Acromiohumeral distance quantification during a variety of shoulder external and internal rotational exercises in recreationally overhead athletes

To determine whether shoulder external (ER) and internal rotational (IR) exercises at five different shoulder abduction angles affect the acromiohumeral distance (AHD). Twenty recreational overhead athletes were included. AHD was measured using real-time ultrasound for each of the five shoulder conditions as follows: neutral shoulder rotation (active-hold) and during ER and IR exercises (isometric and concentric) at five different shoulder-abduction angles (0 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees of abduction). A two-way ANOVA was used to analyze AHD values. Shoulder abduction angle x exercise interaction for AHD was found (F-16,F-304 = 10.92; p < .001; eta 2 = 0.37). For both isometric and concentric conditions, AHD increased during IR exercises (p < .05) yet decreased during ER exercises (p < .05) when compared with each active-hold positions. Shoulder ER and IR exercises influence the AHD in recreational overhead athletes. A larger AHD was observed during shoulder IR exercises, whereas ER exercises failed to maintain the AHD.