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  • Niel Kamra and Thiviya Srikanthan

Ab Exercises

Edited by: Temi Toba-Oluboka


The information provided in this article is not medical advice. Please speak to a medical professional for more information.

The safety of abdominal exercises such as sit-ups and crunches in relation to their benefits have long been debated. With virtually any exercise, there are pros and cons, and in this post I will be covering what the expected benefits of these exercises are.

Back pain is an important issue and has been reported to affect 60-80% of adults at some point in their lives (1). Core stability and muscular strength is a point of emphasis in research in relation to poor sitting posture. A slumped sitting posture occurs when there is more lumbar flexion which occurs from decreased engagement of core muscles such as the lumbar multifidus, iliocostalis lumborum pars thoracis, and the transverse fibers of internal oblique. As a result, these muscles become weaker and prevents maintaining an upright posture. Consequently, soft-tissue degenerative changes in the intervertebral discs, the structures that provide shock absorbance, can ensue as forces are redistributed to the other components, which can create injuries and result in low back pain (1).

Furthermore, patients with low back pain begin sitting with more pronounced lumbar flexion, reinforcing the relationship between sitting posture and low back pain, and accentuates the importance of core strength (1). Physical activity and exercise are beneficial in rehabilitation by increasing blood flow to the injury site, which is crucial to the recovery process. The authors report that core stabilization programmes significantly reduced chronic low back pain (CLBP) by 39-76.8% and a muscular strength regiment significantly decreased CLBP by 61.6%. It is important to note that these improvements are only in CLBP and NOT acute low back pain, for which it is recommended to consult a medical professional promptly (1).

When it comes to crunches specifically, some of the benefits include increasing muscle mass, being beginner friendly, exhausting calories, and improving posture (2). First, the movement is more isolating than sit-ups and solely work the abdominal muscles. Repeated stimulation to any muscle group can increase muscle mass and can help in reaching fitness and aesthetic goals (2). It has also been shown that in the starting weeks of training, and perhaps longer, performing crunch exercises once a week provided the same benefit as more frequent training (3). This can be liberating for those just starting out or recovering from an injury (ref). Despite the small number of calories burned from the movement itself, the muscles that are built by it burn calories (2). As discussed above, core strengthening programmes have been demonstrated to improve posture; however, in addition, a better posture can improve physical appearance without weight loss (2). Now how are crunches properly performed? Proper form can be carried out by the following instructions (4).

  1. Lie down on the floor on your back and bend your knees, placing your hands behind your head or across your chest. Some people find that crossing the arms over the chest helps them avoid pulling on the neck. However, if you find your neck is strained, you can keep one hand cradling the head. If you are putting your hands behind your head, your fingers should gently cradle your head. The idea is to support your neck without taking away from the work of your abs.

  2. Pull your belly button towards your spine in preparation for the movement. 

  3. Slowly contract your abdominals, bringing your shoulder blades about 1 or 2 inches off the floor.

  4. Exhale as you come up and keep your neck straight, chin up. Imagine you're holding a tennis ball under your chin. That's about the angle you want to keep the chin the entire time.

  5. Hold at the top of the movement for a few seconds, breathing continuously.

  6. Slowly lower back down, but don't relax all the way.

  7. Repeat for 15 to 20 repetitions with perfect form for each rep.

Summary points

  • Back pain is a prevalent medical issue and can be attributed to chronic poor posture

  • Poor sitting posture caused by increased lumbar flexion can weaken abdominal muscles and intervertebral disc components which can lead to injury and pain

  • Core strengthening and stability programmes have been found to significantly reduce chronic lower back pain

  • Crunches are an exercise that can increase muscle mass, exhaust calories, improve posture, and is beginner friendly.

  • Refer to above for tips on proper form

It’s Time to Protect Your Back, Ditch Those Sit-Ups!


The information provided in this article is not medical advice. Please speak to a healthcare professional for more information.

