It’s said that 40 is the new 30. But you also hear “it’s all downhill” after 40. So, which is it?

Would you believe, both?

Regular exercise can help you look younger and feel better as you age, but once you hit the big 4-0, you start to lose muscle mass and your metabolism begins to slow down.

“As women age, weight-bearing exercise helps to prevent osteoporosis and research shows that regular activity can help ward off other diseases like breast cancer, heart disease, and diabetes” says Sally Berga, MD, a board-certified obstretrician/gynecologist with Kaiser Permanente Colorado.

For the past four years, this 55-year-old physician and mother of three children has dedicated six hours per week to strength training and cardio. After a 10-minute warm up on the bike, Dr. Berga hits the weights. “If life gets crazy, I will make time for exercise—whether it’s 6 a.m. or 9 p.m. —with my patient schedule you never know. I find time to take a spin class or hop on my elliptical machine,” she adds. Dr. Berga recommends that people find exercise outlets they love and weave them into their schedules. If you enjoy dancing, then make dancing a key component of your exercise routine.

For the 40-plus crowd, the adage “use it or lose it” is true. “You will still lose muscle as you age, but you’ll lose less if you strength train,” says Andrea Groth, MS, Kaiser Permanente prevention specialist. Here’s an over-40 fitness guide.

In addition to preserving muscle mass, strength training also plays a role in maintaining connective tissue. “Over time, your connective tissues weaken. Strength training keeps those tissues as strong as possible and reduces injury risk,” Groth says. For example, regularly incorporating squats into your routine will keep your tendons and other connective tissues strong and resistant to injury.

“Core body strength helps with agility and balance,” Dr. Berga says. “Keeping your body strong and flexible will help prevent falls and common hip and wrist fractures as we age.”

Ready to get started? Just keep these facts in mind:

You need rest. Rest is when your body recovers from the rigors of strength training.

Warm up and cool down. It’s especially important to warm up before any activity to prevent injury and stretch afterward to improve flexibility

Go slow. Some muscle soreness, especially if your body is responding to a new activity, is actually good.

Also, remember to read instructions for resistance bands, balls and weight machines, stay hydrated, and listen to your body! It will tell you when to stop.