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Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance
L Havemann1, S J West, J H Goedecke
1University of Cape Town/Medical Research Council Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, South Africa.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 6, 2005
Summary
A high-fat diet followed by carbohydrate loading increased fat burning in cyclists but reduced sprint performance. This dietary strategy may impact high-intensity exercise capacity.
Area of Science:
- Sports Nutrition
- Exercise Physiology
- Human Performance
Background:
- Dietary strategies significantly influence substrate utilization and athletic performance.
- Understanding the impact of high-fat diets (HFD) followed by carbohydrate loading (CHO) is crucial for optimizing endurance events.
Purpose of the Study:
- To investigate the effects of a 6-day HFD followed by 1 day of CHO loading on substrate utilization, heart rate variability (HRV), perceived exertion (RPE), muscle recruitment (EMG), and 100-km cycling performance.
- To assess physiological and performance adaptations in well-trained cyclists.
Main Methods:
- Eight well-trained cyclists participated in a randomized single-blind crossover study.
- Two dietary conditions were compared: a high-carbohydrate diet (HCD) and an isoenergetic HFD, both followed by a CHO loading phase.
- Measurements included respiratory exchange ratio (RER), plasma free fatty acids, HRV, RPE, EMG, and 100-km time-trial performance, including a 1-km sprint.
Main Results:
- The HFD significantly increased fat utilization, indicated by reduced RER and elevated plasma free fatty acids.
- A trend towards increased sympathetic activation was observed with the HFD-CHO condition.
- While overall 100-km time-trial performance remained unchanged, 1-km sprint power output was significantly lower after the HFD-CHO compared to the HCD-CHO.
Conclusions:
- The HFD-CHO strategy enhances fat oxidation but can impair high-intensity sprint performance in cyclists.
- Potential mechanisms for performance reduction include increased sympathetic activation or altered muscle contractile function.
- Further research is needed to elucidate the precise mechanisms and long-term implications of such dietary interventions.