Background/Objectives: Despite the publication of several systematic reviews on adolescent health literacy, comprehensive evaluations of the relationship between health literacy and health-related behaviors are still limited. This systematic review sought to synthesize and critically appraise the available evidence on associations between health literacy and health behaviors among adolescents. Methods. A systematic search of three databases (Scopus, PubMed, and PsycINFO) was conducted in accordance with PRISMA guidelines. Thirty-seven eligible cross-sectional studies were selected for qualitative synthesis. Methodological quality was evaluated using the Newcastle–Ottawa Scale adapted for cross-sectional studies. Results: The 37 included studies encompassed 71,558 adolescents (mean age range 11.0–17.0 years) and were conducted primarily in Europe (n = 22), with additional studies from the USA (n = 5), Asia (n = 8), and cross-cultural settings (n = 2). Across studies, 11 HL instruments were used (including two eHealth literacy measures), most commonly the Health Literacy for School-aged Children scale (n = 14). Physical activity (n = 22), nutrition-related indicators (n = 26), and smoking/alcohol/drug outcomes (n = 16) were assessed using heterogeneous operationalisations. Overall, higher HL was more often associated with healthier behavioral profiles, with more consistent patterns for nutrition-related outcomes. Findings for physical activity and substance use were more heterogeneous and, in some cases, varied depending on the HL measurement approach (subjective vs. objective) and the behavioral reference period. Conclusions: Current evidence indicates that higher health literacy in adolescents is generally associated with more favorable health behaviors, particularly regarding nutrition-related indicators. However, study heterogeneity and the predominance of cross-sectional designs limit comparability and causal inference. Future research should prioritize standardized measurement tools and longitudinal designs to clarify directionality and underlying mechanisms.

Background: Health literacy (HL) is an important element of public health that is linked to health behavior in children and adolescents. This study aimed to investigate the structural validity and reliability of the HLS₁₉-Q12 in the adolescent population, to measure the general HL of adolescents, and to assess the relationship between adolescents’ HL and health behavior. Methods: This cross-sectional study involved 825 students aged 15–19 years attending Lithuanian gymnasiums. The participants completed an online survey that collected information on key sociodemographic, HL, and health behavior indicators. Factor analysis, Cronbach’s alpha, and McDonald’s omega were used to validate the Lithuanian version of the HLS₁₉-Q12. Health behavior indicators, including physical activity, smoking, alcohol consumption, self-rated health, and body mass index (BMI), were measured. We used regression analyses to assess the associations. Results: The HLS₁₉-Q12 showed an acceptable reliability index (Cronbach’s α = 0.885, McDonald’s omega ω = 0.877) and adequate structural validity (comparative fit index = 0.89, Tucker and Lewis’s index of fit = 0.88, root mean square error of approximation = 0.06). We found that 67.1% of the adolescents had excellent or sufficient HL, 27.7% had problematic HL, and 5.2% had inadequate HL. Compared with girls, boys had greater HL. HL was positively related to physical activity and self-rated health and negatively related to alcohol use and smoking. Conclusions: HLS₁₉-Q12 is a reliable and valid measure of HL among adolescents in upper grades; higher levels of HL have been found to result in better health behaviors.

Background and Objectives: Cardiovascular diseases (CVD) are the primary causes of death throughout the world. Engaging in physical activity (PA) is crucial for the prevention of CVD, as a lack of exercise significantly impacts global health. For health promotion purposes, it is important to optimize PA and develop the main physical components. Multimodal exercise program (MEP) interventions cause unique cardiac changes that can be systematically analyzed using advanced ECG techniques. Using algebraic co-integration methods, this study examined the physiological cardiac adaptations of a 6-week MEP compared to sedentary control subjects. Materials and Methods: A total of 50 physically inactive males, aged 20–35 years, were recruited for a 6-week MEP. The intervention group (IG) consisted of 28 participants, while the control group (CG) included 22 participants. The MEP included balance, endurance, muscle strength, and flexibility exercises in one session. The cardiovascular system (CVS) was assessed using electrocardiography (ECG) and arterial blood pressure during an incremental cycle ergometer test, both before and after the 6-week period. Results: After the post-MEP, the IG’s resting HR showed a slight but insignificant decrease, from 84.5 to 82 bpm, with improved recovery rates at minute 1 (113.1–104.7 bpm). The CG showed a similar trend. pBP in IG significantly increased post-MEP during recovery at minute 1 (73–81) and minute 2 (65–72), where the CG showed a slight but significant difference. DskJT-QRS in IG post-MEP increased significantly during recovery in minutes 1–4, with all values showing p < 0.05. CG showed significance only at minute 3. Conclusions: Both the 6-week MEP and control had a positive impact on the CVS. The statement refers to changes in dynamic interactions between ECG parameters registered during the incremental exercise test and especially during the recovery after workload. Algebraic data co-integration analysis of ECG parameters demonstrated a sensitive assessment of the influence of exercising on the cardiovascular system.

