Influence of parental nativity and perceived neighborhood environment on physical activity and screen time of United States youth.

OBJECTIVE: This study assessed how parental nativity and perceived environment are associated with physical activity and screen time of U.S. children and adolescents. METHODS: Data originated from the 2020-21 U.S. National Survey of Children's Health. We conducted multivariable Poisson regression to assess the cross-sectional association of parental nativity and perceived neighborhood environment variables on parental reports of youth meeting national physical activity and screen time guidelines. We tested interactions of parental nativity and neighborhood environment variables on both outcomes. Analyses were conducted using STATA v17 and p < 0.05 indicated statistical significance. RESULTS: The sample of 24,928 children and 30,951 adolescents was 11.6 years of age, on average, with approximately 39% under 200% of the federal poverty level. About one-third of the sample (27.5%) had foreign-born parents. In adjusted models, we found that compared to youth with U.S.-born parents, those with foreign-born parents had a lower prevalence of meeting physical activity guidelines. Youth whose parents reported living in safe neighborhoods had a higher prevalence of meeting guidelines for physical activity (children: PR = 1.20, 95%CI 1.14, 1.27; adolescents: PR = 1.23, 95%CI 1.14, 1.32) and screen time (children: PR = 1.19, 95%CI 1.13, 1.26; adolescents: PR = 1.16, 95%CI 1.06, 1.28) than youth whose parents reported unsafe neighborhoods. We found similar associations between neighborhoods considered supportive or with many amenities and meeting physical activity and screen time guidelines. CONCLUSIONS: Youth whose parents are foreign-born have a lower prevalence of sufficient activity, and perceived parental neighborhood safety and support may be significant influences on youth physical activity and screen time.

The availability between recreational facilities and physical activity of US adolescents.

Determining the locations where adolescents tend to accumulate greater amounts of physical activity may assist policymakers to address the built environment design and promote PA. This study evaluated the association between the availability of recreational facilities and average minutes of moderate to vigorous physical activity (MVPA) per day of US adolescents in 2017 (n = 1,437). Data for this cross-sectional study were obtained from the 2017 Family Life, Activity, Sun, Health, and Eating study, an internet-based study collecting information on diet and PA of parent and adolescent dyads. Adolescents aged 12-17 from the US were included. Predicted daily minutes of MVPA were calculated. The exposure variables of interest were the availability of school recreational facilities, indoor recreational facilities, playing fields, bike/hiking/walking trails or paths or public parks. Participants were excluded if no information was provided for MVPA or availability of recreational facilities. Unadjusted and adjusted linear regression analysis was used to calculate mean daily minutes of MVPA and their corresponding 95 % confidence intervals. In fully adjusted models, we found statistically significant associations between the type of recreational facility and differences in daily minutes of MVPA for school (p-value < 0.001) and public parks p-value < 0.001), but not for the other recreational facilities. The average daily minutes of MVPA differed by 4.4 min (95 % CI 2.6, 6.2) if participants had school recreational facilities, respectively. School recreational facilities are important for engaging adolescents in PA objectives. Features within school recreational facilities should be studied to further investigate contributions to increased PA levels.

How Societal Forces of Change Are Transforming Youth Physical Activity Promotion in North America.

BACKGROUND: Climate change, increasing recognition of institutionalized discrimination, and the COVID-19 pandemic are large-scale, societal events (ie, forces of change) that affect the timing, settings, and modes of youth physical activity. Despite the impact that forces of change have on youth physical activity and physical activity environments, few studies consider how they affect physical activity promotion. METHODS: The authors use 2 established frameworks, the ecological model of physical activity and the youth physical activity timing, how, and setting framework, to highlight changes in physical activity patterns of youth in North America that have resulted from contemporary forces of change. RESULTS: North American countries-Canada, Mexico, and the United States-have faced similar but contextually different challenges for promoting physical activity in response to climate change, increasing recognition of institutionalized discrimination, and the COVID-19 pandemic. Innovative applications of implementation science, digital health technologies, and community-based participatory research methodologies may be practical for increasing and sustaining youth physical activity in response to these forces of change. CONCLUSIONS: Thoughtful synthesis of existing physical activity frameworks can help to guide the design and evaluation of new and existing physical activity initiatives. Researchers, practitioners, and policymakers are encouraged to carefully consider the intended and unintended consequences of actions designed to respond to forces of change.

Volunteering, Health, and Well-being of Children and Adolescents in the United States.

This cross-sectional study examines whether there is an association between volunteering and well-being among children and adolescents across the United States.

How Blackouts during Heat Waves Amplify Mortality and Morbidity Risk.

