Adrenaline rush in athletes: Visualizing glucose fluctuations during high-intensity races

Under stressful or exciting conditions, athletes can perform beyond their typical capabilities during a so-called "adrenaline rush." In the preliminary study by one sub-elite runner, we found that even in the fasted state, hyperglycemia occurs during high loaded running by the fact that both blood glucose and interstitial fluid glucose levels rose rapidly to 11-12 mM. This suggests that glycogen in the liver is degraded by anti-stress hormones, leading to an increase in glucose concentration. In the next, we analyzed the temporal changes in interstitial glucose concentration before, during, and after races using continuous glucose monitoring (CGM) data obtained from a total of 36 elite long-distance athletes including walking race (non-fasting state). We found that even healthy subjects recorded high glucose levels (mean 8.3 {+/-} 1.5 mM) before the start of the race and the glucose fluctuations during the race were also recorded at 11.2 {+/-} 2.2 mM, suggesting not only blood glucose level fluctuation due to supplementation before the races, but also due to the effects of stress hormones such as epinephrine, cortisol and glucagon. Furthermore, the mean glucose level during the daytime for the three days before the race event was significantly different by 0.3 mM (p<0.001) compared to the mean during the daytime for the three days after the race. These results suggested that efficient utilization of liver glycogen is important to keep high performance throughout the race, since the liver glycogen also consumed under stress.