What's the right way to trim your nails?
UK researchers have finally scratched the surface of the physics of fingernails!
The University of Nottingham-based team have come up with equations governing nail growth, revealing links between the way nails are cut and three common painful nail conditions.
Nails are subject to two main stresses - a growth stress and an adhesive stress - and it is when these are imbalanced that problems like ingrown nails, spoon-shaped nails and pincer nails can happen, says the paper "Physics of nail conditions: why do ingrown nails always happen in the big toes?" published in Physical Biology.
"An imbalance between the growth stress and the adhesion stress can lead to an excess of force," says Cyril Rauch, a physicist and applied mathematician, as well as the lead author of the paper, "which will have a tendency to buckle the nail plate."
The way that you cut your nails can reduce the likelihood of getting certain nail conditions continues Rauch. "If you imagine that you can take your nail out of your finger and put it on to your desk, then the edge that is curved has to follow a parabola."
In other words, the research suggests that your should model your nail on a U shape.
"We found that if the nail follows a parabola the likelihood of developing conditions in your nail that are related to an imbalance of growth and adhesive stress is nil."
A stress imbalance can happen in any fingernail or toenail, but the stress is larger for bigger nails that have flatter edges, which explains why the big toe is the most common location for an ingrown nail.
"The one thing that is completely different between the big toe nail and the other nails, is that the edge is incredibly flat," says Rauch. The flatter the nail the more likely that a stress imbalance will occur.
Listen to the full interview here