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Sarah Spengler and Alexander Woll


Little is known about the relationship between physical activity and health-related quality of life (HRQOL) in adolescents. The purpose of this study was 1) to quantify the predictive power of greater physical activity on higher HRQOL in adolescents and 2) to analyze whether the prediction is better for the sports club setting than for the leisure time setting.


Within the framework of the German Health Interview and Examination Survey for Children and Adolescents and the “Motorik-Modul,” 1828 German adolescents aged 11−17 years completed a questionnaire concerning the amount of weekly physical activity at school, in sports clubs, and during leisure time. The KINDL-R questionnaire was used to assess HRQOL. Linear and multiple regression analyses were used to analyze the effects of physical activity on HRQOL.


In regression analyses controlling for sociostructural variables, greater general physical activity was a significant predictor of higher HRQOL (P < .001). While greater physical activity in sports clubs significantly predicted higher HRQOL, greater physical activity during leisure time predicted higher HRQOL only to a certain level. Overall, the level of explained variance was low.


Being physically active especially in sports clubs is positively linked to higher HRQOL of adolescents.

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Stefan Altmann, Steffen Ringhof, Benedikt Becker, Alexander Woll, and Rainer Neumann

Purpose: To investigate if error-correction-processing (ECP) algorithms in timing lights are able to eliminate or reduce measurement errors (MEs) and false signals due to swinging arms or legs. Methods: First, a dummy was used to check if ECP generally works. Second, 15 male sport students performed sprints over 5 and 10 m. Timing lights with ECP and a high-speed camera as a gold standard were used to simultaneously capture the athletes when passing the timing lights at start, 5 m, and 10 m. MEs of the timing lights were calculated for hip and upper body. Results: The dummy condition revealed that ECP is able to eliminate MEs. In real sprint conditions, MEs were highest for timing light at start and when using the hip as a reference. Overall, out of 120 trials, only 4 false signals were not detected by ECP. They all occurred at the start timing light, with highest MEs being 0.263 s (hip) and 0.134 s (upper body). Regarding 5 and 10 m, all false signals were eliminated. Conclusions: As proven through video analyses, ECP eliminated almost all false signals. The largest MEs at the start timing light were associated with a distinct forward leaning of the athletes. Therefore, clear instructions concerning starting posture should be given to further improve measurement accuracy of the start timing light. This approach could also enhance comparisons between athletes. Nevertheless, based on the results, timing lights employing ECP can be recommended for measuring short sprints.

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Stefan Altmann, Rainer Neumann, Sascha Härtel, Alexander Woll, and Martin Buchheit

Purpose: To assess the value of monitoring changes in fitness in professional soccer players, using changes in heart rate at submaximal intensity (HR12km/h) over the velocity at a lactate concentration of 4 mmol/L (v4mmol/L). The authors reexamined (1) a range of threshold magnitudes, which may improve detecting substantial individual changes and (2) the agreement between changes in these 2 variables. Methods: On at least 2 occasions during different moments of the season, 97 professional soccer players from Germany (first, second, and fourth division) completed an incremental test to determine HR12km/h and v4mmol/L. Optimal thresholds for changes in HR12km/h and v4mmol/L were assessed, using various methods (eg, smallest worthwhile change + typical error [TE], successive reiterations approach). Agreement between both variable changes was examined for the whole sample (225 comparisons), 4 different subgroups (depending on the moment of the season), and in an individual over 6 years (n = 23 tests). Results: Changes of 4.5% and 6.0% for HR12km/h and v4mmol/L, respectively, were rated as optimal to indicate substantial changes in fitness. Depending on the (sub)groups analyzed, these thresholds yielded 0% to 2% full mismatches, 22% to 38% partial agreements, and 60% to 78% full agreements in terms of fitness change interpretation between both variables. Conclusions: When lactate sampling during incremental tests is not possible, practitioners willing to monitor adult professional soccer players’ (Germany; first, second, and fourth division) training status can confidently implement short, 3-minute submaximal runs, with 4.5% changes in HR12km/h being indicative of true substantial fitness changes, with 60% to 78% accuracy. Future studies should investigate the potential role of confounding factors of HR12km/h to improve changes in fitness prediction.

