new paper on grip stiffness

journal.pone.0080889.g001Our paper on human grip stiffness was finally published in PLOS ONE. The related research, performed by Hannes Höppner, showed that there is a linear relationship between grip force F and grip stiffness k(F).  Meaning, when I grip twice as firmly, also the stiffness k(F) of my fingers goes up by a factor two: k(F) = c F.

This means that, in the end, the grip is twice as “stable”. Since, when the stiffness increases, the force \Delta F needed to move my fingers \Delta x away increases by that amount. I.e., \Delta F = k \Delta x.

This in itself is not a shocking result. It is arguably caused by the biomechanical structure of the fingers: the material (tendons, ligaments) that make out the movement and stiffness of our fingers have exponential properties. When you pull at these, the force you need to do so increases exponentially with the displacement. It is a simple mathematical equation to show that that means, that force and stiffness are linearly related.

But the paper shows more than this fact, which was previously discovered by other authors. It shows that, depending on the position of the wrist, you can influence the constant between force and stiffness.  In effect, we have a wrist position where our fingers are used optimally—and, as the paper shows, we exploit it!