Water on porous, nitrogen-containing layered carbon materials: the performance of computational model chemistries.

Porous, layered materials containing sp2-hybridized carbon and nitrogen atoms, offer through their tunable properties, a versatile route towards tailormade catalysts for electrochemistry and photochemistry. A key molecule interacting with these quasi two-dimensional materials (2DM) is water, and a photo(electro)chemical key reaction catalyzed by them, is water splitting into H2 and O2, with the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) as half reactions. The complexity of some C/N-based 2DM in contact with water raises special needs for their theoretical modelling, which in turn is needed for rational design of C/N-based catalysts. In this work, three classes of C/N-containing porous 2DM with varying pore sizes and C/N ratios, namely graphitic carbon nitride (g-C3N4), C2N, and poly(heptazine imides) (PHI), are studied with various computational methods. We elucidate the performance of different models and model chemistries (the combination of electronic structure method and basis set) for water and water fragment adsorption in the low-coverage regime. Further, properties related to the photo(electro)chemical activity like electrochemical overpotentials, band gaps, and optical excitation energies are in our focus. Specifically, periodic models will be tested vs. cluster models, and density functional theory (DFT) vs. wavefunction theory (WFT). This work serves as a basis for a systematic study of trends for the photo(electro)chemical activity of C/N-containing layered materials as a function of water content, pore size and density.

Repeated Sprint Protocols With Standardized Versus Self-Selected Recovery Periods in Elite Youth Soccer Players: Can They Pace Themselves? A Replication Study.

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.

Soccer-Specific Agility: Reliability of a Newly Developed Test and Correlates of Performance.

ABSTRACT: Altmann, S, Neumann, R, Ringhof, S, Rumpf, MC, and Woll, A. Soccer-specific agility: reliability of a newly developed test and correlates of rerformance. J Strength Cond Res 36(5): 1410-1416, 2022-The purpose of this study was to examine the reliability of a newly developed soccer-specific agility test and to determine the correlation of different performance parameters with overall agility performance as measured by the total time. Twenty-two amateur soccer players (age, 25.1 ± 4.0 years) completed a newly developed agility test on 2 separate occasions. The test required the players to conduct 2 changes of direction, one in a preplanned manner and one in response to a stimulus that was provided by a live tester who performed different soccer-specific passing movements. Regarding reliability, very large Pearson's r and intraclass correlation coefficient values were obtained for the total time and the movement time, with moderate and large-to-very large values being evident for the response time and the decision-making time, respectively. The usefulness to detect moderate performance changes was rated as "good" for the total time, the response time, and the movement time. The decision-making time was rated as "OK." The movement time showed a very large relationship with overall agility performance as measured by the total time, while the response time and the decision-making time showed small to moderate relationships. In conclusion, the newly developed soccer-specific agility test is a reliable tool to assess the agility performance of soccer players and can be used by coaches and researchers to detect moderate performance changes. Because physical aspects, represented by the movement time, showed the greatest influence on total agility performance, they are advised to be included in soccer-specific agility training programs of amateur players.

Validity of Single-Beam Timing Lights at Different Heights.

Altmann, S, Spielmann, M, Engel, FA, Neumann, R, Ringhof, S, Oriwol, D, and Haertel, S. Validity of single-beam timing lights at different heights. J Strength Cond Res 31(7): 1994-1999, 2017-The purpose of this study was to quantify the effect of different timing light heights on sprint time and the validity of measurement. Two single-beam timing gate systems were used to measure 30-m sprint time (splits at 5 and 10 m) in 15 healthy and physically active male subjects. System 1 was set up at a height of 0.64 m and system 2 at 0.25 m (initial timing light) and 1.00 m (each following timing light), respectively. Participants performed 3 valid trials. The recordings of a high-speed video camera were used as a reference. Sprint times of system 1 and system 2 differed significantly between each other and from the reference system at all distances (p < 0.001). Intraclass correlation coefficients and Pearson's r values between both timing light systems and the reference system were low to moderate at 5 and 10 m and moderate to high at 30 m. Bland and Altman analysis revealed that the agreement intervals were considerably higher for the comparison between system 1 and the reference system than for system 2 and the reference system. A valid measurement of splits at 5 and 10 m via the systems used in this study is questionable, whereas 30-m times have an acceptable validity, especially when using system 2. This study confirms the influence of methodological approaches on sprint times. Coaches and researchers should consider that results gained by single-beam timing lights at different heights are not comparable.