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Florian A. Engel, Stefan Altmann, Hamdi Chtourou, Alexander Woll, Rainer Neumann, Tomer Yona, and Billy Sperlich

Purpose: Replicating the studies of Gibson et al and Brownstein et al to assess performance, and physiological, and perceived variables during a repeated sprint protocol (RSP) with standardized versus self-selected recovery in youth soccer players. Methods: Nineteen male soccer players (age 13.1 [1.3] y) completed 2 separate RSPs. RSP1: 10 × 30-m sprints with 30-second recovery and RSP2: 10 × 30-m sprints interspersed with self-selected recovery periods. Mean time of both 10 × 30-m RSPs and self-selected recovery periods of RSP2 were assessed. Heart rate, blood lactate concentration, and rates of perceived exertion were measured following RSPs. Results: RSP2 revealed longer recovery periods (RSP1: 30.0 [0.0] s; RSP2: 39.0 [7.7] s; P < .001; effect size d = 1.648) with shorter repeated sprint time (mean 30-m sprint time: RSP1: 4.965 [0.256] s; RSP2: 4.865 [0.227] s; P = .014; d = 0.414). Blood lactate concentration (P = .002–.005; d = 0.730–0.958), heart rate (P < .001; d = 1.353), and rates of perceived exertion (RSP1: 14.9 [1.9]; RSP2: 12.9 [2.1]; P = .016; d = 1.046) were higher following RSP1. Conclusion: In contrast to the original studies, the present replication study demonstrated that self-selected recovery periods during a RSP leads to better repeated sprint performance compared with standardized recovery periods in youth soccer players. The better repeated sprint performance with individual recovery durations in RSP2 was achieved with less physiological and perceived effort.

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Yolanda Demetriou, Antje Hebestreit, Anne K. Reimers, Annegret Schlund, Claudia Niessner, Steffen Schmidt, Jonas David Finger, Michael Mutz, Klaus Völker, Lutz Vogt, Alexander Woll, and Jens Bucksch

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Marco Giurgiu, Carina Nigg, Janis Fiedler, Irina Timm, Ellen Rulf, Johannes B.J. Bussmann, Claudio R. Nigg, Alexander Woll, and Ulrich W. Ebner-Priemer

Purpose: To raise attention to the quality of published validation protocols while comparing (in)consistencies and providing an overview on wearables, and whether they show promise or not. Methods: Searches from five electronic databases were included concerning the following eligibility criteria: (a) laboratory conditions with humans (<18 years), (b) device outcome must belong to one dimension of the 24-hr physical behavior construct (i.e., intensity, posture/activity type outcomes, biological state), (c) must include a criterion measure, and (d) published in a peer-reviewed English language journal between 1980 and 2021. Results: Out of 13,285 unique search results, 123 articles were included. In 86 studies, children <13 years were recruited, whereas in 26 studies adolescents (13–18 years) were recruited. Most studies (73.2%) validated an intensity outcome such as energy expenditure; only 20.3% and 13.8% of studies validated biological state or posture/activity type outcomes, respectively. We identified 14 wearables that had been used to validate outcomes from two or three different dimensions. Most (n = 72) of the identified 88 wearables were only validated once. Risk of bias assessment resulted in 7.3% of studies being classified as “low risk,” 28.5% as “some concerns,” and 71.5% as “high risk.” Conclusion: Overall, laboratory validation studies of wearables are characterized by low methodological quality, large variability in design, and a focus on intensity. No identified wearable provides valid results across all three dimensions of the 24-hr physical behavior construct. Future research should more strongly aim at biological state and posture/activity type outcomes, and strive for standardized protocols embedded in a validation framework.