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Biomedical Bases of Mental Fatigue and Military Fatigue Countermeasures

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Human Factors and Medicine

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Fatigue, Mental endurance, Mission failure, Multifactorial common mechanisms, Neurophysiological status, Neuropsychology, Physical and mental workload, Psychobiology, Restrecovery, Task overload, Time on Task


Endurance is typically conceptualized as the ability to sustain physical performance continuously over an extended period of time. But the concept of endurance is equally applicable to the cognitive realm: mental endurance is likewise the ability to continuously perform a cognitive task (e.g., surveillance duties) over an extended period of time. For both physical and mental performance, extended ‘time on task’ results in the accrual of “fatigue” – broadly defined as a disinclination to continue performing the task at hand. And in both cases, the resulting fatigue can to some extent be counteracted (i.e., performance deficits can be delayed or avoided) by the application of increased “effort.” Much is known about physical (e.g., muscular) endurance, fatigue, and recovery. Less clear is the extent to which mental and physical endurance are mediated via common mechanisms (e.g., sleep, nutrition, mood, etc.) and the extent to which, and how, they interact. For example, it is known that an increased cognitive load results in a subsequently reduced physical ability, but the psychobiological underpinnings of this interaction have not yet been determined. Modern neurobiological technologies and advances now make it possible to map military risk factors for fatigue back to the common final pathways affecting brain and behavior. Previous work by NATO RTG 260 has developed common approaches to physiological monitoring of warfighter status, including a start on sleep and alertness monitoring technologies. Currently, there is a need to extend this work in a panel on the neuropsychology of mental endurance, considering and expanding the technology for enhancing warfighter endurance through biofeedback and providing insights to autonomous systems to improve the effectiveness of man-machine interactions.


The ET-179 panel concluded with a definition of mental fatigue: a psychobiological state induced by prolonged exertion that has the potential to reduce performance. The panel also concluded that warfighter mental endurance is the proper term to describe the objectives of this effort in terms of enhanced warfighter performance and lethality. Expected deliverables are: (1) Significant national and multinational peer reviewed publications derived from panel cooperative discussions and data exchange, as well as multinational research collaborations; (2) Draft STANREC summarizing common definitions, understanding, and strategies to enhance mental endurance; and (3) Cooperative Demonstration of Technology highlighting what has been accomplished for the warfighter during the term of this panel.


• Endurance performance, with emphasis on perception, cognition, motivation, combined stressors, and social interactions (including team working and leadership) • Common neurobiological and neuropsychological mechanisms of mental fatigue resulting from multifactorial mental and physical stressors • Neurophysiological status monitoring technologies, including affective computing • Chronobiology, sleep, and alertness research models • Models of prolonged, exhaustive military operations

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