As the years tick by, our body’s machinery starts to lose a little of its power. Muscles weaken, tendons tighten and movements that once felt effortless can become more difficult. The best way to maintain strength and mobility is through exercise, especially weight training.

But what are the most important parts to train? With more than 600 muscles in the human body, where should you focus your attention as you age?

We put that question to physical therapy and rehabilitation experts and asked them which muscles you should prioritize as you get older.

Butt Muscles and Quads

The most important muscles for aging are the ones that drive us through everyday movements, like getting out of bed and climbing stairs. Asked to pick one muscle group, experts said glutes were probably the most important, because they keep your pelvis level when you walk and help recover your balance when you stumble, particularly when you need to step sideways.

“I come at this as a physical therapist and somebody who specializes in fall prevention, so that’s what I’m thinking about,” said Odessa Addison, a professor of physical therapy and rehabilitation science at the University of Maryland School of Medicine.

Most people who exercise regularly are familiar with the largest of the gluteal muscles, the gluteus maximus, and target it with classic movements like squats and dead lifts.

But the ones along the side of your hips — the “hidden butt muscles” — need more focus as you get older, said Dr. Addison. As many people age they tend to move side-to-side less, she said, and thus don’t use them as much.

“If your hip abductors aren’t working well, then the entire chain of movement below doesn’t work well,” Dr. Addison said.

Keeping quads strong is also critical because they help in standing up from a chair, moving forward and your mobility in general. To test yours, try to stand up from a chair as many times as you can in 30 seconds without using your hands.

There are many exercises that hit both the quads and glutes at the same time. In addition to squats and dead lifts, target side-to-side and rotational movement with clamshells, monster walks and lateral lunges.

Rhomboids

The rhomboid muscles, between your shoulder blades on your upper back, help you keep your spine more upright and your shoulders down and back. As you age, gravity and everyday habits, like looking down at your phone, can gradually cause you to hunch forward and round your shoulders.

This chronically poor posture has consequences: It compromises shoulder mobility and has the potential to increase stress on the tendons and surrounding tissues in your shoulder joint. This can contribute to neck and shoulder pain and headaches, said Nathan LeBrasseur, a physiology and rehabilitation professor at the Mayo Clinic in Rochester, Minn.

Over time, being hunched over can also start to restrict how your rib cage moves and your ability to breathe as you walk. Lastly, leaning forward over time shifts your center of gravity, making it harder to maintain your balance; it could even cause you to fall, said Dr. Erin Futrell, associate professor of physical therapy at Springfield College, in Massachusetts.

Strengthening the rhomboid muscles, an integral part of your scapular retractors, which keep you upright, can help reverse this and change your posture. Experts recommended engaging in any simple rowing movement. Try single-arm rows to target the rhomboids one side at a time while also engaging your core to keep your torso stable.

Calves

Experts were quick to point out that walking speed can be a predictor of longevity and mortality. Our calf muscles help propel us forward when we walk or run and provide power when climbing stairs. They are also important for your balance as you age.

But the calf muscles are often overlooked as we get older; even people who exercise regularly tend to neglect muscles below the knee, Dr. Futrell said.

We know the big calf muscle gets weaker as you age, so training it to maintain strength is important, said Dr. Addison. The experts recommend calf raises and variations like deficit heel raises.

The Deep Core

The core, as the body’s stabilizing center, is a critical component of healthy aging. It provides proper body alignment and positioning, allowing your larger muscles to work effectively.

However, many of the core muscles work in tandem with other muscles, making it difficult to isolate just one during exercise. Dr. Addison went with the belt of muscle that wraps around your trunk, known as your transversus abdominis, which plays a major role in keeping you steady and upright when you’re moving.

“It’s your deepest abdominal muscle,” she said, “like your built-in corset to support the rest of your body.” She recommended gently drawing your belly button in when lying on your back, doing pelvic tilts and then trying bird dogs to really activate it.

Because the core muscles largely work as a team, Dr. LeBrasseur recommended front and side planks. These activate much of the core, engaging both the front and the back of the body.

Plus Three Bonus Muscles

While all the experts agreed that these five muscle groups are important, each had their own pet favorite as well. Dr. LeBrasseur made a strong case for the muscles that support the head, which can be responsible for “tech neck.” He recommended a chin tuck with a head lift: lie flat on your back, tuck your chin and lift your head up and hold for 10 seconds. As you progress, increase the duration to a minute.

Dr. Addison had a particular love for the tibialis anterior, the primary muscle on the front of your shin. This muscle is critical for balance and mobility. It helps lift your foot and toes upward as you walk, keeping you from tripping over a rug, and helping you go up the stairs.

And lastly, Dr. Futrell said that the intrinsic foot muscles, a network responsible for the foot’s fine motor actions and arch support, will always hold a special place for her.

“I’m a big proponent of strengthening your feet, which I think is very neglected in all age groups. Strong feet can help with the whole body,” she said.