title: Fructose Coingestion Does Not Accelerate Postexercise Muscle Glycogen Repletion.
abstract: BACKGROUND
  Postexercise muscle glycogen repletion is largely determined by the systemic availability of exogenous carbohydrate provided.
  
  
  OBJECTIVE
  This study aimed to assess the effect of the combined ingestion of fructose and glucose on postexercise muscle glycogen repletion when optimal amounts of carbohydrate are ingested.
  
  
  METHODS
  Fourteen male cyclists (age: 28 ± 6 yr; Wmax: 4.8 ± 0.4 W·kg⁻¹) were studied on three different occasions. Each test day started with a glycogen-depleting exercise session. This was followed by a 5-h recovery period, during which subjects ingested 1.5 g·kg⁻¹·h⁻¹ glucose (GLU), 1.2 g·kg⁻¹·h⁻¹ glucose + 0.3 g·kg⁻¹·h⁻¹ fructose (GLU + FRU), or 0.9 g·kg⁻¹·h⁻¹ glucose + 0.6 g·kg⁻¹·h⁻¹ sucrose (GLU + SUC). Blood samples and gastrointestinal distress questionnaires were collected frequently, and muscle biopsy samples were taken at 0, 120, and 300 min after cessation of exercise to measure muscle glycogen content.
  
  
  RESULTS
  Plasma glucose responses did not differ between treatments (ANOVA, P = 0.096), but plasma insulin and lactate concentrations were elevated during GLU + FRU and GLU + SUC when compared with GLU (P < 0.01). Muscle glycogen content immediately after exercise averaged 207 ± 112, 219 ± 107, and 236 ± 118 mmol·kg⁻¹ dry weight in the GLU, GLU + FRU, and GLU + SUC treatments, respectively (P = 0.362). Carbohydrate ingestion increased muscle glycogen concentrations during 5 h of postexercise recovery to 261 ± 98, 289 ± 130, and 315 ± 103 mmol·kg⁻¹ dry weight in the GLU, GLU + FRU, and GLU + SUC treatments, respectively (P < 0.001), with no differences between treatments (time × treatment, P = 0.757).
  
  
  CONCLUSIONS
  Combined ingestion of glucose plus fructose does not further accelerate postexercise muscle glycogen repletion in trained cyclists when ample carbohydrate is ingested. Combined ingestion of glucose (polymers) plus fructose or sucrose reduces gastrointestinal complaints when ingesting large amounts of carbohydrate.
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, THE NETHERLANDS.
authors.forename: Jorn
authors.initials: J
authors.lastname: Trommelen
authors.forename: Milou
authors.initials: M
authors.lastname: Beelen
authors.forename: Philippe J M
authors.initials: PJ
authors.lastname: Pinckaers
authors.forename: Joan M
authors.initials: JM
authors.lastname: Senden
authors.forename: Naomi M
authors.initials: NM
authors.lastname: Cermak
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: Van Loon
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004311:Double-Blind Method; D005632:Fructose / Q000008:administration & dosage*; D005947:Glucose / Q000008:administration & dosage; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D064133:Sports Nutritional Physiological Phenomena; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D007328:Insulin; D005632:Fructose; D019344:Lactic Acid; D006003:Glycogen; D005947:Glucose