Are Crunches and Back Extensions Breaking Your Spine?

Are Crunches and Back Extensions Breaking Your Spine?

The answer is most definitely yes. Dr. Stuart McGill, one of the World’s Leading Spinal Research Experts has stated that the number one way to herniate a disc is repeated lumbar flexion. This is exactly what is occurring every single sit-up and crunch. It is the same thing as bending a credit card back and forth. Eventually, it will break. Traditional sit ups, crunches and back extensions do more harm to the lower back than most people realize. What is worse is they do very little to improve core stability and protect the lower back from injury.


A Deep Dive into Biomechanics of Spinal Loading

Experts in spine care strongly advocate that their patients avoid spinal flexion exercises, for example, sit ups and crunches.  One of the strongest advocates for avoiding these exercises is Dr. Stuart McGill, one of the most foremost leaders in spine research.

According to Dr. McGill, here are a couple of reasons to avoid these exercises:

1) “The traditional sit-up imposes approximately 3300 N or about 730 pounds of compression on the spine.” (McGill, 88).  Simply put, every repetition of crunching and or sit up is capable of causing extreme compression of the lumbar disc.

  1. “The National Institute of Occupational Safety and Health has set the action limit for low back compression at 3300 N. Repetitive loading about this level is linked with higher injury rates in workers, yet this is imposed on the spine with each repetition of the sit-up!” (McGill, 88)

3) Back extensions are no better. On the roman chair (this is the piece of equipment that is set at 45 degrees and you can lock your feet and rest your thighs on it so that you can drop and lift your upper body, working the back) performing one back extension, imposes over 4000 N or about 890lbs of compression on the spine (McGill 91). In addition, there are many exercises performed on the floor lying on the stomach where some combination of the arms and legs are raised, or the entire torso is lifted off the ground. These types of exercises impose up to 6000 N or over 1300lbs of spinal load and compression (McGill, 91).


When done correctly, real core training reduces risk of lower back injury.  The role of the core muscles  is to act in concert to stabilize the lower back.  The abdominal muscles and gluteals do not work in isolation.  Therefore doing isolation sit-ups and crunches are not functional at all.  We can best think of the core to include all the muscles around the torso, abdominals and gluteals.  These muscles stabilize the spine and maintain optimal alignment and movement between the pelvis and the spine.  The core checks extreme flexion and extension and prevents excess rotation during movements of the pelvis and extremities.  Simply stated, the core creates a stable platform in the midsection of the body whereby we can transfer force through the extremities can occur without injury to the lower back.

Focus on front support exercises, like front squats and deadlifts.  Focus on side support exercises like side planks and chops.  Focus on anti-rotation exercises like planks, side planks, cable presses, chops, stability ball rollouts, planks on the stability ball.

Here is a taste of some CORE 101 EXERCISES

Read more about Developing Your Core with Real Core Exercises here