For decades, we were told cardio was king. Walk more, run more, get your heart rate up, burn calories. Cardio absolutely has its place, but somewhere along the way, most adults over 40 got the message that cardio was enough. It isn’t.

Cardio is excellent for your heart, lungs, circulation and mood. A brisk 30-minute walk most days of the week is one of the best things you can do for your health. It also helps with sleep, stress and blood sugar control. If you’re doing zero cardio right now, adding some will help you feel better within weeks.

However, cardio does not build muscle. It doesn’t protect bone density. It doesn’t improve your balance in any meaningful way. It doesn’t stop the muscle loss that accelerates in your 40s and beyond. And it doesn’t do much for your metabolism once the workout is over.

This is the part that catches people off guard. You can walk five miles a day and still lose muscle, still see bone density decline, still watch your balance quietly get worse. Cardio alone isn’t enough to protect the things that matter most as you age.

Strength training builds muscle, which is a significant predictor of independence after 60. It protects bone density, critical for anyone worried about osteoporosis or fractures. It improves balance, which prevents falls. It raises your resting metabolism because muscle burns calories even when you’re not using it. And it directly improves your ability to do what real life demands: getting up off the floor, carrying groceries, playing with grandkids, maneuvering a suitcase through the airport.

If you had to pick one over the other, strength training is the answer for most adults over 40. Luckily, you don’t have to choose. Cardio and strength training aren’t in competition; they do different jobs. Think of it this way: Cardio keeps the engine running; strength training keeps the whole car from falling apart. You want both, and you want them for life.

The ideal routine for most adults over 40 looks something like this: two to three strength sessions a week, 30 to 50 minutes each, plus daily walking, ideally outside, for general activity and cardiovascular health. That’s the entire program for the vast majority of people.

If you’re already doing cardio and nothing else, adding strength training is the single most impactful change you can make. If you’re doing neither, start with walking daily and add strength training two days a week. If you’re already doing both, you’re ahead of 90% of people your age.

Cardio adds years to your life. Strength training adds life to your years. You want both.

Gerry Washack is the owner of Strong Republic Personal Training with locations in Palm Desert, La Quinta and Palm Springs. Visit www.strongrepublicpersonaltraining.com.