As previous posters have said, you can't reasonably expect to change him. You can only change your behaviour. You can have a frank discussion about this annoyance, which can result in something productive, or him being defensive. You can let it fester and eventually snap at him. You can respond with annoyance every time, which will most likely cause hurt feelings for him. You can change your being into someone who can bolt up the stairs two at a time and lets out a "Yippeeki-A" at every speedbump, which doesn't seem particularly reasonable...
I bump into things a lot and I chatter to myself a lot. My husband "areyouokay-ed" me constantly (5-20 times a day) because of this. So annoying!. On the verge of snapping at him, I gave him a translation of what the various noises are:
Loud thump, no follow up cursing = I'm really hurt and come find me.
Loud or quiet thump or bang with follow up cursing or ouchies = I'm fine.
Low whispering, murmering, muttering, sighing, or grunting under my breath = If there's no way a reasonable person could expect to understand what I'm saying, you're not the intended audience, so mind your business. I'm talking to myself. I love you.
As for things like the stairs, I've done the same thing as your friend. From my end, I can say that "are you okay?" means "am I going to fast? Would you like me to slow down?" So, it's less of me thinking my friend is too slow, but more like my own pace may be inconsiderate and causing someone discomfort.