Glucose–Fructose Enhances Performance versus Isocaloric, but Not Moderate, Glucose

• Published in: Medicine and science in sports and exercise 2014-09, Vol.46 (9), p.1778-1786
• Main Authors: BAUR, DANIEL A, SCHROER, ADAM B, LUDEN, NICHOLAS D, WOMACK, CHRISTOPHER J, SMYTH, SARAH A, SAUNDERS, MICHAEL J
• Format: Article
• Language: English
• Subjects: Administration, Oral; Adult; Athletic Performance - physiology; Bicycling - physiology; Biological and medical sciences; Blood Glucose - metabolism; Colic - chemically induced; Dizziness - chemically induced; Double-Blind Method; Exercise Test; Fructose - administration & dosage; Fructose - adverse effects; Fundamental and applied biological sciences. Psychology; Glucose - administration & dosage; Glucose - adverse effects; Headache - chemically induced; Heart Rate; Human physiology applied to population studies and life conditions. Human ecophysiology; Human viral diseases; Humans; Immunodeficiencies; Immunodeficiencies. Immunoglobulinopathies; Immunopathology; Infectious diseases; Lactic Acid - blood; Male; Medical sciences; Nausea - chemically induced; Oxygen Consumption; Performance-Enhancing Substances - administration & dosage; Performance-Enhancing Substances - adverse effects; Physical Exertion; Postprandial Period; Pulmonary Gas Exchange; Pulmonary Ventilation; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Viral diseases; Viral diseases of the lymphoid tissue and the blood. Aids; Vomiting - chemically induced; Young Adult
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0000000000000284

PURPOSEThe effects of glucose-and-fructose (GF) coingestion on cycling time trial (TT) performance and physiological responses to exercise were examined under postprandial conditions. METHODSEight 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. RESULTSIn 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. CONCLUSIONSGF ingestion seems to enhance performance, relative to PL and HG. However, it is unclear whether GF improves performance versus moderate doses of glucose.