This study aimed to investigate the changes in internal training intensity, well-being, and countermovement jump (CMJ) performance and to determine their relationship across five weeks of the pre-season training phase in professional soccer players. A total of 22 professional male soccer players (age = 21.7 ± 4 years, body height = 185.9 ± 6.3 cm, body weight = 79 ± 6.3 kg, BMI = 22.8 ± 1.4 kg·m⁻²; VO_2max = 52.9 ± 3.2) from the Croatian Second League voluntary participated in this study. The players spent 2230 ± 117 min in 32 technical/tactical and strength/conditioning training sessions, mostly at the low intensity zone (61%), and played 8 friendly matches at a high intensity (>90%). A one-way repeated measure of analysis ANOVA revealed a significant difference between weeks in CMJ performance (F_(1,22) = 11.8, p < 0.001), with CMJ height in weeks 4 and 5 being likely to very likely higher than that noted in week 1. Moreover, significant differences between weeks were found in all internal training intensity measures (average [F_(1,22) = 74.8, p < 0.001] and accumulated weekly internal training intensity [F_(1,22) = 55.4, p < 0.001], training monotony [F_(1,22) = 23.9, p < 0.001], and training strain [F_(1,22) = 34.5, p < 0.001]). Likewise, differences were observed for wellness status categories (fatigue [F_(1,22) = 4.3, p = 0.003], sleep [F_(1,22) = 7.1, p < 0.001], DOMS [F_(1,22) = 5.7, p < 0.001], stress [F_(1,22) = 15.6, p < 0.001]), mood [F_(1,22) = 12.7, p < 0.001], and overall well-being status score (F_(1,22) = 13.2, p < 0.001). Correlation analysis showed large negative correlations between average weekly internal training intensity and fatigue (r = −0.63, p = 0.002), DOMS (r = −0.61, p = 0.003), and WBI (r = −0.53, p = 0.011). Additionally, fatigue was significantly associated (large negative correlation) with accumulated weekly internal training intensity (r = −0.51, p = 0.014) and training strain (r = −0.61, p = 0.003). Small, but non-significant, correlations were found between CMJ performance and wellness status measures. These findings highlight the utility and simplicity of monitoring tools to improve athletes’ performance.

Soccer is a sport with worldwide popularity but has a substantial risk of injury. Clinical screening tools are an important factor in strategies of injury prevention. The purpose of the study was to examine the relationship between the Star Excursion Balance Test (SEBT) and injury and lower back pain (LBP) in amateur soccer players. The research was performed as a longitudinal cohort study on 42 amateur male soccer players with 15.8 ± 6.6 years of soccer playing (age: 25.5 ± 6 years). Participants were surveyed with regard to their soccer playing, injuries, and LBP, and the SEBT was performed. They were followed for 3.5 months. At the follow-up, an additional set of data regarding injuries and LBP was gathered. Significant differences were found in all directions and in the composite score of the SEBT between uninjured and injured players. Shorter distance in all directions and a lower composite score were associated with injury in general. Shorter distances in all but the anterior direction and a lower composite score were associated with lower extremity injury, and shorter anterior distance was associated with LBP. Amateur soccer players with lower SEBT scores are more prone to injuries in general, as well as injuries of the lower extremities. SEBT presents as a useful clinical screening tool in identifying amateur soccer players at risk of injury.

High-intensity 5 km running offers an ideal framework to analyze the organism's multidimensional responses. Since previous research primarily analyzed isolated aspects of fatigue, this study aimed to examine the integrated acute neuromuscular, metabolic, and perceptual responses to a 5 km run. Twenty-one recreational male runners participated. Pre- and post-race assessments included body composition, blood lactate, m. rectus femoris ultrasound thickness, quadriceps maximal voluntary isometric contraction (MVIC), heart rate, perceived exertion (Borg CR10), and 5 km finish time. Statistical analysis was performed in the Jamovi software,utilizing descriptive statistics, the Shapiro–Wilk test of normality, the Wilcoxon signed-rank test with effect size r calculation, and Spearman’s correlation coefficient, at a significance level of p < 0.05. Post-race measurements revealed a significant decrease in quadriceps MVIC (pre: 305.26 ± 98.83 N vs. post: 258.85 ± 88.47 N; p = 0.002) and an increase in blood lactate (pre: 0.81 ± 0.35 vs. post: 6.90 ± 1.44 mmol/L; p < 0.001), alongside high average heart rates (165 ± 16 bpm). However, ultrasound-assessed muscle architecture remained unchanged. The 5 km run induced pronounced neuromuscular and metabolic fatigue. Unchanged muscle architecture suggests that acute strength decline is primarily mediated by metabolic and neural mechanisms, rather than immediate structural-morphological factors.

