Pressing above the head is an effective way of stressing the lateral and anterior heads of the deltoids, or in other words, the front and side regions of the shoulders. The behind the neck shoulder press is performed with a barbell, with the barbell brought behind the head at the bottom of the exercise. The movement can be performed seated or standing, depending on preference. Performing the exercise whilst seated may be easier if a training partner is near, with the bar at a suitable height for spotting (aiding and over-seeing the lift).
Those with injurious shoulders may be best opting for another over head press variation, with the form of this exercise requiring some flexibility of the shoulder joint, and possibly hazardous for those with rotator cuffs which are prone to injury. Some who do choose to perform the exercise may wish to only bring the barbell down to ear level, minimising stress on the shoulder joint.
As previously mentioned, the front and side heads of the shoulders are recruited during the shoulder press, with the triceps also recruited to extend the arms. A grip should be used which is most comfortable for performing the exercise, with a grip width slightly further than shoulder width likely proving fruitful. If the triceps appear to be over powering the exercise, and the aim is to stimulate the shoulders, try beginning the shoulder workout with an exercise which isolates the shoulders, such as the lateral raise.
The over-head press causes minimal stress to the rear shoulder head, with the front and side heads stimulated most greatly. An exercise which stimulates the rear head, such as the bent over lateral raise, may be wisely implemented into a shoulder workout for completeness. It is worth noting the rear head receives significant stress from the majority of back exercises, however.
Those focusing on muscle strength will likely want to perform the exercise within a low repetition range, anywhere below six repetitions per set. Due to the hazardous form of the exercise, another over-head press exercise may be best chosen for heavy loads. A moderate repetition range would be ideal for gains in muscle hypertrophy (growth).