Winter Cycling - The science behind fingers and toe numbing?

I often overdress and arrive with my chest sweaty but fingers numb. How does the body determine when to shut off circulation to the extremities? Does it have temperature sensors at the fingers? Or are sensors all over the body?

Don't know exactly but I've heard people say that keeping your wrists warm helps keep your fingers warm too, which leads me to believe that temps at the wrist may impact blood flow to the fingers.

I'm not sure if you're actually losing circulation to your fingers and toes, its just that by the time the blood gets out there, its cold. Especially when its passing through the less insulated parts of your body like your shins and forearms.

Here ... read about the theory of the duck (under the Wool Sock section):
http://www.machka.net/whatworks/coldfeet.htm

Oddly enough, when I go out for a ride in the cold, my fingers start out hurting from cold, but after about 2 miles my body warms up enough that all finger coldness goes away. And I don't wear particularly thick gloves either

Oddly enough, when I go out for a ride in the cold, my fingers start out hurting from cold, but after about 2 miles my body warms up enough that all finger coldness goes away. And I don't wear particularly thick gloves either

I actually asked the Dr about that. Reason is (as explained) that your body restricts blood flow to protect the brain 1st and the core 2nd. Once your body recognizes that the head/core are warm it increases supply to the extremeties. Since the hands are smaller than the feet they're most suceptible.

I often overdress and arrive with my chest sweaty but fingers numb. How does the body determine when to shut off circulation to the extremities? Does it have temperature sensors at the fingers? Or are sensors all over the body?

Sounds like it's time for some experimentation. Try warmer gloves and a little less insulation on the core. This might send the signal to your brain to increase the metabolic process slightly.

Also, sometimes when I go out and am warmly dressed and wearing gloves, even warm ones, my fingers will feel a little bit cold. Some of this is just because your fingers don't have much ability to keep themselves warm. There are no muscles in your fingers and not much metabolic activity. So they don't generate as much heat as the rest of your body. So they need more insulation on them than you might think to keep warm.

I have a masters degree,...in science.

Scientifically, a large portion of the problem is that in Winter it is cold outside, and your fingers and toes stick way out into all that coldness. Other factors are also at play, but that is a big one.

jim

I think it's the fact that your fingers and toes are outside your body, not inside. Most of the time.

I have a masters degree,...in science.

Scientifically, a large portion of the problem is that in Winter it is cold outside, and your fingers and toes stick way out into all that coldness. Other factors are also at play, but that is a big one.

jim

+1 :)

Seriously here is what helped me a LOT the past few weeks:
I bought Climmits and Toe Clip coveres from http://www.sidetrak.com/eng_title.html. Total cost was just over $50 including shipping. I now ride in temps down to 12F with thin full fingered gloved that I used to only wear down to 55F. I no longer need my thick winter gloves. What's nice is that the extra body heat can leave my hands much better. Before my gloves (old pair of gortex ski gloves) would start to get clammy, expecially after a longer ride or temps in the high 30's. The toe clip coveres also do wonder for keeping the cold wind off my toes so that I have not had to use Winter boots or full covers until the temps drop in to the single digits. I don't mind using full shoe covers, but I figure that they would not last long when used with toe clips. During the Spring through Fall I'll use SPD pedals and highly venting cycling shoes (nicely prevents sweaty feet, but its impossible to keep my feet warm when you get to around freezing temps). Once the cold sets in during the Fall I'll switch to wearing hicking shoes. They are very comfy, and a lot warmer than my cycling shoes. The shoes are Merril Ventilators, so they are still designed primarily for getting rid of access foot heat, but so gar they work fine to about 12F with the toe covers.

Happy riding,
André