Background: Physical inactivity and sedentary behavior are associated with poor well-being in young people with adverse effects extending into adulthood. To date, there are many studies investigating the relationship between physical activity (PA) and posture, but there are no data on the relationship between the type and intensity of PA and sedentary behavior, their association with thoracic and lumbar spine angles, and with endurance and balance of the trunk muscles, especially in healthy young adults aged 18–25 years. Moreover, there are no data on the relationship between PA and sedentary behavior and musculoskeletal and cardiopulmonary health, as well as quality of life (QoL) and sleep that would provide a more comprehensive picture of physical health status. Aim: Therefore, the aim of this cross-sectional study was to investigate the extent to which PA and sedentary behavior are associated with each other and with changes in spinal curvatures, endurance and balance of trunk muscles in an extended analysis of physical health status in young adults aged 18–25 years by additionally including measures of body composition, cardiorespiratory capacity, and QoL and sleep. Methods: A total of 82 students (58% female, 42% male) aged 18–25 years completed all required tests. Primary outcome measures included the following: PA and sedentary behavior calculated from the long form of International PA Questionnaire (IPAQ-LF), spinal curvatures measured by a Spinal Mouse^® device, endurance and balance of the trunk muscles measured using trunk endurance tests and their ratio. Results: Overall, 50% of students were classified as minimally active and 50% as health-enhancing PA (HEPA) active. The angles of thoracic kyphosis and lumbar lordosis showed no correlation with PA or time spent sitting. However, students with the lowest PA had significantly higher scores on the trunk extensor endurance test and trunk extensor/flexor endurance test ratio, indicating imbalanced trunk muscles. Moreover, these students spent the most their time sitting. Only PA of vigorous intensity and PA during recreation, leisure, and sports significantly correlated with QoL related to physical health. QoL related to physical and psychosocial health had significantly higher scores when students spent less time sitting. In addition, we found significantly better respiratory performance and SQ at higher PA values, i.e., PA during recreation, leisure, and sport. Conclusions: Our results suggest that students with low PA levels and more time spent sitting have imbalanced trunk muscles, worse respiratory function, and poorer QoL and sleep. Moreover, these findings in college students may reflect their lifestyle and suggest that more PA needs to be promoted to prevent the development of chronic diseases including musculoskeletal disorders.

Background/Aim: University students are a particularly vulnerable population, as they spend increasing amounts of time sitting, which poses a major threat to their musculoskeletal health and posture. The aim of this cross-sectional study was to investigate gender differences in the relationships between physical activity (PA) and sedentary behavior, spinal curvatures and mobility, the endurance and balance of the trunk muscles, and the possible presence of non-specific low back pain (NS-LBP) in young adults aged 18–25 years. Methods: A total of 139 students completed all required tests. Results: Male students engaged in significantly more PA related to recreation, sports and leisure and were significantly more likely to be hyperkyphotic than female students. The more the male students participated in sports, the more pronounced the thoracic kyphosis. Female students had significantly more pronounced lumbar lordosis and anterior pelvic tilt that correlated with lumbar lordosis. Female students generally had significantly higher trunk extensor endurance and more balanced trunk musculature than males. NS-LBP correlated with PA in female students who generally had higher levels of NS-LBP than male students, with a statistically significant difference between those who practiced the most PA. Conclusions: Our results suggest that female students practice less PA and have pronounced lordosis and trunk extensor endurance, in contrast to males who practice more PA and have pronounced trunk flexor endurance and hyperkyphosis. Our findings suggest that more PA should be encouraged but implemented with caution and as an individualized gender-specific approach to prevent postural deformities and chronic musculoskeletal disorders, including NS-LBP.

Background: Fatigue can be a useful tool to understand the effects of physical activity (PA) and sedentary behavior on musculoskeletal health in university students. Methods: The aim of this cross-sectional study was to examine gender differences in the relationships between fatigue and specific types and levels of PA, posture, sleep quality (SQ), and non-specific low back pain (NS-LBP) in young adult university students aged 18–25 years. A total of 180 students completed all required tests. Results: Female students had higher total fatigue as they generally engaged in more PA in contrast to male students, who had higher total fatigue when they engaged in less moderate and less vigorous PA. With increasing sedentary behavior, overall fatigue was pronounced in both sexes, although female students spent significantly more time sitting. Poorer SQ correlated with NS-LBP and higher levels of sleep-related fatigue in female students. Males with pronounced hypekyphosis and females with pronounced lordosis were more fatigued. In addition, fatigue was more pronounced in female students with a higher extensor/flexor ratio, suggesting that trunk extensors are more fatigued due to the need to maintain lumbar spine stability. Conclusions: Our findings suggest that the choice of PA should be gender-specific to prevent chronic musculoskeletal disorders and fatigue in young adult university students.

Comprehensive data on sagittal spinal alignment, regional mobility, trunk muscle strength and imbalances in 9–11-year-old children participating in intensively organized sport (IOS) are limited. This cross-sectional study evaluated the association between IOS participation and the aforementioned postural parameters, compared with a non-intensive comparison cohort. A total of 143 children were included (IOS: n = 66; controls: n = 77). Sagittal spinal curvatures (thoracic kyphosis and lumbar lordosis) and regional mobility were assessed using Spinal Mouse^®, software-generated sagittal spinal curvature and trunk muscle imbalance profiles were assessed using Moti Physio 3D system, and absolute trunk muscle strength was measured using a K-Push dynamometer. Statistical analyses included multivariable ANCOVA, multivariable ordinal logistic regression, Fisher’s exact tests, and Benjamini–Hochberg (BH) adjustments, with significance set at p ≤ 0.05. In adjusted ANCOVA models, the IOS group demonstrated significantly higher absolute trunk flexor (20.1 ± 0.5 vs. 16.8 ± 0.5 kgf) and extensor (25.5 ± 0.5 vs. 22.7 ± 0.5 kgf) strength than controls (both p < 0.001), independent of demographic and anthropometric covariates. At the univariate level, the comparison group showed a significantly higher prevalence of software-classified weakness of the m. rectus abdominis (88.3% vs. 72.7%; BH-adjusted p = 0.05) and tightness of the m. psoas major (96.1% vs. 83.3%; BH-adjusted p = 0.05). In contrast, sagittal spinal curvatures and mobility did not differ between groups. After BH adjustment, m. quadratus lumborum differences showed only a non-significant trend (BH-adjusted p = 0.06). Structural parameters were mainly associated with biological factors: age showed an independent association with lumbar lordosis severity (BH-adjusted p = 0.03), whereas sex was independently associated with thoracic (BH-adjusted p = 0.01) and lumbar spine mobility (BH-adjusted p = 0.03). In summary, IOS participation in children aged 9–11 years is associated with greater absolute trunk strength, whereas structural sagittal spinal profiles and software-based muscle-imbalance classifications appear to be driven primarily by age and sex. These findings support integrating non-invasive posture screening with trunk strength assessment when monitoring young athletes and planning developmentally appropriate exercise interventions.