ABSTRACT
PURPOSE: The understanding of fatigue of the human motor system is important in the fields of ergonomics, sport, rehabilitation and neurology. In order to understand the interactions between fatigue and reaction time, we evaluated the effects of two different fatiguing tasks on reaction time. METHODS: 83 healthy subjects were included in a case-control study with three arms where single and double choice reaction time tasks were performed before and after 2 min fatiguing task (an isometric task, a finger tapping task and at rest). RESULTS: After an isometric task, the right-fatigued hand was slower in the choice component of a double choice reaction time task (calculated as the individual difference between single and double choice reaction times); also, the subjects that felt more fatigued had slower choice reaction time respect to the baseline assessment. Moreover, in relationship to the performance decay after two minutes, finger tapping task produces more intense fatigability perception. CONCLUSIONS: We confirmed that two minutes of isometric or repetitive tasks are enough to produce fatigue. The fatigue perception is more intense for finger tapping tasks in relation to the performance decay. We therefore confirmed that the two fatiguing tasks produced two different kind of fatigue demonstrating that with a very simple protocol it is possible to test subjects or patients to quantify different form of fatigue.
Subject(s)
Cognition/physiology , Hand/physiopathology , Muscle Fatigue , Muscle, Skeletal/physiopathology , Reaction Time , Adolescent , Adult , Case-Control Studies , Exercise , Female , Humans , Male , Middle Aged , Young AdultABSTRACT
Background: Multiple sclerosis (MS) is an autoimmune disorder of the CNS in which inflammation, demyelination, and axonal damage of the central nervous system coexist. Fatigue is one of the most disabling symptoms in MS and little is known about the neurophysiological mechanisms involved. Methods: To give more mechanistic insight of fatigue in MS, we studied a cohort of 17 MS patients and a group of 16 age-matched healthy controls. Baseline Fatigue Severity Scales and Fatigue Rating were obtained from both groups to check the level of fatigue and to perform statistical correlations with fatigue-induced neurophysiologic changes. To induce fatigue we used a handgrip task. During the fatiguing task, we evaluated fatigue state (using a dynamometer) and after the task we evaluated the Borg Rating of Perceived Exertion Scale. Transcranial magnetic stimulation and peripheral electric stimulation were used to assess corticospinal tract and peripheral system functions before and after the task. Results: Clinically significant fatigue and central motor conduction time were greater in patients than in controls, while motor cortex excitability was decreased and maximal handgrip strength reduced in patients. Interestingly, fatigue state was positively correlated to perceived fatigue in controls but not in patients. Furthermore, in the presence of similar fatigue state over time, controls showed a significant fatigue-related reduction in motor evoked potential (a putative marker of central fatigue) whereas this effect was not seen in patients. Conclusions: in MS patients the pathogenesis of fatigue seems not driven by the mechanisms directly related to corticospinal function (that characterize fatigue in controls) but seems probably due to other "central abnormalities" upstream to primary motor cortex.
ABSTRACT
La fatiga es definida como un fenómeno relacionado con el tiempo de disminución de la capacidad máxima de generación de fuerza, expresándose, como un deterioro en la contracción máxima voluntaria (CMV). La aparición de la fatiga en el músculo esquelético durante un esfuerzo ha sido de interés para los fisiólogos, especialmente porque la fatiga es un factor limitante, tanto en el rendimiento deportivo como en la realización de cualquier tarea. El objetivo del artículo es analizar la literatura y proporcionar una revisión sistemática sobre la fatiga inducida por tareas de contracción muscular, provocadas por contracciones isométricas o mediante tapping de dedos. Para ello se realizó una investigación basada en la metodología PRISMA (Artículos de informes preferidos para revisiones sistemáticas y metanálisis). Llevando a cabo una búsqueda de artículos en las bases de datos PubMed, Medline, Science Direct y Google Scholar, entre los meses de junio y noviembre de 2017 con fecha posterior al año 2000. De los 315 estudios identificados inicialmente, sólo 12 cumplieron con los criterios de selección establecidos. La variabilidad metodológica de los distintos estudios permite observar como a través de las tareas de tapping (movimientos repetitivos de dedos), o mediante tareas de contracción isométrica se pueden determinar los distintos parámetros de la fatiga que se evalúan en cada estudio, siendo un instrumento muy utilizado para abordar dicho tema. La fatiga muscular se ha estudiado predominantemente cuando es inducida por tareas isométricas, habiendo un mayor número de investigaciones que utilizan este tipo de metodología, ya que, aunque el tapping de dedos sea un procedimiento fiable para evaluar los mecanismos neurofisiológicos subyacentes de la fatiga, apenas se ha explorado
Fatigue has been defined as a phenomenon related to the time of decrease of the maximum capacity of generation of force, expressing itself, generally, as a deterioration in the maximum voluntary contraction (CMV). The appearance of fatigue in skeletal muscle during an effort has long been of interest to physiologists, especially because fatigue is a limiting factor in athletic performance or in the performance of any task. The aim of the article is to analyze the literature and provide a systematic review on fatigue induced by muscle contraction tasks, caused by isometric contractions or by finger tapping. To this end, an investigation was carried out based on the PRISMA methodology (Articles of preferred reports for systematic reviews and meta-analyzes). Conducting a search of articles in the PubMed, Medline, Science Direct and Google Scholar databases, between the months of June and November of 2017 after the year 2000. Of the 315 studies initially identified, only 12 complied with the established selection criteria. The methodological variability of the different studies allows to observe how through the tapping tasks (repetitive movements of fingers), or through isometric contraction tasks, it is possible to determine the different parameters of fatigue that are evaluated in each study, being a very used to address that topic. Muscle fatigue has been predominantly studied when induced by isometric tasks, with a greater number of investigations using this type of methodology, since, although finger tapping is a reliable procedure to evaluate the underlying neurophysiological mechanisms of fatigue, It has been explored
