Special and clinical populations often suffer fatigue. Fatigue involves symptoms that can limit both physical and cognitive function with attributes of performance fatigability and perceived fatigability (1) which are relevant to clinical populations. Performance fatigability is the decline in an objective measure of performance over time. Examples include a reduction in force or power during repeated single limb muscle contractions or the time to complete a six-minute walk test. Perceived fatigability depends on the psychological state and the physiological capacity of the body and reflects the sensations which accompany regulation of the integrity of the performer. Perceived fatigability is measured as a self-reported rating of the sense of ‘fatigue’ during motor performance or at rest. Performance fatigability and perceived fatigability are usually studied as separate attributes in healthy and clinical populations. There is however, minimal understanding of how these attributes of fatigue integrate to affect motor performance and wellbeing, particularly in special and clinical populations.

Past research has typically concentrated on the mechanisms that limit performance fatigability during single limb isometric or dynamic contractions, often in healthy young males, with little distinction between males and females, or consideration of race or ethnicity. In populations such as females, old adults, and ‘clinical’ populations (e.g. people with multiple sclerosis, stroke, cancer, obesity, diabetes, amyotrophic lateral sclerosis, Parkinson’s disease and spinal cord injury to name a few), there is limited knowledge on performance fatigability, the involved mechanisms that limit performance, how fatigability assessed in the laboratory predicts functional tasks in the real world, and the interactions with perceived fatigability.

Understanding how different population characteristics effect fatigability is important but understudied, not only for optimizing rehabilitation interventions but also for understanding the fundamental changes in motor control in special populations. Submission of novel manuscripts are encouraged within the scope of the following: describing performance fatigability, perceived fatigability and altered motor performance in special and clinical populations, and the involved neural and muscular mechanisms, and; understanding the relevance of altered performance fatigability to functional tasks in the real world, and the interactions with perceived fatigability.

Keywords: Fatigue, motor performance, motivation, clinical populations, exercise

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