White blood cell numbers increase during exercise and then decrease by 30-50% below pre-exercise levels for up to 6 hours post-exercise.

“White blood cell numbers have been shown to increase during acute bouts of exercise followed by rapid reduction in immune cell numbers, 30 to 60 minutes post exercise. The drop in immune cell number can be 30% to 50% less than pre-exercise levels and can last up to 6 hours.”