Elbows locked or arms too straight (perhaps too long a reach) was my first thought. Another reason, not fit or comfort related, to always ride with elbows bent (and if you are in the company of other cyclists) rotated out is that position puts yo in a far better place to absorb road shocks from things you didn't see and allows you to quite safely bump elbows with your neighbors. I try to align my handlebars with theirs. That way, even bumping HBs doesn't matter; they cannot get locked. I also keep in mind the concept of a firm grip on the bars (not a death grip!) and my arms relaxed.

This knowledge was passed veteran to rookie in my day. (Passed on like it really mattered; because those veterans didn't like crashing!) If everyone knows these rules, not only is accidental contact safer, you now have the option of moving other riders over when ou have to get around something. I once had to move two riders to get around a washed out pavement edge. I had been regularly pshngmy neighbor fo smaller washouts but this time I had to push him hard enough to move the next guy over. He didn't like it, but he knew why I was going it and since all three of us knew "the rules" it wasn't an issue.

Sadly, I rarely hear of these rules being passed on (except in velodromes).

Ben