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High Incidence of Infraspinatus Muscle Atrophy in Elite Professional Female Tennis Players

Young SW, Dakic J, Stroia K, Nguyen ML, Harris AH, Safran MR. High Incidence of Infraspinatus Muscle Atrophy in Elite Professional Female Tennis Players. Am J Sports Med. 2015 Aug;43(8):1989–93. PubMed #26078449.
Tags: biomechanics, muscle, shoulder, counter-intuitive, odd, sports, etiology, pro, head/neck, exercise, self-treatment, treatment

PainSci summary of Young 2015?This page is one of thousands in the bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided at the bottom of the page, as often as possible. ★★★☆☆?3-star ratings are for typical studies with no more (or less) than the usual common problems. Ratings are a highly subjective opinion, and subject to revision at any time. If you think this paper has been incorrectly rated, please let me know.

This odd little study reports a pattern of infraspinatus atrophy in the shoulder of elite female tennis players. (The infraspinatus is one of the four small “rotator cuff” muscles that control fine movement of the shoulder joint.) Such atrophy is common in “overhead athletes,” but it doesn’t appear to be a problem: in these tennis players, atrophy correlated with better performance, not worse, and had no association with any shoulder problems. This appears to be a “muscle imbalance” that’s actually a good thing: something about elite peformance in tennis actually requires or causes it.

original abstractAbstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

BACKGROUND: Isolated infraspinatus muscle atrophy is common in overhead athletes, who place significant and repetitive stresses across their dominant shoulders. Studies on volleyball and baseball players report infraspinatus atrophy in 4% to 34% of players; however, the prevalence of infraspinatus atrophy in professional tennis players has not been reported.

PURPOSE: To investigate the incidence of isolated infraspinatus atrophy in professional tennis players and to identify any correlations with other physical examination findings, ranking performance, and concurrent shoulder injuries.

STUDY DESIGN: Cross-sectional study; Level of evidence, 3.

METHODS: A total of 125 professional female tennis players underwent a comprehensive preparticipation physical health status examination. Two orthopaedic surgeons examined the shoulders of all players and obtained digital goniometric measurements of range of motion (ROM). Infraspinatus atrophy was defined as loss of soft tissue bulk in the infraspinatus scapula fossa (and increased prominence of dorsal scapular bony anatomy) of the dominant shoulder with clear asymmetry when compared with the contralateral side. Correlations were examined between infraspinatus atrophy and concurrent shoulder disorders, clinical examination findings, ROM, glenohumeral internal rotation deficit, singles tennis ranking, and age.

RESULTS: There were 65 players (52%) with evidence of infraspinatus atrophy in their dominant shoulders. No wasting was noted in the nondominant shoulder of any player. No statistically significant differences were seen in mean age, left- or right-hand dominance, height, weight, or body mass index for players with or without atrophy. Of the 77 players ranked in the top 100, 58% had clinical infraspinatus atrophy, compared with 40% of players ranked outside the top 100. No associations were found with static physical examination findings (scapular dyskinesis, ROM glenohumeral internal rotation deficit, postural abnormalities), concurrent shoulder disorders, or compromised performance when measured by singles ranking.

CONCLUSION: This study reports a high level of clinical infraspinatus atrophy in the dominant shoulder of elite female tennis players. Infraspinatus atrophy was associated with a higher performance ranking, and no functional deficits or associations with concurrent shoulder disorders were found. Team physicians can be reassured that infraspinatus atrophy is a common finding in high-performing tennis players and, if asymptomatic, does not appear to significantly compromise performance.

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