title: Duathlon performance unaltered by short-term changes in dietary fat and carbohydrates.
abstract: OBJECTIVE
  This study investigated the effects of short-term dietary changes on metabolism and duathlon performance.
  
  
  METHODS
  Eleven men underwent a high-fat (HF; >65% fat from energy) or a high-carbohydrate (CHO; HC) diet (>60% CHO from energy). Energy intake was individualized, and commercially available foods were prepared and packaged for each participant 48 hr before they completed a laboratory-based duathlon (5-km run, 30 km cycling, and 10-km run). Blood samples were obtained before, immediately after, and 1 and 2 hr after the duathlon for determination of glucose, insulin, and glucagon. Oxygen consumption, ratings of perceived exertion (RPE), and respiratory-exchange ratio were assessed, and fat and CHO oxidation were estimated before, during, and after the duathlon.
  
  
  RESULTS
  Dietary records indicated a significant difference in fat content ingested before the duathlons (p < .05). Time to complete the duathlon did not differ between the HC- and the HF-diet trials. CHO-oxidation rate was higher during the HC-diet trial than during the HF-diet trial (p = .006). Fat-oxidation rates were higher in the HF-diet trial than in the HC-diet trial (p = .001). No differences in RPE were found between dietary trials. Blood glucose concentration was higher immediately after the duathlon in the HC-diet trial than in the HF-diet trial and remained higher 1 and 2 hr after the duathlon (p < .05).
  
  
  CONCLUSIONS
  Duathlon performance was not altered by short-term changes in dietary fat or CHO composition despite higher blood glucose concentrations under the HC condition.
authors.affiliation: School of Physical Education and Sports, University of Costa Rica.
authors.forename: Jose
authors.initials: J
authors.lastname: Moncada-Jimenez
authors.forename: Eric P
authors.initials: EP
authors.lastname: Plaisance
authors.forename: Michael L
authors.initials: ML
authors.lastname: Mestek
authors.forename: Lance
authors.initials: L
authors.lastname: Ratcliff
authors.forename: Felipe
authors.initials: F
authors.lastname: Araya-Ramirez
authors.forename: James K
authors.initials: JK
authors.lastname: Taylor
authors.forename: Peter W
authors.initials: PW
authors.lastname: Grandjean
authors.forename: Luis F
authors.initials: LF
authors.lastname: Aragonvargas
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004041:Dietary Fats / Q000008:administration & dosage*; D002149:Energy Intake / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D005934:Glucagon / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000187:drug effects* / Q000502:physiology*; D013647:Task Performance and Analysis; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D007328:Insulin; D005934:Glucagon