DNA damage in peripheral blood leukocytes of physically active individuals as measured by the alkaline single cell gel electrophoresis assay.

DNA damage induced by physical activity and/or exercise has been reported under different conditions but not for individuals maintaining physical fitness by regular strenuous exercise. Therefore, we compared levels of DNA damage in blood leukocytes of 40 healthy individuals (35 males, 5 females) who regularly exercised in gymnasiums/health clubs and 15 healthy sedentary controls who had never exercised. The former group was selected (after informed consent) on the basis of how long they had been exercising on a regular basis as well as their exercise schedule and regimen. The length of time since starting a regular exercise regimen ranged from 2 months to 9 years, whereas the daily exercise duration ranged from 40 min to 3 hrs and warm-up sessions ranged from none to 90 min. The length of DNA migration (44.66 +/- 2.68 microm in males, 29.62 +/- 1.69 microm in females) and the percentage of cells with tails (79.86 +/-1.27% in males, 67.20 +/- 0.96% in females) in peripheral blood leukocytes of physically active individuals were increased significantly (P < 0.001) with respect to corresponding values in control males and females (18.85 +/- 1.79 microm, 23.37 +/- 3.94 microm; 24.50 +/- 1.98%, 33.00 +/- 4.44%, respectively). Highly significant differences for DNA damage were also observed between physically active males and females. These observations, in the absence of any other exposures, indicate a correlation between strenuous exercise to keep fit and increased levels of DNA damage. This finding may have relevance in terms of the ageing process, with diseases associated with aging, and with carcinogenesis.