It was 15 degrees on my workout this morning, which is a dip from previous weeks. I was just doing 2's and 4's on the track, a workout i've done fine in previous weeks. Today the 2's were fine, but the 4's were near impossible. Felt like the throat and lungs were just closing up on me. I had a hard time breathing after the 2's.
I had an extended warmup of 7 miles to help warm things up, but my throat and lungs just had a hard time with the hard running in the cold. I found this article, and thought it was interesting. Seems to relate. Then I decided to post a link here.
http://www.erj.ersjournals.com/cgi/reprint/12/4/825.pdf
I figured others might find it useful.