Background: Health literacy, including its digital and vaccination-specific components, is essential for informed health decision-making in adolescence—a developmental period when health attitudes and behaviors are shaped and may persist into adulthood. Although the importance of these competencies is increasingly recognized, little is known about the relationship between digital health literacy (DHL) and vaccination literacy (VL) among adolescents. The aim of this study was to investigate the associations between DHL and VL among Lithuanian adolescents, and to evaluate the psychometric properties of the Digital Health Literacy Questionnaire (HLS19-DIGI) and the Vaccination Literacy Questionnaire (HLS19-VAC) in this population. Methods: A cross-sectional survey was conducted with 9–12 grades students from Lithuanian gymnasiums using HLS19-DIGI and HLS19-VAC instruments. Analyses included confirmatory factor analyses for validity, McDonald’s omega for reliability, ANOVA and chi-square tests for group comparisons, and linear regression to evaluate DHL—VL associations, adjusting for gender, grade, and frequency of digital resource use. Results: A total of 792 students (42.0% male; mean age 16.4 years) completed the survey. The HLS19-DIGI (CFI = 0.945, TLI = 0.923, RMSEA = 0.081) and HLS19-VAC (CFI = 0.986, TLI = 0.959, RMSEA = 0.089) showed satisfactory structural validity, and both scales had good reliability (0.757 and 0.803). Mean DHL and VL scores were 78.28 (SD = 24.24) and 82.64 (SD = 27.22), respectively. Over half of the participants had excellent DHL (55.7%) and VL (63.4%). DHL was a strong predictor of VL (β = 0.429, p < 0.001). The frequency of digital resource use was not significantly related to VL. Conclusions: Higher DHL is associated with higher VL, suggesting that skills in searching for, appraising, and applying online health information can enhance informed vaccination decision-making. Interventions delivered through trusted channels, such as schools and healthcare providers, should aim to strengthen both literacies, address misinformation, and foster critical evaluation competencies to support vaccine uptake in youth.

Background: The nation’s defense relies on a cadre of young individuals with strong physical and mental health. The study aimed to identify health behavior-related correlates of physical and mental health in future conscripts. Methods: This cross-sectional study comprised 676 male school students with an average age of 18.48 (1.15) years. The measures of weekly physical activity, nutrition (Kidmed questionnaire), psychological well-being (WHO-5 Well-Being Index), psychological distress (Kessler scale), cardiorespiratory fitness (20 m Shuttle Run test), weight, and height for calculation of body mass index were taken. Results: Among potential conscripts (17–19-year-old males), 22% have poor cardiorespiratory fitness. More than a quarter of young males have poor psychological well-being. Better cardiorespiratory fitness is related to more recommendations-adherent nutrition (Std β = 0.133 [0.03–0.14], p < 0.05). Engagement in sports is related to better cardiorespiratory fitness (Std β = 0.202 [0.10–0.30], p < 0.05). Higher psychological distress is associated with more time spent passively (Std β = 0.145 [0.12–0.34], p < 0.01); better psychological well-being is associated with more adherent nutrition (Std β = 0.172 [0.14–0.34], p < 0.0001), more hours accumulated in moderate-to-vigorous physical activity (Std β = 0.150 [0.30–1.10], p < 0.01), and less time spent passively (Std β = −0.131 [−0.34–−0.11]). Conclusions: Potential conscripts’ physical fitness and mental health are related to better health behaviors. Behavior change practices and policies applied at school could benefit potential conscripts and youth in general in terms of their physical and mental health.

Background: Health literacy is increasingly recognized as an essential determinant of health, readiness, and safety in the military, especially as health systems become more digitalized. However, evidence on general and digital health literacy in the armed forces remains limited. This study examined levels of general health literacy and digital health literacy among Lithuanian soldiers and explored their associations with sociodemographic, service-related, and health characteristics. Methods: A cross-sectional survey was conducted among 603 military personnel serving in the national armed forces. General and digital health literacy were measured with HLS19-Q12 and HLS19-DIGI. Data on sociodemographic and military characteristics, self-rated health, and self-reported long-term illnesses were collected. Descriptive statistics, correlation analyses, and multivariable regression models were used to analyze the data. Results: The sample was predominantly male (81.9%) with a mean age of 39.08 years (SD = 8.89). The mean general health literacy score was 80.1 (SD = 19.17), whereas the mean digital health literacy score was 67.81 (SD = 30.05). Overall, 45.0% of soldiers had excellent general health literacy, and 12.0% had inadequate general health literacy; 42.1% had excellent digital health literacy, and 35% had inadequate digital health literacy. Higher levels of health literacy were positively associated with better self-rated health and social status. No statistically significant associations were found between health literacy and gender, age, education, length of service, type of military service, and self-reported long-term health complaints. Conclusions: Military personnel in this study displayed relatively high general health literacy, yet digital health literacy was lower and more unevenly distributed, indicating a potential vulnerability for health outcomes as access to information, communication, and care increasingly relies on digital platforms. Given the cross-sectional design, causal inferences cannot be drawn. Military health services may build on existing health literacy strengths while considering strategies to address digital health literacy gaps (e.g., targeted training, tailored support, and user-friendly digital solutions, including service design), acknowledging that feasibility and implementation depend on organizational context and resources.