Second Wind?

What I've noticed about myself during the last two of three races I've joined, is that the first 2 to 3 kilometers were the hardest for me. My breathing becomes more labored soon as I hit the 500 meter mark. Hula lang yung distance pero ganun na din yun. Then when I complete the first 2 or 3 kilometers, the rest of the way to the finish is evidently less difficult for me.

My guess is that through the initial two kilometers my body attempts to adjust to the effort, and as it does, I feel somewhat stronger throughout the rest of the 5K race. A lot of runners probably know this already, but it's a new and significant discovery for this newbie runner.

Image credit: Anonymous (meaning I forgot to look at the URL)