Department of Physical Performance, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway.
Polar Electro Oy, 90440 Kempele, Finland.
Nutrients. 2023 Apr 18;15(8):1941. doi: 10.3390/nu15081941.
Caffeine reduces glucose tolerance, whereas exercise training improves glucose homeostasis. The aim of the present study was to investigate the effect of caffeine on glucose tolerance the morning after an acute bout of aerobic exercise. Methods: The study had a 2 × 2 factorial design. Oral glucose tolerance tests (OGTT) were performed after overnight fasting with/without caffeine and with/without exercise the evening before. Eight healthy young active males were included (Age 25.5 ± 1.5 years; 83.9 ± 9.0 kg; VO: 54.3 ± 7.0 mL·kg·min). The exercise session consisted of 30 min cycling at 71% of VO followed by four 5 min intervals at 84% with 3 min of cycling at 40% of VO between intervals. The exercise was performed at 17:00 h. Energy expenditure at each session was ~976 kcal. Lactate increased to ~8 mM during the exercise sessions. Participants arrived at the laboratory the following morning at 7.00 AM after an overnight fast. Resting blood samples were taken before blood pressure and heart rate variability (HRV) were measured. Caffeine (3 mg/kg bodyweight) or placebo (similar taste/flavor) was ingested, and blood samples, blood pressure and HRV were measured after 30 min. Next, the OGTTs were initiated (75 g glucose dissolved in 3 dL water) and blood was sampled. Blood pressure and HRV were measured during the OGTT. Caffeine increased the area under curve (AUC) for glucose independently of whether exercise was done the evening before ( = 0.03; Two-way ANOVA; Interaction: = 0.835). Caffeine did not significantly increase AUC for C-peptides compared to placebo ( = 0.096), and C-peptide response was not influenced by exercise. The acute bout of exercise did not significantly improve glucose tolerance the following morning. Diastolic blood pressure during the OGTT was slightly higher after intake of caffeine, independent of whether exercise was performed the evening before or not. Neither caffeine nor exercise the evening before significantly influenced HRV. In conclusion, caffeine reduced glucose tolerance independently of whether endurance exercise was performed the evening before. The low dose of caffeine did not influence heart rate variability but increased diastolic blood pressure slightly.
咖啡因会降低葡萄糖耐量，而运动训练则可以改善葡萄糖稳态。本研究的目的是探讨运动后第二天清晨摄入咖啡因对葡萄糖耐量的影响。
本研究采用 2×2 析因设计。受试者前一天晚上禁食后，在摄入或不摄入咖啡因以及运动或不运动的情况下进行口服葡萄糖耐量试验（OGTT）。纳入 8 名健康的年轻活跃男性（年龄 25.5±1.5 岁；体重 83.9±9.0kg；摄氧量 54.3±7.0mL·kg·min）。运动部分由 30 分钟 71%VO2 自行车运动和随后的 4 个 84%VO2 自行车运动的 5 分钟间隔组成，间隔之间有 3 分钟的 40%VO2 自行车运动。运动于 17:00 进行。每次运动的能量消耗约为 976 千卡。运动过程中，血乳酸增加至约 8mM。第二天早上 7:00 点，受试者空腹到达实验室。在测量血压和心率变异性（HRV）之前，先采集静息血样。受试者摄入 3mg/kg 体重的咖啡因或安慰剂（口感相似），30 分钟后测量血样、血压和 HRV。随后，进行 OGTT（75g 葡萄糖溶于 3dL 水中）并采集血样。OGTT 过程中测量血压和 HRV。
咖啡因独立于前一天晚上是否运动，均增加了葡萄糖耐量的 AUC（=0.03；双因素方差分析；交互作用：=0.835）。与安慰剂相比，咖啡因并未显著增加 C 肽的 AUC（=0.096），且 C 肽反应不受运动影响。前一天晚上的急性运动并没有显著改善第二天早上的葡萄糖耐量。OGTT 期间，咖啡因摄入后舒张压略有升高，而前一天晚上是否运动则没有影响。前一天晚上运动或摄入咖啡因均未显著影响 HRV。
总之，咖啡因降低了葡萄糖耐量，而与前一天晚上是否进行耐力运动无关。低剂量的咖啡因不会影响心率变异性，但会略微升高舒张压。
