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.