title: Oxygen consumption and energy expenditure of level versus downhill running.
abstract: OBJECTIVE
  The purpose of this study was to assess and compare submaximal oxygen consumption (VO2) and energy expenditure (kJ) while running at 0, -1.8, -3.6, and -5.4% grades for three individually selected running speeds (9.4 + 0.79, 10.3 + 0.74, 11.3 + 0.73 km.h-1).
  
  
  METHODS
  Subjects completed the four grade conditions in random order via a modified Latin squares design at three self-selected submaximal running speeds for each condition.
  
  
  METHODS
  Thirteen (5 females and 8 males) recreational (< 35 km.wk-1) runners (age: 27.7 +/- 4.3 yrs) volunteered for the study.
  
  
  METHODS
  Two-way repeated measures ANOVA (Grade x Speed) was used to analyze steady-state VO2 and kJ expenditure. Stepwise linear multiple regression was used to develop an equation for predicting VO2 for running at recreational speeds on moderately negative grades.
  
  
  RESULTS
  VO2 and kJ mean values were significantly different between all speed and % grade comparisons. Compared to level grade, the average reductions in VO2 and kJ expenditure ranged from approximately 9% at a grade of -1.8% to 22% at a grade of -5.4%. The relationship between VO2 and % grade for each running speed was linear.
  
  
  CONCLUSIONS
  For a given speed, running at a modest negative grade can significantly decrease VO2 and kJ expenditure compared to level running. The following regression equation can be used to estimate VO2 (ml.kg-1.min-1) for running at recreational speeds on slight downhills: VO2 = 6.8192 + 0.1313 (speed in m.min-1) + 1.2367 (% grade).
authors.affiliation: Center for Exercise and Applied Human Physiology, Johnson Center, University of New Mexico, Albuquerque, NM 87131-1251, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Robergs
authors.forename: D R
authors.initials: DR
authors.lastname: Wagner
authors.forename: K M
authors.initials: KM
authors.lastname: Skemp
mesh_terms: D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D001823:Body Composition; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005544:Forecasting; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration / Q000502:physiology; D012420:Running / Q000145:classification / Q000502:physiology*; D013147:Spirometry; D013990:Tidal Volume / Q000502:physiology