as you need in order to keep the tension on your core.
Tip: If a 30-second interval is too challenging, use numbered reps instead. Start with five reps, rocking forward and backward counts as one full rep.

Exercise ball ab circle:

exercise-ball-ab-circle
Everyone knows how to do crunches on an exercise ball, but those primarily work your six-pack. This move works all your abdominal muscles (rectus abdominis, obliques, transverse abdominis) plus your lower back and hips by getting circular. Do three sets of 15 to 20 reps, changing direction every five reps to strengthen your core 360 degrees around.
How to do it: Sit on an exercise ball and hold a small plate at your chest. Roll forward until your back is resting along the ball and your hips are slightly lower than your head.
Move: Curl your torso up and around, moving in a clockwise circle, coming up as high as you can off the ball while keeping your hips steady and square, and lowering completely back along the curve of the ball at the bottom. Keep your chin off your chest at all times, and try not to let the ball roll around by planting your feet and squaring your hips. Switch directions every five reps and remember to breathe.
Make it harder: Hold the plate behind your head.

Superman:

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Want to feel super? Lie face down with arms and legs extended. Keeping the torso as still as possible, simultaneously raise the arms and legs to form a small curve in the body.20x with 4sets

Sprinter Sit-up

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Want to feel like Flash without getting off the floor?

How to do it:Lie on your back with the legs straight and arms by your side—elbows bent at a 90-degree angle. Now sit up, bringing the left knee toward the right elbow. Lower the body and repeat on the other side.
Again, like in other workouts you can do each exercise for a specified time frame like a minute or until fatigue and then move on to the next. Rest a minute or two between circuits and continue until you have worked at least 20 minutes. 20x with 4sets