Effects of different arm external loads on the scapulo-humeral rhythm.
OBJECTIVE
To investigate the effects of the magnitude of the external load, applied on the hand, on the orientation of the shoulder girdle (scapulo-humeral rhythm).


METHODS
Thirty subjects performed both arms' elevation in three planes of elevation: sagittal (anteflexion), frontal (abduction), and scapular (scaption). Measurements were performed against five levels of external load (0-4 kg), on each plane of elevation.


BACKGROUND
Some controversy exists whether additional load influences the SHR. Moreover, no data are available on the SHR during arm abduction and anteflexion.


METHODS
The SHR was recorded by means of a six degree of freedom electromagnetic tracking device.


RESULTS
The external load applied on the hand affects scapular three-dimensional position: scapular protraction is particularly affected on abduction and scaption; scapular latero-rotation on anteflexion and abduction; and scapular spinal tilt on anteflexion.


CONCLUSIONS
The magnitude of the external load, applied on the hand, influences the scapular position and the scapulo-humeral rhythm, particularly on abduction. Those effects are visible on scapular latero-rotation and spinal tilt, during anteflexion, and on scapular protraction during scaption. Additionally, the initial position of the shoulder girdle seems to play an important role on the definition of the individual SHR pattern. RelevanceThis study can provide a basis for evaluation of shoulder pathology associated with abnormal scapular kinematics.
Pascoal
A G
AG
Faculty of Human Kinetics, Technical University of Lisbon, Lisbon, Portugal.
van der Helm
F F
FF
Pezarat Correia
P
P
Carita
I
I
D000328:Adult; D001132:Arm / Q000502:physiology; D001696:Biomechanical Phenomena; D006801:Humans; D006811:Humerus / Q000502:physiology*; D008297:Male; D012399:Rotation; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*