Nutritional manipulations before and during endurance exercise: effects on performance.
1) Ingesting CHO during prolonged, moderate-intensity (60-85% VO2max) exercise can improve performance by maintaining plasma glucose availability and oxidation during the later stages of exercise. 2) Plasma glucose may be oxidized at rates in excess of 1 g.min-1 late in exercise. Athletes therefore need to ingest sufficient quantities of CHO in order to meet this demand. This can be accomplished by ingesting CHO at 40-75 g.h-1 throughout exercise or by ingesting approximately 200 g of CHO late in exercise. Ingesting CHO after fatigue has already occurred, however, is generally ineffective in restoring and maintaining plasma glucose availability, CHO oxidation, and/or exercise tolerance. 3) No apparent differences exist between glucose, sucrose, or maltodextrins in their ability to improve performance. Ingesting fructose during exercise, however, does not improve performance and may cause gastrointestinal distress. 4) The form of CHO (i.e., solid vs liquid) ingested during exercise is unlikely to be important provided that sufficient water is also consumed when ingesting CHO in solid form. 5) Ingesting 50-200 g of CHO 30-60 min before exercise results in transient hypoglycemia early in exercise, but this does not affect the rate of muscle glycogen utilization or, in most people, cause overt symptoms of neuroglucopenia. Whether performance is impaired, unaffected, or enhanced by such pre-exercise CHO feedings remains equivocal. 6) Ingesting 200-350 g of CHO 3-6 h before exercise appears to improve performance, possibly by maximizing muscle and/or liver glycogen stores or by supplying CHO from the small intestine during exercise itself.(ABSTRACT TRUNCATED AT 250 WORDS)
Coggan
A R
AR
Exercise Physiology Laboratory, Ohio State University, Columbus 43210.
Swanson
S C
SC
D000596:Amino Acids / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D015444:Exercise / Q000502:physiology; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D009132:Muscles / Q000378:metabolism; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology; D013997:Time Factors
D000596:Amino Acids; D004040:Dietary Carbohydrates; D006003:Glycogen