June 2024

Reference: A. Marcotte-Chénard, R. Tremblay, L. Deslauriers, P. Geraldes, M. Gayda, D. Christou, W. Mampuya, J.P. Little and E. Riesco

Affiliations: Research Centre on Aging, CIUSSS de l’Estrie – CHUS, Sherbrooke, QC, Canada; Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke QC, Canada. Research Center of the CHUS, CIUSSS de l’Estrie – CHUS, Sherbrooke, QC. Faculty of medicine and health sciences, University of Sherbrooke, Sherbrooke, QC, Canada.

Take home message
  • A single session of low-volume high-intensity interval training (HIIT; 10 x 1-min) and high-volume HIIT (4 x 4-min) can acutely reduce blood glucose in older women living with type 2 diabetes.
  • Individuals with higher baseline glucose concentrations appear to experience additional improvements in glucose control and variability over a 24-hour period following HIIT.
  • High blood sugar levels as well as glycemic variability (i.e., defined as the fluctuation of blood glucose levels), are often observed in individuals living with type 2 diabetes and could be improved with exercise.
  • The most recent guidelines from Diabetes Canada suggest that HIIT could serve as an alternative to traditional moderate-intensity exercise.
  • One of the most widely used HIIT regimens in both the literature and clinical practice is the Norwegian protocol, involving 4 sets of 4-minute intervals at 90% heart rate max (HRmax) as well as the 10 sets of 1-minute at 90% HRmax regimen.
  • However, no study has yet investigated the effects of these protocols on glucose control and variability, particularly in older women living with type 2 diabetes.
How the study was done
  • A total of 14 older women living with type 2 diabetes (not treated with insulin) underwent three different conditions while wearing a continuous glucose monitor (CGM).
  • Cardiorespiratory fitness (VO2 peak) was measured at baseline, followed by 4-5 familiarization visits to determine the slope and speed needed to elicit 90% HRmax for each participant.
  • On separate days with at least 72 hours between sessions, participants completed a controlled seated condition, low-volume HIIT (10 × 1-minute at 90% HRmax), and high-volume HIIT (4 × 4-minute at 90% HRmax).
  • Glucose control and variability were assessed 24 hours after each condition, following the most recent international consensus statement for CGM use in clinical trials.
What the researchers found
  • Both low-volume HIIT (−2.1 ± 1.1 mmol/L) and high-volume HIIT (−2.1 ± 1.3 mmol/L) acutely (~60 min) reduced glucose compared to control (−0.7 ± 0.8 mmol/L), with no difference between exercise conditions.
  • However, this glucose-lowering effect did not persist over the 24-hour post-exercise period, as neither mean glucose nor glucose variability showed significant differences among conditions.
  • Individuals with less optimal glucose control (who had a higher blood sugar level during the control condition) had lower 24-hour mean glucose (7.4 [7.14–8.92] vs. 8.4 [7.5–9.9] mmol/L), glucose variability, and peak glucose following low-volume HIIT compared to control. Additionally, high-volume HIIT reduced time spent in moderate hyperglycemia compared to control.

A single session of low-volume and high-volume HIIT can acutely reduce blood glucose levels. However, the effectiveness of HIIT in improving CGM glucose variables over 24 hours seems to depend on baseline glucose control. Specifically, individuals with higher blood sugar levels appear to experience greater improvements in glucose control following exercise.