title: Perception of fatigue during simulated competition.
abstract: BACKGROUND
  Previous studies suggest that the rating of perceived exertion (RPE) increases during steady-state, open-loop exercise in proportion to the relative time to fatigue. This suggests that RPE is scalar and integrates physiological status and homeostatic disturbances.
  
  
  OBJECTIVE
  This study assessed the relationship between the rate of change in RPE, and relative distance in time trials at distances of 2.5, 5, and 10 km. It also assessed the rate of change in RPE during 5-km time trials while breathing hypoxic air.
  
  
  METHODS
  The subjects were well-conditioned cyclists. In part 1, each subject completed habituation time trials, and then randomly ordered time trials at each distance. The category ratio RPE was measured in 10% increments throughout each trial. In part 2, each subject completed three 5-km time trials while breathing different inspired gas mixtures (FiO2 = 0.2093 throughout the trial, FiO2 = 0.15 between 2 and 4 km, and FiO2 = 0.15 between 2.5 and 4 km). RPE was measured at 10% increments.
  
  
  RESULTS
  In part 1, when RPE was plotted against relative distance, there was no significant difference in the growth of RPE at proportional distances. In part 2, the decrease in power output during the hypoxic segments was sufficient that the growth of RPE was the same at each proportional distance. In both parts of the study, an RPE of 5 (hard) was achieved after 20% of the time trial distance, and an RPE of 8 was achieved after 80% distance.
  
  
  CONCLUSIONS
  This study supports the hypothesis that RPE increases similarly in relation to relative distance, regardless of the distance performed, and it suggests that the perception of effort has scalar properties.
authors.affiliation: Department of Exercise and Sport Science, University of Wisconsin-La Crosse, La Crosse, WI 54601, USA.
authors.forename: Trent
authors.initials: T
authors.lastname: Joseph
authors.forename: Blair
authors.initials: B
authors.lastname: Johnson
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Battista
authors.forename: Glenn
authors.initials: G
authors.lastname: Wright
authors.forename: Christopher
authors.initials: C
authors.lastname: Dodge
authors.forename: John P
authors.initials: JP
authors.lastname: Porcari
authors.forename: Jos J
authors.initials: JJ
authors.lastname: de Koning
authors.forename: Carl
authors.initials: C
authors.lastname: Foster
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling; D003163:Competitive Behavior; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D010465:Perception; D005082:Physical Exertion; D013647:Task Performance and Analysis