Rationale and protocol for the Time to Move Randomized Crossover Trial: morning versus evening time physical activity and CGM-assessed glucose levels in individuals with pregnancy hyperglycemia.

Background: For most patients with pregnancy hyperglycemia, treatment includes lifestyle behavioral counseling for a healthy diet and physical activity (PA). Outside of pregnancy, emerging evidence suggests that the timing of PA (e.g., in the morning vs. evening) may modify its glucose-lowering effects. PA is an evidence-based, non-pharmacological strategy for managing glucose levels, and recommendations for PA timing could improve glucose levels in individuals with pregnancy hyperglycemia. Objective: To describe the rationale and protocol of the Time to Move Randomized Crossover Trial, which evaluates the effects of morning vs. evening PA on glucose levels across the 24-hour cycle. Methods: The eligibility criteria include singleton pregnancies in patients aged 18-40 years, identified as having gestational glucose intolerance [(GGI), a non-fasted, 50-g glucose challenge test, 1-hour value ≥130 mg/dl] or gestational diabetes mellitus [(GDM), by the one- or two-step procedure, at ≥24 weeks]. Participants who provide consent are randomized to first perform either morning PA (between 5 a.m. and 9 a.m., within 30 min-40 min of starting breakfast) or evening PA (between 4 p.m. and 8 p.m., within 30 min-40 min of starting dinner). All PA episodes consist of 30 min of moderate-intensity walking or stepping. Participants ultimately contribute 2 days in each of the three treatment conditions: morning PA, evening PA, and no PA, with one washout day between treatment conditions. Timestamped glucose measurements are obtained using Dexcom G6 or G7 continuous glucose monitors (CGM). The primary analysis will be intention-to-treat; per-protocol associations will also be explored. PA adherence is assessed using ActiGraph PA monitoring devices (i.e., the CentrePoint Insight Watch, worn on the non-dominant wrist), which provide continuous timestamped estimates of movement. Participants upload photos (i.e., in real time) of all foods and beverages consumed throughout the study period, and the timestamps of these photos are used to identify postprandial periods. One 24-hour dietary recall, aided by photo uploads, is also completed for each treatment condition. Conclusions: The Time to Move Randomized Crossover Trial addresses the gap in scientific knowledge regarding whether the timing of PA may be leveraged to maximize glucose control in individuals with pregnancy hyperglycemia. Clinical trial registration: ClinicalTrials.gov, identifier NCT06125704.