Effects of three consecutive days exercise on lymphocyte DNA damage in young men

Intense exercise affects the immune system. This study examines effects of three consecutive days of 1 h high-intensity exercise on lymphocyte counts, oxidative DNA damage, and apoptosis in young untrained ( n = 8, 23.8 ± 3.2 years; UT) and endurance-trained ( n = 8, 21.1 ± 3.7 years; TR) subjects. The subjects performed cycle ergometer exercise at 75% 1 h daily for three consecutive days (exercise session). Blood samples were collected before exercise on the first day of the exercise session (day 1, D1) and at 24 h after the session (day 4, D4). Total lymphocyte counts, a lymphocyte oxidative DNA damage index using Comet assay with human 8-oxoguanine DNA glycosylase, oxidative stress markers, and apoptosis markers were measured. Lymphocyte counts at D1 in TR were significantly lower than in UT. Lymphocyte counts in TR changed little at D4 (from 1,988 ± 475 to 1,854 ± 363 cell/μl), but the lymphocyte counts in UT decreased significantly at D4 (from 2,583 ± 564 to 1,911 ± 528 cell/μl, P