The recent concurrence of electrical grid failure events in time with extreme temperatures is compounding the population health risks of extreme weather episodes. Here, we combine simulated heat exposure data during historical heat wave events in three large U.S. cities to assess the degree to which heat-related mortality and morbidity change in response to a concurrent electrical grid failure event. We develop a novel approach to estimating individually experienced temperature to approximate how personal-level heat exposure changes on an hourly basis, accounting for both outdoor and building-interior exposures. We find the concurrence of a multiday blackout event with heat wave conditions to more than double the estimated rate of heat-related mortality across all three cities, and to require medical attention for between 3% (Atlanta) and more than 50% (Phoenix) of the total urban population in present and future time periods. Our results highlight the need for enhanced electrical grid resilience and support a more spatially expansive use of tree canopy and high albedo roofing materials to lessen heat exposures during compound climate and infrastructure failure events.

Ambient Temperature Increases and Preschoolers' Outdoor Physical Activity.

This cross-sectional study evaluates the association of high outdoor temperatures with children's engagement in physical activity during play.

Impact of heat on all-cause and cause-specific mortality: A multi-city study in Texas.

BACKGROUND: Studies on the health effects of heat are particularly limited in Texas, a U.S. state in the top 10 highest number of annual heat-related deaths per capita from 2018 to 2020. This study assessed the effects of heat on all-cause and cause-specific mortality in 12 metropolitan statistical areas (MSAs) across Texas from 1990 to 2011. METHODS: First, we determined the heat thresholds for each MSA above which the relation between temperature and mortality is linear. We then conducted a distributed lag non-linear model for each MSA, followed by a random effects meta-analysis to estimate the pooled effects for all MSAs. We repeated this process for each mortality cause and age group to achieve the effect estimates. RESULTS: We found a 1 °C temperature increase above the heat threshold is associated with an increase in the relative risk of all-cause mortality of 0.60% (95%CI [0.39%, 0.82%]) and 1.10% (95%CI [0.65%, 1.56%]) for adults older than 75. For each MSA, the relative risk of mortality for a 1 °C temperature increase above the heat threshold ranges from 0.10% (95%CI [0.09%, 0.10%]) to 1.29% (95%CI [1.26%, 1.32%]). Moreover, elevated temperatures showed a slight decrease in cardiovascular mortality (0.37%, 95%CI [-0.35%, 1.09%]) and respiratory disease (1.97%, 95%CI [-0.11%, 4.08%]), however this effect was not considered statistically significant.. CONCLUSION: Our study found that high temperatures can significantly impact all-cause mortality in Texas, and effect estimates differ by MSA, age group, and cause of death. Our findings generate critical information on the impact of heat on mortality in Texas, providing insights for policymakers on resource allocation and strategic intervention to reduce heat-related health effects.

Heat-Resilient Schoolyards: Relations Between Temperature, Shade, and Physical Activity of Children During Recess.

BACKGROUND: Extreme heat may discourage physical activity of children while shade may provide thermal comfort. The authors determined the associations between ambient temperature, shade, and moderate to vigorous physical activity (MVPA) of children during school recess. METHODS: Children aged 8-10 (n = 213) wore accelerometers and global positioning system monitors during recess at 3 school parks in Austin, Texas (September-November 2019). Weather data originated from 10 sensors per park. The authors calculated shade from imagery using a geographic information system (GIS) and time-matched physical activity, location, temperature, and shade data. The authors specified piecewise multilevel regression to assess relations between average temperature and percentage of recess time in MVPA and shade. RESULTS: Temperature ranged 11 °C to 35 °C. Each 1 °C higher temperature was associated with a 0.7 percentage point lower time spent in MVPA, until 33 °C (91 °F) when the association changed to a 1.5 lower time (P < .01). Each 1 °C higher temperature was associated with a 0.3 percentage point higher time spent under shade, until 33 °C when the association changed to a 3.4 higher time (P < .001). At 33 °C or above, the direct association between shade and MVPA weakened (P < .05), with no interaction effect above 33 °C (P > .05). Children at the park with the most tree canopy spent 6.0 percentage points more time in MVPA (P < .01). CONCLUSIONS: Children engage in less MVPA and seek shade during extreme heat and engage in more MVPA in green schoolyards. With climate change, schools should consider interventions (eg, organizing shaded play, tree planting) to promote heat safe MVPA.

A direct observation tool to measure interactions between shade, nature, and children's physical activity: SOPLAY-SN.

