Pathoanatomy of an elite swimmer’s shoulder

Abstract

Clinicians commonly assess shoulder strength and range of motion (ROM), which have been postulated as factors contributing to swimmer’s shoulder pain. The purpose of this thesis was to identify what constitutes the normal anatomical and physical characteristics common to elite swimmer’s shoulders thereby allowing the review of current concepts relevant to the management of ‘swimmer’s shoulder’ and to optimise clinical assessment and management of shoulder pain in swimmers. This thesis comprises of four published studies.
The first study assessed the validity of hand-held dynamometry (HHD) in shoulder strength assessment comparing the intra-rater and inter-rater reliability of HHD against externally fixed dynamometry (EFD) and isokinetic dynamometry (IKD). Shoulder strength is routinely measured by clinicians working with swimming athletes, but the inter-rater reliability between examiners of different sex and physical characteristics, and years of clinical experience is unknown. In addition, there is very little published on the minimal detectable change (MDC) and standard error of measurement (SEM) for shoulder rotation strength measures. These results from study one, support the clinical use of hand-held dynamometry as the preferred method of testing shoulder internal (IR)and external rotation (ER) strength in swimmers.
Shoulder strength and range of motion normative data in elite swimmers is lacking, making it difficult to identify optimal parameters for shoulder strength and ROM. Study two aimed to determine normative values for shoulder isometric rotation strength parameters compared to body weight in elite Australian swimmers and investigate potential associations with shoulder pain. The results from study two provided a normative data set for shoulder rotation strength in elite swimmers as a percentage of bodyweight (BW). Mean shoulder internal rotation strength 0.29 Nm/kg for male swimmers and 0.26 Nm/kg for female swimmers, while mean shoulder external rotation strength was 0.19 Nm/kg and 0.18 Nm/kg, respectively. The shoulder ER/IR strength ratio as approximately 0.70 bilaterally across all participants. No difference was found between dominant and non-dominant arms, suggesting that the detection of side-to-side differences in shoulder rotation strength and/or rotation strength ratios in swimmers is a clinically significant findings for swimmers with unilateral shoulder pain. There were no associations found between any shoulder strength parameters and shoulder pain.
Study three aimed to determine normative values for shoulder rotation ROM in elite swimmers incorporating humeral torsion characteristics, in order to establish optimal rotation ROM parameters and any relationship with shoulder pain patterns. This study demonstrated that elite swimmers do not display a greater degree or humeral torsion or passive IR ROM than an age-matched population not involved in competitive swimming, however, where an increased humeral torsion was present, it was positively associated with increased IR and decreased ER ROM. Additionally, elite swimmers displayed approximately 15° more passive ER ROM than an age-matched population not involved in competitive swimming. There were no associations between any rotation variables and current or prior history of shoulder pain.
Published research utilising magnetic resonance imaging (MRI) to assess pathology in elite Swimmer’s shoulders is limited, primarily identifying the supraspinatus tendon and subacromial bursa as the primary contributors to shoulder pain in swimmers, with little mention of other pathologies. The fourth study examined patho-anatomical changes in the largest cohort of elite swimmers assessed to date using MRI and compared those with a cohort of healthy age and gender matched non-upper limb athletes.
This study indicated that subscapularis tendon abnormality is as prevalent as supraspinatus tendon abnormality in elite swimmers. There was no significant difference between dominant and non-dominant shoulders for either tendinopathy, however, Grade 3 tendinopathy was significantly more prevalent in the subscapularis than in supraspinatus (P < 0.01). Significantly more abnormalities were reported in swimmer’s shoulders in both subscapularis and supraspinatus tendons as well as in the labrum and acromioclavicular joints. Pathology was not a predictor of current pain. This suggests that the anatomical abnormalities found on MRI in elite swimmer’s shoulder maybe indicative of normal adaptive changes due to the high training loads performed in these elite swimmers.
The new knowledge gained from the findings of this thesis have added to the body of research on shoulder pain in elite swimming populations. It has also provided clinicians with new information that can potentially improve decision-making when managing swimmers with shoulder pain. It also sheds new light on the possible mechanisms and pathological processes involved in the development of ‘swimmer's shoulder’. This work has directly informed clinical practice for the management of Swimming Australia’s high-performance athletes by supporting effective management of shoulder pain and injury.

Date of Award	2025
Original language	English
Supervisor	Gordon WADDINGTON (Supervisor) & Craig Boettcher (Supervisor)