Do you want to strengthen your core? Like others, you may want to strengthen your abdominal muscles for aesthetics, strength, posture, balance and stability, or for back protection. There are many exercises that can help you achieve these goals, but the exercises to ditch are those crunches and sit-ups you learned about in elementary school. Surprisingly, a classic sit-up causes more damage than expected.

When you do a sit up, you bring your chest to your knees while lying down. This bending causes your spine into go into full flexion. This is not ideal, especially when you add repetition and forces. According to McGill and Axler (1997), a classic full sit-up can place 3300 Newtons (N) of compressive force on the spine. 3300 N is the equivalent to 742lbs! The spine is made up of bones called vertebrae. Between each vertebrae, there is a spinal disc. With compressive force and repetitive full range flexion of the spine, the jelly portion of your spinal disc (called the nucleus pulposus) can bulge out and irritate your nerves. This nerve irritation can cause back pain and a potential disc herniation (Veres, et al., 2009).

Also, when you do a crunch or sit-up, you are actively using your hip flexor muscles. The hip flexor muscles have attachment points on your thigh bone (femur), pelvis, and low back spine (lumbar vertebrae). When you repetitively complete a sit-up, the hip flexor muscles are actively pulling the pelvis into an anterior tilt, which puts extra stress on your low back causing discomfort and pain (Burden and Redmond, 2013).

To reduce back injuries, crunches and sit-ups should be avoided, but there are other exercises that are safe to do. Dr. McGill suggests exercises such as modified curl-ups, side bridges, and birddog to spare the spine while strengthening your core (McGill and Karpowicz, 2009). These “Big 3” exercises keep your spine is in a neutral position and reduces compressive forces to prevent injury.

Overall, crunches and sit-ups should be avoided if you are prone to low-back pain or if you are someone who wants to protect their back while strengthening your core.

Summary Points

  • Crunches and Sit-Ups are abdominal exercises that surprisingly harms your back.

  • A classic full sit-up can place 3300 Newtons (N) of compressive force on the spine. The combination of compressive forces, full flexion, and repetition can lead to back injuries such as disc bulges or herniations.

  • These exercises actively use the hip flexor muscles which put additional stress on your low back leading to discomfort and pain.

  • There are alternative abdominal exercises that maintain the neutral spine while strengthening the core such as the modified curl-up, side bridge, and birddog.


Axler, C. T., & McGill, S. (1997). Low back loads over a variety of abdominal exercises: Searching for the safest abdominal challenge. Medicine &Amp Science in Sports &Amp Exercise, 29(6), 804–811.

Burden, A. M., & Redmond, C. G. (2013). Abdominal and hip flexor muscle activity during 2 minutes of sit-ups and curl-ups. Journal of strength and conditioning research, 27(8), 2119–2128.

McGill, S. M., & Karpowicz, A. (2009). Exercises for spine stabilization: motion/motor patterns, stability progressions, and clinical technique. Archives of physical medicine and rehabilitation, 90(1), 118–126.

Veres, S. P., Robertson, P. A., & Broom, N. D. (2009). The morphology of acute disc herniation. Spine, 34(21), 2288–2296.


  1. Gordon, R., & Bloxham, S. (2016). A Systematic Review of the Effects of Exercise and Physical Activity on Non-Specific Chronic Low Back Pain. Healthcare (Basel, Switzerland), 4(2), 22.

  2. Cherney, K. (2020, June 29). Sit-ups vs. crunches. Healthline. Retrieved November 16, 2021, from 

  3. Juan-Recio, C., López-Vivancos, A., Moya, M., Sarabia, J. M., & Vera-Garcia, F. J. (2015). Short-term effect of crunch exercise frequency on abdominal muscle endurance. The Journal of sports medicine and physical fitness, 55(4), 280–289.

  4. Waehner, P. (2020, March 4). Work your ABS properly by learning the perfect crunch. Verywell Fit. Retrieved November 16, 2021, from 

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