Socially cued developmental plasticity in web-building spiders.

BACKGROUND: Socially cued anticipatory plasticity (SCAP) has been proposed as a widespread mechanism of adaptive life-history shifts in semelparous species with extreme male mating investment. Such mating systems evolved several times independently in spiders and male reproductive success should critically depend on timely maturation and rapid location of a receptive and, ideally, virgin female. We experimentally investigated socially cued anticipatory plasticity in two sympatric, closely related Nephila species that share many components of their mating systems, but differ in the degree to which male reproductive success depends on mating with virgin females. Juveniles of both species were reared either in the presence or absence of virgin female silk cues. We predicted strong selection on socially cued plasticity in N. fenestrata in which males follow a highly specialized terminal investment strategy, but expected a weaker plastic response in N. senegalensis in which males lost the ability to monopolize females. RESULTS: Contrary to our predictions, N. fenestrata males presented with virgin female silk cues did not mature earlier than siblings reared isolated from such cues. Males in N. senegalensis, however, showed a significant response to female cues and matured several days earlier than control males. Plastic adjustment of maturation had no effect on male size. CONCLUSIONS: Our results indicate that a strong benefit of mating with virgins due to first male sperm priority does not necessarily promote socially cued anticipatory plasticity. We emphasize the bidirectional mode of developmental responses and suggest that this form of plasticity may not only yield benefits through accelerated maturation, but also by avoiding costs of precipitate maturation in the absence of female cues.

Does a 20-week aerobic exercise training programme increase our capabilities to buffer real-life stressors? A randomized, controlled trial using ambulatory assessment.

PURPOSE: The cross-stressor adaptation hypothesis suggests that regular exercise leads to adaptations in the stress response systems that induce decreased physiological responses to psychological stressors. Even though an exercise intervention to buffer the detrimental effects of psychological stressors on health might be of utmost importance, empirical evidence is mixed. This may be explained by the use of cross-sectional designs and non-personally relevant stressors. Using a randomized controlled trial, we hypothesized that a 20-week aerobic exercise training does reduce physiological stress responses to psychological real-life stressors in sedentary students. METHODS: Sixty-one students were randomized to either a control group or an exercise training group. The academic examination period (end of the semester) served as a real-life stressor. We used ambulatory assessment methods to assess physiological stress reactivity of the autonomic nervous system (heart rate variability: LF/HF, RMSSD), physical activity and perceived stress during 2 days of everyday life and multilevel models for data analyses. Aerobic capacity (VO2max) was assessed pre- and post-intervention via cardiopulmonary exercise testing to analyze the effectiveness of the intervention. RESULTS: During real-life stressors, the exercise training group showed significantly reduced LF/HF (ß = -0.15, t = -2.59, p = .01) and increased RMSSD (ß = 0.15, t = 2.34, p = .02) compared to the control group. CONCLUSIONS: Using a randomized controlled trial and a real-life stressor, we could show that exercise appears to be a useful preventive strategy to buffer the effects of stress on the autonomic nervous system, which might result into detrimental health outcomes.

Different Starting Distances Affect 5-m Sprint Times.

The purpose of this study was to quantify the effect of different starting distances on 5-m sprint time and the accuracy of the initial timing gate. A single-beam timing gate system (1 m high) was used to measure 5-m sprint time in 13 male sports students. Each subject performed 3 valid trials for 3 starting distances: 0.3, 0.5, and 1.0 m from the initial timing lights, respectively. A high-speed video camera was used to track a reflective marker placed on the subjects' hip within a field of view around the initial timing gate. Accuracy of the initial timing gate was defined as the time between the initial timing light trigger and passing of the reflective marker by the initial timing gate. Sprint times were significantly faster for the 1.0-m starting distance (0.98 ± 0.06 seconds) than for the 0.5-m (1.05 ± 0.07 seconds) and the 0.3-m (1.09 ± 0.08 seconds) starting distances (p < 0.001). There were no differences in initial timing gate error between starting distances (p = 0.078). Hence, starting distance influenced sprint times but not the accuracy of the initial timing gate. Researchers and coaches should consider the effect of starting distance on 5-m sprint time and ensure consistent testing protocols. Based on the results of this study, we recommend a starting distance of 0.3 m that should be used for all sprint performance tests.

