If you want to get your abs back in shape consider avoiding sit-ups and try planks instead. While sit-ups do strengthen your abdominal muscles, they do not strengthen them in a functional way and can actually cause excessive stress on your lower back. Think about how your abs work during a normal day. They stabilize your trunk so your arms and legs can move freely. You rarely need to bring your chest toward your hips with daily activities.
Repetitive bending of the lower back (which is the action taken when doing a sit-up) can slowly damage your discs, and could lead to disc problems. A spinal disc problem, put simply, is when a disc between your spinal vertebrae tears/protrudes and causes low back pain. Rather than over-strengthening your abs in a non-functional manner with sit-ups, consider performing some core exercises to balance your back muscles, abdominal muscles, and buttock muscles.
There are many good exercises for balancing your core muscles and not overloading your lower back. Here are my top three recommendations:
Prone plank: When performing the prone plank, you should brace your abdominalmuscles (like someone is coming to punch you in the stomach) because bracing improves stability of your core muscles. Avoid “sucking in” or hollowing your abs because this actually reduces efficiency of your core muscles. A prone plank should initially be held for 5-10 seconds for a few repetitions and slowly build up to a 60-second hold.
Side-lying plank: Lie on your side with your knees bent and hand on your oppositeshoulder. Lift hips off the table and shift hips forward so your body is in a straight line, brace your stomach (see above for tips how to do this in prone plank exercise) and hold for 5-10 seconds initially. As you get stronger with this exercise, build up to a longer hold time (max 60 sec).
Mini-squat : Stand with feet a shoulder-width apart, brace your abdominal region, bendyour knees, push buttocks back, and go down a few inches. Return to standing and repeat about 10-15 repetitions. This is a similar motion to sitting down and getting up from a chair.
At Sports PT, we can assist you with creating a functional and spine-sparing exercise routine to improve your core stability without doing a single sit-up.
McGill, Stuart Ph.D. Designing Back Exercise: from Rehabilitation to Enhancing Performance. http://backfitpro.com/pdf/selecting_back_exercises.pdf. Accessed March 9, 2012. McGill, S.M (2007) Low back disorders: Evidence based prevention and rehabilitation, Second Edition, Human Kinetics Publishers, Champaign IL, USA.