Objective: To estimate the motor unit numbers in normal adult hand muscles using manual incremental technique and F-wave technique.

Method: We estimated the motor unit numbers in abductor pollicis brevis muscles of twenty normal adults. In manual incremental technique, we estimated the motor unit numbers using motor unit count program setted in electrodiagnostic equipment (Dantec, Keypoint). In F-wave technique, we estimated the motor unit numbers dividing maximal M-potential amplitude by mean amplitude of surface motor unit action potential.

Results: There was no significant difference of motor unit numbers between right and left abductor pollicis brevis in both manual incremental and F-wave technique. Motor unit numbers using F-wave technique were significantly greater than motor unit numbers using manual incremental technique.

Conclusion: The difference of motor unit numbers using manual incremental technique and F-wave technique was considered as a difference of functional electrical stimulation. F-wave technique was more physiologic and functional method of motor unit numbers estimation than manual incremental technique.

Keywords :Motor unit number, Manual incremental technique, F-wave technique