Circulation, Cell-free DNA for Monitoring Player Load in Professional Football.

PURPOSE:: Player monitoring in elite sports settings is becoming increasingly important. Beside questionnaire based methods, biomarkers, such as circulating, cell-free DNA (cfDNA) are sug-gested for load monitoring. cfDNA concentrations were shown to increase dependent on total distance covered in football and was associated with overtraining in weightlifters. Thus, the objective of this study was to examine whether cfDNA is feasible as a monitoring tool in elite football players.

METHODS:: We collected capillary blood samples from 22 male elite football players over 4 months of a regular season. Sampling was conducted the day before, one day after or several days after regular season games and/or training. In addition, each player filled in a Visual-Analogue-Scale questionnaire (VAS) including the items "general perceived exer-tion", "muscular fatigue" and "mental fatigue". Performance during training and games was tracked by the Catapult system (training) and with the OPTA system (games), respectively.

RESULTS:: cfDNA values were significantly elevated in players the day after regular season games (1.4-fold; p=0.0004) in line with the scores of the VAS. Both parameters showed sig-nificantly higher values during midweek game weeks. While cfDNA concentrations correlated with training data, the VAS was correlated with the tracking of the season games. However, cfDNA and VAS did not correlate with each other.

CONCLUSIONS:: Here we show that 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.