Effect of a single bout of morning or afternoon exercise on glucose fluctuation in young healthy men.

Yoshiaki Tanaka, Hitomi Ogata, Insung Park, Akira Ando, Asuka Ishihara, Momoko Kayaba, Katsuhiko Yajima, Chihiro Suzuki, Akihiro Araki, Haruka Osumi, Simeng Zhang, Jaehoon Seol, Keigo Takahashi, Yoshiharu Nabekura, Makoto Satoh, Kumpei Tokuyama

Journal: Physiological reports 2021;9(7):e14784

PMID: 33904659

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Plain Language Summary

Maintaining stable blood sugar levels is important for metabolic health, even in young and healthy individuals. Exercise is known to influence blood sugar regulation, but it is unclear whether the timing of exercise during the day affects blood sugar fluctuations. Because circadian rhythms [the natural cycle of physical, mental, and behaviour changes that the body goes through in a 24-hour cycle] influence metabolism, understanding whether morning or afternoon exercise produces different blood sugar responses may help optimise health recommendations.This randomised crossover trial aimed to investigate whether a single bout of moderate-intensity exercise performed in the morning (07:00) or afternoon (16:00) affects blood sugar fluctuation differently in young healthy men.

The results from the continuous glucose monitor showed that both morning and afternoon exercise influenced blood sugar patterns compared to the control condition. Afternoon exercise was associated with more stable blood sugar levels and reduced blood sugar variability indices compared to morning exercise. Morning exercise produced greater short-term fluctuations in blood sugar levels. However, overall blood sugar remained within the normal physiological range in all conditions.

The study concluded that the timing of exercise may influence daily blood sugar fluctuations in healthy young men, with afternoon exercise appearing to promote greater blood sugar stability. Healthcare professionals may use these findings to individualise exercise timing recommendations, particularly for individuals aiming to optimise metabolic control or prevent future blood sugar dysregulation.

Abstract

The timing of exercise plays an important role in the effect of the exercise on physiological functions, such as substrate oxidation and circadian rhythm. Exercise exerts different effects on the glycemic response to exercise and meal intake depending on when the exercise performed. Here, we comprehensively investigated the effects of the timing (morning or afternoon) of exercise on glucose fluctuation on the basis of several indices: glycemic variability over 24 h (24-h SD), J-index, mean amplitude of glucose excursions (MAGE), continuous overall net glycemic action (CONGA), and detrended fluctuation analysis (DFA). Eleven young men participated in 3 trials in a repeated measures design in which they performed a single bout of exercise at 60% of their maximal oxygen uptake for 1 h beginning either at 7:00 (morning exercise), 16:00 (afternoon exercise), or no exercise (control). Glucose levels were measured using a continuous glucose monitoring system (CGMs). Glucose fluctuation was slightly less stable when exercise was performed in the afternoon than in the morning, indicated by higher CONGA at 2 h and α in DFA in the afternoon exercise trial than in the control trial. Additionally, decreased stability in glucose fluctuation in the afternoon exercise trial was supported by the descending values of the other glucose fluctuation indices in order from the afternoon exercise, morning exercise, and control trials. Meal tolerance following exercise was decreased after both exercise trials. Glucose levels during exercise were decreased only in the afternoon exercise trial, resulting in less stable glucose fluctuations over 24 h.

Address: Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, Ibaraki, Japan.; Graduate School of Humanities and Social Sciences, Hiroshima University, Hiroshima, Japan.; International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki, Japan.; Department of Somnology, Tokyo Medical University, Shinjuku, Tokyo, Japan.; Department of Nutritional Physiology, Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama, Japan.; Faculty of Health Science, Tsukuba International University, Tsuchiura, Ibaraki, Japan.; R&D Center for Tailor-Made QOL, University of Tsukuba, Tsukuba, Ibaraki, Japan.

DOI: 10.14814/phy2.14784