The purpose of this study was to examine the validity of two wearable smartwatches (the Apple Watch 6 (AW) and the Galaxy Watch 4 (GW)) and smartphone applications (Apple Health for iPhone mobiles and Samsung Health for Android mobiles) for estimating step counts in daily life. A total of 104 healthy adults (36 AW, 25 GW, and 43 smartphone application users) were engaged in daily activities for 24 h while wearing an ActivPAL accelerometer on the thigh and a smartwatch on the wrist. The validities of the smartwatch and smartphone estimates of step counts were evaluated relative to criterion values obtained from an ActivPAL accelerometer. The strongest relationship between the ActivPAL accelerometer and the devices was found for the AW (r = 0.99, p < 0.001), followed by the GW (r = 0.82, p < 0.001), and the smartphone applications (r = 0.93, p < 0.001). For overall group comparisons, the MAPE (Mean Absolute Percentage Error) values (computed as the average absolute value of the group-level errors) were 6.4%, 10.5%, and 29.6% for the AW, GW, and smartphone applications, respectively. The results of the present study indicate that the AW and GW showed strong validity in measuring steps, while the smartphone applications did not provide reliable step counts in free-living conditions.

The purpose of this study was to identify the association between physical activity (PA), sedentary behavior (SB), satisfaction with sleep fatigue recovery (SSFR), and smartphone dependency in South Korean adults. We analyzed data from the National Health and Nutrition Examination Survey 2020 data. We selected participants who answered Internet addiction-related questions as “Very much” (n = 241) and answered Internet addiction-related questions as “Not at all” (n = 241) in the questionnaire. The participants were matched by age and gender, then divided into two groups. Between the two groups, there were considerable differences in the number of days participating in moderate to vigorous PA (5 days or more, p = 0.01), the number of strength training days (1 day, p = 0.02), the number of light PA days for more than 60 min (every day for the last 7 days, p = 0.01), and the SSFR over the past 7 days (p < 0.05). Additionally, the mean smartphone usage time and mean sedentary behavior time between the two groups showed significant differences. The study demonstrated that there were significant associations between PA, SB, SSFR, and smartphone dependency among Korean adolescents matched by age and gender. Additionally, this study highlights the importance of increasing overall PA and number of days participating in MVPA, decreasing SB time and smartphone usage time could reduce the incidence of smartphone overdependence.

Metabolic carts are commonly used to estimate oxygen consumption (V̇O₂) during exercise, but are largely limited to controlled laboratory settings. The V̇O₂ Master Pro (VMP) is a newer, portable metabolic analyzer designed to address this limitation; however, few studies have evaluated the validity of this device at varying activity levels. This study aimed to assess the validity of the VMP in measuring V̇O₂ compared with a stationary metabolic cart, the COSMED Quark CPET (CQ), during sedentary activity and treadmill walking/jogging in a laboratory setting. Twenty-seven healthy adults (mean age = 22.1 ± 7.6 years; female = 51.8%) participated in two laboratory trials on separate days. In a counterbalanced order, participants used the CQ and VMP during 10 min conditions of the following activities: sedentary activity (sitting quietly), slow walking (3.2 km/h), brisk walking (5.6 km/h), and jogging (7.2 km/h). The agreement between the two measures was evaluated using equivalence testing, mean absolute percentage error (MAPE), percentage bias, intraclass correlation coefficients (ICCs), and Bland–Altman analyses. The devices showed low agreement and significant proportional biases across all activity levels (ICCs = 0.135–0.323). Equivalence testing did not demonstrate statistically significant equivalence between the devices ( p > 0.05), with the VMP underestimating V̇O₂. The smallest error appeared during jogging (MAPE = 20.05%; percentage bias= −19.29%). The VMP underestimated V̇O₂ at all tested intensities, demonstrating low accuracy and agreement relative to the reference measure. This may be attributed to limited ventilatory flow capture or sensor responsiveness during submaximal activities. Observed bias and within-subject variability suggest caution when using the VMP across different submaximal activity levels.

The current study is to examine the disparities in physical activity (PA), sedentary behavior (SB), and stress levels in Korean adolescents concerning changes in their perception of family socio-economic status (SES) during COVID-19. Among a total of 6144 Korean adolescents aged 12 to 18, the participants were categorized into two groups based on their responses regarding changes in their family SES during COVID-19: Lower SES (n = 3072) and Non-changed SES (n = 3072), with matching in terms of age, gender, and BMI. All variables were assessed using the 16th year (2020) of the Korean Youth Risk Behavior Survey. Statistical analyses were conducted using SPSS 26.0 version, employing independent t-tests to examine anthropometrics’ differences and multinominal logistic regression to predict the impact of perception of family SES on PA, SB, and stress while comparing the two groups. The significance level was set at α = 0.05. Adolescents in the Lower SES group were less likely to engage in vigorous-intensity PA (VPA) and muscular strength activities compared to those in the Non-changed SES group (p < 0.001) and were 2.3 times more likely to experience a very-severe stress level than the Non-changed SES group (p < 0.001). These results shed light on the importance of promoting VPA and muscular strength activities in adolescents for their physical and mental well-being, particularly during potential future pandemics. Understanding the impact of perceived SES changes on health behaviors can inform targeted interventions and support strategies to improve the health outcomes of adolescents during challenging times.

Background : Regular physical activity (PA) benefits mental health, but most research focuses on Western and affluent populations, limiting generalizability. This study explored how PA’s effects on mental health vary by household income in Korean adults. Methods : Data from 8235 participants (55.2% female; mean age = 63.35 [15.20] y) in the Korea Health Panel Study II (2019–2020) were analyzed. PA (regular vs irregular) and household income (low, middle, and high) were assessed in 2019, and mental health outcomes (stress, depression, anxiety, and suicidal thoughts) were measured in 2020. Multinomial logistic regression and interaction analyses examined associations between PA, income, and mental health outcomes, controlling for covariates. Results : Regular PA reduced odds of high stress across income groups: low income (odds ratios [OR] = 0.61, 95% CI, 0.51–0.73), middle income (OR = 0.78, 95% CI, 0.66–0.93), and high income (OR = 0.64, 95% CI, 0.55–0.76). Regular PA also lowered odds of anxiety (OR = 0.64, 95% CI, 0.42–0.98) and depression (OR = 0.61, 95% CI, 0.44–0.85) in high-income groups. High-income participants showed reduced odds of suicidal thoughts (OR = 0.65, 95% CI, 0.43–0.98). Significant interactions between PA and income were observed for all outcomes ( P < .001). Conclusions : Regular PA and higher income independently and interactively reduce adverse mental health outcomes. Promoting PA and addressing income disparities are essential for effective mental health interventions and policies.

1. Shift work has become increasingly prevalent worldwide due to the growing demand for 24/7 production and service industries (Monk and Buysse 2013). Shift work refers to work schedules outside th...