Effects of intravenous dextrose infusion on muscle glycogen resynthesis after intense exercise


Animal Science, NSW 2006, Australia.


Muscle glycogen resynthesis rates were studied in 6 Standardbred geldings that were exercised on a treadmill inclined at 10% slope to deplete muscle glycogen prior to treatments. Each horse completed 15 min at 50% V̇O2max, 15 min at 70% V̇O2max, 5 min at 90% V̇O2max then rested for 30 min. This was followed by 6, 1 min sprints at 100% V̇O2max with 5 min rest periods between sprints. Muscle biopsies were taken from the middle gluteal muscle at a depth of 8 cm using the same locations in each horse. Samples were taken before, at the end of exercise and 3, 6, 9, 12 and 24 h after treatment. Blood samples were collected before exercise, immediately after exercise, then every 60 min for 8 h after treatment. Thirty min after exercise each horse was treated with either 6 g/kg dextrose i.v. as a 20% solution in an isotonic electrolyte solution at a mean (± s.e.) infusion rate of 1.67 ± 0.05 1/h, or with a solution of equivalent volume of polyionic isotonic fluid (control) at the same infusion rate. Mean pre-exercise and post infusion peak plasma glucose concentrations were 4.9 ± 0.1 and 28.6 ± 2.8 mmol/l and 4.7 ± 0.2 and 6.0 ± 0.5 mmol/l, for treatment and control respectively. Mean pre-exercise and peak insulin concentrations were 0.007 ± 0.002 and 0.123 ± 0.022 μu/l and 0.006 ± 0.001 and 0.012 ± 0.002 μu/l, for treatment and control respectively. There were significant effects of both time and treatment for glucose and insulin (P<0.05). Mean rates of glycogen resynthesis for the first 12 h were 14.6 ± 2.6 mmol/kg/h and 2.6 ± 3.1 mmol/kg/h respectively for treatment and control and 7.0 ± 1.6 mmol/kg/h and 3.8 ± 1.2 mmol/kg/h for the first 24 h after treatments. The administration of large doses of dextrose i.v. after exercise increases the rate of muscle glycogen resynthesis.