No one should ever do sit ups or crunches anywhere, for any reason, ever. Not ever.

Medical organizations and medical professionals have come out against the exercises for reasons dependent on their focus: Orthopedic and geriatric organizations are concerned about the inordinate pressure exerted on the thoracic spine and the propensity for back injury. OB/Gyn's and professionals interested in child development note the inordinate pressure exerted on the pelvic and abdominal organs and on the pelvic floor (from a direction that promotes prolapse).

Exercise specialists disown the exercises because they don't work and because they recruit the use of and end up working the psoas, a muscle you don't want to work in this way or you run the risk of chronic low back pain. There is a finite number of flexes in your spine before it fatigues, leaving it prone to disc herniation. This is called 'fatigue life'; sit ups and crunches are pronounced flexions.

All abdominal work should be done by engaging the transverse abdominus (by pushing out the TA just above the pubic bone) and moving the legs. This can be done with a person in plank position or on her back.

But never, ever do sit ups or crunches. Your back and your bottom will thank you.

The pendulum keeps swinging back and forth between two camps. There are those who say that we should pull in our tummies to keep our abdominals strong and promote core strength and there are those who advocate for not pulling in our tummies, that we should maintain our lumbar curves. Right now we are in an era of 'let it all hang out'. Actually, the two camps are not entirely mutually exclusive, yet both are wrong.

We do want to activate our transvers abdominus throughout our day, while maintaining our lumbar curve and while allowing our tummies to move with our breath. This means pulling in our tummies slightly, about an inch, while not maintaining a rigidity to that hold. The transverse abdominus is a component of the core, which provides stabilization for functional movement and contributes to balance and proprioception. We do want to strengthen our core. But more importantly, we want to engage our core in concert with functional movement. In this way we educate our bodies in neuro-muscular coordination. A strong muscle without neuro-muscular coordination is a bully to its neighbors.