The role of combined training timing strategies in mitigating the dawn phenomenon in older adults with type 2 diabetes in Nanjing, China: a randomized controlled trial

To evaluate the effectiveness of a novel periodic exercise protocol on the dawn phenomenon in Chinese patients with type 2 diabetes and examine the impact of different inter-cycle rest days. 93 participants in Nanjing, China (recruited from September 2023 to October 2023) were randomized into four groups for an intervention conducted from October 2023 to January 2024. Three intervention groups performed nine 5-day mini-cycles (90-min sessions of combined training) with inter-cycle rest days of 1, 2, or 3 days, respectively. Continuous glucose monitoring and lipid profiles were assessed pre- and post-intervention. 85 participants completed the study. All intervention groups showed significant improvements in glucose and lipid parameters ( P < 0.05). Dawn phenomenon decreased below 1.11 mmol/L in all exercise groups, with the 1-day rest group showing the earliest and most pronounced improvements and a continuous decline from cycles 4 to 9. The protocol effectively improved the dawn phenomenon and metabolic outcomes. Shorter inter-cycle rest days produced more sustained benefits, suggesting that glycemic improvements are influenced by homeostatic regulation. • Periodic exercise significantly reduced the dawn phenomenon in type 2 diabetes. • Shorter inter-cycle rest days yielded earlier and sustained glucose improvements. • All exercise groups showed significant glucose and lipid improvements over control. • The 1-day rest group demonstrated the greatest dawn phenomenon reduction. • Findings suggest a homeostatic ceiling effect in glucose fluctuation improvements.