title: Prolonged mental exertion does not alter neuromuscular function of the knee extensors.
abstract: OBJECTIVE
  The aim of this study was to test the hypotheses that prolonged mental exertion (i) reduces maximal muscle activation and (ii) increases the extent of central fatigue induced by subsequent endurance exercise.
  
  
  METHODS
  The neuromuscular function of the knee extensor muscles was assessed in 10 male subjects in two different conditions: (i) before and after prolonged mental exertion leading to mental fatigue and (ii) before and after an easy cognitive task (control). Both cognitive tasks lasted 90 min and were followed by submaximal isometric knee extensor exercise until exhaustion (endurance task), and a third assessment of neuromuscular function.
  
  
  RESULTS
  Time to exhaustion was 13% ± 4% shorter in the mental fatigue condition (230 ± 22 s) compared with the control condition (266 ± 26 s) (P < 0.01). Prolonged mental exertion did not have any significant effect on maximal voluntary contraction torque, voluntary activation level, and peripheral parameters of neuromuscular function. A similar significant decrease in maximal voluntary contraction torque (mental fatigue condition: -26.7% ± 5.7%; control condition: -27.6% ± 3.3%, P < 0.001), voluntary activation level (mental fatigue: -10.6% ± 4.3%; control condition: -11.2% ± 5.2%, P < 0.05), and peripheral parameters of neuromuscular function occurred in both conditions after the endurance task. However, mentally fatigued subjects rated perceived exertion significantly higher during the endurance task compared with the control condition (P < 0.05).
  
  
  CONCLUSIONS
  These findings provide the first experimental evidence that prolonged mental exertion (i) does not reduce maximal muscle activation and (ii) does not increase the extent of central fatigue induced by subsequent endurance exercise. The negative effect of mental fatigue on endurance performance seems to be mediated by the higher perception of effort rather than impaired neuromuscular function.
authors.affiliation: 1Endurance Research Group, School of Sport & Exercise Sciences, University of Kent at Medway, Chatham Maritime, Kent, UNITED KINGDOM; and 2Laboratoire INSERM U1093, Université de Bourgogne, Faculté des Sciences du Sports-UFR STAPS, Dijon, FRANCE.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Pageaux
authors.forename: Samuele M
authors.initials: SM
authors.lastname: Marcora
authors.forename: Romuald
authors.initials: R
authors.lastname: Lepers
mesh_terms: D004576:Electromyography; D005080:Exercise Test; D005602:France; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007719:Knee Joint; D008297:Male; D005222:Mental Fatigue; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011795:Surveys and Questionnaires; D019415:Torque; D055815:Young Adult