BACKGROUND: Most physical activity (PA) during school occurs at recess; however, recess PA may be influenced by children's thermal comfort and interaction with nature, neither of which have concurrently been measured reliably in previous studies. This study tests the reliability of SOPLAY-SN, an adaption of the validated System for Observing Play and Leisure Activity in Youth (SOPLAY) to measure Shade and Nature (SN) alongside PA, and associations between children's PA and interaction with shade and nature during recess to highlight the utility of the tool. METHODS: Interactions with shade and nature were measured using systematic direct observation at two playgrounds (primary-grade = ages 5-8, upper-grade = ages 9-12) during recess at an elementary school in Phoenix, Arizona (USA). Pairs conducted observations over four warm days (primary = 29-34 °C, upper-grade = 32-36 °C) in May 2021 (N = 179 scans). Intraclass correlation coefficients (ICC) were used to calculate inter-rater reliability. Mean counts, frequencies, and Kendall rank correlation coefficient tests were used to assess relations between PA level and interactions with shade and nature. RESULTS: Reliability was good for sedentary behavior (ICC = 0.98); light PA (LPA; ICC = 0.80) and moderate-to-vigorous PA (MVPA; ICC = 0.94); shade interaction (ICC = 0.95); and nature interaction (ICC = 0.80) and average agreement was good (86% overall PA, 88% shade, 90% nature). Most (60%) primary-grade children were observed in the shade, with 64% under a covered play structure where children were mainly (47%) sedentary. Of the 11% of primary-grade students observed interacting with nature, 90% occurred in a grass field with trees. Among upper-grade children, 23% were observed in the shade with 53% in grass fields where 48% of play was light. Few (7%) upper-grade children were observed interacting with nature, with most instances (76%) in a grass field with trees. Among primary-grade children, shade was correlated with sedentary behavior (τb = 0.63, p < .05); LPA (τb = 0.39, p < .05); MVPA (τb = 0.56, p < .05); and nature interactions with sedentary behavior (τb = 0.16, p < .05). Among upper-grade children, shade was correlated with sedentary behavior (τb = 0.27, p < .05) and LPA (τb = 0.21, p < .05). CONCLUSIONS: SOPLAY-SN is a reliable tool for measuring children's interaction with shade and nature and participation in PA. Understanding how shade and nature impact movement during recess can inform playground design for children's health and well-being.

Youth physical activity and the COVID-19 pandemic: A systematic review.

The purpose of the systematic review was to identify, evaluate, and synthesize evidence from available published literature examining the impact of the coronavirus disease 2019 (COVID-19) pandemic on youth physical activity (PA). A systematic review of the literature was conducted for years 2020-2021. Published articles were searched in eight databases. Inclusion criteria included: availability of full-text, written in English language, and reported quantitative or qualitative results of original or secondary data on PA and COVID-19 related factors among youth (ages 5-17 years). A standard quality assessment tool assessed risk of bias and quality of included articles. The search retrieved 2,899 articles with 51 articles ultimately meeting inclusion criteria. The majority of articles (65 %) investigated change in PA from before to during the pandemic. Most evidence indicated an overall decrease in youth PA levels during the pandemic with differences observed among sub-populations (e.g., age, sex or gender), type, and location. Findings suggest pandemic-related closures hindered PA participation due to a high reliance on school- and sport-based PA. Programmatic strategies (e.g., activity breaks, active curriculum, free online activities/lessons) should include aligning intervention measures and geared towards evolving and ongoing PA promotion based on the latest findings.

Home Smoke-Free Policies as Children Age: Urban, Rural, and Suburban Differences.

INTRODUCTION: Parents/guardians can effectively reduce tobacco smoking and secondhand smoke exposure among youth by adopting and enforcing rules against indoor tobacco smoking (ie, home smoke-free policies). We investigate home smoke-free policies from childhood to adolescence in the United States and across rural, suburban, and urban households. AIMS AND METHODS: We analyzed 2019-2020 National Survey of Children's Health data from n = 5,955 parents of youth aged 0-17, living at home with a tobacco smoker in the United States (U.S). Geographical categories were: rural, suburban, and urban. Home smoke-free policy reflected prohibiting tobacco smoking inside the home. Weighted logistic regressions examined the (1) association between youth age and home smoke-free policies, (2) interaction between geographic category and youth age, and (3) differing associations between youth age and home smoke-free policies by geography. Models controlled for youth race, ethnicity, sex, parental education, household annual income, and home structure. RESULTS: Approximately 13.2% of U.S. households with a smoker did not have a home smoke-free policy. Stratified analyses found one-year increase in youth age was associated with lower odds of having a home smoke-free policy in rural (aOR:0.91; 95%CI: 0.87-0.95) and urban (aOR: 0.96; 95%CI: 0.92-1.00; p = .039), but not suburban (aOR:1.00; 95%CI: 0.95-1.05) households, controlling for covariates. CONCLUSION: Odds of having a smoke-free home in the U.S. declined significantly in rural (9% per year) and urban (4%) but not suburban (0%) households. We quantify declines in home smoke-free policies as children age and identify geographic disparities for this environmental determinant of health. IMPLICATIONS: Health promotion efforts targeting secondhand smoke prevention is needed, particularly for parents of older youth. Furthermore, there is a clear geographic bias in secondhand smoke exposure among all youth particularly older youth. Tailored interventions are needed to address geographic disparities in secondhand smoke exposure among rural and urban youth.

