The effects of 2 weeks of interval vs continuous walking training on glycaemic control and whole-body oxidative stress in individuals with type 2 diabetes: a controlled, randomised, crossover trial

Aims/hypothesis The aim of this study was to evaluate the effects of oxygen consumption-matched short-term interval walking training (IWT) vs continuous walking training (CWT) on glycaemic control, including glycaemic variability, in individuals with type 2 diabetes. We also assessed whether any training-induced improvements in glycaemic control were associated with systemic oxidative stress levels. Methods Participants (n=14) with type 2 diabetes completed a crossover trial using three interventions (control intervention [CON], CWT and IWT), each lasting 2 weeks. These were performed in a randomised order (computerised generated randomisation) and separated by washout periods of 4 or 8 weeks after CON or training interventions, respectively. Training included ten supervised treadmill sessions, lasting 60 min/session, and was performed at the research facility. CWT was performed at moderate walking speed (75.6% +/- 2.5% of walking peak oxygen consumption [VO2peak]), while IWT was performed as alternating 3 min repetitions at slow (58.9% +/- 2.0% VO2peak) and fast (90.0% +/- 3.6% VO2peak) walking speed. Before and after each intervention, the following was assessed: 24 h continuous glucose monitoring (CGM) and urinary free 8-iso prostaglandin F-2 alpha (8-iso PGF(2 alpha); a marker for oxidative stress), physical fitness and body composition. Neither participants nor assessors were blinded to the interventions. Results No intervention-induced changes were seen in physical fitness or body composition. Compared with baseline, IWT reduced mean glucose levels non-significantly (-0.7 +0.3 mmol/l, p = 0.08) and significantly reduced maximum glucose levels (-1.8 + 0.5 mmol/l, p = 0.04) and mean amplitude of glycaemic excursions (MAGE; -1.7 + 0.4 mmol/l, p = 0.02), whereas no significant within-group changes were seen with CON or CWT. Although 8-iso PGF(2 alpha) was associated with minimum glucose levels at baseline, no change in 8-iso PGF(2 alpha) was seen with any intervention, nor were there any associations between changes in 8-iso PGF(2 alpha) and changes in glycaemic control (p>0.05 for all). No adverse effects were observed with any of the interventions. Conclusions/interpretation Short-term IWT, but not CWT, improves CGM-derived measures of glycaemic control independent of changes in physical fitness and body composition in individuals with type 2 diabetes. Systemic oxidative stress levels are unaffected by short-term walking and changes in oxidative stress levels are not associated with changes in glycaemic control.