This study aimed to examine the physical fitness (PF) levels of primary school children and to determine the associations among PF, concentration, and health-related quality of life (HRQOL) in a subcohort. PF was assessed in 6533 healthy primary school-age children (aged 6–10 years, 3248 boys and 3285 girls) via standardized test batteries. Concentration was measured with the d2-R test, and KINDL questionnaires were used to determine HRQOL. Analysis of variance showed an increase in PF with age in all PF dimensions (all p < 0.001), except cardiopulmonary fitness (estimated VO2max) in girls (p = 0.129). Boys performed better in nearly all PF dimensions, except curl-ups, in all children aged ≥7 years (p < 0.05). Concentration levels increased in boys and girls aged 7–9 years (p < 0.001), whereas HRQOL did not (p = 0.179). The estimated VO2max had a strong impact on concentration (β = 0.16, p < 0.001) and HRQOL (β = 0.21, p < 0.001) in 9- to 10-year-olds. Cardiopulmonary fitness is important for improved concentration and better HRQOL in primary school-age children. However, longitudinal data are needed to provide further insight into the intraindividual relationships of PF and concentration over the course of child development and set up targeted prevention programs.

Aerobic adaptations following interval training are supposed to be mediated by increased local blood supply. However, knowledge is scarce on the detailed relationship between exercise duration and local post-exercise blood supply and oxygen availability. This study aimed to examine the effect of five different exercise durations, ranging from 30 to 240 s, on post-exercise muscle oxygenation and relative changes in hemoglobin concentration. Healthy male subjects (N = 18) performed an experimental protocol of five exercise bouts (30, 60, 90, 120, and 240 s) at 80 % of peak oxygen uptake V . O 2 peak $$ \left({\overset{.}{\mathrm{V}}\mathrm{O}}_{2\mathrm{peak}}\right) $$ in a randomized order, separated by 5-min recovery periods. To examine the influence of aerobic fitness, we compared subjects with gas exchange thresholds (GET) above 60 % V . O 2 peak $$ \overset{.}{\mathrm{V}}{\mathrm{O}}_{2\mathrm{peak}} $$ (GET60+) with subjects reaching GET below 60 % V . O 2 peak $$ \overset{.}{\mathrm{V}}{\mathrm{O}}_{2\mathrm{peak}} $$ (GET60−). V . O 2 $$ \overset{.}{\mathrm{V}}{\mathrm{O}}_2 $$ and relative changes in concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, and total hemoglobin were continuously measured with near-infrared spectroscopy of the vastus lateralis muscle. Post-exercise oxygen availability and local blood supply increased significantly until the 90-s exercise duration and reached a plateau thereafter. Considering aerobic fitness, the GET60+ group reached maximum post-exercise oxygen availability earlier (60 s) than the GET60− group (90 s). Our results suggest that (1) 90 s has evolved as the minimum interval duration to enhance local oxygen availability and blood supply following cycling exercise at 80 % V . O 2 peak $$ \overset{.}{\mathrm{V}}{\mathrm{O}}_{2\mathrm{peak}} $$ ; whereas (2) 60 s is sufficient to trigger the same effects in subjects with GET60 + .

Oxidative stress is a key driver of endothelial dysfunction and early cardiovascular risk. Antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPX) are vital for vascular protection, especially during growth. While exercise-induced redox adaptations are well established in adults, data in pediatric athletes are limited. This cross-sectional study examined associations between training load and systemic antioxidant enzyme activity in 203 youth athletes aged 10–16 years, also considering sex, age, sports discipline, and redox phenotypes. Physical activity was assessed via validated questionnaires and expressed as weekly hours and MET-hours. Fasting blood samples were analyzed for SOD and GPX. Statistical tests included t-test, ANOVA, regression, and k-means clustering. Antioxidant enzyme levels were stable across training volumes, sports disciplines, and age groups. Boys showed significantly higher SOD than girls (259.43 ± 54.02 U/mL vs. 226.93 ± 48.22 U/mL, p < 0.001); GPX levels were similar between sexes. Cluster analysis identified three distinct redox profiles with differing training and sex distributions. No linear association was observed between training load and enzyme activity. Findings suggest that youth athletes exhibit robust antioxidant defenses, with individual and sex-related factors playing a more prominent role than training volume. These results highlight the value of regular physical activity for vascular health during development and the need for longitudinal studies to track redox adaptation.

