The deltoid is the rounded shoulder muscle that covers the joint connecting the arm to the torso. Because of its location, the anterior, medial and posterior deltoids are responsible for a large amount of the control needed to move the arm through the high range of motion of the shoulder joint. During exercises like the bench press or lateral raise, the deltoids are often in a position of heavy stress that can cause pain and injury to the muscle. Most deltoid pain can be avoided with proper warm-ups and stretching, as well as careful strengthening of the rotator cuffs.
Warming Up the Deltoids
It is important that you warm up your deltoids -- and any other muscles that will be recruited -- before performing upper-body exercises. To do a warm-up, hold your arms out straight at shoulder-level with palms facing down, and begin to move your arms in small circles, in either direction. Slowly make the circle progressively larger until you reach the maximum range of motion, where your hand should be pointing straight up at the top of the circle. Then start over, moving your arms in the opposite direction. Always warm up the muscle before exercising or stretching.
Stretching the Deltoids
To stretch the front deltoid, stand near a doorframe or the corner of a wall, extend your arm so the elbow is slightly bent and place the palm of your hand against the wall slightly below shoulder level; gently rotate your body to face away from the wall, and hold in a comfortable position for about 20 seconds. To stretch the rear deltoid, hold your arm across your body at shoulder height with elbow slightly bent, and then use your other arm to pull the first closer to your chest. Hold comfortably for about 20 seconds.
Rotator Cuffs and Deltoid Pain
The source of deltoid pain is often the overuse or straining of the rotator cuffs, a structure of four smaller muscle groups that stabilize the shoulder joint. Compared to other local muscles like the trapezius or latissimus dorsi, the rotator cuffs are very weak and can be injured easily. All shoulder exercises that recruit the deltoids also recruit the rotator cuffs, and doing exercises to strengthen them will improve shoulder -- and deltoid -- stability and safety. Rotator cuff exercises, such as lateral external rotation, should be done with very light weights, resistance bands, or no weight at all.
Recovery and Safety
Always remember to be careful when choosing the amount of weight to use in any deltoid exercise. If an exercise has been causing pain, lower the weight dramatically and build back up to a comfortable level. Also be sure to research and implement proper form. If the pain is from muscle soreness, you can apply an ice pack to the affected area for 10 minutes after exercise. If you think you have a serious injury, or the pain remains chronic, consult a licensed physician or physical therapist before continuing your exercise regimen.