Swimmer’s shoulder is a common overuse injury in aquatic athletes. The highly repetitive nature of swimming strokes, which can involve thousands of arm rotations in a single practice, places immense stress on the shoulder joint. This condition is not a single diagnosis but an umbrella term for various shoulder pathologies, with the prevalence of shoulder pain in competitive swimmers reported to be between 40% and 91%. Understanding the underlying mechanism and contributing factors is the first step toward effective management and prevention.
The Anatomy of Shoulder Impingement
Swimmer’s shoulder most often refers to shoulder impingement syndrome, a mechanical issue where soft tissues are pinched between the bones of the shoulder joint. The primary space of concern is the subacromial space, a narrow area located directly beneath the acromion, the bony roof of the shoulder blade. The shoulder is a highly mobile ball-and-socket joint.
Within this space lie the tendons of the rotator cuff muscles, particularly the supraspinatus, and a fluid-filled sac called the bursa. Impingement occurs when the head of the humerus, or upper arm bone, rubs against or squeezes these structures against the acromion during overhead arm movements. This mechanical irritation leads to inflammation, causing tendinitis in the rotator cuff tendons or bursitis in the subacromial bursa.
The inflammation causes swelling, which further reduces the subacromial space, creating a vicious cycle of increased pinching and pain. In swimmers, the pathology is often linked to subtle instability that causes the humeral head to move improperly during the stroke, leading to a functional impingement.
Recognizing the Symptoms
The subjective experience typically begins as a mild, nagging discomfort that increases gradually over time. The pain is commonly felt in the front or side of the shoulder and can sometimes radiate down the arm. Initially, pain may only be present during or immediately after a swimming workout. As the condition worsens, it can persist even at rest or at night.
Specific movements during the swim stroke often aggravate the pain, such as the hand entry or the initial “pull-through” phase. Reaching overhead or reaching behind the back, such as when getting dressed, can also elicit a sharp increase in discomfort. Other signs include a reduced range of motion, weakness in the affected arm, or an audible clicking or popping sensation within the joint.
Training and Technique Factors
The high incidence of this injury is connected to the biomechanical demands of the sport, combining extreme repetition with the need for power. Competitive swimmers may perform up to 4,000 strokes per shoulder in a single session, a volume that leads to microtrauma if recovery is insufficient. A sudden increase in training yardage or intensity without adequate preparation is a frequent trigger for symptom onset.
Poor stroke mechanics significantly increase mechanical stress on the shoulder joint. For instance, a hand entry that crosses the midline of the body or inadequate body roll forces the shoulder into an internally rotated position. This narrows the subacromial space and promotes impingement, placing excessive strain on the tendons and ligaments.
A primary factor is the development of muscular imbalances around the shoulder girdle. Swimming predominantly strengthens the large internal rotator muscles, such as the pectorals and latissimus dorsi. This leads to relative weakness in the smaller, stabilizing muscles, specifically the external rotators of the rotator cuff and the muscles that control the shoulder blade, known as the scapular stabilizers. This imbalance allows the humeral head to move improperly during the stroke, causing the soft tissues to be pinched.
Recovery and Long-Term Prevention
Initial management of swimmer’s shoulder involves reducing the inflammation and pain. This requires a period of relative rest, such as a temporary reduction in swimming volume or a complete break from the pool, coupled with the use of ice and anti-inflammatory medications. A professional diagnosis from a physician or physical therapist is important to create a comprehensive treatment plan.
Physical therapy is the cornerstone of recovery, focusing on restoring muscle balance and optimizing joint movement. Treatment involves specific exercises to strengthen the weak external rotators and the scapular stabilizing muscles, such as the serratus anterior and lower trapezius. These targeted exercises help ensure the shoulder blade is positioned correctly, allowing the arm to move overhead without pinching.
Long-term prevention relies on maintaining this muscular balance and addressing any underlying stroke flaws. Swimmers should work with a coach to review and correct their technique, focusing on proper hand entry and adequate body rotation to minimize internal rotation of the shoulder. Incorporating a consistent strength and conditioning program that emphasizes core stability and shoulder mobility is necessary against the repetitive demands of training.