Even though the 20 percent rule is outdated, I think its vital we have some sort of 'rule'.
It is not as outdated as you may think, there was some more recent research that suggested that 20% was a comfortable load, however you can argue with the research for all sorts of reasons.
The huge trouble with all of this is that it is hard to set a rule where not one but two living people are involved. I know that there is an ongoing debate about the phrase 'riding light' but the fact remains that some people are easier to carry than others, due to all sorts of reasons, their coordination, balance, and skill level being the prime factors.
Also weight is deceptive, some people weigh a lot more or less than you think when you look at them, depending on how that weight is distributed. I also wonder when we are talking about weight if people judge differently when making distinctions.
This person is 5' tall and weighs 250 pounds
This person is 6' tall and weighs 250 pounds
Would they both get the same reception when they turn up to ride I wonder? Photos from My Body Gallery
Next question the 20% rule was set for horses working all day every day, does the same rule apply for a horse working an hour a day?
Do we say 21% you can't ride, but 20% you can go out and do a cross country course. Did you know BTW that we expect our soldiers to carry up to 45% of their body weight while marching?
Again I come back to if 20% is the norm, but we say that certain breeds are weight carriers what is their norm? Seeing as this thread was specifically about Arabians, and I have seen 25 - 30% mentioned for them, anecdotaly, but can find nothing to back this up.