Evaluating the effect of arm dominance on supraspinatus thickness in college badminton players

Background: Badminton is a sport that requires a high level of shoulder mobility and stability in abduction and external rotation, during over-shoulder motion on the favoured dominant side. This may lead to hypertrophy of the rotator cuff muscles involved. The supraspinatus muscle is the largest muscle of the rotator cuff. The effects of arm dominance in this active subject group are unknown. Objectives: To determine if a difference exists in the muscle thickness of the supraspinatus muscle, between dominant and non-dominant shoulders, in college badminton players. To highlight the relationship between muscle size and strength. Methods: Ultrasound scanning and muscle strength testing was used to bilaterally assess the thickness and strength of the supraspinatus muscles in 20 senior college badminton players (aged 18-30). Intra-rater reliability, Mann-Whitney U and Spearman's rank correlation coefficient tests were carried out. Results: High interclass correlation coefficients ranged from 0.92 to 0.983. No statistically significant differences were found between the dominant and non-dominant size and strength (p=0.117) (p=0.185) respectively. The mean % difference in thickness on the dominant side was 8.6% greater than the non-dominant side with a SD+/- 6.6%. Correlation between size vs. strength with Spearman's rank correlation coefficient of 0.548(Dominant) and 0.378(Non-dominant). Conclusions: This study has demonstrated a measureable difference in supraspinatus thickness in the dominant and non-dominant shoulders in badminton players; however these values are not statistically significant. Further research using a larger subject group is required to quantify its true significance.