Shoulder Abduction With Weights
A powerful abductor of the arm, when you study the medial or middle deltoid during a side lateral raise with electromyography (EMG), you find the rate of fatigue is faster then the other shoulder, trap and scapula muscles. This is a good thing since the middle deltoid is exactly what you are trying to isolate in this movement. Knowing the rate of fatigue is faster it is imperative that you maintain form during the movement, as it is easy to rotate your shoulder slightly and substitute with your anterior shoulder not completely engaging this failing muscle.
Raise your arms slightly above parallel with palms facing the floor. Use a weight that can be paused for a full second without any discernible movement for the chosen range of repetitions. Maintain good posture to Get Strong.