Adsorption and photocatalytic splitting of water on graphitic carbon nitride: a combined first principles and semiempirical study.

Graphitic carbon nitride, g-C3N4, is a promising organic photo-catalyst for a variety of redox reactions. In order to improve its efficiency in a systematic manner, however, a fundamental understanding of the microscopic interaction between catalyst, reactants and products is crucial. Here we present a systematic study of water adsorption on g-C3N4 by means of density functional theory and the density functional based tight-binding method as a prerequisite for understanding photocatalytic water splitting. We then analyze this prototypical redox reaction on the basis of a thermodynamic model providing an estimate of the overpotential for both water oxidation and H(+) reduction. While the latter is found to occur readily upon irradiation with visible light, we derive a prohibitive overpotential of 1.56 eV for the water oxidation half reaction, comparing well with the experimental finding that in contrast to H2 production O2 evolution is only possible in the presence of oxidation cocatalysts.

Assessing the usefulness of submaximal exercise heart rates for monitoring cardiorespiratory fitness changes in elite youth soccer players.

AIM: This study aimed to assess the value of monitoring fitness in elite youth soccer players (U15 to U19 age groups) by analyzing the concomitant changes in heart rate at submaximal intensity (HR12km/h) and the velocity at a lactate concentration of 4 mmol/l (v4mmol/l). METHODS: Players were tested by means of an incremental treadmill test on two occasions during the summer pre-season in two consecutive seasons. Based on data from a total of 170 test comparisons from the U15 (n = 48 test comparisons), U16 (n = 40 test comparisons), U17 (n = 46 test comparisons), and U19 (n = 36 test comparisons) age groups, the agreement between substantial changes in HR12km/h and v4mmol/l was analyzed using the threshold combination of HR12km/h = 4.5% and v4mmol/l = 6.0%. RESULTS: Results revealed 2% full mismatches, 36% partial agreements, and 62% full agreements for the whole sample in terms of fitness change interpretation between both variables. The respective values for the U15 to U19 age groups ranged between 0% and 5% full mismatches, 28-44% partial agreements, and 56-68% full agreements with no meaningful differences between age groups. CONCLUSION: In conclusion, our findings confirm the practical value of using HR12km/h to monitor fitness changes in elite youth soccer players when lactate sampling during incremental tests is not possible.

Acute effects of moderate vs. vigorous endurance exercise on urinary metabolites in healthy, young, physically active men-A multi-platform metabolomics approach.

Introduction: Endurance exercise alters whole-body as well as skeletal muscle metabolism and physiology, leading to improvements in performance and health. However, biological mechanisms underlying the body's adaptations to different endurance exercise protocols are not entirely understood. Methods: We applied a multi-platform metabolomics approach to identify urinary metabolites and associated metabolic pathways that distinguish the acute metabolic response to two endurance exercise interventions at distinct intensities. In our randomized crossover study, 16 healthy, young, and physically active men performed 30 min of continuous moderate exercise (CME) and continuous vigorous exercise (CVE). Urine was collected during three post-exercise sampling phases (U01/U02/U03: until 45/105/195 min post-exercise), providing detailed temporal information on the response of the urinary metabolome to CME and CVE. Also, fasting spot urine samples were collected pre-exercise (U00) and on the following day (U04). While untargeted two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) led to the detection of 608 spectral features, 44 metabolites were identified and quantified by targeted nuclear magnetic resonance (NMR) spectroscopy or liquid chromatography-mass spectrometry (LC-MS). Results: 104 urinary metabolites showed at least one significant difference for selected comparisons of sampling time points within or between exercise trials as well as a relevant median fold change >1.5 or <0. 6 ¯ (NMR, LC-MS) or >2.0 or <0.5 (GC×GC-MS), being classified as either exercise-responsive or intensity-dependent. Our findings indicate that CVE induced more profound alterations in the urinary metabolome than CME, especially at U01, returning to baseline within 24 h after U00. Most differences between exercise trials are likely to reflect higher energy requirements during CVE, as demonstrated by greater shifts in metabolites related to glycolysis (e.g., lactate, pyruvate), tricarboxylic acid cycle (e.g., cis-aconitate, malate), purine nucleotide breakdown (e.g., hypoxanthine), and amino acid mobilization (e.g., alanine) or degradation (e.g., 4-hydroxyphenylacetate). Discussion: To conclude, this study provided first evidence of specific urinary metabolites as potential metabolic markers of endurance exercise intensity. Future studies are needed to validate our results and to examine whether acute metabolite changes in urine might also be partly reflective of mechanisms underlying the health- or performance-enhancing effects of endurance exercise, particularly if performed at high intensities.

