Purpose: Individuals with type 1 diabetes mellitus (T1DM) are encouraged to reduce rapid-acting insulin and consume CHO to prevent hypoglycemia during or after exercise. However, research comparing the metabolic and performance effects of different CHO is limited. This study compared the alterations in metabolism and fuel oxidation in response to performance running after preexercise ingestion of isomaltulose or dextrose in T1DM.
Methods: After preliminary testing, on two occasions, seven T1DM individuals consumed 0.6 g·kg⁻¹ body mass of either dextrose (DEX; glycemic index = 96) or isomaltulose (ISO; glycemic index = 32), 2 h before a discontinuous incremental run to 80% V˙O2peak on a motorized treadmill followed by a 10-min all-out performance test on a nonmotorized treadmill. Blood glucose (BG), acid-base, and cardiorespiratory parameters were measured 2 h before, during, and after both run tests. Data (mean ± SEM) were analyzed using repeated-measures ANOVA.
Results: Preexercise BG area under the curve was lower under ISO in comparison with DEX (ISO = +4.0 ± 0.3 mmol·L⁻¹·h⁻¹ vs DEX = +7.0 ± 0.6 mmol·L⁻¹·h⁻¹, P < 0.01). Resting blood lactate concentrations and rate of CHO oxidation under ISO were greater than those elicited under DEX (P < 0.05). There were no metabolic or cardiorespiratory differences between conditions in response to submaximal exercise despite lower BG concentrations under ISO (P < 0.05). T1DM individuals completed the same distance at the same speed during the 10-min run test under both conditions (not significant).
Conclusions: Consumption of isomaltulose alongside rapid-acting insulin reduction improves BG responses to exercise and produces a similar high-intensity run performance compared with dextrose in T1DM individuals.