Agence Science-Presse (www.sciencepresse.qc.ca)
Runner’s toenail, tennis toe, black toenail: these expressions refer to the same phenomenon, not necessarily painful, but intriguing. And you don’t have to be a marathon runner to suffer from these, note the Rumor Detector and the Office for Science and Society of McGill University.
A black or deep purple toenail is common among those who run long distances or engage in intense physical exercise. That includes playing tennis, or also soccer or climbing. Websites devoted to sports or health say the same thing: there is no need to worry.
The Science of Toenails
Let’s first review what a healthy toenail is composed of.
Toenails and fingernails are composed principally of a protein called keratin. It’s the same material found in our hair, horses’ hooves, and dogs’ claws. A healthy nail is attached to our finger or toe by the nail bed, the skin underneath the nail plate.
Our body is constantly producing new keratin molecules at the nail matrix. This matrix is a layer of specialized cells at the base of the nail. When new keratin is produced the nail grows, which is why we have to trim our nails regularly.
At the base of the nail is a pale half-moon. We call that the lunula (from “luna”, which is Latin for “moon”). It is the visible portion of the nail’s matrix.
Blood Accumulation
The medical term for runner’s toe is a subungual hematoma. “Subungual” means “under the nail,” and “hematoma” means a pool of blood, an accumulation of blood due to a ruptured blood vessel. When we run, our nails bump against the top or sides of our running shoes. These repetitive shocks over long distances can cause blood vessels to rupture underneath the nail, and thus, a hematoma.
It’s a phenomenon similar to when you drop a heavy object on your toe and the nail turns purple. But when we run or do other physical exercise over a long period, the effect is stretched out over time.
When runners observe a purple or black toenail after a long week of training, what they’re really seeing is a collection of blood that has formed on the skin underneath the nail. Sometimes, if the hematoma is considerable, it puts pressure on the nail. The nail may detach from its bed. It will fall off, but this process can take weeks if not months. We can sometimes see a mini-nail where the nail has just detached. That’s a sign that the matrix has already begun producing new keratin under the detached toenail.
Runner’s toe isn’t the inevitable consequence of intense physical exercise. The effects can be reduced with larger running shoes, or above all, better adjusted shoes.
– This article is adapted from a text by Maya McKeown, published on the website of the Office for Science and Society of McGill University.
– Link to the original article: https://www.sciencepresse.qc.ca/actualite/detecteur-rumeurs/2024/09/10/courir-peut-noircir-ongles-orteil-vrai
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