I paced my buddy who was doing a 2 mile AT run. He ran 14:42 and I ran 800, lap off, 800, 2 laps off, 400. The only reason I didn't do two laps on the last one was that my left foot cramped up. It didn't bother me at all on the much slower paced warm down. Not sure of the cause. I might have tied my shoelaces too tight.
Winning back pace is tough. I was never in oxygen debt but the effort was still a stretch.