Investigating the Impact of Time of Day on Glycaemia in Response to Postprandial Supramaximal Sprints in Adults With Type 1.

Objectives: In this study, we explore the impact of postprandial exercise timing (morning vs evening) on glycemia in individuals with type 1 diabetes (T1D) during short all-out sprints on a cycle ergometer.

Methods: Ten healthy, physically sedentary male (n=7) and female (n=3) volunteers with T1D, 22.8±2.8 years of age, and with a diabetes duration of 9.7±5.5 years and glycated hemoglobin level of 8.6±1.2%, underwent comprehensive screening and assessment of their physical health and fitness status before study participation, under the guidance of a physician. Each participant underwent 2 postprandial exercise sessions on separate days: the first in the morning at 8:00 AM and the second in the evening at 8:00 PM, both conducted 60 minutes after a standardized meal.

Results: Morning exercise showed a less pronounced reduction in plasma glucose (PG) levels compared with evening exercise (-2.01±1.24 vs -3.56±1.6 mmol/L, p=0.03). In addition, higher cortisol levels were observed in the morning vs evening (128.59±34 vs 67.79±26 ng/mL, p<0.001).

Conclusions: Morning repeated sprint exercise conducted in the postprandial state consistent with the protective effect of higher cortisol levels resulted in a smaller reduction in PG levels compared with evening exercise. This highlights the potential influence of exercise timing on glycemic responses and cortisol secretion in the management of T1D.