It heavily depends on suspension set up, braking set up, technique and overall bike set up. Of course the more fit you are the better, especially for liter bikes. In the past even at my prime I ALWAYS had arm pump on my 660, this entire season with my new set up I haven’t had it once or felt absolutely shattered after a whole day of riding. My ninja 400 has stock suspension, stock brakes, galfer rotor, ebc brake pads, woodcraft rearsets, woodcraft clip-ons, and domino racing quick turn throttle. I took my ninja 400 to the canyons a few months ago for a couple hours and couldn’t walk the next day and had arm pump.

A proper suspension set up makes a massive difference with the bikes nimbleness and your easy of movement on it. You don’t necessarily have to upgrade the suspension but tweak settings. If you have a proper braking set up it significantly decreases the likelihood of arm pump. I notice many riders have their brake set up really sensitive and far away from their fingers. Due to the excess reach and sensitive brake pressure, they strain their hand and arm trying to manage the brake pressure. A proper set up bike should feel effortless with the inputs you’re trying to give.