A few weeks ago I posted a question asking whether getting the hands cold and stiff repeatedly causes irreversible damage.
No one answered. I've since had an opportunity to present the question to a university professor of physiology. He seemed quite competent in answering, and I have had trouble finding information with Google, so I thought I'd pass his answer on. The stiffness that we perceive in cold hands is mostly from two sources. The first is that the deep blood vessels expand to increase the supply of blood. The second is that the muscles are contracting in an effort to generate heat (this is somewhat like shivering). He said that the tissues are just fine after rewarming (assuming, of course, that the temperature stays well above frostbite level). To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html