The novel Coronavirus Disease 2019 (COVID-19) pandemic was first diagnosed in December, 2019 in China (1) and has since changed the world in ways we have not witnessed in recent times. The efforts to contain this pandemic have brought unprecedented efforts to institute the practice of physical/social distancing in countries all around the world, resulting in shutdowns of day-to-day functioning and changes in interaction and activity patterns. (2) These important steps to mitigate the spread of COVID-19, (2, 3) will undoubtedly lead to both short-and long-term mental and physical health consequences. (4, 5) Multiple studies have explored the National Health and Nutrition Examination Survey (NHANES) data to determine sitting time and physical activity behavior of adults in the United States (US) prior to the pandemic (e.g. in 2015-2016(6,7)); however, there is limited data on sedentary time and physical activity levels during the time when most of the US was under a stay-at-home order. Therefore, this short report examines the prevalence of patterns in joint categories of sitting time and physical activity among US adults between April 3 rd , 2020 and May 4 th , 2020.
Data for this study were obtained from two separate cross-sectional surveys that examined physical activity, sedentary time, and COVID-19 lifestyle changes. Participants in each study were recruited through mass emails, snowball sampling, researcher networks, and posts to social media pages. Interested participants were directed to a link to an anonymous electronic survey to read and consent to enrollment in the study.
The first survey (study 1) was administered by researchers at Iowa State University (approval #: 20-144-00) to 5,021 US adults from April 3 rd -May 4 th , 2020. Inclusion criteria were being ≥18 years of age and current US residence. The full survey took 20-30 minutes to complete and included demographic information and health history (i.e. age, gender, sex, race, education, marital status, occupational status, height, weight, and current chronic health conditions), COVID-19-related restrictions participants were following (i.e., quarantined or self-isolating, under a shelter-in-place or stay-at-home order, and social distancing), COVID-19-related health behaviors and their changes (i.e., smoking and drinking status, average daily time spent sitting, average daily minutes in moderate and vigorous activity (MVPA), and average daily screentime), and mental health questionnaires. Participants self-reported daily time spent in physical activity and sedentary behavior by answering: "How much time on an average day have you spent [in moderate activity, in vigorous activity, sitting] since making COVID-related behavioral changes?"
The second survey (study 2) was administered by researchers at Clarkson University (approval #20-5.1) and George Mason University (approval #1592393-1) to 1,250 US adults from April 14 th -May 4 th , 2020. Inclusion criteria were: being ≥18 years of age. The full survey took ~18 minutes to complete and included demographic information (i.e., sex, education, relationship status, occupation status) mood, trait moods, grit, sitting time, moderate physical activity, and vigorous physical activity using the International Physical Activity Questionnaire-Short Form (IPAQ-SF).
The following variables from each survey were harmonized and used in the present analysis: demographic information (including age, sex, employment status, relationship status, living situation, education level, presence of chronic disease), average minutes of sitting, moderate physical activity and vigorous physical activity.
For sitting, individuals were grouped by the following amounts of self-reported sitting time: 0 to <4 hours, 4 to <6 hours, 6-8 hours, or >8 hours per day. In accordance with the US Physical Activity Guidelines,(8) weekly physical activity was categorized as weekly minutes of moderate activity plus twice the number of minutes of vigorous activity. Individuals were then grouped by weekly physical activity level as inactive (0 minutes), insufficiently active (1-150 min/day), sufficiently active (150-300 min/day), or highly active (>300 min/day). 8 Data are presented as percentages with 95% confidence intervals in-text and with sample sizes in tables.
A total of 5,036 US Adults with complete data (80.3% of total) provided physical activity and sitting time data across two pooled studies. The sample was predominantly female (65.3%), without chronic conditions (67.3%) married (58.0%) and had a college degree (81.0%;
Supplementary Material 1). Overall, 42.6% of the sample reported sitting for more than 8 hours per day (95% CI: 41.2%-44.0%) and 72.5% (95% CI, 71.2%-73.7%) of the sample reported being either sufficiently (150-300 minutes of MVPA) or highly active (>300 minutes). From the stratification analyses ( Figure) , the greatest proportion of people self-reported being highly active and sitting for more than 8 hours per day (24.0%; 22.8%-25.2%), followed by being highly active and sitting for 6 to 8 hours per day (20.9%; 19.8%-22.1%). Of the inactive participants (0 minutes of MVPA; 20.5% of the sample), most self-reported either sitting for 0 to <4 hours per day (7.6%; 6.9%-8.3%) or >8 hours per day (8.8%; 8.1%-9.6%). Sitting and activity patterns appeared similar between the sexes, while there was evidence of some differences across age categories (Table) . For example, more young adults (18-34) appeared to self-report being inactive and more appeared to sit for >8 hours per day compared to the other age groups.
Compared to a previously reported nationally representative sample from the 2015-2016 wave of NHANES,(6) many more people in the present sample report sitting more >8h per day (42.6% v. 25.7%). However, the current population also reported being more physically active with 61.6%
reporting high physical activity compared to 25.2% in the sample in 2015-2016. Interestingly a majority of our physically active participants also reported being sedentary for >8h per day. This may be an interesting development during the COVID-19 pandemic as many people were forced to work from home and could have used physical activity as an outlet for socialization or found the lack of their commute may have provided more leisure time. Our younger population reported the most sitting time, however, this group was also the group that mostly dichotomously fell into the inactive or highly active group, while most older adults (79.4% of those 65+) reported being at least sufficiently active. These results differ greatly from Ussery et al.'s NHANES report(6) as physical activity levels declined with age in that sample, although they are similar to data collected during COVID-19 in the United Kingdom.(9) As high sedentary time is associated with higher mortality risk independent of physical activity participation,(10) the present high prevalence of >8h/day of sitting time during the response to COVID is troubling. This is concerning as high levels of sedentary time are associated with worse overall health across many metrics (11) and lifestyle risk factors (such as inactivity) have been found to be associated with an increased risk for hospitalization due to COVID-19.(12) As increased screen time and reduced activity during the pandemic have been associated with worse mental health (13) , the high levels of sitting in this dataset are of significant public health concern. The limitations of this study are that: our sample was not a nationally representative sample, was highly educated, and was collected through convenience sampling which introduces selection bias. As NHANES was a nationally-representative sample, contrasts between the present findings and previous NHANES data adds context to the present findings, but differences in the samples limit direct comparison. Additionally, there is inherent bias in self-reported data generally leading to over-reporting of physical activity and under-reporting of sedentary time.
Both high sedentary behavior and physical inactivity have deleterious mental and physical health effects (14, 15) and US adults reported engaging in high levels of sitting time but also high levels of activity during the initial COVID-19 lockdown phase in April 2020. If major workplace and societal shifts are needed (e.g. during this or future pandemics), evidence-based strategies to limit sitting time, increase physical activity, or both would be potentially beneficial to most US adults, particularly young adults. Practitioners and researchers should support efforts to develop and implement programs, practices and policies that can provide physically distant interventions to help US adults sit less and become more physically active. In particular, strategies that minimize or limit required sitting time may be particularly influential given the present high prevalence of sitting time.
Acknowledgements: JM, MH, CM, JL, CB, FS, LS, MT were involved in the conception, design and acquisition of data for study 1, while JL, SC, NC and AB were involved in the conception, design and acquisition of data for study 2. JM and AB pooled the data and ran the analyses for this manuscript. All authors were involved in drafting and revising the work critically for important intellectual content. The contents of this article have not been previously presented elsewhere.
Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
None.