Your core consist of several muscles at your mid-line. While most people think of core work as building great looking abs with sit-ups, the truth behind a strong core is also in your obliques, lower back, and glutes (and a few other muscles involved to a lesser extent). The main function of the core is not only flexion and extension of the trunk but more importantly stabilization. That’s why doing crunches and back extensions don’t necessarily mean you have a strong core – those don’t build much stabilization. They also don’t serve for good joint mobility and functionality.
Exercises like deadlifts, squats, kettlebell turkish getups, etc. are far better functional movements; they all require a lot of core strength and stability to protect the spine. To complete a heavy deadlift, you need to have solid stabilization in all your core muscles or injuries will happen. Proper form and technique are also crucial, but the best form won’t save your back if your core isn’t engaged correctly, even if you stand correctly (assuming you’re lifting a reasonable weight – although how often do people “throw out their back” reaching for a can of soup?).
You’ll limit your potential and spinal longevity by not training core stability, strength, functionality and mobility over the individual muscles. And in fact having a, “six pack,” has little to do with sit-ups and crunches and more to do with deadlifts and diet.
How much core do you use daily? It depends on the exercise and number of repetitions. I base core stabilization on the number of reps I plan to complete. I can’t hold my abs at 100% contraction for 30 reps – I wouldn’t last. So I have to stabilize based on the volume and load.
How much stabilizing should you do?
If I am walking around the house or walking down the street, I’m probably roughly 20 – 30% contracted. My abs are always engaged. You’ll be hard pressed to every find me in a position where my “gut hangs out.” If I’m doing high volume reps in the 20 – 50 range, I’m probably 40 – 50% contracted. Reps 10 – 20 range about 60 – 70% contracted. Reps 3 – 10 range 80 – 90% contracted and a one rep max is 100% contracted.
Completing an exercise like a heavy shoulder press should leave not only your shoulders burning but your abs too. To execute a dumbbell shoulder press in the standing position, your pelvic floor must be equal top to bottom, your ribs have to be properly aligned and your shoulders have to be pulled back in a proper position. The locked arm overhead position can be quite difficult for people to properly hold without hyperextending the spine or not having the arms properly overhead. Your core is what holds everything where it needs to be (if you know how to do it).
So at your next workout, be sure to think about your abs and their involvement in all functional movements. That’s not to say never use a piece of gym equipment, but certainly limit the use. Let your body do the work of stabilizing rather than a machine. It will lead you to a longer more functional life with good spinal health.