title: Glucose-fructose enhances performance versus isocaloric, but not moderate, glucose.
abstract: OBJECTIVE
  The effects of glucose-and-fructose (GF) coingestion on cycling time trial (TT) performance and physiological responses to exercise were examined under postprandial conditions.
  
  
  METHODS
  Eight trained male cyclists (age, 25 ± 6 yr; height, 180 ± 4 cm; weight, 77 ± 9 kg; V˙O2max, 62 ± 6 mL·kg·min) completed the study. Subjects ingested either an artificially sweetened placebo (PL), a moderate-glucose beverage (MG, 1.03 g·min), a high-glucose beverage (HG, 1.55 g·min), or a GF beverage (1.55 g·min, 2:1 ratio) during approximately 3 h of exercise, including 2 h of constant-load cycling (55% Wmax, 195 ± 17 W), immediately followed by a computer-simulated 30-km TT. Physiological responses (V˙E, V˙O2, RER, HR, blood glucose level, blood lactate level, and RPE) and incidences of gastrointestinal distress were assessed during early (15-20 min), middle (55-60 min), and late exercise (115-120 min) and during the TT. Magnitude-based qualitative inferences were used to evaluate differences between treatments.
  
  
  RESULTS
  In comparison with that in PL (52.9 ± 3.7 min), TT performances were faster with GF (50.4 ± 2.2 min, "very likely" benefit), MG (51.1 ± 2.4 min, "likely" benefit), and HG (52.0 ± 3.7 min, "possible" benefit). GF resulted in a "likely" improvement versus HG (3.0%) and an "unclear" effect relative to MG (1.2%). MG was "possibly" beneficial versus HG (1.8%). Few incidences of GI distress were reported in any trials.
  
  
  CONCLUSIONS
  GF ingestion seems to enhance performance, relative to PL and HG. However, it is unclear whether GF improves performance versus moderate doses of glucose.
authors.affiliation: Human Performance Laboratory, Department of Kinesiology, James Madison University, Harrisonburg, VA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Baur
authors.forename: Adam B
authors.initials: AB
authors.lastname: Schroer
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Luden
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Womack
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Smyth
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Saunders
mesh_terms: D000284:Administration, Oral; D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D001786:Blood Glucose / Q000378:metabolism; D003085:Colic / Q000139:chemically induced; D004244:Dizziness / Q000139:chemically induced; D004311:Double-Blind Method; D005080:Exercise Test; D005632:Fructose / Q000008:administration & dosage* / Q000009:adverse effects; D005947:Glucose / Q000008:administration & dosage* / Q000009:adverse effects; D006261:Headache / Q000139:chemically induced; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009325:Nausea / Q000139:chemically induced; D010101:Oxygen Consumption; D058573:Performance-Enhancing Substances / Q000008:administration & dosage* / Q000009:adverse effects; D005082:Physical Exertion; D019518:Postprandial Period; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D014839:Vomiting / Q000139:chemically induced; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D058573:Performance-Enhancing Substances; D005632:Fructose; D019344:Lactic Acid; D005947:Glucose