The protective effect of high-intensity interval exercise compared with continuous moderate exercise on glycaemic decline is more pronounced in the postabsorptive vs postprandial state in adults with type 1 diabetes: a randomised crossover trial.

aims/hypothesisThe objective of this randomised crossover study was to determine, in adults with type 1 diabetes, whether the glycaemic effects of high-intensity interval exercise (HIIE) vs moderate-intensity continuous exercise (CONT) differ between the postprandial (PP, higher insulin-on-board) and postabsorptive (PA) states.

methodsTwenty physically active adults (inclusion criteria: type 1 diabetes for >1 year, 18-55 years old; nine female; mean ± SD age 33.4 ± 9.4 years) completed four iso-mechanical 25 min cycling sessions (HIIE-PA and HIIE-PP including 1'-1' bouts at 100% maximal aerobic power [MAP]; CONT-PA and CONT-PP at 50% MAP) in randomised order, at the EURASPORT facility of Lille University. Capillary glucose (primary outcome), lactate, cardiorespiratory variables, perceived exertion and enjoyment were assessed during exercise. Interstitial glucose, dietary intake and insulin administration were recorded over 24 h post-exercise. Mixed models assessed effects of exercise modality, prandial state, and their interaction on glycaemic excursions.

resultsDespite similar mechanical load, HIIE induced a greater physiological response than CONT (higher oxygen consumption, heart rate, blood lactate concentration and perceived exertion; p<0.05) without reducing exercise enjoyment. During exercise, capillary glucose declined less in the PA state than in the PP state (p=0.003) and less during HIIE than during CONT (p=0.038), with the protective effect of HIIE being more pronounced in the PA state (p=0.001) (HIIE-PA, -0.72 ± 1.71 mmol/l; CONT-PA, -1.73 ± 1.48 mmol/l; HIIE-PP, -2.33 ± 1.61 mmol/l; CONT-PP, -2.61 ± 1.27 mmol/l). Over the 24 h post-exercise period, participants spent less time at <3.0 mmol/l following HIIE than following CONT (after adjustment for carbohydrate intake and insulin doses) despite a lower dietary glycaemic load. CONCLUSIONS/

interpretationIn adults with type 1 diabetes, HIIE provides a greater training stimulus than iso-mechanical CONT while limiting the decline in capillary blood glucose during exercise and reducing exposure to clinically relevant hypoglycaemia during late recovery. Importantly, the protective effect of HIIE vs CONT against exercise-induced decrease in glucose levels was more pronounced in the PA than in the PP state, with HIIE performed in the PA state showing the smallest decreases.

trial registrationClinicalTrials.gov NCT07365176

fundingPlan d'investissement France 2030 DATA AVAILABILITY: The individual deidentified participant data and the datasets generated during and/or analysed in the current study are available on https://entrepot.recherche. DATA: gouv.fr/ platform ( https://doi.org/10.57745/YGYJSH ) with no time limit scheduled. The only restriction on the use of the data will be for commercial purposes.