Influence of one bout of intensive running on lymphocyte micronucleus frequencies in endurance-trained and untrained men.

Exercise induced chromosomal damage was evaluated in trained and untrained subjects, who performed treadmill running at 85% of maximal oxygen uptake for 30 min. The subjects had their peripheral blood taken before, immediately after and 30 min after the running test for the analysis of lymphocyte chromosomal damage that was evaluated by micronucleus assay. The blood samples were also subjected to X-ray irradiation in vitro to examine the modification of exercise induced chromosomal damage by a secondarily induced oxidative stress. Spontaneous chromosomal damage in lymphocytes did not significantly increase at least until 30 min after the running both in the trained and untrained subjects. However, the X-ray-induced chromosomal damage was significantly enhanced at 30 min after the running in the untrained group, but not in the trained group. The ratio of X-ray-induced/spontaneous chromosomal damage also tended to increase after the running only in the untrained group. These preliminary results suggest that intensive exercise induced very slight chromosomal damage only in the untrained group, which could be intensified by the secondarily induced oxidative stress.