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Nils Haller, Suzan Tug, Sarah Breitbach, Arne Jörgensen and Perikles Simon

Purpose:

Increases in concentrations of circulating cell-free DNA (cfDNA) have recently been demonstrated to occur in a variety of exhausting and vigorous exercise settings. Here, the authors assessed the association of cfDNA with exercise duration and intensity in a controlled test–retest setting of a regenerative up-to-moderate-level aerobic run.

Methods:

In a pretest, the lactate threshold (LT) was determined in 13 participants (range 10.8–13.4 km/h) by using a step-wise incremental running test. The speed of the 2 endurance runs was set to 9.6 km/h for 40 min; for the participants with an LT below the median (12.8 km/h; G1), this was a moderate aerobic run, and for those with an LT above the median, this was a regenerative run (G2). Capillary cfDNA, lactate, and rating of perceived exertion (RPE) were assessed before, every 10 min during, and after the runs.

Results:

During the last 30 min of the 2 runs, lactate did not increase, whereas cfDNA increased steadily (3.46-fold for G1 and 2.05-fold for G2). Intraclass correlation for cfDNA was high (r = .81, P < .0001) for all runners but higher for male participants (r = .92, P < .0001). The correlations of cfDNA and lactate with RPEs were r = .58 (P < .0001) and r = .32 (P < .05), respectively.

Conclusions:

Both duration and level of intensity were significantly associated with accumulation of cfDNA. The correlation with RPE and the high test–retest reliability suggest that cfDNA might be applicable as a marker to monitor individual training load for aerobic and intermittent exercises. Future randomized, controlled, longitudinal training studies will have to reveal the full potential of cfDNA as an exercise-physiology marker.

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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.

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Pavel Dietz, Rolf Ulrich, Andreas Niess, Raymond Best, Perikles Simon and Heiko Striegel

Nutritional supplements (NS) are defined as concentrated sources of nutrients and other substances that have a nutritional or physiological effect and that are used in high frequency among athletes. The study aimed to create a prediction profile for young elite athletes to identify those athletes who have a higher relative risk for using NS. The second objective was to examine the hypothesis that the consumption of NS paves a gateway for the use of illicit drugs and doping substances. A self-designed anonymous paper-and-pencil questionnaire was used to examine the prevalence of NS consumption, doping, and illicit drug use in elite athletes with a mean age of 17 years (SD = 4 years). Logistic regression analysis was employed to assess whether NS consumption can be predicted by independent variables (e.g., biographical data, training characteristics, drug consumption behavior) to create the prediction profile for NS use. 55% and 5% of the athletes (n = 536) responded positively to having used NS and illicit drugs, respectively. Nutritional supplement consumption was positively correlated with age (OR: 1.92; CI: 1.21 to 3.05), the desire to enhance performance to become an Olympic or World Champion (OR: 3.72; CI: 2.33 to 6.01), and being educated about NS (OR: 2.76; CI: 1.73 to 4.45). It was negatively correlated with training frequency (OR: 0.55; CI: 0.35 to 0.86) and the use of nicotine (OR: 0.29; CI: 0.1 to 0.74) but did not correlate with illicit drug use and alcohol consumption. The present results show that NS are used on a large scale in elite sports. The prediction profile presented in this article may help to identify those athletes who have a high risk for using NS to plan potential education and prevention models more individually.