title: Central fatigue induced by short-lasting finger tapping and isometric tasks: A study of silent periods evoked at spinal and supraspinal levels.
abstract: The neural substrates of fatigue induced by muscular activity have been addressed in depth in relation to isometric tasks. For these activities, when fatigue develops, it has been noted that the duration of the silent periods (SPs) increases in response to both transcranial magnetic stimulation (TMS) of primary motor cortex or electric cervicomedullary stimulation (CMS). However, fatigue is known to be task-dependent and the mechanisms giving rise to a decrease in motor performance during brief, fast repetitive tasks have been less studied. We hypothesized that fatigue induced by repetitive fast finger tapping may have physiological mechanisms different from those accounting for fatigue during an isometric contraction, even in cases of matched effort durations. In these tasks, we examined the contribution of spinal and supraspinal motor circuits to the production of fatigue. The tapping rate and maximal voluntary contractions (MVC), and TMS- and CMS-evoked SPs were obtained at the time of fatigue, and while subjects maintained maximal muscle activation after fast finger-tapping (or isometric activity) of different durations (10 or 30s). Results showed different mechanisms of fatigue triggered by isometric contraction and repetitive movements, even of short duration. Short-lasting repetitive movements induce fatigue within intracortical inhibitory circuits. They increased TMS-SPs, but not CMS-SPs. On the other hand, isometric contraction had a clear impact on spinal circuits. The consideration of these differences might help to optimize the study of fatigue in physiological conditions and neurological disorders.
authors.affiliation: NEUROcom, Neuroscience and Motor Control Group, Department of Medicine-INEF-Physiotherapy-INIBIC, University of A Coruña, Spain. Electronic address: pabloarias.neurocom@udc.es.
authors.forename: P
authors.initials: P
authors.lastname: Arias
authors.affiliation: NEUROcom, Neuroscience and Motor Control Group, Department of Medicine-INEF-Physiotherapy-INIBIC, University of A Coruña, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Robles-García
authors.affiliation: NEUROcom, Neuroscience and Motor Control Group, Department of Medicine-INEF-Physiotherapy-INIBIC, University of A Coruña, Spain.
authors.forename: Y
authors.initials: Y
authors.lastname: Corral-Bergantiños
authors.affiliation: NEUROcom, Neuroscience and Motor Control Group, Department of Medicine-INEF-Physiotherapy-INIBIC, University of A Coruña, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Madrid
authors.affiliation: NEUROcom, Neuroscience and Motor Control Group, Department of Medicine-INEF-Physiotherapy-INIBIC, University of A Coruña, Spain.
authors.forename: N
authors.initials: N
authors.lastname: Espinosa
authors.affiliation: EMG Unit, Neurology Service, Hospital Clinic, Department of Medicine, University of Barcelona, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Valls-Solé
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
authors.forename: K L
authors.initials: KL
authors.lastname: Grieve
authors.affiliation: FENNSI Group, Hospital Nacional de Parapléjicos, SESCAM, Toledo, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Oliviero
authors.affiliation: NEUROcom, Neuroscience and Motor Control Group, Department of Medicine-INEF-Physiotherapy-INIBIC, University of A Coruña, Spain; Centro de Estimulación Cerebral de Galicia. Instituto Médico Arriaza, A Coruña, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Cudeiro
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005221:Fatigue / Q000209:etiology* / Q000473:pathology*; D005260:Female; D005385:Fingers / Q000503:physiopathology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000502:physiology*; D011601:Psychophysics; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: central fatigue; human; repetitive movements