Just step down and lift your foot—and that's it: New shoes reveal your circulation [Health LAB]

[Financial News] Pressing the skin firmly and releasing it makes the blanched spot turn red again almost immediately. In hospitals, clinicians measure how long it takes for the color to return to check whether blood is flowing well all the way to the fingertips and toes. Now, however, shoes can perform this test simply by walking.
On the 15th, POSTECH (Pohang University of Science and Technology) said a research team comprising Professor Hwang In-seok, master's student Lee Gyu-sik, and Kang Dong-hyeon, a student in an integrated program, from POSTECH's Department of Computer Science and Engineering had developed CapWear, a smart shoe system that repeatedly monitors peripheral blood circulation during everyday walking. The findings are scheduled to be presented at ACM ISWC 2026 (International Symposium on Wearable Computers), an international conference in the field of wearable computing.
The time it takes for blood to refill skin after it has been pressed and for the skin to regain its original color is called capillary refill time (CRT). It is an indicator of how well blood is flowing to the body's extremities. The method is simple, but it has been difficult to use because someone has to press the skin directly and watch for the color to change.
The research team focused on people's “steps.” When people walk, weight is placed on the soles of their feet and then lifted off—a process much like the CRT test, in which the skin is pressed and released. In effect, each step could serve as a test.
CapWear brings this idea into a shoe. Beneath the heel is a small optical module equipped with a light, a compact camera, and a pressure sensor. The inside of a shoe is cramped and dark, making it difficult to capture images, but the module illuminates the skin at a consistent level so it can reliably capture even subtle color changes. The pressure sensor detects the moments when the foot touches the ground and lifts off. When the foot steps down, the skin on the heel is pressed and briefly turns pale; when the foot lifts, blood returns and the skin regains its color. CapWear analyzes this change to estimate CRT.
However, because the foot quickly touches the ground again while walking, the video that could be captured was only a little over a second long. That is barely enough time to watch the skin fully regain its color. The team addressed this by setting up separate measurement sessions that allowed them to observe the color-return process long enough, then building a personalized model using the CRT values obtained in those sessions. By accounting in advance for differences in each person's skin and blood-flow characteristics, the system can estimate CRT from just a short video.
The team also checked the accuracy. It compared CRT estimates from CapWear with measurements made directly by an emergency medicine clinician who reviewed videos of the heels, and found a strong correlation between the two, with a correlation coefficient of 0.71. The result shows that shoes can monitor blood circulation with every step, just as a pedometer counts steps.
Professor Hwang In-seok of POSTECH said, “This study demonstrates the possibility of naturally and repeatedly measuring capillary refill time while walking, without a separate measurement procedure,” and expressed hope that it “will develop into a healthcare technology that naturally and continuously monitors changes in peripheral perfusion associated with various diseases or health problems in everyday life.”
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