Showers But Not Heaters
It won’t surprise most of us that showers and baths that stay just short of scalding will help, but it may be surprising that heaters aimed at only part of your body or that turn on and off every few minutes tend to make you feel locally colder.
Hot Shower or Bath
A hot shower is good for warming my capillarian blood for maybe an hour after I get out, long enough to get into bed and under my blanket. The shower is, I guess, about 110 to 120 degrees Fahrenheit, not hot enough to scald me but nice, for maybe 40 minutes. (Some health authorities prefer 140 degrees F. even with a risk of scalding, because the higher heat prevents a disease.) Even at night, I’m somewhat colder before the shower and warmer after I come out. And I like being warm. If I didn’t have other things to do and if no one else might need it, I might stay for an hour or more. (I did once for seven hours.) A hot bath would be the same, if you have a water heater for the tub turned on for the whole time.
What happens is that blood that’s warmed up in the skin gives off warmth throughout your whole body. Usually, blood is warmed by your large muscles, mainly in your chest. Actually, it doesn’t matter where your blood gets warmed, so long as it does.
Cold showers may have a different benefit, that of conditioning you to the cold outside. According to a very accomplished mountain climber, it’s helpful to spend two weeks preparing for a mountain climb by (among other things) taking showers that are, at first, a little bit cooler than the usual and then cooler each day until it's cold, but never ice cold. However, I don’t do this for city living in the winter. I’d rather have a warm shower.
Space Heaters and Radiators — Maybe Not
Heaters aimed at limited parts of your body (like a space heater under your desk) probably confuse your body. Radiators that cook only your legs are just as bad. So are hot plates (plus they’re dangerous when not watched). The contrast of cool to warm makes part of you feel cooler. You’re not warming enough of your blood. You’re probably better off without the thing.
Heaters that cycle on and off every few minutes probably overtax your body. I don’t think it can compensate for that in opposite ways every few minutes. Make the whole room warm or get warm clothes.
Get a sweater. If business demands a jacket and tie, get thick undershirts and put on a shirt and a suit jacket that are a little larger, snug but not tight.