Role of exercise timing on health in prediabetes and type 2 diabetes
Creators: name: Remchak, Mary-Margaret Elizabeth
Publisher: name: No Publisher Supplied
Year: 2024

description: Type 2 diabetes (T2D) is associated with a 3-fold cardiovascular disease (CVD) mortality risk compared with healthy controls. It is estimated that 30 million adults in the United States have the disease. Circadian biology demonstrates that people tend to become glucose intolerant and insulin resistant into the evening compared with morning, whereas endothelial function tends to become better into the evening compared with morning. Yet, little is understood of the impact of the time of day that exercise is performed on both glucose tolerance and endothelial function in metabolically impaired populations. Recent findings suggest that acute exercise increases blood pressure similarly irrespective of exercise timing, but these studies have only been done in healthy populations. Conversely, higher intensity aerobic exercise performed later in the day may out-perform morning exercise in improving glycemic control in T2D. The present study sought to examine whether a 2-week high intensity aerobic exercise intervention (two bouts of 5 consecutive sessions, separated by a single rest day) performed in either the morning (MORN; 0600 – 1100) or afternoon (AFT; 1500 – 1900) affected cardiometabolic health parameters in a sample of adults with prediabetes and T2D. Additionally, explorative analysis of subjective and objective sleep parameters was performed to better understand the effect of exercise timing (MORN/AFT) on sleep health. All aims used data from the same sample and all analyses adjusted for baseline group differences in age and BMI. Aim I assessed whether high intensity aerobic exercise conducted during the afternoon (AFT; 1500 – 1900) would outperform work-matched morning exercise (MORN; 0600 – 1100) in improving glucose tolerance in individuals with prediabetes or T2D. No significant difference in glucose tolerance was observed. Aim II examined whether MORN improved post-prandial endothelial function compared to AFT in individuals with prediabetes or T2D. Exercise timing did not alter endothelial function, but afternoon exercise reduced blood pressure significantly more than morning exercise at 120 minutes post-glucose load. Aim III evaluated the relationship of exercise timing and subjective sleep quality in individuals with prediabetes or T2D. Secondary, explorative analysis was completed to characterize the influence of exercise timing on objective sleep duration and circadian alignment. Exercise timing did not significantly impact on subjective sleep quality. Further, no group difference in objective sleep period was observed. However, morning exercise did appear to promote a phase advance in melatonin onset, but these results need to be replicated prior to making strong conclusions. Taken together, the present study was inconclusive, but preliminarily suggests that morning exercise may be related to circadian alignment, while afternoon exercise may affect post-prandial blood pressure in this sample of people with prediabetes or T2D. Further studies with larger, more homogeneous samples are warranted, as is the use of validated objective sleep methodologies to understand the association of sleep and cardiometabolic health in metabolically-impaired populations.