Measurement of skin mobility in the upper back.

On manual testing for skinfold tenderness greater resistance has been reported in patients with marked skinfold tenderness. On objective measurement of skin mobility, by raising a skinfold with a vacuum pump and by establishing a stress/strain curve, no difference in skin mobility was found between subjects with and without skinfold tenderness. Furthermore, contrary to manual testing, the suction testing causes no pain in subjects with clinical skinfold tenderness. In a second series of suction tests, comparing skin mobility in a subject with relaxed and contracted underlying muscles, it was found that muscular contraction reduces skin mobility by 50%. The conclusion is that resistance felt by manual skinfold testing is not inherent in the structures, but is caused by contraction of underlying muscles because of pain caused by the manual skinfold test.