Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C038

Oral Communications

Afternoon exercise is more efficacious than morning exercise at improving blood glucose levels in men with type 2 diabetes.

B. Gabriel1, M. Savikj1,2, J. Smith1, A. Krook1, J. Zierath1,3, H. Wallberg-Henriksson1

1. Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. 2. Faculty of Medicine, University of Oslo, Oslo, Norway. 3. Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.


Exercise is a recommended intervention for prevention and treatment of type 2 diabetes (T2DM). Low-volume High Intensity Interval Training (HIIT) remodels skeletal muscle and the cardio-respiratory system to a similar or greater extent than continuous moderate-intensity training, with reduced time commitment and exercise volume. Even though perturbed circadian rhythms are associated with metabolic dysfunction, time of day at which most robust adaptions to exercise can be achieved is unknown. We compared the efficacy of morning and afternoon HIIT in lowering blood glucose levels in participants with T2DM. Eleven men with T2DM underwent a randomized cross-over trial with either 2 weeks morning or afternoon HIIT (3 bouts/week), followed by a 2-week washout period and a subsequent period of the opposing training regime. Continuous glucose monitoring (CGM) based blood glucose levels were recorded throughout the study and hourly time-point means were compared. Blood samples were collected pre-training and after both training regiments.During week 1 of training, afternoon HIIT reduced CGM-based glucose levels as compared to either pre-training (mean change 0.9 mmol/l, p<0.05) or morning HIIT (1.1 mmol/l, p<0.05) at 4 and 10 time-points throughout the day, respectively. Conversely, during week 1 of training, morning HIIT increased CGM-based glucose levels as compared with pre-training (1.2 mmol/l, p<0.05) at 4 time-points throughout the day. During week 2 of training, afternoon HIIT reduced CGM-based glucose levels as compared to either pre-training (0.9 mmol/l, p<0.05) or morning HIIT (0.9 mmol/l, p<0.05) at 4 and 6 time-points throughout the day, respectively. Conversely, during week 2 of training, morning HIIT increased CGM-based glucose levels as compared with pre-training (0.9 mmol/l, p<0.05) at 2 time-points throughout the day. The elevated glucose concentration with morning HIIT persisted even into the subsequent days after exercise. Additionally, plasma T4 was decreased and TSH was increased following the training as compared with pre-training, suggesting a hormonal mechanism behind the differing responses, as these changes were potentiated following afternoon HIIT. Plasma triglycerides levels were elevated following morning HIIT as compared with pre-training, suggesting changes in fuel utilization with morning training. This was a field-based study in ‘free-living' individuals, thus the specific factors responsible for the differing blood glucose levels between morning and afternoon exercise remain to be elucidated. Afternoon HIIT is more efficacious than morning HIIT in controlling blood glucose levels in men with T2DM whereas morning HIIT may even be deleterious for optimal blood glucose control. Our data highlight the importance of optimizing the timing of exercise bouts to improve glycaemic control in people with T2DM.

Where applicable, experiments conform with Society ethical requirements