title: Effect of mental fatigue on induced tremor in human knee extensors.
abstract: In this study, the effects of mental fatigue on mechanically induced tremor at both a low (3-6Hz) and high (8-12Hz) frequency were investigated. The two distinct tremor frequencies were evoked using two springs of different stiffness, during 20s sustained contractions of the knee extensor muscles at 30% maximum voluntary contraction (MVC) before and after 100min of a mental fatigue task, in 12 healthy (29±3.7years) participants. Mental fatigue resulted in a 6.9% decrease in MVC and in a 9.4% decrease in the amplitude of the agonist muscle EMG during sustained 30% MVC contractions in the induced high frequency only. Following the mental fatigue task, the coefficient of variation and standard deviation of the force signal decreased at 8-12Hz induced tremor by 31.7% and 35.2% respectively, but not at 3-6Hz induced tremor. Similarly, the maximum value and area underneath the peak in the power spectrum of the force signal decreased by 55.5% and 53.1% respectively in the 8-12Hz range only. In conclusion, mental fatigue decreased mechanically induced 8-12Hz tremor and had no effect on induced 3-6Hz tremor. We suggest that the reduction could be attributed to the decreased activation of the agonist muscles.
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin 4, Ireland. Electronic address: francesco.budini@gmail.com.
authors.forename: Francesco
authors.initials: F
authors.lastname: Budini
authors.affiliation: School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Dublin 4, Ireland.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Lowery
authors.affiliation: Department of Biomedical Sciences, Faculty of Health & Life Sciences, Northumbria University, Newcastle upon Tyne, UK.
authors.forename: Rade
authors.initials: R
authors.lastname: Durbaba
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin 4, Ireland.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: De Vito
mesh_terms: D000328:Adult; D000465:Algorithms; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction; D007717:Knee / Q000503:physiopathology; D008297:Male; D005222:Mental Fatigue / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D012026:Reflex, Stretch / Q000502:physiology*; D014202:Tremor / Q000503:physiopathology*
keywords: Loop gain; Mental fatigue; Spring load; Stretch reflex; Tremor