Daytime fluctuations of endurance performance in young soccer players: a randomized cross-over trial.

OBJECTIVES: Fluctuations of physical performance and biological responses during a repetitive daily 24-h cycle are known as circadian rhythms. These circadian rhythms can influence the optimal time of day for endurance performance and related parameters which can be crucial in a variety of sports disciplines. The current study aimed to evaluate the daytime variations in endurance running performance in a 3.000-m field run and endurance running performance, blood lactate levels, and heart rate in an incremental treadmill test in adolescent soccer players. RESULTS: In this study, 15 adolescent male soccer players (age: 18.0 ± 0.6 years) performed a 3.000-m run and an incremental treadmill test at 7:00-8:00 a.m. and 7:00-8:00 p.m. in a randomized cross-over manner. No significant variations after a Bonferroni correction were evident in endurance running performance, perceived exertion, blood lactate levels, and heart rates between the morning and the evening. Here, the largest effect size was observed for maximal blood lactate concentration (9.15 ± 2.18 mmol/l vs. 10.64 ± 2.30 mmol/l, p = .110, ES = 0.67). Therefore, endurance running performance and physiological responses during a field-based 3.000-m run and a laboratory-based test in young male soccer players indicated no evidence for daytime variations.

Using Submaximal Exercise Heart Rate for Monitoring Cardiorespiratory Fitness Changes in Professional Soccer Players: A Replication Study.

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.

Agility testing in amateur soccer: A pilot study of selected physical and perceptual-cognitive contributions.

The purpose of this study was to examine the relationships of physical and perceptual-cognitive factors with agility performance in amateur soccer players. Fifteen male amateur soccer players (age, 24.5 ± 1.9 years) completed a linear-sprint test with splits at 5 m, 10 m, and 30 m, a change-of-direction test of 12 m with 2 pre-planned directional changes of 45° at 2 m and 7 m, and a soccer-specific agility test with same movement pattern as the change-of-direction test but with the inclusion of a human stimulus performing passing movements. Additionally, the perceptual-cognitive deficit (agility performance minus change-of-direction performance) was calculated. In relation to agility performance, linear-sprint performance showed large relationships, which were higher with increasing sprint distance (5 m, r = 0.57; 10 m, r = 0.59; 30 m, r = 0.69), change-of-direction performance a very large relationship (r = 0.77), and the perceptual-cognitive deficit a large relationship (r = 0.55). The findings of this study highlight the relatively high contribution of both physical (i.e., linear-sprint and change-of-direction performance) and perceptual-cognitive factors (i.e., perceptual-cognitive deficit) in relation to soccer-specific agility performance at an amateur level. Consequently, such elements might be recommended to be included in training programs aimed at improving agility performance at this playing level. Moreover, the here introduced perceptual-cognitive deficit allows for a convenient and likewise thorough analysis of agility performance. Future studies should investigate the effects of both physically and perceptual-cognitive oriented training interventions on agility performance, which is considered a key element for success in soccer.

