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Med Sci Sports Exerc. 2014 Sep;46(9):1778-86. doi: 10.1249/MSS.0000000000000284.

Glucose-fructose enhances performance versus isocaloric, but not moderate, glucose.

Author information

1
Human Performance Laboratory, Department of Kinesiology, James Madison University, Harrisonburg, VA.

Abstract

PURPOSE:

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.

PMID:
25134001
DOI:
10.1249/MSS.0000000000000284
[Indexed for MEDLINE]

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