title: The effect of cognitive fatigue on prefrontal cortex correlates of neuromuscular fatigue in older women.
abstract: BACKGROUND
  As the population of adults aged 65 and above is rapidly growing, it is crucial to identify physical and cognitive limitations pertaining to daily living. Cognitive fatigue has shown to adversely impact neuromuscular function in younger adults, however its impact on neuromuscular fatigue, and associated brain function changes, in older adults is not well understood. The aim of the study was to examine the impact of cognitive fatigue on neuromuscular fatigue and associated prefrontal cortex (PFC) activation patterns in older women.
  
  
  METHODS
  Eleven older (75.82 (7.4) years) females attended two sessions and performed intermittent handgrip exercises at 30 % maximum voluntary contraction (MVC) until voluntary exhaustion after a 60-min control (watching documentary) and 60-min cognitive fatigue (performing Stroop Color Word and 1-Back tests) condition. Dependent measures included endurance time, strength loss, PFC activity (measured using fNIRS), force fluctuations, muscle activity, cardiovascular responses, and perceived discomfort.
  
  
  RESULTS
  Participants perceived greater cognitive fatigue after the 60-min cognitive fatigue condition when compared to the control condition. While neuromuscular fatigue outcomes (i.e., endurance time, strength loss, perceived discomfort), force fluctuations, and muscle activity were similar across both the control and cognitive fatigue conditions, greater decrements in PFC activity during neuromuscular fatigue development after the cognitive fatigue condition were observed when compared to the control condition.
  
  
  CONCLUSIONS
  Despite similar neuromuscular outcomes, cognitive fatigue was associated with blunted PFC activation during the handgrip fatiguing exercise that may be indicative of neural adaptation with aging in an effort to maintain motor performance. Examining the relationship between cognitive fatigue and neuromuscular output by imaging other motor-related brain regions are needed to provide a better understanding of age-related compensatory adaptations to perform daily tasks that involve some levels of cognitive demand and physical exercise, especially when older adults experience them sequentially.
authors.affiliation: Department of Environmental and Occupational Health, School of Public Health, Texas A&M University, College Station, TX, 77843, USA. ashortz@sph.tamhsc.edu.
authors.forename: Ashley E
authors.initials: AE
authors.lastname: Shortz
authors.affiliation: Department of Environmental and Occupational Health, School of Public Health, Texas A&M University, College Station, TX, 77843, USA. pickens@sph.tamhsc.edu.
authors.forename: Adam
authors.initials: A
authors.lastname: Pickens
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Texas A&M University, College Station, TX, 77843, USA. qzheng@sph.tamhsc.edu.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zheng
authors.affiliation: Department of Environmental and Occupational Health, School of Public Health, Texas A&M University, College Station, TX, 77843, USA. rmehta@tamu.edu.
authors.forename: Ranjana K
authors.initials: RK
authors.lastname: Mehta
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003071:Cognition; D004576:Electromyography; D015444:Exercise; D005260:Female; D018737:Hand Strength; D006439:Hemodynamics; D006801:Humans; D005222:Mental Fatigue / Q000503:physiopathology* / Q000523:psychology; D009119:Muscle Contraction; D018763:Muscle Fatigue; D053580:Muscle Strength; D010101:Oxygen Consumption; D010807:Physical Endurance; D017397:Prefrontal Cortex / Q000503:physiopathology*; D057190:Stroop Test