High-intensity 5 km running offers an ideal framework to analyze the organism’s multidimensional responses. Since previous research primarily analyzed isolated aspects of fatigue, this study aimed to examine the integrated acute neuromuscular, metabolic, and perceptual responses to a 5 km run. Twenty-one recreational male runners participated. Pre- and post-race assessments included body composition, blood lactate, m. rectus femoris ultrasound thickness, quadriceps maximal voluntary isometric contraction (MVIC), heart rate, perceived exertion (Borg CR10), and 5 km finish time. Statistical analysis was performed in the Jamovi software, utilizing descriptive statistics, the Shapiro–Wilk test of normality, the Wilcoxon signed-rank test with effect size calculation, and Spearman’s correlation coefficient, at a significance level of p < 0.05. Post-race measurements revealed a significant decrease in quadriceps MVIC (pre: 305 ± 99 N vs. post: 259 ± 88 N; p = 0.002) and an increase in blood lactate (pre: 0.8 ± 0.4 vs. post: 6.9 ± 1.4 mmol/L; p < 0.001), alongside high average heart rates (165 ± 16 bpm). However, ultrasound-assessed muscle architecture remained unchanged. The 5 km run induced pronounced neuromuscular and metabolic fatigue. Unchanged muscle architecture suggests that acute strength decline is primarily mediated by metabolic and neural mechanisms, rather than immediate structural–morphological factors. These findings highlight the value of an integrated assessment approach for understanding acute fatigue responses following high-intensity 5 km running and may contribute to more precise training-load prescription and recovery monitoring in recreational runners.

The importance of physical activity, as one of the crucial resources for maintaining and improving physical health, was diminished during the Covid-19 pandemic. Except for the impact it has on physical health, physical activity may have various psychological benefits, especially during the development period of adolescence. The current findings of physical activity show that adolescents are more physically inactive during the pandemic than usual. Also, there are increasingly negative psychological outcomes in adolescents. The purpose of this study was to explore the levels of physical activity, negative affectivity, coping and preoccupation with the pandemic in an adolescent sample. The study involved 2409 adolescents (53.5% girls, 46.5% boys) from elementary and high schools aged 10 to 19. The Depression, Anxiety and Stress Scale (DASS-21) was applied, and information about levels of physical activity, coping and preoccupation with pandemic and isolation measures were collected. Participants answered on a Likert-type scale. Findings of this research show that on average male adolescents are more likely to engage in physical activities than females. Also, a relation of physical inactivity distress and preoccupation was obtained for adolescent girls. No similar finding was found for males. However, very high physical activity (five or more times a week) was a protective factor for coping and preoccupation with coronavirus infection. The conclusion of this research indicates that levels of physical activity have a different effect on male and female adolescents during the Covid-19 pandemic. It can be concluded that female adolescents that are less physically active are more at risk of depression, anxiety and stress.

Background and Study Aim. Physical activity contributes to physical and mental health, while body satisfaction and body appreciation are indicators of psychological well-being. Body image is shaped by multiple interacting factors. Despite the recognised role of physical activity in health promotion, its relationship with body image remains a subject of practical interest. The aim of this study was to examine the relationship between physical activity and body image among young adults, with particular attention to the role of body mass index and sex differences. Materials and Methods. The study included 720 university students from Croatia, Montenegro, Serbia, and Bosnia and Herzegovina, with a mean age of approximately 21 years. Data were collected using the International Physical Activity Questionnaire Short Form, the Body-Esteem Scale for Adolescents and Adults, and the Body Appreciation Scale. Body mass index was calculated from self-reported body height and body mass. Descriptive statistics, Pearson’s correlation coefficient, and the independent-samples t-test were used in the statistical analysis. Results. Body mass index was negatively associated with appearance satisfaction (r = −0.11; p < 0.01), weight satisfaction (r = −0.18; p < 0.001), attribution (r = −0.08; p < 0.05), and body appreciation (r = −0.26; p < 0.001). Associations between physical activity and the dimensions of body image satisfaction and body appreciation were generally very weak. Significant sex differences in favour of male students were found in body mass index [t(718) = 8.83; p < 0.001; d = 0.71], vigorous physical activity (t(718) = 6.82; p < 0.001; d = 0.54), moderate physical activity (t(718) = 5.05; p < 0.001; d = 0.40), and total physical activity [t(718) = 5.62; p < 0.001; d = 0.45]. Differences in body satisfaction dimensions and body appreciation were not significant. Conclusions. The findings indicate that a higher body mass index is associated with lower body satisfaction and lower body appreciation, whereas physical activity itself is not clearly associated with a more positive body image. These results confirm the complexity of the relationship between lifestyle behaviours and body-related perceptions in young adults. Health promotion programmes in student populations should therefore consider physical, psychological, and sociocultural aspects of health rather than focusing only on the level of physical activity.