What is the proper use of the abdominal muscle to reduce injury?

Question

When performing different body strengthening exercises, I am at a loss on how to properly use my core abdominal muscles to complement the muscles that I am actively engaging. I know that one can specifically target the abdominal muscles through sit ups and crunches, but when lifting weights, punching, and kicking, I have no idea. I want to learn how to protect myself from injury by strengthening my core, but also learning how to use my core properly.

What is the proper use of the abdominal muscle to reduce injury?

Answer 1

It's a really good question, and rectus abdominis (abs) was a tough one for me to figure out personally. For a lot of exercises like the deadlift and front squat (and back squat, but so much more clearly on the front) you want to have your back locked into a neutral position.

For a demonstration, try locking your forearm into a 45 degree bend at the elbow (halfway between the classic bicep muscle squeeze and being straight armed). You'll notice that your tricep and bicep are both tensed: the cool term for this is that one is a stabilizer and the other is an antagonistic stabilizer.

In order to lock your back into a neutral and safe position, so that the muscles are taking the load and not your vertebrae, you need both your back muscles and your abdominal muscles locked, just like your bicep and tricep.

Specifically answering your question of What is the proper use of the abdominal muscle to reduce injury?, I'll keep stealing from exrx with this quote regarding abdominal weakness:

Increased risk of lower back injury can occur during hip flexion, extension, stabilization and back extension activities. Erector Spinae muscles can hyperextend lower back more than usual if abdominal muscles are weak. The abdominal muscles tilt the pelvis forward, improving the mechanical positioning of the Erector Spinae, specifically when the lumbar spine becomes straight. When abdominal strength/endurance is not adequate to counter the pull of the antagonist Erector Spinae under load, these low back muscles are put at a mechanical disadvantage (active insufficiency) further placing additional stresses on these very same lower back muscles. Iliopsoas can pull on the spine during hip flexor activities if the abdominal muscles are weak. Risk is compounded when abdominal weakness is combined with hip flexor inflexibility.

As a reminder to myself, when doing a lift where I need my abs tight, I try to imagine one of my children jumping onto my stomach. Or maybe the split second before you know you're about to be sucker punched: that tensed up feeling where you harden your abs and increase abdominal pressure. This is also linked closely with the valsalva maneuver.

Some people frown on holding your breath when you lift heavy weights, but in my experience the protection to your back is worth it and it's completely natural: if you were to try to push a car to roll-start it (as an example), you would probably hold your breath on your first push.

Answer 2

Honestly, your body is going to try to use them properly and all you have to do is let it. Using good posture and good form when executing lifts, punches, kicks, walking, standing, and every other aspect of life and your core will support you.
If you want more of a personal demonstration than I would suggest seeking out a personal trainer or other fitness professional and they would be more than happy to explain how your core supports you.