Fructose and glucose ingestion and muscle glycogen use during submaximal exercise

glycogen use during submaximal exercise. J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 55(6): 1767-1771, 1983.-Substrate utilization after fructose, glucose, or water ingestion was examined in four male and four female subjects during three treadmill runs at-75 % of maximal O2 uptake. Each test was preceded by three days of a carbohydrate-rich diet. The runs were 30 min long and were spaced at least 1 wk apart. Exercise began 45 min after ingestion of 300 ml of randomly assigned 75 g fructose (F), 75 g glucose (G), or control (C). Muscle glycogen depletion determined by pre- and postexercise biopsies (gastrocnemius muscle) was significantly (P < 0.05) less during the F trial than during C or G. Venous blood samples revealed a significant increase in serum glucose (P < 0.05) and insulin (P < 0.01) within 45 min after the G drink, followed by a decrease (P < 0.05) in serum glucose during the first 15 mi