Shoulder injury in Swimmers
Swimming is a great non weight-bearing, full body form of cardiovascular exercise. Because stroke propulsion relies so heavily on upper extremity movement, up to half of swimmers are prone to shoulder injury with a 50% recurrence rate. A correlation has been found between intensity and duration of workouts and shoulder pain rather than swimmer’s age, number of years of swimming or age at which swimming commenced.
Swimmers have been found to have hypermobile joints (knees, elbows and digits). One could theorize their larger range of motion provides them with an anatomical advantage. However, there is no correlation between swimming and gleno-humeral joint symptomatic instability.
As a result of this hypermobility, the muscular stability demands of the gleno-humeral joint will also increase. Because swimming strokes are all open kinetic chain the additional lack of proprioceptive input puts these muscular demands at a biomechanical disadvantage.
Caution should be emphasized to prevent over-stretching the anterior capsule, increasing hypermobility without addressing stability
Clinically, positive Hawkins Test, suggesting subacromial impingement, was found more frequently in swimmers than in controls.
Biomechanical studies (high-speed film study) have demonstrated normal patterns of movement throughout swimming strokes (eg: hand entry and hand exit and elbow height through recovery). Further fine wire EMG studies have established specific force couples throughout the four phases of each stroke (hand entry and early pull-through, mid pull-through, late pull-through and hand exit and recovery) which maintain ideal scapular position as well as normal gleno-humeral joint alignment.
For example in front crawl during in early pull-through, the upper trapezius, rhomboids and serratus anterior create a force couple which effectively tethers the scapula at all three corners. These studies found that serratus anterior was one of the only muscles to be activated throughout all phases of the stroke.
At the gleno-humeral joint the supraspinatus forms a force couple with anterior and middle deltoid during hand entry. Being that the supraspinatus insertion is closer to the axis of rotation than deltoids, this muscle maintains compression of the humeral head into the glenoid fossa and prevents the deltoid from levering the humeral head postero-inferiorly. A similar force couple is created between latissimus dorsi and subscapularis throughout mid to late pull-through.
The force couples have been shown to become altered in swimmers with shoulder pain. Serratus anterior and other key muscles required for accurate stroke technique decrease in activity decrease in each phase of the stoke. Additionally, opposing rotator cuff muscles increase in activity; for example subscapularis has been found to decrease in activity and infraspinatus to increase in activity, thus magnifying dysfunctional stroke technique during mid to late pull-through. The combination can lead the observable “lazy elbow” during the recovery phase of front crawl.
As such, poor stroke technique becomes a result of shoulder pain instead of the primary cause. The original cause of shoulder pain likely being due to training errors; excessive volume or excessive intensity with inadequate rest.
Preventing the first episode of shoulder pain can eliminate this cascade of events which seem to unravel normal shoulder mechanics. An exercise program focusing on rotator cuff and scapular stabilizers is a good first step preventative intervention for swimmers. Education for coaches regarding training techniques would also be of utmost importance.
Incidentally, clinicians looking for similar shoulder dyskensia can find comparable patterns of muscular inhibition and facilitation in non-swimmers with shoulder pain.
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