1) The National Academy of Sports Medicine (NASM) recommends a marching exercise that can be done lying on your back on the floor. Start by lying down with your feet flat on the floor and your knees bent. Next, raise your left knee up towards your chest until it is pulled tight against your body. Hold it there with your back flat and your knee perpendicular to the floor. After a few seconds, lower your leg to the starting position, and repeat the exercise with your right left. Throughout this exercise, your neck should be relaxed and supported by the floor.
2) A plank is performed in a kneeling position, and it will exercise your whole body (including your abs) without putting pressure on your neck. Once you are kneeling, place your palms down onto the floor at the height of your shoulders, and then extend your legs out behind you (keeping your abs engaged). Making sure that you keep your back straight at all times, you should hold this position for up to thirty seconds before you go back to the initial kneeling position. When you are performing a plank, be careful to face the floor to avoid straining or arching your neck.
3) One version of the reverse crunch is particularly well suited to those with a neck injury. It is called the reverse crunch with rotation, and allows you to exercise and tone all of your abdominal muscles without straining your neck. Lie flat on your back with your knees bent, then slowly lift both knees up towards your left shoulder while your lower back rises from the floor. Hold this position for five seconds, then lower your hips and your back until your feet are on the floor again. You should then repeat the exercise, this time lifting your knees at an angle towards your right shoulder.
4) There is also an alternative version of the reverse crunch that involves lifting your knees straight up towards your chest (instead of at the angle involved in the reverse crunch with rotation). To perform the straight reverse crunch, lie flat on your back with the soles of your feet flat on the floor and your knees bent. With your abs engaged, your arms by your sides, and your back tight against the floor, pull your knees up towards your chest until you are holding them right against your body. Try to hold this position for about five seconds, then lower your legs until your feet are back on the floor (keeping your back flat against the floor at all times).
5) An exercise called the leg raise does not demand any upper body movement, and your neck can rest comfortably on the floor throughout. You should begin by once again lying on your back with your feet flat on the floor, and you should let your arms rest by your sides. Pull your knees up until they are tight against your chest, then unbend your knees and raise your legs straight up above the hips. Slowly lower your legs down towards the floor, keeping your back flat and your legs straight, and stop when you feel as though your lower back is about to rise up off the floor. At this point, hold your position for a few seconds, and then pull your legs back up towards your chest to repeat the exercise.
If you perform all of the above five exercises correctly, you should be able to tone your abdominal muscles without aggravating your neck injury. However, if you do experience any pain during any of the exercises, stop immediately, and make sure that you remove that particular exercise from your routine.
source : Five Exercises That Will Tone Your Abs Without Causing or Worsening a Neck Injury
