Dynamic acromiohumeral interval changes in baseball players during scaption exercises.
OBJECTIVE
Elevation of the arm during a dynamic scaption exercise will result in a progressive narrowing of the acromiohumeral interval (AHI); however, the addition of a load will not significantly affect the AHI in healthy baseball players.


METHODS
Thirteen healthy baseball players performed a seated scaption exercise from 0° to 90°, with and without a normalized additional load. Dynamic AHI intervals were measured using digital fluoroscopic videos with the arm at the side, and at 30°, 45°, 60°, and 75° of humeral elevation.


RESULTS
The mean AHI for unloaded and loaded scaption decreased significantly (P < .001) from the arm at the side (12.7 mm) until 45° (4.9 mm), further changes in the mean AHI between 45°, 60°, and 75° were not significantly different. Generally, loaded scaption resulted in smaller AHI values at 45°, 60°, and 75°; however, only the differences at 60° (P = .005) and 75° (P = .003) were significant.


CONCLUSIONS
Narrowing of the AHI during dynamic motion was similar to previous reports of static AHI, with the exception of the trend towards widening of the AHI seen at 75° during both conditions. The additional AHI narrowing observed at 60° and 75° during the loaded exercise may indicate that scapular positioning is more influential in this range.


CONCLUSIONS
An additional AHI narrowing of 11% during loaded scaption, did not result in any clinical impingement during the exercise, but may have more serious implications in other healthy and pathologic populations.
Department of Kinesiology, Louisiana State University, Baton Rouge, LA, USA. Mhargr2@lsu.edu
Melissa D
MD
Thompson
Dennis
D
Landin
Phillip A
PA
Page
D000174:Acromion / Q000000981:diagnostic imaging / Q000502:physiology*; D054874:Athletic Performance / Q000502:physiology*; D005471:Fluoroscopy; D006801:Humans; D006811:Humerus / Q000000981:diagnostic imaging / Q000502:physiology*; D055815:Young Adult