title: Effect of free versus constant pace on performance and oxygen kinetics in running.
abstract: OBJECTIVE
  This study tested the hypothesis that free versus constant pace enhanced the performance (i.e., distance run) in suprathreshold runs between 90 and 105% of the velocity associated with the maximal oxygen consumption determined in an incremental test (v.VO(2max)). Moreover, we hypothesized that variable pace could decrease the slow phase of oxygen kinetics by small spontaneous recoveries during the same distance run at an average velocity.
  
  
  METHODS
  Eleven long-distance runners performed nine track runs performed until exhaustion. Following an incremental test to determine v.VO(2max), the runners performed, in a random order, four constant-velocity runs at 90, 95, 100, and 105% of v.VO(2max) to determine the time to exhaustion (tlim90, tlim95, tlim100, and tlim105) and the distance limit at 90, 95, 100 and 105% of v.VO(2max) (dlim90, dlim95, dlim100, and dlim105). Finally, they performed the distance limit determined in the constant velocity runs but at variable velocity according to their spontaneous choice.
  
  
  RESULTS
  The coefficient of variation of velocity (in percent of the average velocity) was small and not significantly different between the four free pace dlim (4.2 +/- 1.3%, 4.8 +/- 2.4%, 3.6 +/- 1.1%, and 4.6 +/- 1.9% for dlim90, dlim95, dlim100, and dlim105, respectively; P = 0.40). Performances were not improved by a variable pace excepted for the dlim at 105% v.VO(2max) (4.96 +/- 0.6 m.s-1 vs 4.86 +/- 0.5 m.s-1, P = 0.04). Oxygen kinetics and the volume of oxygen consumed were not modified by this (low) variation in velocity.
  
  
  CONCLUSIONS
  These results indicate that for long-distance runners, variable pace modifies neither performance nor the oxygen kinetics in all-out suprathreshold runs.
authors.affiliation: Faculty of Sport Science, University of Lille 2, Lille, France. veronique.billat@wanadoo.fr
authors.forename: V L
authors.initials: VL
authors.lastname: Billat
authors.forename: J
authors.initials: J
authors.lastname: Slawinski
authors.forename: M
authors.initials: M
authors.lastname: Danel
authors.forename: J P
authors.initials: JP
authors.lastname: Koralsztein
mesh_terms: D000328:Adult; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D010806:Physical Education and Training / Q000379:methods*; D010807:Physical Endurance / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology; D011897:Random Allocation; D012420:Running / Q000502:physiology*; D013647:Task Performance and Analysis; D013997:Time Factors
chemical_list: D019344:Lactic Acid