I’ve seen photos of Muslims in prayer - knees on the floor, head bowed down all the way to the ground. That pose would be impossible for a Muslim who is old or infirm - are they just expected to do the best they can? Do they have to get like a special dispensation from a cleric to be excused from bowing down?
You don’t need “special dispensation”, it’s not Catholisim.
To answer your question, if illness or old age makes prostration difficult or impossible, then you might pray sitting down. In some mosques, I have seen people bring in portable chairs or stools.
The decision to do so is yours alone.
Even Catholicism is not totalitarian. If you are too infirm to kneel or stand during mass, you don’t need a dispensation frm the priest or bishop to remain seated.
I haven’t been to a lot of mosques, but if they are anything like catholic churches, there may be a mild taboo against doing the movements incorrectly, but there certainly is a very strong taboo against anyone telling anyone else that they’re doing it wrong. Especially if they are old and/or infirm. And that’s a religion with a head honcho who might reasonably make proclamations about such things.
Most religions use common sense for stuff like this rather than being very strict. Another example would be that pregnant women can eat during the day during Ramadan.
In addition to pregnant women, travelers, the ill, children, and anyone whose health would be endangered by fasting is also excused from the Ramadan fast.
There’s an Arabic phrase, I think it’s transliterated as “Insha’Allah”, that basically means “as Allah wills”. In this situation, if Allah willed this person to be too infirm to genuflect properly, then it’s his will and therefore, it’s okay.
By various accounts I’ve read, correct Islamic doctrine is sensibly tolerant of any adjustments that adherents need to make, according to their situation.
Another example, in addition to the above, is the requirement for all Muslims who are able to make the pilgrimage to Mecca.
I’ve worked with Muslims quite a bit. Once, when driving back from a meeting, I had an Egyptian General in my car. He mentioned to me that he had to pray; knowing the normal ritual, I asked him if he wanted me to stop somewhere. He said no, given the circumstances he would pray while we were driving, he just wanted to let me know why he wasn’t saying anything to me for a few minutes.
True gentleman, he was.
God doesn’t mind. If you can’t bow down, you can’t bow down.
Same with Ramadan. Nobody expects a small child or old or sick person to fast all day.
Another example is, if you’re in a town and everyone is praying in the wrong direction, you join with them and pray the same direction they are. The togetherness of the activity is more important than the exact direction of the qibla.
(Which can be pretty wide anyway; aiming in the correct quarter is good enough.)
Cause and effect are in play here. Someone who routinely kneels down several times a day can do so far into their later years.
Some adults haven’t actually sat on the ground since they were young kids. Kids are constantly sitting down, kneeling, crawling, and jumping. Adults seem to stop doing that stuff even by high school. No surprise that they find it difficult getting up and down in middle age. I’ve seen guys in their thirties at work groaning just getting up off the carpet after sitting down to connect some server wiring.
Muslim prayer, is also a work out. 
Yeah, I did not mean to cast aspersions on Catholicism and Catholics; I just said that since you often read about diispensations receieved to do something in Catholicism; typically a middle ages monarch to marry someone.
That’s not what the phrase means. That phrase is used when talking about something that might happen in the future, as in: I’ll be healthy next year, God willing.
Are you serious? A “mild taboo”? “Doing the movements”? A “very strong taboo”? I was raised Catholic in stricter times than these, and never saw or experienced any such thing.* And the Pope doesn’t care–I can guarantee that.
*Except in high school in the 1960s, the nuns would not let us sit with our legs crossed at Mass.
ETA: In Judaism, not only is a sick person not expected to fast on Yom Kippur, s/he is required not to. Health comes first.
Somehow, it’s comforting to know that Musilms have their fair share of obnoxious pedants who would get into a snit over something like this. "No! No! qibla is 1 degree further south!
There’s an App for it (of course there is) and I can just imagine a holy war starting between users of iphone and android apps showing different directions for the Qibla
You never experienced any what thing? The behavior (a Catholic telling someone how to pray correctly), or the taboo against it? You seem to be disagreeing with both sides of a “but,” which is hard to parse.
To be clear what mean is:
[ul]
[li]Person sitting in mass but not kneeling/standing when everyone else kneels/stands → “I wonder what his deal is” (especially if his deal is not obvious).[/li][li]Someone coming up to someone else and saying, “You should really be kneeling right now! Kneel damn it!” → “Wow! What a rude asshole!” (i.e. the person who spoke up, not the person who wasn’t kneeling).[/li][/ul]
This.
I have never experienced or seen anyone at Mass looking askance at someone sitting, standing, kneeling, or not, or any criticism of “doing the movements” correctly or otherwise. What the hell does “doing the movements” mean anyway? It’s not the Macarena, after all.
I recently had occasion to go to a Catholic funeral. I hadn’t been in a Catholic church in many years. I observed that some people now raise their arms at certain times (like during the “Our Father” aka “The Lord’s Prayer”). Some people did. Some people didn’t.
Of course, the ones who didn’t raise their arms, i.e., “do the movements correctly,” were dragged out by their hair and flogged on the front steps. When I left, someone was on Face Time with the Pope, and the congregants were piling straw around the offenders’ feet and bringing out the gasoline cans. Is that the kind of thing you’re talking about?