Here are two easy but effective exercises you can do to work your core. You will need a regular exercise ball and/or a small medicine ball (preferably a five to ten pound ball depending on your fitness level). Check out these ball exercises that work your core.
Medicine Ball Twist. Have a seat on the floor with your legs in front of you and knees bent. Your feet should be pressed together. Hold the medicine ball with both hands and turn/twist at the waist from side to side, each time making an effort to twist as far to the right or left as possible.
Exercise Ball Hip Extension. Lying flat on the floor, place your heels atop the exercise ball. Try to lift your hips from the floor by tightening your abs and squeezing your glues. Your body should form a diagonal line between the floor (where your head and shoulders are) and the ball. Do a five second count and then slowly lower your hips back down. Try for three sets of ten repetitions.
These exercises really work your abs. They can be difficult at first but don’t give up!