I've seen effect used by a number of photographers and although I'm not sure I like it, I'm interested in understanding how it was achieved.
As dpollitt suggests, this photographer has overcooked the local contrast in the midtones of their image. In Adobe speak, this is what the "clarity" slider achieves in Lightroom/Photoshop, and in more generic terms it is what you get if you apply a high pass filter to an image and perform low radius sharpening.
Here's an image I sourced through googling for "portrait" with zero, middling and maximum levels of clarity applied in Lightroom:
These are both higher than I would personally choose to boost local contrast, but this sort of look (often achieved with appropriate lighting as well as darkroom techniques) is certainly a popular one at the moment.