Objectives. The most prevalent disorders of the shoulder are related to the
muscles of rotator cuff. In order to develop a mechanical method
for the evaluation of the rotator cuff muscles, we created a database
of isometric force generation by the rotator cuff muscles in normal
adult population. We hypothesised the existence of variations according
to age, gender and dominancy of limb. Methods. A total of 400 healthy adult volunteers were tested, classified
into groups of 50 men and women for each decade of life. Maximal
isometric force was measured at standardised positions for supraspinatus,
infraspinatus and subscapularis muscles in both shoulders in every
person. Torque of the force was calculated and normalised to lean body
mass. The profiles of mean torque-time curves for each age and gender
group were compared. Results. Our data showed that men gradually gained maximal strength in
the fifth decade, and showed decreased strength in the sixth. In
women the maximal strength was gained in the fourth decade with
gradual decline to the sixth decade of life. The dominant arm was
stronger in most of the tested groups. The torque profiles of the
rotator cuff muscles in men at all ages were significantly higher
than that in women. Conclusions. We found previously unrecognised variations of rotator cuff
