Objective: To investigate the independent and combined associations between physical activity and sedentary time with sleep quality among Chinese college students. Methods: A cross-sectional study was conducted among Chinese college students (N = 2347; M age = 20 years; 67.1% students were female). We used the International Physical Activity Questionnaire—Short Form, the Adolescent Sedentary Activity Questionnaire, and the Pittsburgh Sleep Quality Index to assess the subjects’ physical activity level, sedentary time, and sleep quality, respectively. Analyses were conducted using a multivariate logistic regression model. Result: Of the total participants, 48.6% had poor sleep quality and 10% were at low physical activity levels, and the mean (±SD) sedentary time was 5.33 ± 2.34 h/day. No significant association was found between physical activity and sleep quality (OR = 1.27, 95% CI: 0.95~1.70) among Chinese college students after adjustment for potential confounders. Sedentary time was significantly positively associated with poor sleep quality (OR = 1.37, 95% CI: 1.14~1.65). The risks for those with a low physical activity level and high sedentary time, and a moderate physical activity level and high sedentary time were 2.78 (OR = 2.78, 95% CI: 1.61~4.80) and 1.49 (OR = 1.49, 95% CI: 1.13~1.95) times higher, respectively, than those with a high physical activity level and low sedentary time. Conclusion: Among Chinese college students, high sedentary time was significantly negatively associated with sleep quality. A low physical activity level was insignificantly associated with sleep quality. A moderate physical activity level and high sedentary time, and a low physical activity level and high sedentary time were interactively associated with increased risks of poor sleep quality, respectively.

Background: Adherence to the World Health Organization’s 24-hour movement behavior (24-HMB) guidelines is associated with various health outcomes. However, its relationship with bone mineral density (BMD) in young children has not been investigated. This study aimed to examine the cross-sectional and longitudinal associations between adherence to the 24-HMB guidelines and BMD in young children. Methods: A total of 120 children aged 3–5 years were recruited from three kindergartens in Changsha, Hunan, China. Physical activity (PA) was objectively measured using ActiGraph wGT3X-BT accelerometers, and BMD was assessed using the Sunlight Omnisense 7000P ultrasound device. Screen time (ST) and sleep duration (SD) were reported by parents. Logistic regression was used to analyze the associations between guideline adherence and BMD. Results: Only 5.5% of the participants met all three guidelines for PA, ST, and SD, while 16.5% did not meet any. In the cross-sectional analysis, young children who met both ST and SD guidelines (OR = 0.29, 95% CI: 0.09, 0.95) had a lower risk of insufficient BMD compared to those who met none. In the one-year cohort follow-up, young children who met the PA guideline at baseline (OR = 0.22, 95% CI: 0.07, 0.71), as well as those who met both the PA and ST guidelines (OR = 0.18, 95% CI: 0.04, 0.83) or all three (OR = 0.13, 95% CI: 0.03, 0.69), had a lower risk of insufficient BMD at one year. Conclusions: Adherence to the 24-HMB guidelines may promote bone health in young children. Future research should prioritize achievable goals, such as limiting ST and ensuring adequate SD, while gradually increasing MVPA to optimize bone development.

Poor mood states pose the most frequent mental health, creating a considerable burden to global public health. Sedentary behavior is an essential factor affecting mood states, however, previous measures to reduce sedentary time in Chinese young adults have focused only on increasing physical activity (PA). Sedentary, PA, and sleep make up a person’s day from the standpoint of time use. It is not known whether reallocating sedentary time to different types of PA (e.g. daily PA and structured PA) or sleep during an epidemic has an effect on mood states. Therefore, this study aimed to examine the association between replacing sedentary time with different types of PA or sleep during the pandemic and the mood states of Chinese young adults and to further examine whether this association varies across sleep populations and units of replacement time. 3,579 young adults aged 18 to 25 years living in China and self-isolating at home during the COVID-19 outbreak were invited to complete an online questionnaire between February from 23 to 29, 2020. Subjects’ PA, sedentary time, and mood states were assessed using the International Physical Activity Questionnaire and the Chinese version of the Profile of Mood States, respectively. Participants also reported sleep duration and some sociodemographic characteristics. Participants were divided into short sleepers (< 7 h/d), normal sleepers (7–9 h/d), and long sleepers (> 9 h/d) based upon their reported sleep duration. Relevant data were analyzed using Pearson correlation analysis and isotemporal substitution model (ISM). Sedentary time was negatively associated with mood states in Chinese young adults during the pandemic (r = 0.140) and correlated strongest among short sleepers (r = 0.203). Substitution of sedentary time with structured PA was associated with good mood states (β=-0.28, 95% CI: -0.49, -0.08). Additionally, substituting sedentary time with daily PA (e.g. occupational PA, household PA) was also associated with good mood states among normal sleepers (β=-0.24, 95% CI: -0.46, -0.02). The substitution of sedentary time with sleep could bring mood benefits (β=-0.35, 95% CI: -0.47, -0.23). This benefit was particularly prominent among short sleepers. Furthermore, for long sleepers, replacing sedentary time with sleep time also resulted in significant mood benefits (β=-0.41, 95% CI: -0.69, -0.12). The longer the duration of replacing sedentary behavior with different types of PA or sleep, the greater the mood benefits. A reallocation of as little as 10 min/day of sedentary time to different types of PA or sleep is beneficial for the mood states of young adults. The longer the reallocation, the greater the benefit. Our results demonstrate a feasible and practical behavior alternative for improving mood states of Chinese young adults.

