Inclusion Criteria:  ALS patient group: 20 patients with confirmed or proposed ALS meeting the 1998 revised El Escorial diagnostic criteria for limb onset ALS. CMT group: 20 patients with peroneal muscular dystrophy meeting the genetically confirmed diagnosis, who signed an informed consent form. KD group: 20 patients with genetically confirmed Kennedy's disease consistent with genetic diagnosis, signed informed consent.  healthy controls:  age-matched healthy adults who volunteered to participate; definite exclusion of tremor, tonicity, and prior brain disease; exclusion of common disorders affecting peripheral nerves such as entrapment peripheral neuropathy, diabetic peripheral neuropathy, and alcoholic peripheral neuropathy; signed informed consent.  Exclusion Criteria:  signs of sensory impairment; significant sphincter dysfunction; visual and oculomotor impairment; autonomic dysfunction; signs of extravertebral symptoms; severe cortical dysfunction; ALS-like syndrome.