I've found myself in a terrible mood following long runs recently. What could be the cause? From what I understand, if blood Ph level gets too out of whack, that could be a factor. I was also under impression that anaerobic running is mostly causes Ph level changes. My long runs have been easy pace. I have increased their duration 10% week over week. Last 3 runs have worked up from 93 mins, to 102 mins, to 112 mins.