The Rule

If your posture is good, perform double the amount of work for your spinal erectors as you do for every crunch variation. Why? Read on.

How Crunches Became "Bad"

Not long ago, crunches were staple exercises. Everyone did them. Nowadays, they're shunned by those "in the know." What happened?

Back in the 70's and 80's, physical therapist Vladimir Janda found that posture is the result of our daily habits. How we sit and stand, and how LONG we sit and stand, directly influences skeletal structure. He said it was our daily habits that caused our hip flexors to become hyperactive, thereby leaving our gluteus muscle groups underactive, or inhibited, through a process called reciprocal inhibition.

When the hip flexors become very stiff, they pull our pelvis downward (anteriorly) and create excessive curvature at our lumbar spine. In laymen's terms, tight hips create a tight lower back, which doesn't help anybody.

Light Bulb Syndrome

Janda also formulated a guess about the upper body. He said that if we develop a posture where our shoulders slouch forward, we place damaging stress on the vertebra in our mid to upper backs and neck. Some call this "light bulb" syndrome, but clinically this is called kyphosis.

The issue with these defective postures is the position of the spine. Excess concave curvature of the lumbar spine in an anterior pelvic tilt and excess convex curvature of the thoracic and cervical spine put your disks, spinal cord, and nerve function in compromising positions. Ultimately, that realization was how the crunch went from center stage to shame in the exercise world.

Since both postures place stress on the spine, any forward bending motion will either increase the hyperactivity of the hip flexors (in an anterior pelvic tilt), or damage the spine in the upper back to neck region. The problem with that rationale is that crunches present a necessary function of your six-pack – spinal flexion.

Spinal flexion – what you accomplish when you do crunches – is a necessary component of the abdominal wall as it assists in bringing the upper torso forward by shortening the anterior abdomen. This helps MMA athletes land bigger punches, gives gymnasts the ability to tuck and roll safely, and for the average guy, lets him walk the beach with pride.

Should Everyone Do Crunches?

That depends. Whether or not you perform any spinal flexion exercise (i.e., crunches) depends on a few factors:

1. If your hips are tight enough to cause lower back pain, no. Work on hip mobility and core isometrics first.
2. If you have forward-head posture, work on fixing it before you start doing crunches. Get your head away from your phone, stop Tindering, and actually talk to the next woman you meet. Do so with a strong, confident posture by retracting and depressing your shoulder blades.
3. If you've got anterior pelvic tilt, kyphosis, or any other kind of postural issue, you're already compromising the spine. Chances are you just need a better training program.

If none of these conditions apply, you're cleared to do take advantage of the training rule above.

Double the Lower Back Work

Balance any crunch work with direct work to the antagonist muscle groups – your spinal erectors and lower back musculature – which are the muscles that keep you standing upright. For every spinal flexion exercise you do, you need to do two movements for the spinal erectors. So if you do a set of floor crunches, rope crunches, or medicine ball slams, you need to do two of the following:

• Rack pull
• Superman isometric
• Good morning
• Reverse plank
• Glute bridge variation
• Hip thrust variation
• Palloff press

Anything else that isolates the erectors and combats the effects of spinal flexion will work here.

Get to Work

Remember, whatever number of times you're bending at the waist to work your abs, you need to do twice that amount of work using the opposite motion.

This isn't about condemning crunches or the advice of physical therapists. It's about understanding proper exercise selection and having a scientific rationale for formulating your decisions. If you have tight hips, lower back or neck pain, or walk around like a light bulb, work on improving those areas before attempting crunch exercises.