Here a 6 key core exercises to reduce that flab and tone the stomach, back and pelvis. You should see in improvement in strength, balance, and stability after just one week of core strength training. Most exercises should be held for 15-30 seconds and repeated 5-10 times. Start at the lower numbers and work your way up. Always remember to breath deeply through the diaphragm while strengthening the core muscles. It is recommended to use a mat or do exercises on a carpeted area. (If you cannot comfortably accomplish core exercise on the floor use a mat or stability ball to build up strength and then move to harder positions.)
Plank– Start lying on your stomach on the floor. Then with your arms parallel and bent at a 90-degree angle lift up on your forearms and your toes almost in a push up position. Modified versions allow for you to be on your knees rather than your toes. Your head, neck, back and buttocks should be in all in a straight line. Your shoulders should be directly over your elbows. Tighten your abdominals. To increase the resistances move your elbows and toes/knees closer to each other.
Side Plank– Start on your left side. Lift up on your left hand and side of your left foot. The left arm should be straightened in line with your wrist, elbow and shoulder. Extend your right arm above your body straight towards the sky. Tighten your abdominals. Then switch sides.
Bridge– Lie on your back with your knees bent. Lift your buttocks up, keeping your shoulders on the ground. Tighten your abdominals and keep your stomach in line with your thighs. Hold for 15-30 seconds. Release, then repeat. To make this more difficult you can add a stability ball underneath your feet.
Superman– Lay on your stomach. Lift both your arms and legs off the floor at the same time. Lift as high as you can without strain. Hold 15-30 seconds. Then relax. Repeat.
Quadruped– Start on you hands and knees on the floor. Make sure your shoulders are over your hands and your hips are aligned with your knees. Tighten your abdominals. Raise your right arm up in front of you so it is in line with your back. Now raise your left leg straight up behind you. Hold for 5-10 seconds while breathing slowly. Relax and raise the opposite arm and leg. Repeat 12-15 repetitions. Crunch– There are many different ways to do abdominal crunches. While lying on your back bend your knees with your feet up against a wall parallel to the floor. If necessary leave them planted on the ground until strength has improved to modify it. Cross your hands over your chest and raise your head and shoulders off of the ground in the direction of your abs. This should contract the abdominals. To isolate specific muscles you can hold the position at certain intervals of the crunch. To strengthen the transverse abdominals move opposite shoulders towards the opposite knee. To increase the difficulty raise knees in the air with knees bent at 90-degree angle. Keep raised while going through the entire motion of a crunch.
Sarah Labdar, “6 Core Exercises to Improve Stability & Balance”, Everyday Health