Context: Muscle fatigue due to repetitive and prolonged overhead sports activity is considered an important factor contributing to impingement-related rotator cuff pathologic conditions in overhead athletes. The evidence on scapular and glenohumeral kinematic changes after fatigue is contradicting and prohibits conclusions about how shoulder muscle fatigue affects acromiohumeral distance.Objective: To investigate the effect of a fatigue protocol resembling overhead sports activity on acromiohumeral distance and 3-dimensional scapular position in overhead athletes.Design: Cross-sectional study. Setting: Institutional laboratory. Patients or Other Participants: A total of 29 healthy recreational overhead athletes (14 men, 15 women; age ¼ 22.23 6 2.82 years, height ¼ 178.3 6 7.8 cm, mass ¼ 71.6 6 9.5 kg).Intervention(s): The athletes were tested before and after a shoulder muscle-fatiguing protocol.Main Outcome Measure(s): Acromiohumeral distance was measured using ultrasound, and scapular position was determined with an electromagnetic motion-tracking system. Both measurements were performed at 3 elevation positions (08, 458, and 608 of abduction). We used a 3-factor mixed model for data analysis.Results: After fatigue, the acromiohumeral distance increased when the upper extremity was actively positioned at 458 (D ¼ 0.78 6 0.24 mm, P ¼ .002) or 608 (D ¼ 0.58 6 0.23 mm, P ¼ .02) of abduction. Scapular position changed after fatigue to a more externally rotated position at 458 (D ¼ 4.978 6 1.138, P , .001) and 608 (D ¼ 4.618 6 1.908, P ¼ .001) of abduction, a more upwardly rotated position at 458 (D ¼ 6.108 6 1.308, P , .001) and 608 (D ¼ 7.208 6 1.658, P , .001) of abduction, and a more posteriorly tilted position at 08, 458, and 608 of abduction (D ¼ 1.988 6 0.418, P , .001).Conclusions: After a fatiguing protocol, we found changes in acromiohumeral distance and scapular position that corresponded with an impingement-sparing situation.Key Words: shoulder, subacromial impingement syndrome, injury prevention, ultrasonography Key PointsAfter a fatiguing protocol, acromiohumeral distance increased, and scapular position was more upwardly and externally rotated and posteriorly tilted when the upper extremity was actively held at 458 or 608 of abduction. The changes in acromiohumeral distance and scapular position corresponded with a protective, impingementsparing situation that could be explained by the scapula compensating for glenohumeral shoulder-muscle fatigue.

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The AHD is larger on the dominant side compared with the nondominant side and in elite female athletes compared with recreational female athletes. Moreover, less reduction of the AHD occurs in the elite athlete group during the first 45 degrees of abduction.

The aim of this study is to investigate if there is a change in oxygen saturation and blood flow in the different parts of the trapezius muscle in office workers with and without trapezius myalgia during a standardized computer task. Twenty right-handed office workers participated; ten were recruited based on pain in the trapezius and ten as matching controls. Subjects performed a combination of typing and mousing tasks for 60 min at a standardized workstation. Muscle tissue oxygenation and blood flow data were collected from the upper trapezius (UT), the middle trapezius (MT) and the lower trapezius (LT), both on the left and right side at seven moments (at baseline and every tenth minute during the 1-h typing task) by use of the oxygen to see device. In all three parts of the trapezius muscle, the oxygen saturation and blood flow decreased significantly over time in a similar pattern (p < 0.001). Oxygenation of the left and right UT was significantly higher compared to the other muscle parts (p < 0.001). Oxygen saturation for the MT was significantly lower in the cases compared to the control group (p = 0.027). Blood flow of the UT on the right side was significantly lower than the blood flow on the left side (p = 0.026). The main finding of this study was that 1 h of combined workstation tasks resulted in decreased oxygen saturation and blood flow in all three parts of the trapezius muscle. Future research should focus on the influence of intervention strategies on these parameters.