The shoulder press is an exercise designed to work the deltoid muscles. It uses these muscles and the triceps to lift weights from shoulder level straight up the frontal plane and back down again to the starting position.
Analysis of fitness movements, such as the shoulder press can identify the joints and muscle groups that are active. This can enable trainers to find the right exercises to use based on a clients fitness goals.
It can help to know how these types of movements affect the joints, tendons and muscles to assist in kinesiology research into injury prevention or recovery.
The ‘five stages of movement analysis’
The five stage model for the analysis of movement is a universal way to analyse any form of human movement from start to finish.
The tables below show the analysis of the shoulder press. It identifies the muscle used and the type of muscle action used to perform the movement.
The shoulder press uses a number of different muscles to complete this exercise.
When moving from the starting position to the finish position, the deltoid muscles contract and shorten, this is concentric muscle action and is used to produce movement against resistance (gravity and added weight). In this case, the deltoid is acting as an agonist because it is the ‘prime mover’ of this exercise, it is pulling the arm upwards.
The triceps also work concentrically in this phase of the shoulder press. This muscle is an agonist and is pushing the arm upwards to cause extension of the elbow joint.
The biceps are acting as an antagonist here by relaxing to allow this movement to occur.
As well as the deltoids and the triceps, the infraspinatus and teres major muscles that are located in the upper middle back use abduction to move the shoulder joint away from the midline in a concentric action.
These back muscles are synergists because they assist the deltoids and tricep muscles with this movement to help produce enough power to reach the finish position.
When moving from the finish position to completion, the deltoids act eccentrically. As it contracts, it lengthens, this is so that the muscle stays in control while using gravity to lower the weight.
The triceps also work eccentrically causing flexion in the elbow joint. Both the deltoid and triceps are working as agonists and are controlling this movement.
The synergists, infraspinatus and teres major muscles use adduction to move the shoulder joint inwards towards the midline which assists the deltoids and triceps to control the resistance in the downward movement.
During the shoulder press many muscles will be working to perform this movement. When a muscle contracts without lengthening or shortening this is called an isometric muscle action. This happens when a muscle is acting as a fixator to stabilise a joint or limb.
As the shoulder joint abducts, the trapezius and pectoralis minor isometrically contract and act as fixator muscles to stabalize the initial movement from start to finish.
Just before the weight reaches the finish position, stabilization occurs from the abdominal and lower back muscles. These fixator muscles allow good posture to be maintained as well as to assist in producing enough power to complete the movement.
Other muscles act isometrically to stabilize the body, the muscles in the back and neck will be contracting to keep the upright posture of the body, as well as muscles surrounding the spine.
The muscles in the wrist and forearm will be contracting to ensure that the weights stay still and the leg muscles will also contract to ensure the body stays up straight in the standing position.
Although the shoulder press looks like a simple movement, clearly, it is much more complex.
Each muscle has a different role to play individually but it takes combined muscle action to perform any movement.
The shoulder press uses concentric, eccentric and isometric muscle actions. That is why using free weights is an excellent way to work out the whole body.
Thanks for reading, this is a very very modified version of an essay I had to write for my degree. I tried to make it more readable for all levels.