This was suggested to me by somebody and I do this if I have a big job to do, or I feel there is a danger of getting absorbed and unaware of time passing. Get an alarm clock and set it to ring in 20 minutes or half an hour or whatever. Leave the alarm clock somewhere where you HAVE to get up and walk to it to switch it off. When you switch it off reset it for another half hour or so. The only thing you have to watch is that the alarm does ring for a long time otherwise you are tempted just to let it stop by itself!
My Boss has been brilliant since I went back to work – he also now asks me to do jobs for him that require me to move from my desk and that also helps. I really don’t mind making tea and coffee or washing up even though there are more junior people to do that. I’ve always found heat better than cold for my hands but maybe that is just me.