Brief summary: Intense, prolonged exercise causes a rise in WBC (leukocyctes) in order to promote tissue repair, but is then followed by a decline as the WBC move into the muscle tissue it is trying to repair. So intense prolonged exercise is no good if WBC are low anyway. Refers to a study done of prolonged marching for 16 hours! In 1987.
https://www.livestrong.com/article/480886-wbc-count-during-exercise/
