The Impact of COVID-19 Restrictions on Physical Activity among Chinese University Students: A Retrospectively Matched Cohort Study.

Objectives: In this study, we estimated the impact of COVID-19 on physical activity (PA) for Chinese university students during the pandemic period. Methods: The International Physical Activity Questionnaire was completed online by 1487 students (947 males and 513 females; age 19.72 ± 1.32 years, BMI = 21.12 ± 4.50) from one university in China during the pandemic period, and students retrospectively recalled pre-pandemic PA levels (March 29- April 15, 2020). We analyzed the data using a paired-samples t-test. Results: Overall, COVID-19 produced a 27.89% reduction in total weekly minutes (40.62) of vigorous PA, a 43.38% reduction in total weekly minutes (73.92) of moderate PA, and a 24.36% reduction in total weekly minutes of walking (44.69). Results by sex showed that moderate PA decreased the most, by 47.15% (males) and 37.13% (females), and total PA decreased by 48.29% (males) and 40.18% (females). Conclusions: COVID-19 led to a reduction in PA among Chinese university students. PA decreased more for male than female students. Public policy action might be needed to increase the level of PA of Chinese university students.

The Impact of COVID-19 Pandemic Restrictions on Sedentary Behavior Among Chinese University Students: A Retrospectively-Matched Cohort Study.

Purpose: This study was to estimate the impact of COVID-19 pandemic restrictions on sedentary behavior (SB) for Chinese university students during the pandemic period, as well as explore how sedentary behavior changed as a function of sex. Methods: We conducted an online questionnaire (the Sedentary Behavior Questionnaire) on students from one university in China during the pandemic period (March 29-April 15, 2020) and students retrospectively recalled pre-pandemic physical activity levels (before January 26, 2020). Sedentary behavior was measured using the short version of the Sedentary Behavior Questionnaire (SBQ). SB in a typical week during the COVID-19 pandemic period and before the COVID-19 pandemic restrictions were measured based on SBQ. The data was analyzed using a paired-samples t-test. Chi-square tests were to compare categorical variables. Results: A total of 1487 (947 males & 513 females; Age 19.72± 1.32yr., BMI = 21.12 ± 4.50) participated in this study. Before the COVID-19-associated lockdown restriction, on weekdays, survey participants averaged engaged in 11.41 (SD =3.93) hours of SB, 10.97 (SD = 3.85) hours of SB in males, 12.25 (SD =3.94) hours of SB in females; on weekends, survey participants averaged engaged in 13.18 (SD =4.06) hours of SB, 12.74 (SD = 3.96) hours of SB in males, 14.04 (SD =4.11) hours of SB in females. During the COVID-19-associated lockdown restriction, on weekdays, survey participants averaged engaged in 13.34 (SD =3.78) hours of SB, 12.90 (SD = 3.67) hours of SB in males, 14.19 (SD =3.83) hours of SB in females; on weekends, survey participants averaged engaged in 14.48 (SD =3.93) hours of SB, 14.10 (SD = 3.81) hours of SB in males, 15.22 (SD =4.04) hours of SB in females. Overall, on weekdays, The COVID-19-associated lockdown restriction on average appeared to increase SB by 1.93 (16.91%↑, 95% CI = 1.74, 2.12) hours, an increase in daily total SB by 1.92 (17.50%↑, 95% CI = 1.92, 2.15) hours for males, and an increase 1.94 (15.84%↑, 95% CI = 1.62, 2.27) hours in females. On weekends, The COVID-19-associated lockdown restriction on average appeared to increase SB by 1.30 (9.86%↑, 95% CI = 1.12, 1.48) hours, an increase in daily total SB by 1.36 (10.68%↑, 95% CI = 1.13, 1.58) hours for males, and an increase 1.18 (8.40%↑, 95% CI = 0.87, 1.50) hours in females. Conclusions: The COVID-19 restriction may lead to an increase in SB of Chinese university students. The total sedentary time of female students per week was higher than that of male students. Public policy action might be urgently needed to decrease the sedentary behavior of Chinese university students.

Timing the termination of the Doushantuo negative carbon isotope excursion: evidence from U-Pb ages from the Dengying and Liuchapo formations, South China.

The Doushantuo negative carbon isotope excursion (DOUNCE) is the largest known marine inorganic carbon isotope anomaly. The origin of this pronounced negative excursion is still an enigmatic issue that attracts geologists. Time constraints on the excursion are the critical information that would provide insight into its genesis. In previous decades, the timing of its termination has been constrained by the widely cited zircon U-Pb age of 550.5 ±â€¯0.8 Ma for the tuff at the top of the Miaohe Member at the Jiuqunao section in the Yangtze Gorges area, South China. However, results of recent studies indicate that the reliability of this time constraint needs to be re-evaluated. Here, a geochronological study was carried out using two K-bentonites from Fanglong in South China. A K-bentonite in the lower Dengying Formation yielded a U-Pb age of 557 ±â€¯3 Ma, while a K-bentonite in the basal Liuchapo Formation yielded an age of 550 ±â€¯3 Ma. Based on regional correlations between the Ediacaran successions in South China, the age (557 ±â€¯3 Ma) for the K-bentonite in the lower Dengying Formation may serve as a second critical timing constraint for the ending of the DOUNCE. Combined with available estimates of the DOUNCE duration, our new data indicate that the DOUNCE has a maximum onset age ∼570 Ma.