title: Curvilinear dose-response relationship of carbohydrate (0-120 g·h(-1)) and performance.
abstract: BACKGROUND
  There is a lack of consensus regarding the optimal range of carbohydrate (CHO) ingestion rates recommended for endurance athletes.
  
  
  OBJECTIVE
  This study investigated the relationship between CHO dose and cycling time trial performance to identify an optimal range of CHO ingestion rates for endurance performance.
  
  
  METHODS
  Fifty-one cyclists and triathletes (28 ± 7 yr, mean ± SD) across four research sites completed four trials. Each trial consisted of a 2-h constant load ride at 95% of the workload that elicited a 4-mmol·L(-1) blood lactate concentration immediately followed by a computer-simulated 20-km time trial, which subjects were asked to complete as quickly as possible. Twelve CHO electrolyte (18 mmol·L(-1) Na, 3 mmol·L(-1) K, and 11 mmol·L(-1) Cl) beverages (three at each site) were tested in a double-blind manner, providing subjects 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 g CHO (1:1:1 glucose-fructose-maltodextrin) per hour during the 2-h constant load ride at a fluid intake rate of 1 L·h(-1). All subjects also consumed a noncaloric placebo on one counterbalanced test occasion. Data were natural log transformed, subjected to a mixed-model analysis, and are reported as adjusted treatment means.
  
  
  RESULTS
  We estimate incremental performance improvements of 1.0%, 2.0%, 3.0%, 4.0%, and 4.7% at 9, 19, 31, 48, and 78 g·h, respectively, with diminishing performance enhancement seen at CHO levels >78 g·h(-1).
  
  
  CONCLUSIONS
  CHO beverage ingestion and endurance (∼160 min) performance appear to be related in a curvilinear dose-response manner, with the best performance occurring with a CHO (1:1:1 glucose-fructose-maltodextrin) ingestion rate of 78 g·h(-1).
authors.affiliation: Gatorade Sports Science Institute, Barrington, IL, USA.
authors.forename: Johneric W
authors.initials: JW
authors.lastname: Smith
authors.forename: David D
authors.initials: DD
authors.lastname: Pascoe
authors.forename: Dennis H
authors.initials: DH
authors.lastname: Passe
authors.forename: Brent C
authors.initials: BC
authors.lastname: Ruby
authors.forename: Laura K
authors.initials: LK
authors.lastname: Stewart
authors.forename: Lindsay B
authors.initials: LB
authors.lastname: Baker
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Zachwieja
mesh_terms: D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001628:Beverages; D001642:Bicycling / Q000502:physiology*; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007773:Lactates / Q000097:blood; D008297:Male; D010807:Physical Endurance / Q000187:drug effects*; D012044:Regression Analysis; D012420:Running / Q000502:physiology*; D013550:Swimming / Q000502:physiology*
chemical_list: D004040:Dietary Carbohydrates; D007773:Lactates