Effects of a 36-hour fast on human endurance and substrate utilization
Autor: | B. A. Zinker, K. Britz, George A. Brooks |
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Rok vydání: | 1990 |
Předmět: |
Blood Glucose
Glycerol Male medicine.medical_specialty Time Factors Physiology Hydroxybutyrates Physical exercise Fatty Acids Nonesterified Carbohydrate metabolism chemistry.chemical_compound Oxygen Consumption Physiology (medical) Internal medicine medicine Humans Lactic Acid Respiratory exchange ratio Pulmonary Gas Exchange Chemistry VO2 max Fasting Metabolism Carbohydrate Lactic acid Endocrinology Lactates Physical Endurance |
Zdroj: | Scopus-Elsevier |
ISSN: | 1522-1601 8750-7587 |
DOI: | 10.1152/jappl.1990.69.5.1849 |
Popis: | To determine if prolonged fasting affects substrate utilization and endurance time, seven trained men exercised to exhaustion on a cycle ergometer at 50% maximum oxygen consumption (VO2max) in an overnight-fasted [postabsorptive (PA)] state and after a 36-h fast (F). Fasting produced significant elevations in the resting concentrations of blood free fatty acids (FFA; 1.16 +/- 0.05 vs. 0.56 +/- 0.06 mM, F vs. PA, respectively, a 107% increase), beta-hydroxybutyrate (beta-OH, 2.06 +/- 0.66 vs. 0.15 +/- 0.06 mM, a 1,270% increase), and glycerol (0.12 +/- 0.03 vs. 0.04 +/- 0.01 mM, a 200% increase), with a significant decline in glucose (79.79 +/- 2.12 vs. 98.88 +/- 3.11 mg/dl, a 19% decrease). Exercise in the F trial increased FFA, decreased glucose, and significantly elevated beta-OH and glycerol over the PA trial. There was no difference in blood glucose concentration between trials at exhaustion. However, F produced a significant decrement in exercise endurance time compared with the PA trial (88.9 +/- 18.3 vs. 144.4 +/- 22.6 min, F vs. PA, a 38% decrease). Based on the respiratory exchange ratio, fasting led to a greater utilization of lipids during rest and exercise. It was concluded that 1) a 36-h fast significantly altered substrate utilization at rest and throughout exercise to exhaustion, 2) glucose levels do not appear to be the single determinant of time to exhaustion in submaximal exercise, and 3) despite the apparent sparing of carbohydrate utilization with the 36-h fast, endurance performance was significantly decreased. |
Databáze: | OpenAIRE |
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