Aerobic exercise can decrease postprandial blood glucose responses in individuals predisposed to type 2 diabetes (T2D). Evidence indicates that daily diurnal rhythms exist in numerous physiological processes, including glucose metabolism. However, it is unclear whether the time of the day when exercise is performed differently affects postprandial glycaemic responses. We compared the acute effects of performing an aerobic exercise bout either in the morning or afternoon on postprandial blood glucose regulation.
Currently, 8 young adults (age: 24.6 ± 3.7 y, BMI: 29.2 ± 4.2 kg/m2) with a family history of T2D have undergone a two-day, randomised cross-over trial in which 30 min of moderate intensity cycling (65% of VO2peak) was performed at either 0800 h (AM condition) or 1600 h (PM condition) on day 1. Identical isocaloric breakfast, lunch, and dinner meals were provided at 0900 h, 1300 h and 1700 h, across the two laboratory visits with interstitial glucose measured from 0800 on Day 1 to 1630 on Day 2 using continuous glucose monitoring (CGM). Participants remained inactive throughout the laboratory visits.
The total area under the curve (AUC) for interstitial glucose was not different between conditions in the 24 h following each exercise bout (P = 0.50) or over the 33 h total measurement duration (P = 0.37). Additionally, the 3 h postprandial incremental AUC (iAUC) were not different following any of the standardised meals between the two conditions.
Preliminary data indicate no acute difference between the exercise performed in the morning and afternoon on postprandial blood glucose regulation. These data indicate that performing a single aerobic exercise bout in either the morning or afternoon impart similar effects on glycaemic control individuals with a family history of T2D.