title: The Dynamics of Speed Selection and Psycho-Physiological Load during a Mountain Ultramarathon.
abstract: BACKGROUND
  Exercise intensity during ultramarathons (UM) is expected to be regulated as a result of the development of psycho-physiological strain and in anticipation of perceived difficulties (duration, topography). The aim of this study was to investigate the dynamics of speed, heart rate and perceived exertion during a long trail UM in a mountainous setting.
  
  
  METHODS
  Fifteen participants were recruited from competitors in a 106 km trail mountain UM with a total elevation gain and loss of 5870 m. Speed and gradient, heart rate (HR) and ratings of perceived exertion (dissociated between the general [RPEGEN] and knee extensor fatigue [RPEKE] and collected using a voice recorder) were measured during the UM. Self-selected speed at three gradients (level, negative, positive), HR, RPEGEN and RPEKE were determined for each 10% section of total event duration (TED).
  
  
  RESULTS
  The participants completed the event in 18.3 ± 3.0 h, for a total calculated distance of 105.6 ± 1.8 km. Speed at all gradients decreased, and HR at all gradients significantly decreased from 10% to 70%, 80% and 90%, but not 100% of TED. RPEGEN and RPEKE increased throughout the event. Speed increased from 90% to 100% of TED at all gradients. Average speed was significantly correlated with total time stopped (r = -.772; p = .001; 95% confidence interval [CI] = -1.15, -0.39) and the magnitude of speed loss (r = .540; p = .038; 95% CI = -1.04, -0.03), but not with the variability of speed (r = -.475; p = .073; 95% CI = -1.00, 0.05).
  
  
  CONCLUSIONS
  Participants in a mountain UM event combined positive pacing strategies (speed decreased until 70-90% of TED), an increased speed in the last 10% of the event, a decrease in HR at 70-90% of TED, and an increase in RPEGEN and RPEKE in the last 30% of the event. A greater speed loss and less total time stopped were the factors associated with increased total performance. These results could be explained by theoretical perspectives of a complex regulatory system modulating motor drive in anticipation of perceived difficulties such as elevation changes.
authors.affiliation: School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, Australia.|Laboratoire de Physiologie de l'Exercice, EA-4338, Université Savoie Mont Blanc, Le Bourget-du-Lac, France.
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Kerhervé
authors.affiliation: Human Performance Laboratory, University of Calgary, Calgary, Canada.|Laboratoire de Physiologie de l'Exercice, Université de Lyon, F-42023, Saint-Etienne, France.
authors.forename: Guillaume Y
authors.initials: GY
authors.lastname: Millet
authors.affiliation: School of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, Australia.
authors.forename: Colin
authors.initials: C
authors.lastname: Solomon
mesh_terms: D000328:Adult; D059031:Anticipation, Psychological; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010465:Perception; D005082:Physical Exertion; D012420:Running / Q000502:physiology* / Q000523:psychology*