Morning (Fasting) vs Afternoon Resistance Exercise in Individuals With Type 1 Diabetes: A Randomized Crossover Study

Objective: To determine the effect of morning exercise in the fasting condition vs afternoon exercise on blood glucose responses to resistance exercise (RE). Research Design and Methods: For this randomized crossover design, 12 participants with type 1 diabetes mellitus [nine females; aged 31 +/- 8.9 years; diabetes duration, 19.1 +/- 8.3 years; HbA1c, 7.4% +/- 0.8% (57.4 +/- 8.5 mmol/mol)] performed similar to 40 minutes of RE (three sets of eight repetitions, seven exercises, at the individual's predetermined eight repetition maximum) at either 7 AM (fasting) or 5 PM. Sessions were performed at least 48 hours apart. Venous blood samples were collected immediately preexercise, immediately postexercise, and 60 minutes postexercise. Interstitial glucose was monitored overnight postexercise by continuous glucose monitoring (CGM). Results: Data are presented as mean +/- SD. Blood glucose rose during fasting morning exercise (9.5 +/- 3.0 to 10.4 +/- 3.0 mmol/L), whereas it declined with afternoon exercise (8.2 +/- 2.5 to 7.4 +/- 2.6 mmol/L; P = 0.031 for time-by-treatment interaction). Sixty minutes postexercise, blood glucose concentration was significantly higher after fasting morning exercise than after afternoon exercise (10.9 +/- 3.2 vs 7.9 +/- 2.9 mmol/L; P= 0.019). CGM data indicated more glucose variability (2.7 +/- 1.1 vs 2.0 +/- 0.7 mmol/L; P = 0.019) and more frequent hyperglycemia (12 events vs five events; P = 0.025) after morning RE than after afternoon RE. Conclusions: Compared with afternoon RE, morning (fasting) RE was associated with distinctly different blood glucose responses and postexercise profiles.