Written by: Clement Golliet
***Clément is the Director of ACE Fitness overseeing the fitness component of all ACE Tennis High Performance programs. He also offers private and group fitness sessions for ACE and OTA players as required. Clément is a member of the Ontario Kinesiology Association and has a Bachelor of Science degree in Kinesiology from UQÀM – Université du Québec à Montréal. Accredited to use many different types of equipment including, but not limited to T-Rx, Kettle-bell and Viper Clément is a Certified personal trainer with “Pep” and has worked in a clinic with a multidisciplinary team as a kinesiologist in rehabilitation. His duty was to design programs for people with musculoskeletal injuries. A fitness coach for a variety of sports, such as basket-ball, soccer, track running and tennis. Clément’s main interests are in back rehabilitation, injury prevention, performance and biomechanics applied to sports physical conditioning. A high level basketball and cross country runner who has practiced resistance training for over 14 years Clément has a passion for sport.
Philosophy: Applying a methodical and biomechanics approach to physical conditioning, while sparing the joints and the musculoskeletal system is vital to an athletes success.
If you have any questions for Clement, he can be reached here.***
The Sit-up is one of the most used and well-known exercises. The sit-ups exercise and test has been widely performed, but does it have real benefits? Today there is enough data and scientific evidence available to do a critical analysis of its effectiveness and safety.
Typically the sit-up test can be described as follows: you start by lying on the back with the knees bent about 90 degrees and feet flat on the floor. You have to hold your hands crossed resting on top of your shoulders while the feet are held stationary by an assistant. Then you flex the hips and curl the upper body from the floor, including the head and the shoulders, until you reach your knees with your elbows. To go back to the starting position, it means extending the hips and lower the trunk, until the shoulder blades touch the mat. The score is recorded by the how many sit-ups are completed in 1 minute.
Firstly, many people do sit-ups just to work the rectus abdominals, but in reality they work the hip flexor as well. The sit-up involves a hip flexion which is made mostly by the hip flexors (psoas and iliacus, tensor fasciae latae, rectus femoris, sartorius muscle). They (rectus abdominals) do not span the hip joint; thus, it cannot be involved in the hip flexion motion. But the rectus abdominis and obliques can do a trunk flexion and can be involved primarily in the first degrees of the sit-up until the pelvis raises from the floor, as well as being involved to keep a round back during the rest of the motion. According to Lacote, if the low back starts curving during the sit-up, it means that the hip flexors (psoas and iliacus muscles) are strong comparatively to the rectus abdominis or it means simply that the rectus abdoninis are weak.
A very interesting study found that the lumbar compressive loads during a regular sit-up were greater than 3000N both with straight legs or bent knees. Other studies have identified that repeated flexion of an intervertebral disc is the mechanism that produces posterior herniations. And it has been demonstrated that shear forces (tow forces in opposite direction which make the vertebra slip) on the spine are significantly higher with a greater degree of lumbar flexion; therefore the risk of injury are greater for the spine.
Other studies have focused on the transfer of loads between lumbar tissues during the flexion-relaxation phenomenon. The lumbar extensor muscles are neutrally “relaxed” (myoelectric silence) during full flexion, so the whole load is transferred to the passive tissue (the interspinous and supraspinous ligaments), and results in stretching the lumbar erector spinae muscle. Data show that an average person with only 8 kg held in the hands can sustain almost 3000N in compressive load and about 755N of anterior shear force during a full flexion. Therefore, this puts the soft tissue highly at risk of injury.
Herniated disc appears to result from cumulative trauma with little concomitant load on the spine. So the easiest way to create herniation is repeated flexion motion with compressive loading. Some data show that some herniation is produced with 867N of load and an average of 22 000 and 28 000 cycles of spine flexion and with 1472N and 5000 to 9500 cycles of spine flexion. Don’t forget that a sit-up is over 3000N load on the spine. Then you can imagine what the stress on the spine is when the exercise is repeated several times on a regular basis.
Many people who sit all day at the office and perform exercises like sit-ups just after work, are at risk to create more back pain. Creep response of the lumbar spine during a prolonged full flexion is the cause. Sitting for a period of over 20 minutes increases the flexion spine by 5.5. It takes 30 minutes to recover half of the form of the stress put on the back (joint stiffness). Therefore, I do not recommend performing sit-ups in the half hour that follows a whole day sitting at a desk in front of a computer for example.
Also, it is not recommended to perform sit-ups in the morning, because spine flexion puts more stress at this time of the day. In the morning, the ligaments of the spine are tauter due to the disc fluid which has higher hydraulic pressure. 54% of loosened disc occur during the first 30 minutes after getting up from bed and the range of lumbar flexion is increased by 5 to 6 degree during the day.
In conclusion, I think that the sit-up is a poorly designed exercise for fitness. There is so much scientific data that proves it is hard for the back and can lead to discogenic injuries. Doing sit-ups on a regular basis (entailing lots of repetitions) at the wrong time of the day (morning or after sitting for a long period), even worse with a load, can be harmful.
I think it is very hard to justify why it is good to do this exercise. The statistics show that 80 % of the population will experience back pain in their life. People should be more careful about training and should develop a better fitness philosophy. 300 sit-ups every day won’t make you feel better but will do the opposite (please refer to my article on Spine Stability). If a few people will get away with it, most of them won’t.
McGill, Stuart. Low Back Disorders: Evidence-based Prevention and Rehabilitation. Champaign, IL: Human Kinetics, 2007. Print. pp96, pp46, pp 88 89 90, pp 102
Kendell, F. (2007). Les muscles. Bilan et étude fonctionnels, anomalies et douleurs posturales. Pradel (Ed.) France. pp 104
M.Lacote. A.M. Chevalier. Evaluation Clinique de la fonction musculaire. Maloine (2008) pp 264, 265, 270, 274.
McGill SM. The mechanics of torso flexion: situps and standing dynamic flexion maneuvers. http://www.ncbi.nlm.nih.gov/pubmed/11415551
McGill SM. Kippers V. Transfer of loads between lumbar tissues during the flexion-relaxation phenomenon. http://www.ncbi.nlm.nih.gov/pubmed/7809753
McGill SM. Brown S. Creep Response of the lumbar spine to prolonged full flexion. http://www.ncbi.nlm.nih.gov/pubmed/23915616