In pushing hard on the current project on deadline, I discovered the following:
It is possible to write so fast, so long, that you blister the heels of your hands, where you rest them on the "rest" of the keyboard.
The heel of the hand is useful for many things you might not notice until you have blistered one.
It's a combination of pressure sore and friction (the friction now being cured by a bandage on one and a hand towel on the keyboard.
And it continues to hurt after you put the bandage on. Not a bad hurt, particularly, but one of those insistent little "Hey--did you notice? Raw here? " sensations.
The story having gone pear-shaped more than once, I had to rip off body parts (of the story) and re-invent them, hence the frantic effort that resulted in another Perils of Writing Fiction (and you thought this was a sedentary life of ease, didn't you?)