Enhanced endurance in trained cyclists during moderate intensity exercise following 2 weeks adaptation to a high fat diet.
These studies investigated the effects of 2 weeks of either a high-fat (HIGH-FAT: 70% fat, 7% CHO) or a high-carbohydrate (HIGH-CHO: 74% CHO, 12% fat) diet on exercise performance in trained cyclists (n = 5) during consecutive periods of cycle exercise including a Wingate test of muscle power, cycle exercise to exhaustion at 85% of peak power output [90% maximal oxygen uptake (VO2max), high-intensity exercise (HIE)] and 50% of peak power output [60% VO2max, moderate intensity exercise (MIE)]. Exercise time to exhaustion during HIE was not significantly different between trials: nor were the rates of muscle glycogen utilization during HIE different between trials, although starting muscle glycogen content was lower [68.1 (SEM 3.9) vs 120.6 (SEM 3.8) mmol.kg-1 wet mass, P < 0.01] after the HIGH-FAT diet. Despite a lower muscle glycogen content at the onset of MIE [32 (SEM 7) vs 73 (SEM 6) mmol.kg-1 wet mass, HIGH-FAT vs HIGH-CHO, P < 0.01], exercise time to exhaustion during subsequent MIE was significantly longer after the HIGH-FAT diet [79.7 (SEM 7.6) vs 42.5 (SEM 6.8) min, HIGH-FAT vs HIGH-CHO, P < 0.01]. Enhanced endurance during MIE after the HIGH-FAT diet was associated with a lower respiratory exchange ratio [0.87 (SEM 0.03) vs (SEM 0.02), P < 0.05], and a decreased rate of carbohydrate oxidation [1.41 (SEM 0.70) vs 2.23 (SEM 0.40) g CHO.min-1, P < 0.05].(ABSTRACT TRUNCATED AT 250 WORDS)
Liberty Life Chair of Exercise and Sports Science, University of Cape Town Medical School, Observatory, South Africa.
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Lambert
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Speechly
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Dennis
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Noakes
D020155:3-Hydroxybutyric Acid; D000222:Adaptation, Physiological; D000328:Adult; D001642:Bicycling; D001784:Blood Gas Analysis; D001786:Blood Glucose / Q000378:metabolism; D050260:Carbohydrate Metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005990:Glycerol / Q000097:blood; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D006885:Hydroxybutyrates / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D006885:Hydroxybutyrates; D006003:Glycogen; D005990:Glycerol; D020155:3-Hydroxybutyric Acid