Standing Breaks in Lectures Improve University Students' Self-Perceived Physical, Mental, and Cognitive Condition.

While adolescents and adults should limit high levels of sedentary behavior, university students spend large amounts of time on sedentary activities. The aim of this study was to investigate the effect of this prolonged sitting on students' self-perceived physical, mental, and cognitive condition and to answer the question of whether simple standing breaks in lectures can help students improve these conditions and for example feel more concentrated, motivated, or less tense in class. A five-minute standing break was introduced using a designed presentation slide for one semester in five different 90-min lectures. In addition, an active break as well as an open break with no trigger were implemented in two further lectures to explicitly investigate the effects of a standing break. Before, during, and after the semester, the students were surveyed about their physical, mental, and cognitive condition (836 respondents at start, 634 during semester, and 528 at the end). To evaluate the practicality and acceptance of the standing break, lecturers were interviewed about their experience. At all survey time points, the standing break was highly accepted by the university students. About three quarters of the students felt a relaxation of the muscles in the neck and shoulder as well as in the back and the legs. More than three quarters perceived an increase in concentration, receptiveness and retentiveness, motivation, and well-being. Results of the statistical analysis indicate that a standing break as well as an active break are more effective than an open break to improve the self-perceived physical and psychological well-being of the university students. The increase in cognitive skills is reported by all groups, including the group who were offered open breaks. Hence, standing breaks in university lectures receive a high level of acceptance and practicability and have the potential to increase students' physical, mental, and cognitive condition and contribute to students' physical activity and health. While field research provides opportunities such as the testing of measures in the natural environment and producing real-life results relevant to the students and lecturers, it also imposes limitations as lecture settings differed, not all disturbances could be controlled, and the participation in the study might have led to social-desirability bias. For a sustainable development of a standing-friendly teaching and learning culture at universities, further interventions as well as the consideration of the topic in all processes and decisions within the universities are necessary. Since this study has taken place, student-life has changed drastically with COVID-19 measures. While this current paper is based on research conducted in 2019 and has only tested live lectures on campus, the tools tested could also be used for online lectures.

Sex-Specific Relationship between the Cardiorespiratory Fitness and Plasma Metabolite Patterns in Healthy Humans-Results of the KarMeN Study.

Cardiorespiratory fitness (CRF) represents a strong predictor of all-cause mortality and is strongly influenced by regular physical activity (PA). However, the biological mechanisms involved in the body's adaptation to PA remain to be fully elucidated. The aim of this study was to systematically examine the relationship between CRF and plasma metabolite patterns in 252 healthy adults from the cross-sectional Karlsruhe Metabolomics and Nutrition (KarMeN) study. CRF was determined by measuring the peak oxygen uptake during incremental exercise. Fasting plasma samples were analyzed by nuclear magnetic resonance spectroscopy and mass spectrometry coupled to one- or two-dimensional gas chromatography or liquid chromatography. Based on this multi-platform metabolomics approach, 427 plasma analytes were detected. Bi- and multivariate association analyses, adjusted for age and menopausal status, showed that CRF was linked to specific sets of metabolites primarily indicative of lipid metabolism. However, CRF-related metabolite patterns largely differed between sexes. While several phosphatidylcholines were linked to CRF in females, single lyso-phosphatidylcholines and sphingomyelins were associated with CRF in males. When controlling for further assessed clinical and phenotypical parameters, sex-specific CRF tended to be correlated with a smaller number of metabolites linked to lipid, amino acid, or xenobiotics-related metabolism. Interestingly, sex-specific CRF explanation models could be improved when including selected plasma analytes in addition to clinical and phenotypical variables. In summary, this study revealed sex-related differences in CRF-associated plasma metabolite patterns and proved known associations between CRF and risk factors for cardiometabolic diseases such as fat mass, visceral adipose tissue mass, or blood triglycerides in metabolically healthy individuals. Our findings indicate that covariates like sex and, especially, body composition have to be considered when studying blood metabolic markers related to CRF.

Endurance Capacities in Professional Soccer Players: Are Performance Profiles Position Specific?

