December 12, 2015 at 9:29 am #23134BuddyParticipant
A recent topic has been discussed on this forum in regards to the safety of a ‘sit-up’ which I would love to add some insight to. I will chime in as my career is in physical therapy and exercise physiology.
There is no yes or no answer to this when talking generally. Unfortunately, a question like this is trying to fit a square peg in a round hole. After studying and looking at many cadavers over the years, I have learned that all of our skeletal and muscular systems are similar to an untrained eye, but vastly different when looked at closely. These changes in structure will determine what one range of motion one joint is capable of on one person compared to another person. These anatomical changes will dictate whether an exercise(external force into muscle tissue using a mechanical structure as a vehicle for said tissue) is safe or contraindicated for a person.
Here are the ‘nuts and bolts’ of what is occurring on the muscular system during a supine sit-up using gravity as an external force. Upon activation of the abdominal and hip musculature the moment before the torso leaves the ground, the hip flexors activate to anchor the pelvis to the ground followed by two multijoint muscles (psoas major, psoas minor) which provide anterior lumbar stability into a position known as lordosis (lumbar natural curve), at the same time the spinal lumbar and lower thoracic spinal extensors (low back muscles) activate and provide posterior lumbar lordosis. Next as the torso begins to move further into the ‘sit-up’ the spinal flexors distal to the axis rectus abdominus, both internal and external obliques along with the the transverse abdominus activate but do not shorten substantially, this also stabilizes the spine by creating intra abdominal pressure, these tissues remain in a isometric position during the entire motion. The end result of a sit up is an isometric on the “abs” and an isotonic on the hip flexors.
So the question remains, are they BAD for you? Potentially Yes. A typical scenario which causes joint dysfunctions in the lumbar spine is when a person goes into a sit-up and DOES NOT correctly recruit muscles for proper activation which stabilizes lordosis or their spinal structures do not allow for adequate lordosis. When this happens we find that excessive compressive and shearing force is redirected from the upper lumbar vertebrae to the lower lumbar vertebra L4-L5 and the discs in between (L4-L5,L5-S1) become compressed, this can lead over time to herniated discs and other vertebral dysfunctions (osteophites, spinal stenosis, spondylitis ect.) In my opinion the risk of doing these exercises in a non controlled environment outweigh the reward. In my experience many people, are unable to correctly perform a safe sit up, that doesn’t mean it’s not possible, but slim. If one ‘feels’ it’s a necessary thing to do. I would highly suggest a micro-progression of sorts. Perhaps, sitting on a graded hill facing downhill and beginning with sit-ups that way while correctly maintaining lordosis. A sit up speed speed of 3 seconds up and 2 seconds down would be a good controlled start. Once this is mastered, then move to a flat position and finally to a declined position. However, as I said earlier there is more risk than reward and mostly all people are doing them incorrectly for their joint structure and anatomy.
A very good compromise to ‘sit-ups’ would be to do two separate exercises which essentially create the same stimulus as a sit up. Exercise 1) crunches work the spinal flexors. Exercise 2) hanging bent leg lifts, which influence the hip flexors. Both of these exercises will achieve the same stimulus without potential risk of injury.
LEGAL British immigrant, who embraces the freedoms of the US Constitution and lives happily in good old South Carolina(one of the last free states).
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