A small Danish study of patients with type 2 diabetes has shown that interval walking training has a beneficial effect on glycaemic control by increasing insulin sensitivity while maintaining insulin secretion.

Twenty men and 12 women, with type 2 diabetes of at least two years’ duration, took part in this open, randomised, partial crossover trial. Exclusion criteria included the use of insulin, weight instability, high levels of physical activity (> 150 min/wk), evidence of liver, renal or cardiopulmonary disease or of diseases precluding physical activity.

Participants were randomly allocated to a control group with no exercise intervention, a continuous walking training group and an interval walking training group. After completing the control programme, five patients were re-randomised to one or other of the active arms. This gave eight patients in the control group, 12 in the continuous walking group and 12 in the interval walking group.

The exercise sessions were 60 minutes long and for five days a week. Step recorders were used to ensure the amounts of exercise were equivalent in the two exercise groups.

VO2 max was used to demonstrate the increased aerobic intensity of the interval exercise training. Concordance with the exercise regimens was high. The study duration was four months.

Although HbA1c was measured, this was not the main outcome measure for the glycaemic control. The subjects underwent continuous glucose monitoring over 48 hours and had fasting insulin measurements. They were also tested with a hyperglycaemic clamp. This maintained the blood at a post-prandial level of glucose, and the further addition of a GLP-1 agonist infusion completed the simulation of the post-prandial state. Sophisticated biochemical testing (including biopsies of skeletal muscle) was performed to assay whether insulin signaling was having its effect on cell markers, and whether there were changes in mitochondrial metabolism.

Improvements in glycaemic control, measured by these detailed investigations, were only seen in the interval training group. In this group insulin secretion remained the same, but the sensitivity to insulin as measured by the fall in glucose rose by 49.8 ± 14.6%; P < 0.001, and the peripheral glucose disposal increased by 14.5 ± 4.9%; P < 0.05.

No changes were seen to suggest mitochondrial metabolism was altered, and the authors postulate that the improvements are the result of increased sensitivity to insulin in the interval exercise group.

The results must be interpreted with caution, because the study is small, and the lack of any improvement at all in the continuous exercise group is not consistent with other studies in the field. However, there has been considerable interest of late in the possibility that short bursts of higher intensity exercise are better than longer, lower intensity sessions, and this research adds weight to this.

In the future we will need to be more specific on the types of exercise regimens we recommend for patients to achieve the maximum benefit. In the meantime, I am still very happy to see any increase in activity levels at all in the majority of my diabetes patients.

Dr Matthew Lockyer