5 moves for strong abs

Place your forearms in the middle of the stability ball with your feet on the floor, slightly wider than shoulder-width apart. Maintain a straight spine while you brace (tighten) your abdominals and glute muscles. Do not let your shoulder blades shrug or your midsection sag.

Hold the plank position for 30 to 90 seconds. Increase your hold by 10 seconds each workout until you can complete 90 seconds.

Lie flat on your back with your hands behind your head. Keep one leg straight and one leg bent with your ankle to the floor. Hinge at the hips as you raise your torso off the floor. While maintaining a tall posture, shift your weight onto your bent knee and raise yourself from a bottom lunge position to a standing position. Lower yourself back to the floor slowly by reversing the steps. Alternate legs each repetition.

Perform 8 to 12 total reps.

Trainer Tip - as you raise your back off the floor, be sure to hinge at the hip. Avoid rounding your low back.

Stand with your feet at a comfortable width with your hands raised to touch your ears.

Initiate the exercise by raising your left leg and slowly flexing your trunk and rotating your upper body so your right elbow approaches your raised left knee. Your knee and elbow do not have to make contact. The key to the exercise is to maintain a tall posture and avoid rounding the low back. Repeat the sequence on the opposite side.

Perform 12 to 20 total repetitions.

Trainer Tip - be sure to raise your knee towards your elbow. Do not sag at the waist or pull down on your head with your hands in order for your knee to meet your elbow.

Stand tall with your arms relaxed at your side. This is your starting position.

Bend at the waist and lower your body down to the floor. Walk your hands out into a push-up position. Hold the push-up position as you raise your left knee to the outside to meet your left elbow. Repeat for the right side and then walk yourself back to the starting position.

Perform 8 to 12 reps per side

Trainer Tip - maintain a straight spine during the push-up position. Do not increase the number of reps until you can keep your hips from sagging towards the floor.

Lie on a sturdy bench and grasp the bench firmly above your head. Raise your legs and torso so that you are resting all of your weight on the back of your shoulders. Slowly lower your body back to the bench as you maintain a tight grip on the bench. 

Do not arch your low back. Bend at the waist if necessary and gradually try to maintain straight legs as you become stronger and more proficient at the exercise.

Since this is a more challenging exercise only 3 to 5 reps are required when performed properly. 

Trainer Tip - to protect your spine, maintain internal pressure in your abdomen by exhaling slowly under control. Never fully empty your lungs of air or relax your abdomen during the exercise

Source: womenshealthandfitness