The Marine Corps started phasing sit-ups out of their PT tests recently. Is it possible that the exercise is too difficult for some of the most fit soldiers walking the planet? The answer is no. It turns out, sit-ups are bad for your spine and can lead to injury. One study found that 56% of soldiers’ injuries during the fitness test were related to sit-ups. They are now looking to replace sit-ups with an exercise known as the plank.
Biomechanically, it makes sense that full sit-ups injure the spine and its discs. There is a normal range of alignment for the spine, just like there is a normal range for blood pressure and body temperature. Sit-ups force the spine forward of a neutral position. There is a certain percentage of load that is typically split between the posterior column of the spine and the anterior column – which includes the vertebral body and disc. Sit-ups force excessive pressure on the anterior elements which will squeeze the vertebral bodies and discs beyond normal. This increased pressure forces the disc to bulge backwards which can lead to a herniation and further injury.
Also, this type of excessive flexion obstructs the electrical wiring of your body (spinal cord and nerves). The proper operation of your body is no different than the proper operation of your house or car. If you have an electrical obstruction in your house you may find that your lights flicker, outlets don’t work, and your microwave clock constantly resets itself. What do you think might happen if there is an obstruction of the electrical system that controls your muscles, glands, and organs?
Fighting wars is hard enough without being sent to battle injured already. It is great that the military is now altering some of their programs as research about the spine continues to be published. There are many more ergonomic recommendations we would make for soldiers, but this is a great start!