Comparing the subcromial space at 90° shoulder abduction with and without external humerus rotation and during upright row postures in young healthy subjects: an ultrasound evaluation

Introduction The lateral rises performed with or without humerus rotation (shoulder abduction up to 90° and above), and the upright row (UR) performed with dumbbells or barbells implying an internal humerus rotation (shoulder abduction >90°) (Durall et al., 2001) are common exercises employed by people in gyms. However, the UR can be related to the onset of subacromial impingement syndrome (SIS) (Kolber et al., 2014). Conversely, it seems that the lateral rises with an external humerus rotation are not associated with SIS onset. Since one of the factors involved in the onset of SIS is the reduction of subacromial space (SS), we evaluated SS at different shoulder postures that reproduced the final positions of the abovementioned exercises. Methods Twenty-five healthy males (age, 24±5 yrs; stature 175±8 cm; body mass 74±12 kg) underwent SS ultrasound evaluation of the right arm with sagittal anterior approach. A line was marked on the skin at the mean point of the anterior acromial aspect found by ultrasound. Scans were taken while executing with (WL) and without (NL) 4-kg load: 90° shoulder abduction (SA) with no humerus rotation (90°n); 90° SA maximum external rotation (90°er); SA during upright row (UR). A fluid goniometer was attached with a Velcro® strap on the back of the arm to check the SA degrees. Reliability was assessed. Repeated measures ANOVA 3x2 and paired samples t-test were employed (=0.05). Results Significant differences between loads (p=0.003, 2=0.37), angles (p<0.001, 2=0.72), and significant interaction (p=0.004, 2=0.45) were found. SS values were higher at 90°er compared to 90°n and UR (p<0.001 for both) in WL. Differences were found between 90°n and both 90°er (p=0.002) and UR (p=0.009) in NL. Differences between NL and WL were found at 90°er (p<0.001). Intra-observer reproducibility was optimal for all measurements (range 0.97–0.99). Conclusion In our participants, postures of SA at 90°er showed larger SS than at 90°n and UR both WL and NL. This could imply that excluding the external humerus rotation during SA may be potentially dangerous in susceptible subjects, favouring the onset of SIS.