Yes. I am THAT out of shape.
Just to clarify, I use my arms regularly. Really. But I guess they’re not used to having pressure against them, while pointed upward. HK, my dance partner, is a very strong lead, so when she wants me to turn, by golly, I turn. And when you have a solid frame, the pressure against your arms is pretty substantial.
Not a dancer? Can’t fathom how partner dancing can make your arms sore?
Okay, I give you homework!
Find a partner. Preferably someone taller and a bit bigger than you.
Stand, facing each other. Have your partner raise their left arm. You raise your left arm and put the fingers of your hand flat against the palm of their hand. Act like you’re going to walk to the left of your partner. Have them exert pressure, with their left arm, against your left hand.
Feel that? That’s leading and following. When you haven’t done that in 10 years, an hour of it will make you sore.
It’s a good kind of sore, though.