Of course, I don't need to describe what it is to stand up, what it looks like or what it feels like, but it makes me uncomfortable just writing scenes where this is going on; I'm inside the characters, you see, it doesn't matter what details of a scenario I actually need write about.
In real life, people have standing conversations all the time. I do that sometimes, like when I go to the door, someone's trying to sell me something and I'm too polite to interrupt. But my standing conversations are a bit like when Lara Croft is swimming underwater; as she steadily runs out of oxygen, so do my legs, and I can almost see the side bar filling with red (it's a very long time since I played Tombraider, so my memory may be wrong about what that gauge looked like). If I'm stood up when you're talking to me, I'm probably not listening.
And queuing. I find it distressing to even think about people standing in line and waiting for an indefinite period. Standing is generally a bad idea – when The Weakest Link first came on the telly I thought it a horrible quiz simply because everyone had to stand up – what a relief it must be if you were voted out.! Human beings evolved to walk on their hind legs, but I reckon we're simply not built for standing still. Personally, I wasn't even particularly good at standing still before I was ill; I could walk or swim, even run for miles (well, jog), but in the St. John's Ambulance Cadets we once had to stand to attention for about an hour for inspection and after about twenty-five minutes, I fainted (could have fainted in worse places; further injuries were sustained in the crush to put me into the recovery position).
As I've said, drawing attention to pain makes pain worse and on bad days, thus thinking about characters standing up for a long time makes things worse. But otherwise, I find that I make characters sit down sooner and for much longer than they really would. This isn't a big deal, but it has surprised me; I thought I was immune to this particular problem.
Authors don't do too badly writing about bodies that are different from their own, so long as they don't feel too different. The most recent example I came across was in a thriller where the hero had arthritis in his spine. From the acknowledgments, it became clear that the author's best friend had this condition (and was himself praised a hero of suffering so bravely) and the author had done a fair amount of research.
So, for example, there were worthy attempts at writing scenes of sexual tension whilst the hero has frozen vegetables stuffed down his trousers (inexplicably, this was the only relief the hero could obtain; nobody had suggested a cooling pack or gel; every night it was the frozen vegetables). And whilst I've known people with arthritis whose conditions vary significantly, well I've never know anyone who was curled up in pain one minute, then carrying a grown woman about in his arms, then writhing on the floor in agony, then having athletic sex with aforementioned damsel – the sort of sex which would be bad news for anyone's spine.
All this was happening from moment to moment and he spent a great deal of time in between moaning about how very miserable his life was – a mindless cycle of casual sex and frozen peas – with lots of statistics about arthritis that happened to come to the hero's mind:
The murdered man was said to have been worth twenty-one million dollars. Smith noticed that this number of dollars happened to coincide with the number of Americans living with osteoarthritis.(I exaggerate somewhat but it was quite bad).
It was an American novel, and of course this chap had missed out on a great sporting career when he started getting twinges in his back. There are lots of American heros in books and films who tragically missed out on a great sporting career; I guess it must be character-forming.