Your deltoid muscles make up a main muscle group in your upper body. They’re connected with many other muscles and bones in your upper back, neck, and shoulder region and are extremely mobile.

To build muscle mass, you need around 1.2–1.7 grams of protein per kilogram of body weight (g/kg) or 0.5–0.8 grams per pound of body weight. However, your protein needs depend on many factors, such as ...