Have you ever felt a nagging pain in your shoulder that just wouldn’t quit? Or woken up to a shoulder so stiff and painful you could barely move? Join the club: Up to 20 percent of adults complain of shoulder pain, and the most common source is a problem with the rotator cuff, a group of muscle and tendons designed to keep your shoulder stable in its socket.

Aging, poor posture and repetitive overhead movements — from tennis playing to painting and throwing baseballs — can leave those muscles damaged, inflamed and even torn, according to the Mayo Clinic.

The most at-risk age group is people from ages 25 to 50 who are active, but have a lifestyle or job that enables slouching, says physical therapist Scott Weiss, DPT, CSCS, co-founder of Bodhizone in New York City.

The first step in preventing or even reversing shoulder strains, says Weiss, is simple: Watch your posture. The next is to get your shoulder in better shape. Weiss suggests doing these five exercises in circuit form to protect yourself from rotator cuff injuries. Try doing them as a short workout or as a warm-up to a more intensive strength-training session.

Prone External Rotation Abduction

Lie face down on a bench or stretching table with your arms hanging off the side. Make a thumbs-up with one hand and slowly raise your arm up and straight out perpendicular from your body, aiming your thumb toward the ceiling, as high as you can without picking up your chest from the bench. Slowly lower back to start. Do 20 to 30 repetitions (reps), then do the same with your other arm.

Band or Cable Rows

Set up a two-pulley cable or a double-handled resistance band so it’s at shoulder height when you’re standing in front of it. If using the cable machine, load it with low weights (maybe 15 to 20 pounds). Grasp the handles with your arms out straight and the band/cable at slight tension, palms facing the floor. Row your arms back so your elbows bend and go wide but stay parallel to the floor. Squeeze your shoulder blades together tightly, then slowly release your arms. Do 20 to 30 controlled reps.

Shoulder Flexion and Scaption

From a standing position, hold two light dumbbells (say, 2 to 5 pounds) with your arms down by your sides. For flexion, slowly raise your arms straight out from your body, fingertips facing in, stopping when your hands are at the same level as your shoulders. Resist the weight to lower your hands back down. Scaption is a similar movement, but instead of keeping your arms parallel to each other, raise the weights away from your body so they form a 90-degree angle from each other (and each 45 degrees from your torso). Do 20 to 30 reps of each, beginning with the flexion exercise followed by the scaption reps.

Micro Dips

Support your body on your arms between two parallel bars. (No bars? Sit on the ground and place your hands flat on the ground alongside your hips.) Gently shrug your shoulders so that they come up closer to your ears. Then press out (on the bars or on the floor) so your body comes slightly off the ground and your shoulders move away from your ears. Slowly repeat this small motion to fully work the shoulders for 20 to 30 reps.

Micro Push-Ups

Start out in full push-up position on the floor. Keeping your arms straight the entire time, allow your shoulder blades to come together on your back so your chest slightly dips down and your upper back becomes concave. Then spread your shoulder blades apart so the back re-flattens out. Repeat this small movement for 20 to 30 reps.

Making the exercises second nature

Weiss cautions that if you’re injured, you should avoid lifting or moving anything overhead. But if you’re recovering from an injury and your doctor approves the conditioning exercises, you're good to go.

The American Academy of Orthopaedic Surgeons (AAOS) recommends doing shoulder conditioning exercises such as these two to three times a week. AAOS experts also suggest warming up with 5 to 10 minutes of low-impact exercise, such as walking, and talking with your doctor or physical therapist if you feel any pain.

Once you’ve made shoulder exercises part of your daily routine, you may find that nagging rotator cuff pain is a thing of the past.

Amy Roberts is a certified personal trainer. She writes about fitness, health and a variety of other topics for many well-known publications.