Should CrossFitters rethink the use of the sit-up?

Should CrossFitters rethink the use of the sit-up?

Part 1
Sit-ups have been around in training programs for years and have been thought to help downsize the winter keg to a summer 6-pack. Sit-ups have made their way into military functional testing, high school physical fitness testing, and in multiple CrossFit benchmark WODs (Angie, Barbara, Annie) as a technique to test abdominal endurance. However, the US Army is beginning to phase out sit-ups as part of their functional testing and I encourage gym goers and CrossFit athletes to do the same.

The “fitness” world can be very confusing as new exercises come out day after day after day… so why should you get rid of sit-ups that are such a long time staple in training programs? With any exercise we have to weigh benefit vs risk, obviously if the benefit far outweighs the risk then the exercise is worth performing.

Recent evidence suggests that this may not be the case with sit-ups. In 2005, 1,532 soldiers stationed at Fort Bragg were given a questionnaire to identify acute injury during fitness testing. From this group, 117 reported acute injury with sit-ups being attributed to 56 percent of all injuries. People may be thinking “well it was a questionnaire, maybe the soldiers falsely reported sit-ups causing their injury in hopes of it going away?”… let’s be real... nobody actually enjoys performing max effort sit-ups in a 2 minute period. Let’s take a different approach.

When talking about spine health and appropriate loading, Dr. Stuart McGill is the pioneer of the field and his work must be mentioned. The National Institute of Occupational Safety and Health has set their action limit for lower back compression to 3,330 Newtons (730 lbs) during the work day, as repetitive loading of the spine above this level has caused increased back injury rates. Dr. McGill has found that sit-ups cause up to 730 lbs of compression force in the lower back. This means each time you do a sit-up you are loading your spine to the upper limits of OSHA guidelines set forth to reduce low back injuries!

Everyone is different and you may know people that do well over 100 sit-ups per day and experience no low back pain. This is mostly due to individual differences in tissue adaptation and tolerance, not due to less compression forces. Dr. McGill believes that we all have a certain number of flexion/extension spinal movements before injury occurs and that this number is individualized. He has done multiple experiments with pig spines (very similar to our spines, CrossFit was not around when he conducted these experiments so they were unable to get people crazy enough to do thousands of sit-ups per day) and found after continuous cycles of bending, disc herniations were becoming present. Furthermore, biomechanical studies suggest performing a sit-up causes spinal disc pressure to increase up to 210 percent, which could lead to injury.

Lastly, we have to ask the question “what is the purpose of the sit-up?” If your answer is to strengthen your core/abdominals, then there are other exercises to use to achieve this goal that are less risky and more specific to abdominal function. Our lumbar spine has very limited motion and the main function of our core is to prevent spinal movement, especially in loaded patterns such as a back squat or deadlift. If your goal is to improve your benchmark WOD time of Annie then you do not have to train sit-ups to become better at sit-ups.

Hopefully, this post makes you rethink the sit-up. In part 2, we will discuss exercises to perform instead of this long time gut wrenching movement.

Dr. Dillon Caswell, PT, DPT

References:
Evans R, Reynolds K, Creedon J, Murphy M. Incidence of acute injury related to fitness testing of U.S. Army personnel. Mil Med. 2005;170(12):1005-11.
McGill S. Low Back Disorders, Evidence-based Prevention and Rehabilitation. Champaign, IL; Windsor, Ont. : Human Kinetics; 2002.
Norris CM. Abdominal muscle training in sport. Br J Sports Med. 1993;27(1):19-27.
Childs JD, Teyhen DS, Benedict TM, et al. Effects of sit-up training versus core stabilization exercises on sit-up performance. Med Sci Sports Exerc. 2009;41(11):2072-83.