Anatomy of Swimmers’ Shoulder and Impingement
Written submission by: Carrie Viola, MPT
(The original version of this blog post was written for the SeaHiker blog)
Swimming generates a large range of movement in the shoulder joint. Combine that with lots of repetition and this makes the shoulder more prone to injury.
The primary focus of this series of articles will be to:
- provide an overview of the functional anatomy of the shoulder in different phases of the swim stroke (freestyle)
- identify common causes of shoulder impingement in swimmers
- discuss how posture can affect shoulder mechanics and how to correct poor postural habits
- provide tips to prevent and fix shoulder pain
- provide a dry land training program for prevention of shoulder injuries
As a physiotherapist, I see clients in the clinic with varying degrees of swimming related shoulder pain. If you’ve been swimming for years to maintain fitness or are just picking up the sport as a new hobby or training for a triathlon, shoulder injury can really put a wrench in your plans. It is important to see a physiotherapist if you are having shoulder issues for proper treatment to address the root cause of the injury, and to provide proper treatment including useful prevention strategies. A physiotherapist can also offer insight into training methods and stroke mechanics to help you stay injury free.
Part 1: Functional Anatomy of the Swimmers Shoulder
Swimmers of all ages and abilities need injury prevention strategies. Education is an important part of any injury prevention strategy, and when it comes to swimming this involves awareness of what muscles are propelling you through the water and how these muscles function optimally to keep you from getting hurt. Being able to identify and then develop strength in these muscles will enhance your ability to learn and modify swim techniques – which will then help to improve performance.
Research indicates the most common injury in swimmers involve the shoulder. Through a basic overview of shoulder anatomy, a swimmer can gain a better understanding of how their shoulder can break down.
Unlike most other sports where your legs initiate the propulsive force, swimming relies on the arms to propel your body forward. Out of all the joint systems in your body, the shoulder is designed to give you the most range of motion. Unfortunately, this huge range of motion also means the shoulder is an inherently unstable joint – the excessive mobility is controlled by ligaments and the elaborate muscle system that surround the joint.
The shoulder complex is made up of three bones: the humerus (arm bone), scapula (shoulder blade) and clavicle (collar bone). The joints between these bones are the glenohumeral, acromioclavicular and sternoclavicular joints. All three of these joints need to have full mobility for the shoulder complex to function normally. The glenohumeral is a ball and socket joint, made up of the head of the humerus (ball) and glenoid fossa (socket) of the scapula. The glenoid fossa is very shallow, and depends on the ligaments, joint capsule and the surrounding muscles for stability.
For the glenohumeral joint to be stable, the head of the humerus must be centered in the glenoid fossa. Instability results from the inability to maintain the humerus in the centre of the glenoid fossa.
The ‘rotator cuff’ is a group of muscles designed to hold the arm bone (humerus) within the glenoid fossa of the scapula (shoulder blade). The four muscles comprising the rotator cuff are the supraspinatus, subscapularis, infraspinatus and teres minor. These muscles are crucial in keeping your shoulder stable.
The long head of the biceps muscle also assists the rotator cuff in stabilization of the glenohumeral joint. Other muscles such as the trapezius, levator scapulae, rhomboids and serratus anterior assist in positioning the scapula. Arms get their power from the deltoid, pectorals and latissimus dorsi muscles.
Phases of the Freestyle Swim Stroke
Now that you know where the important muscles are located, we should look at how these muscles work together in the different phases of the freestyle swim stroke.
Pull Phase: is powered mostly by the pectoralis major and latissimus dorsi muscles. Teres minor, supraspinatus, subscapularis, serratus anterior and deltoid also contribute to the pull. The biceps and brachialis muscles work to bend the elbow as it moves through the ‘catch’ phase whereas the triceps work near the end of the movement to extend the elbow.
Recovery & Extension Phase: uses the rhomboids, deltoid, serratus anterior, trapezius, subscapularis and infraspinatus to bring the hand out of the water to the overhead position for re-entry. The extension or reach for re-entry is powered by the deltoid, trapezius, and rhomboids.
The shoulder blade acts as a stable base of support through these two phases and is supported by the pectoralis minor, rhomboids, levator scapulae, trapezius and serratus anterior muscles. Core stabilizers (transversus abdominus, rectus abdominus, internal and external obliques, erector spinae) are also an important part of the stroke providing the link between upper and lower body movements for proper coordination of the body roll.
Swimmers Shoulder and Shoulder Impingement
Ideally, all your ligaments, bones, joints and muscles would be in perfect working condition to propel your swim stroke, but typically that’s not the case. You may have heard of the term ‘swimmers shoulder’ which is used to cover a wide range of shoulder conditions. Most of the injury pain is centered around the front and side of the shoulder and/or just below the acromion (termed the subacromial space). Swimmers shoulder can be the result of any one or more of the following:
- poor posture and core stability
- decreased shoulder complex mobility
- poor muscle control or performance
- joint hypermobility and instability
- training volume (ie. sudden increases)
- faulty technique and poor mechanics
- pre-existing injuries in the muscles, tendons, joints, bones
The most common form of swimmers shoulder is impingement syndrome. So how does your stroke set you up for impingement syndrome?
As I outlined earlier, the pull phase relies heavily on the pectoralis major and latissimus dorsi muscles to generate the power to pull through the water. The excessive development of these muscles along with the inability of the scapular stabilizing muscles to generate a proper counterforce, creates a muscle imbalance along with pulling the humerus into a more forward position in the glenoid fossa.
The more forward position of the humerus can cause the rotator cuff tendon and long head of biceps tendon to repeatedly rub against the acromion as the arms move through the swim stroke. With the highly repetitive nature of swimming, this constant rubbing creates inflammation in the tendons. Inflammation can lead to tendon fraying and weaker muscles along with decreased mobility.
Besides muscular imbalances, some common mistakes in swim technique that may cause impingement are:
- insufficient body roll
- lateral or thumb down entry into the water for catch phase
- hand crossing the midline in the pull phase
Knowing how these muscles and joints work together to pull you through the water will give you better insight on how to fix any faulty stroke techniques you may be using. If you’re already experiencing shoulder discomfort see a physiotherapist who can properly identify the root cause of the problem. Also consult your swim coach who can offer insight into any faulty mechanics.
In the next blog post, I will discuss postures that lead to muscle imbalances and how it contributes to impingement. I will also explain how to correct common poor postural habits. Stay tuned!