Instrumental straight-leg raising: results in healthy subjects.

The instrumental performance of Lasègue's test (instrumental straight-leg raising) provides information about the extensibility, elasticity, and electrical activity of hamstrings and back muscles and about pelvic rotation. Because relevant data on these variables are not known in literature, instrumental straight-leg raising was performed in healthy subjects. Using the toe-touch test, three groups of eight subjects were selected: a flexible group, able to touch the ground with their hands flat, a medium group, able to touch the ground with their finger tips, and a stiff group, not able to touch the ground at all. Measurements showed a considerable difference in the extensibility of the hamstrings between the groups with only a slight difference in the extensibility of the back muscles. They also showed clear differences in elasticity of the hamstrings and the back muscles in the subjects within the groups. Between the groups, however, muscle elasticity was not systematically different. Electromyogram activity was most often present in the subjects of the stiff group, predominantly in the hamstrings. It began only after the leg had been raised to a considerable extent, showed a gradual increase with leg raise, and never reached a high level.