Unusually high levels of physical exertion do cause oxidative stress, but this does not result in any long-term damage to DNA. This is just one of the many outcomes revealed by an extraordinary research project funded by the Austrian Science Fund FWF that are now published. As part of this project, 42 male athletes took part both in a triathlon and an extensive biomedical study, which examined numerous physiological values parameters during the period from two days before to 19 days after the triathlon.
The range of personal views on the benefits - or otherwise - of physical activity covers everything from "sport is good for you" to "sport is a killer". From a scientific perspective, there is no doubt that regular sporting activity has physiological benefits, however, there is no such clear evidence of the benefits of extreme endurance sports. Indeed, there are indications that ultra distance runners, for example, may suffer increased health risks due to high oxidative stress. This generates aggressive oxygen radicals and metabolites which can damage cells and cell components. The question of whether this exercise induced stress also causes the DNA damage often observed as a consequence is now set to be answered by the Austrian Science Fund FWF project.
Cast Iron Science
The project comprised 42 male participants in the Ironman Austria competition. Of these, 24 participants were then used to investigate possible DNA damage. Head of the study, Prof. Karl-Heinz Wagner of the Department of Nutritional Sciences at the University of Vienna, comments on the results: "Reactive oxygen species lead to oxidative stress in the body which can also cause DNA damage. We were able to gather clear evidence of a short-term increase in certain indicators for oxidative stress during the competition and have already published these results. However, now we were also able to demonstrate that, despite this increase, no notable and persistent damage was caused to the athletes' DNA. This is a surprising result which initially appears to contradict the data gathered in similar studies."
Recently, other studies showed that runners in an ultra marathon experienced increased DNA damage during the race. This was also true of marathon runners immediately after the race. However, these studies did not consider competitions which required a period of physical exertion lasting longer than 8 hours, nor was data collected over such an extended timeframe as in Prof. Wagner's project. In total, the Austrian research team took blood samples from the triathletes at five different time points - 2 days prior to the race, then 20 minutes and 1, 5 and 19 days after the race.