Adolescence is a critical window for cardiovascular (CV) development, yet the molecular drivers of vascular adaptation to regular exercise in youth remain poorly understood. This cross-sectional study assessed vascular structure and function alongside endothelial, metabolic, and lipoprotein biomarkers in 203 healthy young athletes (aged 10–16). Vascular phenotyping included carotid intima-media thickness (IMT), pulse wave velocity, and carotid deformation indices (strain, strain rate). Circulating nitric oxide (NO), endothelin-1, free triiodothyronine (fT3), leptin, low-density lipoprotein, and high-density lipoprotein were analyzed. Associations were examined using hierarchically adjusted multivariable linear regression, mediation and moderation were tested and sex-stratified/matched analyses were conducted. While training volume was not associated with endothelial markers, leptin was correlated positively with NO and negatively with diastolic strain rate, suggesting dual vascular actions. fT3 was inversely associated with IMT, indicating a potential protective role in vascular remodeling. Lipoprotein profiles showed no independent associations with vascular parameters. Hemodynamic load, particularly systolic blood pressure, emerged as the dominant determinant of arterial stiffness. Sex-specific differences across biomarkers and vascular indices support a multifactorial model: in active youth, vascular phenotype reflects hemodynamics, body composition, and endocrine–metabolic signals more than training; longitudinal mechanistic studies should clarify causal pathways and guide individualized cardiovascular risk profiling.

Vasoactive molecules are central regulators of vascular tone, angiogenesis and inflammation. Key molecular agents include nitric oxide (NO), endothelin-1 (ET-1), prostacyclin, free triiodothyronine (fT3), leptin, low-density lipoprotein (LDL), high-density lipoprotein (HDL), superoxide dismutase (SOD), and glutathione peroxidase (GPX). Dysregulation of these compounds can lead to endothelial dysfunction, an early predictor of atherosclerosis and cardiovascular diseases (CVD). Maintaining endothelial health is thus essential for vascular homeostasis and cardiovascular risk prevention. Regular exercise serves as a vital protective measure against CVD and the risk of cardiovascular conditions. However, young athletes often significantly exceed recommended levels of training load, engaging in highly intensive training that leads to substantial physiological adaptations. Despite this, research on the impact of exercise on vasoactive substances in children and adolescents, particularly young athletes, is limited and inconsistent. Most studies focus on those with pre-existing conditions, like obesity or diabetes mellitus. Existing findings suggest exercise may favorably affect vascular biomarkers in youth, but methodological variations hinder consistent conclusions. This literature review examines 68 studies on the effects of exercise on vascular molecules in children and adolescents, young athletes, and children and adolescents with pre-existing conditions, offering deeper insights into how exercise may influence vascular health at the molecular level.

The prevalence of stress and burnout in higher education exceeds rates of the general working population, affecting students’ health and increasing university drop-out rates. Study engagement—a positive state of energy, dedication, and absorption—acts as a protective factor. A healthy lifestyle is neglected by many students, especially early in their studies. Since habits like diet, physical activity, weight management, and substance use impact mental health and resilience, their role in stress and burnout should be explored. In a cross-sectional online survey of 1955 German university students, sociodemographic data were collected and perceived stress, study engagement, and burnout were assessed. Associations with health habits, including diet, fitness, and tobacco and alcohol use, were examined. Physical activity was measured via the International Physical Activity Questionnaire, and alcohol consumption was measured via the Alcohol Use Disorders Identification Test. Among the students, 73.4% experienced moderate to high stress, with females reporting higher levels. Almost one-third had frequent burnout symptoms, while less than half (44.5%) reported high study engagement, with no sex differences. Active lifestyles, healthy diets, and fitness were linked to stress, burnout, and engagement. Perceived fitness and diet had the strongest associations with stress (d = 0.198–0.906), burnout (d = 0.277–0.483), and engagement (d = 0.218–0.272), while BMI (d = 0.089–0.186), sitting hours (d = 0.172–0.203), and physical activity (d = 0.096–0.141) played a comparatively minor role, regarding their small effect size. Personal habits are significantly linked to burnout and engagement, possibly by enhancing resilience. Health literacy regarding study demands is key for effective prevention and targeted student health management. More objective fitness data could further validate these findings.