Question: 

Increases of free circulating DNA (cirDNA) levels occur under strenuous exercise conditions in endurance and power athletes. To directly compare different exercise disciplines, standardized and controlled testing conditions need to be established. For the first time, we investigated the effect of an exhaustive cycling exercise on blood cirDNA levels.

Methods: 

10 B-level cyclists performed exhaustive incremental cycling tests under a standardized protocol before and after the competitive season. Venous blood samples were collected from the subjects before, immediately after and 90 minutes after the test. Blood plasma was separated from the cellular fraction via centrifugation and total cirDNA concentrations were measured by NanoDrop 3300 fluorospectrometer and by quantitative real-time PCR.

Results: 

Directly after the incremental cycling test, mean cirDNA concentrations were increased approximately six-fold in the blood plasma of the participants. However, cirDNA levels returned to baseline levels after 90 minutes of recovery.

Conclusions: 

Our results indicate that exhaustive incremental cycling tests can be an adequate method to measure the effect of exercise on cirDNA. Furthermore, we could show that both increase and decrease of the cirDNA level are rapid processes that have to be analyzed in detail in further studies. In addition, exhaustive incremental treadmill and cycling tests under similar conditions and testing the same subjects could be used to compare the impact of both test types on free circulating DNA levels in the blood plasma The increases induced by cycling exercise are approximately 25% lower compared to mean cirDNA changes measured in running tests in other studies.