Chair Crunch Sit tall with your arms folded across your chest. Raise them so that they are perpendicular to your shoulders. Engaging your abs, curl your torso towards the ground until your elbows touch your knees. Slowly raise your body back to starting position. Repeat until your start to feel a burn in your abs. Chair Oblique Bends Sit up straight with your elbows bent and your hands behind your head. To perform the exercise, simply bend at the waist as you lean to one side as far as you can. Contract your abs to raise your torso back to starting position. Repeat the motion on the other side. Perform 10 reps on each side. Chair Twist This exercise will strengthen both your internal and external obliques. To start, place your feet shoulder width apart and sit up tall with your hands behind your head. Engaging your abs, raise your right knee across your chest as you lower your left elbow to meet it. Return to starting position, then raise your left knee and lower your right elbow across your chest. Perform 10 reps on each side. Leg Raises To work your lower abs, lean back into your chair and grip the sides. Bring your feet together and tuck them under your chair, then extend them until they are nearly parallel to the floor. The further you lean back, the harder the workout will be. Perform 10 reps. Scissor Kicks Lean back in your chair so that your back is at a 45-degree angle to the floor. Grip the front of the chair with your hands to stabilize yourself. Bring your feet and legs together and point your toes at the floor. Keeping your legs bent, raise your thighs until they are at a 45-degree angle with the seat of your chair. Use your abs to slowly lower your legs back to the floor until your thighs are parallel with it again. Perform 10 reps. Knee Pull-Ins Lean back in your chair and grip the front of your seat with your hands on either side of your thighs. Straighten your legs so that they are parallel to the floor. Then, using your abs, pull your knees into your chest. Push them out until your legs are straight again. Repeat until your start to feel a burn in your abs.