Keeping your body physically active and powerful for many decades requires two key orthopedic elements: stable joints and core stability. A stable body happens all over, not with just abdominal crunches. There are hundreds of core exercises you can do intentionally, and many you can do in everyday life with just a little increased awareness of good posture.
Here are a few of our favorites:
Go around as much of the day as possible pretending like someone is going to punch you in the stomach. You'll feel your stomach, back, and even gluteus muscles contract inward to stabilize you as you prepare for the fake impact.
Stand up straight and balance on one leg.
Balance on one leg, keep the upper body erect, and squat down, keeping your knees over your ankles.
Plank: get into the top of a push-up position and hold your abs, lower back, and gluteus muscles in. For added difficulty, balance your feet on a bosu ball (1/2 exercise ball). Side planks with the body sideways and one arm up are also great for the core.
Even during aerobic activity, be mindful of your core. Use it to stabilize your movement instead of letting your moving limbs pull you around