Are you doing this core exercise?
So now that you know how to brace your core, I wanted to share one of my favorite exercises for strengthening the core. While there is nothing wrong with popular core exercises such as crunches and sit-ups, these exercises will predominantly work the rectus abdominis (six-pack muscle). And the role of the rectus abdominis is to flex the trunk which isn't what you want to occur while you're squatting or deadlifting. These exercises can be great for building a six-pack, but they won't help you maintain a stiff and stable trunk while squatting/deadlifting.
Deadbugs (and it's many variations) are one of my go-to core strengthening exercises because it trains the core musculature to maintain a stiff trunk, same as you want while you're lifting weights. I've included the deadbug exercise, as well as an easier version and an advanced version below. There are many more variations of this exercise that I haven't included. I recommend picking a variation that is challenging but allows you to perform about 10-15 reps with proper form.
For all variations...
- Start by bracing your core (see this article), and maintain this throughout the exercise. Make sure your low back stays flat against the floor the entire time, and doesn't arch away from the floor as you extend your arm/leg. Perform 2-3 sets of 10-15 reps (or until muscular fatigue).
- Bring both legs up to 90 degrees with knees bent and both arms extended towards the ceiling. Extend one leg, and at the same time, extend opposite arm overhead. Return to start, and repeat with other leg and arm. That's one rep.
- Bring both legs up to 90 degrees with knees bent, and arms at your side. Keeping knee bent, tap one heel down to the ground, then return it to start. Repeat with other leg. That's one rep.
- Same as Deadbugs, but you'll start with your legs straight and keep them straight throughout the exercise.
Give these a try and let me know how they go!