Background: University students may remain sedentary for large parts of the day, spending >9 hours per day sitting. Prolonged sitting is associated with increased risk for adverse health outcomes in adulthood. Light-intensity physical activity (LIPA) can be integrated into university students’ daily routines to counteract the negative effects of prolonged sitting on cognitive function and musculoskeletal health. Objective: This protocol describes a trial conducted in Singapore to evaluate the acute (immediate) and short-term delayed effects of two 5-minute LIPA modalities (sit-cycling [S-C] and stand-twisting [S-T]) on neurocognitive and somatic outcomes (prefrontal cortical oxygenation, cognitive performance, subjective sleepiness, and back pain) in physically inactive university students compared to a modality-matched passive control condition. Methods: The study comprised a main study (N=22) and a methodological substudy (n=6, 27.3%). In the substudy, students’ oxygen uptake was measured during 5-minute bouts of S-C and S-T to verify that both modalities meet the operational definition of LIPA. In the main study, physically inactive university students were allocated in a 1:1 ratio to either S-C or S-T (between-participant factor). Each participant completed two laboratory visits within their assigned modality: an experimental LIPA visit and a corresponding modality-matched passive control visit of equal duration (passive sitting for S-C and S-T), enabling within-person intervention-control comparisons. The primary endpoint is the change in bilateral dorsolateral prefrontal cortex (DLPFC) oxygenated hemoglobin (O2Hb) from baseline to immediately after the intervention during cognitive task performance (intervention vs control), measured with functional near-infrared spectroscopy (fNIRS). Secondary outcomes include O2Hb persistence at 20 minutes postintervention, cognitive performance (n-back test and Stroop Color and Word Test [SCWT]), subjective sleepiness, and back pain. Results: The study was funded by the Sendai University International Collaborative Research Grant in April 2023, and the trial was registered with ClinicalTrials.gov on November 21, 2024. Participant recruitment and data collection were completed in December 2024. The substudy results showed that both 5-minute S-C and S-T bouts fell within the LIPA range of <3 metabolic equivalents (METs) and could be implemented as brief, standardized LIPA breaks in the main trial. For the main trial, data cleaning and preliminary analyses are ongoing, and the outcomes will be reported in a subsequent outcomes paper (anticipated in late 2026). Conclusions: This protocol provides a prespecified framework to test whether brief 5-minute LIPA bouts may be a practical strategy to interrupt prolonged sitting and acutely improve prefrontal oxygenation and related neurocognitive and somatic outcomes in physically inactive university students. Trial Registration: ClinicalTrials.gov NCT06703424; https://clinicaltrials.gov/study/NCT06703424 International Registered Report Identifier (IRRID): PRR1-10.2196/82510

BACKGROUND University students may remain sedentary for large parts of the day, spending >9 hours per day sitting. Prolonged sitting is associated with increased risk for adverse health outcomes in adulthood. Light-intensity physical activity (LIPA) can be integrated into university students’ daily routines to counteract the negative effects of prolonged sitting on cognitive function and musculoskeletal health. OBJECTIVE This protocol describes a trial conducted in Singapore to evaluate the acute (immediate) and short-term delayed effects of two 5-minute LIPA modalities (sit-cycling [S-C] and stand-twisting [S-T]) on neurocognitive and somatic outcomes (prefrontal cortical oxygenation, cognitive performance, subjective sleepiness, and back pain) in physically inactive university students compared to a modality-matched passive control condition. METHODS The study comprised a main study (N=22) and a methodological substudy (n=6, 27.3%). In the substudy, students’ oxygen uptake was measured during 5-minute bouts of S-C and S-T to verify that both modalities meet the operational definition of LIPA. In the main study, physically inactive university students were allocated in a 1:1 ratio to either S-C or S-T (between-participant factor). Each participant completed two laboratory visits within their assigned modality: an experimental LIPA visit and a corresponding modality-matched passive control visit of equal duration (passive sitting for S-C and S-T), enabling within-person intervention-control comparisons. The primary endpoint is the change in bilateral dorsolateral prefrontal cortex (DLPFC) oxygenated hemoglobin (O2Hb) from baseline to immediately after the intervention during cognitive task performance (intervention vs control), measured with functional near-infrared spectroscopy (fNIRS). Secondary outcomes include O2Hb persistence at 20 minutes postintervention, cognitive performance (n-back test and Stroop Color and Word Test [SCWT]), subjective sleepiness, and back pain. RESULTS The study was funded by the Sendai University International Collaborative Research Grant in April 2023, and the trial was registered with ClinicalTrials.gov on November 21, 2024. Participant recruitment and data collection were completed in December 2024. The substudy results showed that both 5-minute S-C and S-T bouts fell within the LIPA range of <3 metabolic equivalents (METs) and could be implemented as brief, standardized LIPA breaks in the main trial. For the main trial, data cleaning and preliminary analyses are ongoing, and the outcomes will be reported in a subsequent outcomes paper (anticipated in late 2026). CONCLUSIONS This protocol provides a prespecified framework to test whether brief 5-minute LIPA bouts may be a practical strategy to interrupt prolonged sitting and acutely improve prefrontal oxygenation and related neurocognitive and somatic outcomes in physically inactive university students. CLINICALTRIAL ClinicalTrials.gov NCT06703424; https://clinicaltrials.gov/study/NCT06703424 INTERNATIONAL REGISTERED REPORT PRR1-10.2196/82510