The aim of this study was to investigate position-specific endurance performance of soccer players. 136 professional players competing in the 1st and 2nd division in Germany were divided into the positional groups goalkeepers (GK), central defenders (CD), wingers (WI), central midfielders (CM), and forwards (FW). All players performed an incremental treadmill test with blood lactate sampling until exhaustion with the following endurance parameters being obtained: Fixed aerobic threshold (v2mmol/l), fixed anaerobic threshold (v4mmol/l), individual aerobic threshold (vLT), individual anaerobic threshold (vIAT), and maximum velocity (vmax). Results revealed significant differences between GK and all outfield playing positions for all endurance parameters (p ≤ 0.03; ES 0.87-2.19). No significant differences among outfield playing positions were evident for any of the parameters. However, trends were found in favor of the CM compared to the WI (p = 0.11; ES = 0.68) and the FW (p = 0.06; ES = 0.47) relating to vLT as well as in favor of the CM compared to the WI (p = 0.10; ES = 0.56) relating to vIAT. Findings suggest that goalkeepers possess the lowest endurance capacity compared to other playing positions. While outfield players in general showed similar endurance performance, CM seem to possess the highest aerobic capacity of all positions as indicated by all lactate-based thresholds, however, with only small to moderate ES. These findings could lead one to question the appropriateness of current endurance training regimes to prepare all players adequately for their positional match-running demands. Indeed, endurance training of players should be specific to their match-running demands. However, it remains unknown to what extent these demands are position or player specific.

An NMR-Based Approach to Identify Urinary Metabolites Associated with Acute Physical Exercise and Cardiorespiratory Fitness in Healthy Humans-Results of the KarMeN Study.

Knowledge on metabolites distinguishing the metabolic response to acute physical exercise between fit and less fit individuals could clarify mechanisms and metabolic pathways contributing to the beneficial adaptations to exercise. By analyzing data from the cross-sectional KarMeN (Karlsruhe Metabolomics and Nutrition) study, we characterized the acute effects of a standardized exercise tolerance test on urinary metabolites of 255 healthy women and men. In a second step, we aimed to detect a urinary metabolite pattern associated with the cardiorespiratory fitness (CRF), which was determined by measuring the peak oxygen uptake (VO2peak) during incremental exercise. Spot urine samples were collected pre- and post-exercise and 47 urinary metabolites were identified by nuclear magnetic resonance (NMR) spectroscopy. While the univariate analysis of pre-to-post-exercise differences revealed significant alterations in 37 urinary metabolites, principal component analysis (PCA) did not show a clear separation of the pre- and post-exercise urine samples. Moreover, both bivariate correlation and multiple linear regression analyses revealed only weak relationships between the VO2peak and single urinary metabolites or urinary metabolic pattern, when adjusting for covariates like age, sex, menopausal status, and lean body mass (LBM). Taken as a whole, our results show that several urinary metabolites (e.g., lactate, pyruvate, alanine, and acetate) reflect acute exercise-induced alterations in the human metabolism. However, as neither pre- and post-exercise levels nor the fold changes of urinary metabolites substantially accounted for the variation of the covariate-adjusted VO2peak, our results furthermore indicate that the urinary metabolites identified in this study do not allow to draw conclusions on the individual's physical fitness status. Studies investigating the relationship between the human metabolome and functional variables like the CRF should adjust for confounders like age, sex, menopausal status, and LBM.

Stand Up, Students! Decisional Cues Reduce Sedentary Behavior in University Students.

