The Interaction of Mental and Neuromuscular Fatigue and the Impact of Mental Fatigue on Function Across Different Age Groups
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Date
2019-09-18
Authors
Morris, Amanda
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
Fatigue is a multidimensional concept with physical and psychological components. While neuromuscular fatigue has been studied extensively, its effects on cognitive function have been studied, few studies have focused on its impact on cognitive function. Further, the effect of mental fatigue on neuromuscular measures or physiological outcomes is not fully understood. Three studies were conducted to determine the interactions between mental and neuromuscular fatigue and the impact of mental fatigue on function and, to determine age related differences in these interactions.
Study one investigated neuromuscular function in the tibialis anterior of young and older adults (transcranial magnetic stimulation, electrical stimulation, and force measurements) before and after a 20-minute mental fatigue task. Results suggested that mental fatigue may cause increased cortical inhibition in both age groups and that 20 minutes of a mentally fatiguing task may cause a decrease in the ability to produce maximal force in young adults, providing evidence of an interaction between mental fatigue and physical function.
Study two examined the effect of neuromuscular fatigue on cognitive function in young and older adults. Measures of cognitive function (reaction time and errors during a 3-minute cognitive task) were taken before and after 16-minutes of intermittent isometric contraction of the ankle dorsiflexor muscles. Neuromuscular fatigue negatively affected cognitive function (slowed reaction time) in young adults only. Results suggested that a neuromuscular fatigue task may negatively affect cognitive function in young but not older adults.
Study three examined the postural response to force platform perturbations in young and older women in response to mental fatigue. Only young women experienced mental fatigue (slower reaction times) and this was accompanied by significantly faster center of pressure velocity during the mental fatigue condition compared with the control condition. Performance of the mental fatigue task, not necessarily development of mental fatigue, affects neuromuscular activation in young women only, but does not affect the magnitude of postural response to perturbation.
Taken together, these studies demonstrate that there is a complex and age-specific relationship between mental fatigue and physical function and physical fatigue and cognitive function.
This dissertation includes unpublished co-authored material.
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Keywords
Aging, Mental Fatigue, Neuromuscular Fatigue, Postural Balance Control, Transcranial Magnetic Stimulation