Glucose effectiveness, but not insulin sensitivity, is improved after short-term interval training in individuals with type 2 diabetes mellitus: a controlled, randomised, crossover trial

Abstract

Aims/hypothesis: The role of glucose effectiveness (SG) in training-induced improvements in glucose metabolism in individuals with type 2 diabetes is unknown. The objectives and primary outcomes of this study were: (1) to assess the efficacy of interval walking training (IWT) and continuous walking training (CWT) on SG and insulin sensitivity (SI) in individuals with type 2 diabetes; and (2) to assess the association of changes in SG and SI with changes in glycaemic control. Methods: Fourteen participants with type 2 diabetes underwent three trials (IWT, CWT and no training) in a crossover study. Exclusion criteria were exogenous insulin treatment, smoking, pregnancy, contraindications to structured physical activity and participation in recurrent training (>90 min/week). The trials were performed in a randomised order (computerised-generated randomisation). IWT and CWT consisted of ten supervised treadmill walking sessions, each lasting 60 min, over 2 weeks. IWT was performed as repeated cycles of 3 min slow walking and 3 min fast walking (aiming for 54% and 89% of V· O 2 peak, respectively, which was measured during the last minute of each interval), and CWT was performed aiming for a moderate walking speed (73% of V⋅ O 2 peak). A two-step (pancreatic and hyperinsulinaemic) hyperglycaemic clamp was implemented before and after each trial. All data were collected in a hospitalised setting. Neither participants nor assessors were blinded to the trial interventions. Results: Thirteen individuals completed all procedures and were included in the analyses. IWT improved SG (mean ± SEM: 0.6 ± 0.1 mg kg−1 min−1, p < 0.05) but not SI (p > 0.05), whereas CWT matched for energy expenditure and time duration improved neither SG nor SI (both p > 0.05). Changes in SG, but not in SI, were associated with changes in mean (β = −0.62 ± 0.23, r2 = 0.17, p < 0.01) and maximum (β = −1.18 ± 0.52, r2 = 0.12, p < 0.05) glucose levels during 24 h continuous glucose monitoring. Conclusions/interpretation: Two weeks of IWT, but not CWT, improves SG but not SI in individuals with type 2 diabetes. Moreover, changes in SG are associated with changes in glycaemic control. Therefore, increased SG is likely an important mechanism by which training improves glycaemic control in individuals with type 2 diabetes. Trial registration:: ClinicalTrials.gov NCT02320526 Funding:: CFAS is supported by a grant from TrygFonden. During the study period, the Centre of Inflammation and Metabolism (CIM) was supported by a grant from the Danish National Research Foundation (DNRF55). The study was further supported by grants from Diabetesforeningen, Augustinusfonden and Krista og Viggo Petersens Fond. CIM/CFAS is a member of DD2—the Danish Center for Strategic Research in Type 2 Diabetes (the Danish Council for Strategic Research, grant no. 09–067009 and 09–075724).