title: Direct demonstration of reduction of the output of the human motor cortex induced by a fatiguing muscle contraction.
abstract: A brief period of strong muscle contraction suppresses the amplitude of EMG responses evoked in relaxed muscle by transcranial magnetic stimulation (TMS) of the contralateral motor cortex. Here we investigate this phenomenon in more detail by recording the descending motor volleys evoked by TMS from electrodes in the cervical epidural space of three conscious patients implanted with chronic electrical stimulators for control of pain. We confirm that fatigue suppresses I waves evoked by TMS. In addition, D waves were suppressed in two of the patients, suggesting that axonal excitability might also be compromised by a period of intense muscle contraction.
authors.affiliation: Institute of Neurology, Università Cattolica, L go A Gemelli 8, 00168 Rome, Italy. vdilazzaro@rm.unicatt.it
authors.forename: V
authors.initials: V
authors.lastname: Di Lazzaro
authors.forename: A
authors.initials: A
authors.lastname: Oliviero
authors.forename: P A
authors.initials: PA
authors.lastname: Tonali
authors.forename: P
authors.initials: P
authors.lastname: Mazzone
authors.forename: A
authors.initials: A
authors.lastname: Insola
authors.forename: F
authors.initials: F
authors.lastname: Pilato
authors.forename: E
authors.initials: E
authors.lastname: Saturno
authors.forename: M
authors.initials: M
authors.lastname: Dileone
authors.forename: J C
authors.initials: JC
authors.lastname: Rothwell
mesh_terms: D000328:Adult; D001369:Axons / Q000502:physiology; D002574:Cervical Vertebrae; D004599:Electric Stimulation Therapy; D004567:Electrodes, Implanted; D004576:Electromyography; D004824:Epidural Space; D006801:Humans; D008280:Magnetics; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D059408:Pain Management