Core principles: Minimize sit-ups in training
By Guy Leahy, Health Promotions Program Coordinator
/ Published March 07, 2017
KIRTLAND AIR FORCE BASE, N.M. --
Developing a strong core musculature is important for injury prevention, as well as for performance on the physical training test.
However, there are many mythologies regarding core training.
One of these is that it is possible to isolate the upper front core from the lower front core with specific exercises. This isn’t the case.
The entire front core contracts at the same time, so isolating the upper segment from the lower segment is not possible.
Another myth is that only core-specific exercises improve core strength. This is also false.
For example, anytime you lift a weight over your head, such as with a shoulder press or squat exercise, your core is activated. The core is not involved in moving the weight, but it is heavily involved in preventing the lifter from tipping one direction or another.
That is why squats are excellent core exercises.
It is also why people who are overweight or pregnant frequently develop lower back pain. The extra load shifts the center of gravity forward, causing the spine muscles to have to work extra hard to keep the person from falling over.
Another myth is that sit-ups are the best core exercise. Sit-ups certainly train the core, but not all segments of it, and high volumes of sit-ups may greatly increase the risk of back injury.
Intervertebral discs sit between each vertebrae of the spine. Each disc has a spongy center and a tough fibrous outer layer.
These discs are well designed to withstand compression; they are very similar in function to the shock absorbers in your car.
For example, when you run, the discs protect your spine from the shock of each foot strike. In fact, if you measure your height before and after a run, you’re slightly shorter afterward, because the repetitive pounding from running temporarily flattens the discs.
The discs spring back later, once the repetitive shock has subsided. Those discs do not like sheer forces across them, which is what flexion and extension of the spine produces.
Therefore, if Airmen participate in high numbers of sit-ups on a regular basis — some have told me they perform 500-plus sit-ups per week — this volume may place their spines at high risk for a disc injury.
With repeated bending of the spine, the discs may eventually progress into a bulging disc, which may eventually progress to a disc herniation. This extremely painful condition may require surgery to fix.
Some back extension exercises, such as those where the leg is braced on a bench, can produce even higher spinal forces than sit-ups and should be avoided entirely.
Fortunately, there are several exercises available to effectively train the core with a minimum of back flexion and extension. These exercises are so safe even pregnant women can perform them.
There are three major segments of the core — front, side and lower back — and they each need to be trained separately. No one exercise will train all segments.
An excellent exercise for the front core is the front plank. This is significantly better than the typical sit-up, with a lower risk of injury.
If I attach electrodes to your front core muscles to measure how hard they work, the activation of those muscles is twice as high with a front plank compared to a sit-up.
Another exercise for the front core is a curl-up, but a strongly modified one.
With this exercise, you lie on your back with one leg straight and one bent at the knee. It doesn’t matter which leg is bent.
Place your hands underneath your lower back, press your tongue against the roof of your mouth and lift your upper back up from the floor by only an inch or so.
A good exercise for the side core is a side bridge. Research has shown this exercise results in measurable increases in the size of the side core musculature.
A recommended exercise for the lower back is the “bird dog.” This exercise improves lower back strength, but the spine doesn’t bend at all, so it is very safe.
All of these exercises should be performed two to three days per week. Start out with intervals. Hold the position for 10 seconds, relax for five seconds and repeat.
The goal at first is to increase the number of repetitions you can perform, not the duration of each repetition. Once your back becomes stronger, you can increase the duration of each interval, until you hold the position for up to one minute.
If you want to see examples of these exercises, go to YouTube, and search for “Dr. Stuart McGill” and “core values.” This excellent video will show you how these exercises should be properly performed.