Shoulder Muscle Strength - Part 1

(Deltoid, triceps, Biceps)

When strengthening the shoulder, especially after an injury, the rotator cuff complex is an area of great interest for physiotherapists and trainers alike. Most of you that have had an injury to the shoulder have been told that it is because of the “rotator cuff”, which has given these stabilising muscles a stigma.

The shoulder joint is called a “ball and socket” joint, and is relatively shallow in nature needing accessory structures to keep it stable when in use. It has a ring of cartilage, known as the labrum, within it to help keep the joint in place. Also, the rotator cuff complex is a group of muscles that protect and stabilise the joint when you are moving or using it. This muscle group also has a close relationship with the scapular, or shoulder blade, which is super important in correct shoulder movement.

To learn more about this complex group of muscles, injuries to the rotator cuff and tretatment recommendations read our rotator cuff rehab blog post.

The rotator cuff complex is known as a stabiliser, with so much focus around it. What about your movers?

Lets take a look at the other muscles that we might be more familiar with around the shoulder.

1. The Deltoid is sometimes described as the “shoulder pad” muscle.

   It surrounds the joint from front to back; and consist of fibres from front (anterior), middle and back (posterior). It originates at the end of the collar bone and the spine of the shoulder blade, and its fibers travel downwards to its site of attachment, on the outside of the humerus. The humerus is the long bone of the upper arm.

   Its job is simply to elevate the arm, and it works in close succession with the rotator cuff muscles to achieve this movement. Depending on what part of the muscle is contracting, the arm can move in all planes of elevation from anterior to posterior.

   To strengthen Deltoids, use a resistance band or hand weights to resist shoulder forward elevation, sideways elevation or backwards elevation, or flexion, abduction and extension, respectively. These exercises are also known as front raises, side raises and rear deltoid raises.

2. The Biceps muscle, also called Biceps Brachii as it has two heads of origin, which merge into one muscle belly.

   The shorter of the heads originates at a bony prominence of the scapula called the coracoid process. The longer head of biceps travels further upward, and is attached within the shoulder, known as the supra-glenoid tubercle. The long head has large clinical value to us, as it is a common cause of shoulder pain.

   It can be problematic due to a tendinous issue from repetitive shoulder flexion, or can be irritated from its close contact with the Pectoralis muscle, Pectoralis Major in this case. In older populations, degeneration can affect the tendons of the Bicep muscle, and cause a “Popeye Effect”, in which the muscle belly droops downwards on the arm due to its damaged tendon attachment.

   In terms of strengthening, Bicep curls are an exercise that have been used since workouts were created. Very popular with body-builders and athletes, the exercise consists of flexing or bending the elbow while gripping a hand weight. The contraction usually includes a twist of the forearm so that the palm is face up at full flexion. This is because the Biceps is a forearm supinator as well as elbow flexor.

   Resisted shoulder flexion targets the long head of the Biceps, but isolation is near impossible as the deltoid and rotator cuff muscles also flex the shoulder.

   You thought a muscle with two heads was confusing? How about three?

3. The triceps muscles have three heads.

   It’s belly travels along the back of the humerus. Like the Biceps, it has a long head, which originates on the lateral border of the scapula. It’s two other heads are categorised by their position beside each other and are called the medial and lateral heads. These both attach along the back of the humerus, the lateral head originating a little higher up.

   The muscle inserts below the elbow joint, on a bony landmark of the Ulna called the Olecranon. The Triceps main action is to extend or straighten the elbow. So why do we include it as a muscle of the shoulder? Well, due to its long head’s attachment on the scapula, we can assume that it plays a role in linking the humerus and the scapula, and possible helps stabilise the scapula also.

   There is evidence to show a link between Tricep activation and shoulder stability, but the link remains small when compared to other stabilisation muscles, such as the rotator cuff complex, Pectoralis and even the Biceps. For physiotherapists, I think this link between the scapula and the Tricep, no matter how small, should be taken into account when strengthening the shoulder, especially post dislocation or trauma.

   One study has interestingly shown that the three heads of the Triceps work differently, depending on position and what speed the activity is being undertaken.

   Exercises that are commonly used in Tricep strength are resisted elbow extension in what is called a Tricep push or Tricep extensions. Starting with humerus by your side, but elbow totally flexed, a band or cable machine resists elbow extension until the entire arm is extended by your side. To include some stability practice, and incorporate other muscles, a Tricep extension can be done overhead, again going from elbow flexed to elbow fully extended overhead, resisted by a hand or a hand weight. Push-ups, and in particular push-ups with elbows tucked in by your side also result in very high amount of Tricep activation, and are a great body weight exercise to strengthen this muscle.

Look out for our next blog post in which we delve deeper into more muscles that move and stabilise the shoulder girdle.

References

https://www.ncbi.nlm.nih.gov/pubmed/22959695

https://www.frontiersin.org/articles/10.3389/fphys.2020.00112/full