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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
biochemistry, genetics and molecular biology
Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance
Journal of Applied Physiology, Volume 100, No. 1, Year 2006
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Description
The aim of this study was to investigate the effect of a high-fat diet (HFD) followed by 1 day of carbohydrate (CHO) loading on substrate utilization, heart rate variability (HRV), effort perception [rating or perceived exertion (RPE)], muscle recruitment [electromyograph (EMG)], and performance during a 100-km cycling time trial. In this randomized single-blind crossover study, eight well-trained cyclists completed two trials, ingesting either a high-CHO diet (HCD) (68% CHO energy) or an isoenergetic HFD (68% fat energy) for 6 days, followed by 1 day of CHO loading (8-10 g CHO/kg). Subjects completed a 100-km time trial on day 1 and a 1-h cycle at 70% of peak oxygen consumption on days 3, 5, and 7, during which resting HRV and resting and exercising respiratory exchange ratio (RER) were measured. On day 8, subjects completed a 100-km performance time trial, during which blood samples were drawn and EMG was recorded. Ingestion of the HFD reduced RER at rest (P < 0.005) and during exercise (P < 0.01) and increased plasma free fatty acid levels (P < 0.01), indicating increased fat utilization. There was a tendency for the low-frequency power component of HRV to be greater for HFD-CHO (P = 0.056), suggestive of increased sympathetic activation. Overall 100-km time-trial performance was not different between diets; however, 1-km sprint power output after HFD-CHO was lower (P < 0.05) compared with HCD-CHO. Despite a reduced power output with HFD-CHO, RPE, heart rate, and EMG were not different between trials. In conclusion, the HFD-CHO dietary strategy increased fat oxidation, but compromised high intensity sprint performance, possibly by increased sympathetic activation or altered contractile function. Copyright © 2006 the American Physiological Society.
Authors & Co-Authors
Havemann, Lize
South Africa, Cape Town
University of Cape Town
West, Sacha J.
South Africa, Cape Town
University of Cape Town
Goedecke, Julia H.
South Africa, Cape Town
University of Cape Town
Macdonald, Ian A.
United Kingdom, Nottingham
University of Nottingham Medical School
St.Clair Gibson, Allan
South Africa, Cape Town
University of Cape Town
Noakes, Timothy D.
South Africa, Cape Town
University of Cape Town
Lambert, E. Victoria
South Africa, Cape Town
University of Cape Town
Statistics
Citations: 168
Authors: 7
Affiliations: 2
Identifiers
Doi:
10.1152/japplphysiol.00813.2005
ISSN:
87507587
e-ISSN:
15221601
Research Areas
Disability