Background: Pre-exercise carbohydrate (CHO) ingestion is an effective strategy for reducing the occurrence of hypoglycemia during or after exercise in individuals with type 1 diabetes (T1DM). The metabolic effects of ingestion of different CHOs for glycemic or performance gains have been under-researched. This study compared metabolic responses and fuel use during sub-maximal and high-intensity performance running following pre-exercise ingestion of waxy barley starch (WBS) or dextrose (DEX) in T1DM.
Methods: Seven participants attended the laboratory on two separate occasions following preliminary testing. On each visit participants consumed either 0.6 g/kg body mass of DEX or WBS 2 hours before a 26-minute discontinuous incremental treadmill protocol (4-minute running: 1.5-min rest) finishing at 80±4% V̇O2peak followed by a 10-min performance run on a non-motorized treadmill. Capillary blood samples were taken at rest, during and following exercise and analyzed for glucose (BG) and acid-base variables. Data (mean ± SEM) were analyzed using repeated measures ANOVA (P<0.05).
Results: BG reached similar peak values one hour after CHO ingestion and immediate pre-sub-maximal exercise BG were comparable. Resting CHO oxidation was elevated and lipid oxidation lower under WBS (P<0.05). There were no metabolic or cardio-respiratory differences during the sub-maximal exercise (P>0.05). In the final quartile of the performance run, a greater distance was completed under WBS (WBS 323±21 vs. DEX 301±20 m, P=0.02).
Conclusions: Consumption of WBS demonstrated similar hyperglycemic responses to dextrose ingestion but a greater rate of CHO use at rest. Interestingly, T1DM individuals displayed an improved performance at the latter stages of a high-intensity run test.