In recent years, in Japan, the progression of locomotive syndrome and sarcopenia has become a serious social issue, leading to a decline in healthy life expectancy among older adults. Because of this, technologies that can visualize exercise load and muscle condition at the metabolic level and help control appropriate exercise intensity are becoming increasingly important. Creatine kinase (CK) is widely used as an indicator of muscle fatigue. In addition, recent studies have shown that blood uric acid levels are correlated with CK levels.
Based on this, we considered whether muscle fatigue and damage could be estimated from uric acid levels using our previously developed uric acid sensor. In this study, we first investigated whether uric acid levels in sweat correlate with those in blood. Human experiments showed a significant correlation between sweat and blood uric acid (correlation coefficient: r ≈ 0.69). Furthermore, cross-correlation analysis suggested that changes in sweat uric acid follow those in blood with a delay of about 3 minutes (lag ≈ 200 seconds).

These results were presented at the 42nd Symposium on Sensors, Micromachines and Applied Systems of The Institute of Electrical Engineers of Japan, under the title:
“High-sensitivity and continuous monitoring of sweat uric acid using a thread-driven capillary flow channel and a multi-walled carbon nanotube-modified electrode.”