Relaxation time of the adductor pollicis muscle in Duchenne muscular dystrophy carriers: a new method for detecting carriers.

The half relaxation time (T1/2R) of adductor pollicis muscle contraction after supramaximal ulnar nerve stimulation was measured in normal women and carriers of Duchenne muscular dystrophy. The T1/2R after a single stimulus did not differ in these two groups. The decrease of T1/2R after 2-per-second stimulations, however, was significantly greater in the carriers. The percentage of the T1/2R decrease after 2-per-second stimulations in all of the carriers was below the mean -2 SD value for the controls. These findings suggest that determination of the decrease of the T1/2R of the adductor pollicis muscle with 2-per-second stimulations of the ulnar nerve may be a reliable method for detecting Duchenne muscular dystrophy carriers.