Blood glucose responses to reductions in pre-exercise rapid-acting insulin for 24h after running in individuals with type 1 diabetes

In this study, we examined pre-exercise insulin reductions on consequent metabolic and dietary patterns for 24h after running in individuals with type 1 diabetes. Seven participants self-administered their Full rapid-acting insulin dose or 75%, 50% or 25% of it, immediately before consuming a 1.12-MJ meal. After 2h, participants completed 45min of running at 70% peak oxygen uptake ([Vdot]O2peak). Blood glucose and insulin were measured for 2h before and 3h after exercise. Blood glucose, diet, and administered insulin were self-recorded for 24h after exercise. Data were analysed using repeated-measures analysis of variance. Pre-exercise peak insulin concentrations were greatest with the Full dose and consequently elicited the lowest blood glucose concentrations (P0.05). Blood glucose decreased under all conditions with exercise, with the fall with the Full dose (-6.1mmol center dot l-1, sx=0.4) greater than with 25% insulin (-3.2mmol center dot l-1, sx=0.4; P0.05). There was little change in blood glucose from 0 to 3h post-exercise under all conditions (P0.05). Blood glucose at 3h post-exercise was greatest with the 25% dose. Over the next 21h, blood glucose area under the curve was greater with the 25% dose compared with all other trials despite consuming less energy and fewer carbohydrates (P0.05). A 75% reduction to pre-exercise insulin results in the greatest preservation of blood glucose, and a reduced dietary intake, for 24h after running in individuals with type 1 diabetes.