I don't think I'd call it sexy. When someone makes something difficult look effortless I would call it graceful. I can appreciate grace without getting turned on. Ha!
Depends what they are doing?
Sexy? Hardly. Admirable? Extremely.
Mmmm, I like the way your fingers worked that keyboard when you effortlessly typed out this question. Those keys were naughty and deserved the spanking you just gave them.
What would be sexy about watching someone doing manual labor.
Down vote? Really?
Sexy? No, but I do get envious that they make it look so easy and I know better.
It can be, but it depends what it is. The sexiest thing I've seen in a woman is confidence, especially calmly and politely rejecting a guy who's hitting on her in a sleezy kind of way.