Background: University students are prone to sedentary behavior (SB) which is associated with multiple negative health outcomes. Sit-stand desks may allow for a reduction of SB through standing bouts. To promote standing in university students, decisional cues might be a low-cost approach that can easily be implemented. Purpose: To investigate the effects of decisional cues on students' SB, standing, and active behavior. Method: Over 3 weeks, students were observed in a building on a German university campus, which provides sit-stand-desks in study areas, using an adapted version of the SOPLAY protocol. Baseline data was collected in the first week (T1), before posters and table plaques containing decisional cues were set up in the study areas. Effects were measured in the following 2 weeks (T2 and T3). Results: 2,809 (33% female) students were observed. Sitting decreased from 92.9% [SD = 14.9] to 84.5% [SD = 22.1] from T1 to T3 [F (1, 141) = 15.6; p < 0.01; η2 = 0.10]. Standing increased from 5.6% [SD = 13.5] to 10.9% [SD = 14.4] [F (1, 141) = 9.0; p < 0.01; η2 = 0.06] and being active from 1.5% [SD = 6.9] to 4.5% [SD = 14.8] from T1 to T3 [F (1, 141) = 4.2; p < 0.05; η2 = 0.03). Main effect analyses revealed more students standing in the afternoon compared to morning and lunchtime [F (2, 140) = 3.2; p < 0.05; η2 = 0.04). Discussion: Decisional cues could decrease students' SB and promote standing or being active as alternatives. Future research should use a more rigorous study design. The content of the decisional cues should be explored more and expanded to other health promotion areas on campus.

Validity and reliability of speed tests used in soccer: A systematic review.

INTRODUCTION: Speed is an important prerequisite in soccer. Therefore, a large number of tests have been developed aiming to investigate several speed skills relevant to soccer. This systematic review aimed to examine the validity and reliability of speed tests used in adult soccer players. METHODS: A systematic search was performed according to the PRISMA guidelines. Studies were included if they investigated speed tests in adult soccer players and reported validity (construct and criterion) or reliability (intraday and interday) data. The tests were categorized into linear-sprint, repeated-sprint, change-of-direction sprint, agility, and tests incorporating combinations of these skills. RESULTS: In total, 90 studies covering 167 tests were included. Linear-sprint (n = 67) and change-of-direction sprint (n = 60) were studied most often, followed by combinations of the aforementioned (n = 21) and repeated-sprint tests (n = 15). Agility tests were examined fewest (n = 4). Mainly based on construct validity studies, acceptable validity was reported for the majority of the tests in all categories, except for agility tests, where no validity study was identified. Regarding intraday and interday reliability, ICCs>0.75 and CVs<3.0% were evident for most of the tests in all categories. These results applied for total and average times. In contrast, measures representing fatigue such as percent decrement scores indicated inconsistent validity findings. Regarding reliability, ICCs were 0.11-0.49 and CVs were 16.8-51.0%. CONCLUSION: Except for agility tests, several tests for all categories with acceptable levels of validity and high levels of reliability for adult soccer players are available. Caution should be given when interpreting fatigue measures, e.g., percent decrement scores. Given the lack of accepted gold-standard tests for each category, researchers and practitioners may base their test selection on the broad database provided in this systematic review. Future research should pay attention to the criterion validity examining the relationship between test results and match parameters as well as to the development and evaluation of soccer-specific agility tests.

Short-term slackline training improves task-specific but not general balance in female handball players.

Slackline training has been shown to improve balance and neuromuscular performance. However, recent studies suggested that balance is task-specific, implying that transferability of balance skills is limited and might depend on the similarity of the tasks. This study therefore investigated if short-term slackline training could improve performance in balance tasks that are either more or less similar to the trained slackline task. Furthermore, we assessed potential transfer effects to other neuromuscular performance tests. 25 female handball players (23.7 ± 3.9 years) participated in our study and were matched to either a slackline training (SLT; n = 14) or a control group (CON; n = 11). The intervention comprised 12 sessions with overall 120 minutes of slackline training using single and double slacklines. Slackline standing time and measures of dynamic and static balance were assessed before and after the intervention, as well as power and sprint-related performance parameters. Two-way repeated-measures ANOVA found a significant group × time interaction for slackline standing time, indicating larger training effects for SLT. For the remaining dynamic and static balance tests, no significant interactions were found. With regard to neuromuscular performance, there was a significant group × time interaction only in change of direction. In essence, the study showed that slackline training induced task-specific balance improvements without affecting general balance. This adds further evidence to the task-specificity principle of balance, although the specificity of the sample as well as the briefness of the intervention should be taken into account when generalizing our findings. Nonetheless, this study contains practical implications for team sports interventions and future balance training studies, highlighting the importance of selecting appropriate balance exercises to yield rapid and the desired training outcomes.