In dead bodies, the front and middle parts of the shoulder muscle are best at lifting the arm out to the side, while certain chest and back muscles are better at pulling the arm back down because of how they're positioned.

The front part of your shoulder muscle is better at lifting your arm forward, while the side part works harder when you lift your arm backward — they’re specialized for different directions.

Rotating your shoulders outward when doing overhead presses makes the front shoulder muscle work harder than the side one.

Lifting your arms out to the side or slightly backward, especially with your palms turned down, works your side shoulder muscles the most — this move might be the best way to build stronger shoulders.

When you lift your arm out to the side, the middle part of your shoulder muscle works best at the start, but the front part takes over more when your arm goes way up past shoulder height.

When you lift your arm out in front of you, certain shoulder muscles are better at helping the movement because of how they're positioned, while others are stronger at pulling the arm back down.