I have spend many hours (days) at crazy low temp on mountains. I have spent many hours with my feet clipped into pedals despite no longer feeling that I have any feet at all. So......what’s the remedy?
I suffer from mild Reynauld’s and certainly from bad blood flow due to frostbite damage. So I have to take careful action.
The key thing in my view is not to say ‘my hands are cold so I need to make my hands warm’. That’s not right in terms of physiology really...what you want this to get the blood into your extremities. It is restricted by unsuitable bends in the body - at the ankle, at the wrist, and by restrictions such as over-tight shoes - the blood to the foot is carried over the arch in the main, and a restriction here can create real problems. But blood flow will be restricted by the body when it thinks ‘it’s cold outside’ and interestingly can reduce blood flow to hands and feet if your core is cold and your extremities are warm. The big thing is to get the core temp up, and then the blood flow really gets to the extremities. Before investing in hand warmers, get the angles right for your wrists, make sure the blood flow to your feet is not restricted, and really get your core temp up. This means layers, including merino wool, but with long zip which allow venting, to stop perspiration building up - that’s a real killer, chilling will occur really quickly. Idea is: temp up, sweat whicked away from the body. Job done.