Crunches are an effective way to tone and strengthen your abdominal muscles, but it's not always possible to find the time or space to perform them. However, one of the advantages of crunches is that they can easily be performed in a chair, which is helpful if you are sitting in an office or can't get down on the ground to execute a standard crunch. Not only are sitting crunches convenient, they are also effective at giving your abdominal muscles a workout.
Knee Raise Crunch
Sit on the edge of a sturdy chair with your feet flat on the floor and your arms crossed across your chest. Keep your back straight, and your shoulders tense to help keep your upper body supported during the movement.
Flex your abdominal muscles and slowly lift your right leg toward your chest while simultaneously curling forward at your shoulders, stopping when your right arm touches your right leg.
Hold that contracted position for 1 to 2 seconds then lower your leg back to the ground while returning to the upright position.
Repeat the movement with your left leg. Perform the exercise for 1 to 2 sets of 10 repetitions each with the movement of both legs counting as one repetition.
Back of Chair Crunch
Sit in a chair with your back pressed firmly against the back of the chair. Hold onto the edge of the chair for support.
Round your back by leaning forward and flexing your abdominal muscles, then lift both knees off the ground, getting as close to your chest as you can.
Hold that flexed position for 5 to 10 seconds, then release and return to your original position. Repeat the movement for one to two sets of 8 to 10 repetitions each or until you get fatigued, which ever comes first.
Sitting Oblique Crunch
Sit at the edge of a bench or chair with your hands behind your head and your elbows out to the side. Keep your back straight and your feet flat on the floor.
Flex your abdominal muscles then lift your left leg 1 to 2 inches off the ground and move your right elbow towards your left knee, getting as close as possible to your left knee without losing your balance. The exercise works the outer part of your abdominal muscles known as the obliques.
Hold the contracted position for 1 to 2 seconds, then return to your starting position.
Repeat the movement with your right knee and left elbow. Perform 1 to 2 sets of 8 to 10 repetitions each with the movement of both the right and left sides constituting one repetition.