Activation of shoulder muscles in healthy men and women under isometric conditions.
OBJECTIVE
Due to the low osseous lead of the shoulder joint a large portion of the shoulder muscles, in addition to executing movements, deals with stabilising tasks. This requires a permanent readjustment of the intermuscular co-ordination of all involved muscles. The aim of the study was to verify the existence of gender dependent differences in intramuscular co-ordination patterns of shoulder muscles.


METHODS
Fifteen healthy men and nine healthy women, who executed 24 isometric exercises in sagittal, frontal and horizontal planes with a loading of 50% of their individual isometric maximum force, were investigated. In every plane, four angular positions were chosen and both opposite force directions were measured, respectively. SEMG was taken from 13 muscles of the shoulder and the upper arm. Due to inter-individual differences SEMG amplitudes were normalised.


RESULTS
Gender specific differences of functional intermuscular co-ordination patterns could be proven systematically. Women showed less activation of muscles acting in the main force direction. In addition, those muscles less necessary for the actual force production were more activated in women than in men.


CONCLUSIONS
Functionally comparable shoulder function showed a gender dependency in terms of functional intermuscular co-ordination.
Anders
Christoph
C
Institute for Pathophysiology and Pathobiochemistry, Friedrich-Schiller-University Jena, D-07740 Jena, Germany. cand@moto.uni-jena.de
Bretschneider
Susanne
S
Bernsdorf
Annette
A
Erler
Kerstin
K
Schneider
Wolfgang
W
D000328:Adult; D004576:Electromyography; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012737:Sex Factors; D012782:Shoulder / Q000502:physiology*