I can't disagree with Tom Beck, as we all have different bodies, and different ages, and different aches and pains. Nor can I suggest that his winter in the UK has been an easy one. But perhaps we each have different reactions to our local environments, and to the relatively fixed positions we take when playing an instrument.
Someone mentioned a "middle aged body" on this thread. I've got one of those, and in fact one that by most definitions is considered elderly (and it had a rather nasty session with a crippling case of polio in 1945, but seems to be doing alright). So far, since the beginning of December, I've shoveled out from two snowstorms of two feet each - then come back to temperate temperature. Tonight it is 5 degrees F. (minus 15 C.), four days ago it was 50 F. (10 C.), and it will be back and forth all winter. New Jersey is a lousy place to keep and instrument in tune, but luckily the human body is a bit more flexible than the wood of a harp or lute. If I have any suggestion to offer for those with aches and pains from either practice or play it would be this. Move a bit between pieces, scratch your cat if you have one - or scratch your knee if you are absent the feline companion. Break before you hurt, then you can do it very briefly. If you are performing be Italian and talk with your hand (while waving your arms) as you introduce the next piece. Best, Jon PS, if you don't have a friendly cat a hot water bottle can be a help. jwm