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Suzan Tug, Matthias Mehdorn, Susanne Helmig, Sarah Breitbach, Tobias Ehlert and Perikles Simon

Purpose:

Intensive exercise is known to be accompanied by a rapid release of cell-free DNA (cfDNA). The physiological significance of cfDNA release for performance diagnostics has not been studied. The authors analyzed the release of cfDNA during bicycle exercise and its correlation with physiological parameters.

Methods:

Eleven male athletes performed an incremental cycling test. Venous blood was collected before and immediately after exercise and after 90 min of recovery. Since the amount of cfDNA is influenced by preanalytical parameters like DNA extraction and quantification method, the authors applied different measurement approaches based on quantitative real-time polymerase chain reaction. They compared a direct measurement procedure not requiring cfDNA extraction for a short (L1PA290) and a long fragment (L1PA2222) and a procedure for extracted cfDNA for a short (LTR570) and long fragment (LTR5323) with primers targeting the repetitive sequences L1PA2 and LTR5 in both assays, respectively.

Results:

With the exception of LTR5323, the procedures revealed significant increases of cfDNA postexercise, whereas the direct approach showed lower interindividual variance in cfDNA values. When linking cfDNA levels to parameters of exercise performance the authors observed that, especially, the measurement based on L1PA2222 correlated significantly with exercise markers. These correlations were similar to the relationship of the performance markers among themselves.

Conclusions:

cfDNA is a possible physiological marker to assess and predict exercise performance in athletes. In addition, the results indicate that using cfDNA as a marker in exercise physiology requires careful selection of a suitable measurement technique, whether it is eluted DNA or directly quantified.

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Nils Haller, Tobias Ehlert, Sebastian Schmidt, David Ochmann, Björn Sterzing, Franz Grus and Perikles Simon

Purpose: Player monitoring in elite sport settings is becoming increasingly important. Questionnaire-based methods and biomarkers such as circulating, cell-free DNA (cfDNA) are suggested for load monitoring. cfDNA concentrations were shown to increase depending on total distance covered in football and were associated with overtraining in weight lifters. Thus, the objective of this study was to examine whether cfDNA is feasible as a monitoring tool in elite football players. Methods: Capillary blood samples from 22 male elite football players were collected over 4 mo of a regular season. Sampling was conducted the day before, 1 day after, or several days after regular-season games and/or training. In addition, each player filled in a visual analogue scale (VAS) questionnaire including the items “general perceived exertion,” “muscular fatigue,” and “mental fatigue.” Performance during training and games was tracked by the Catapult system and with the OPTA system, respectively. Results: cfDNA values were significantly elevated in players the day after regular-season games (1.4-fold; P = .0004) in line with the scores of the VAS. Both parameters showed significantly higher values during midweek-game weeks. cfDNA concentrations correlated with training data, and VAS was correlated with the tracking of the season games. However, cfDNA and VAS did not correlate with each other. Conclusions: cfDNA concentrations at rest and VAS scores are influenced by previous load in professional football players. Future studies will reveal whether cfDNA might serve as a practically applicable marker for player load in football players.