During a military press, what type of contraction occurs in the anterior head of the deltoid as the barbell is lifted overhead?

In the context of a military press, as the barbell is lifted overhead, the anterior head of the deltoid muscle undergoes a concentric contraction. This occurs because concentric contractions are characterized by muscle shortening while generating tension to overcome resistance—in this case, the upward force needed to lift the barbell.

When the lifter pushes the barbell upwards, the anterior deltoid fibers actively shorten to facilitate the movement, pulling the arm and barbell into an overhead position. This is essential for performing the lift effectively, as the deltoid muscles are primarily responsible for shoulder flexion and stabilization of the shoulder joint during this action.

In contrast, eccentric contractions involve muscle lengthening under tension, isometric contractions occur when the muscle produces force without changing length, and isokinetic contractions verify that the muscle contracts at a constant rate, which typically requires specialized equipment. None of these conditions apply to the lifting phase of the military press like the concentric contraction does.