Background: Previous studies have shown a high correlation between blood glucose (BG) and interstitial fluid glucose (ISFG). However, ISFG may better indicate overall glucose status than BG, which is strongly influenced by homeostatic mechanisms. We aimed to evaluate the relationship between BG and ISFG and to examine site-specific differences in ISFG by simultaneously measuring the ISFG in the leg and arm during running exercise, which transiently elevates BG.
Methods: Twelve adult women who regularly performed moderate-to-vigorous exercise were included. A lactate curve test was performed to determine the running speed in subsequent running tests. Continuous glucose-monitoring sensors were simultaneously attached to two sites on each subject's upper arm and thigh. BG was measured by fingertip blood sampling before, and every 30 min up to 120 min after running, with ISFG, also measured in the arms and legs.
Results: After high-speed running, BG rose transiently, and ISFG increased in both the arms and legs, similar to BG. The increase in BG and ISFG persisted for 15 min after running, with ISFG exhibiting a more pronounced elevation. There were no apparent changes in BG after low-speed running. However, the ISFG of the arms and legs increased compared to before running, with a more significant increase in the legs than in the arms.
Conclusion: This study revealed that the ISFG levels remain elevated, even when BG levels do not. Moreover, under conditions in which the BG is transiently elevated, the ISFG is elevated similarly, but the elevation persists longer in the legs than in the arms.