Climate change and physical activity: ambient temperature and urban trail use in Texas.

Individuals in the USA are insufficiently active, increasing their chronic disease risk. Extreme temperatures may reduce physical activity due to thermal discomfort. Cooler climate studies have suggested climate change may have a net positive effect on physical activity, yet research gaps remain for warmer climates and within-day physical activity patterns. We determined the association between ambient temperatures (contemporary and projected) and urban trail use in a humid subtropical climate. At a trail in Austin, TX, five electronic counters recorded hourly pedestrian and cyclist counts in 2019. Weather data were acquired from World Weather Online. Generalized additive models estimated the association between temperature and trail counts. We then combined the estimated exposure-response relation with weather projections from climate models for intermediate (RCP4.5) and high (RCP8.5) emissions scenarios by NASA NEX-GDDP. From summer to autumn to spring to winter, hourly trail counts shifted from bimodal (mid-morning and early-evening peaks) to one mid-day peak. Pedestrians were more likely to use the trail between 7 and 27 °C (45-81°F) with peak use at 17 °C (63°F) and cyclists between 15 and 33 °C (59-91°F) with peak use at 27 °C (81°F) than at temperature extremes. A net decrease in trail use was estimated by 2041-2060 (RCP4.5: pedestrians = - 4.5%, cyclists = - 1.1%; RCP8.5: pedestrians = - 6.6%, cyclists = - 1.6%) and 2081-2100 (RCP4.5: pedestrians = - 7.5%, cyclists = - 1.9%; RCP8.5: pedestrians = - 16%, cyclists = - 4.5%). Results suggest climate change may reduce trail use. We recommend interventions for thermal comfort at settings for physical activity.

School-Level Economic Disparities in Police-Reported Crimes and Active Commuting to School.

Perceived safety remains one of the main barriers for children to participate in active commuting to school (ACS). This ecological study examined the associations between the number of police-reported crimes in school neighborhoods and ACS. The percentage of active travel trips was assessed from a teacher tally survey collected from students across 63 elementary schools that were primarily classified as high-poverty (n = 27). Geographic Information System (GIS) was used to create a detailed measure of police-reported crimes during 2018 and neighborhood covariates that occurred within a one-mile Euclidean buffer of the schools. Statistical analyses included linear fixed effects regressions and negative binomial regressions. In fully-adjusted models, reported crime did not exhibit significant associations with ACS. Medium-poverty schools were indirectly associated with ACS when compared to high- and low-poverty schools in all models (p < 0.05). Connectivity and vehicle ownership were also directly associated with ACS (p < 0.05). Low- and medium-poverty schools were indirectly associated with all types of reported crime when compared to high-poverty schools (p < 0.05). Although reported crime was not associated with school-level ACS, differences in ACS and reported crime do exist across school poverty levels, suggesting a need to develop and promote safe and equitable ACS interventions.

School Parks as a Community Health Resource: Use of Joint-Use Parks by Children before and during COVID-19 Pandemic.

Parks are settings for physical activity that can support the physical and mental health of children during the COVID-19 pandemic. We determined the impact of the pandemic on the use of joint-use parks outside of school hours by children in Austin, TX, United States. In autumn of 2019 and autumn of 2020 (i.e., before and during the COVID-19 pandemic), we used an adapted version of the System for Observing Play and Recreation in Communities to observe whether children aged 1-12 participated in physical activity (i.e., sedentary, light and moderate, vigorous) at three parks located at schools serving mostly economically disadvantaged Latinx families. In 2020, we also observed whether children maintained social distance and wore face coverings. Results of negative binomial regression modeling revealed the pandemic was associated with a 46% [95% CI: 20-63%] and 62% [95% CI: 39-76%] decrease in the number of girls and boys at parks, respectively, and a 42% [95% CI: 16-59%] and 60% [95% CI: 36-75%] decrease in the number of girls and boys engaging in physical activity, respectively (p < 0.01). In total, 60.6% of girls and 73.6% of boys were not social distancing, and 91.8% of the time no children wore masks. Interventions should be considered to safely reintroduce children to parks for health benefits during pandemics.

Y-PATHS: A Conceptual Framework for Classifying the Timing, How, and Setting of Youth Physical Activity.

BACKGROUND: Multiple models and frameworks exist for the measurement and classification of physical activity in adults that are applied broadly across populations but have limitations when applied to youth. The authors propose a conceptual framework specifically designed for classifying youth physical activity. METHODS: The Youth Physical Activity Timing, How, and Setting (Y-PATHS) framework is a conceptualization of the when (timing), how, and where (setting) of children's and adolescents' physical activity patterns. The authors developed Y-PATHS using the design thinking process, which includes 3 stages: inspiration, ideation, and implementation. RESULTS: The Y-PATHS includes 3 major components (timing, how, and setting) and 13 subcomponents. Timing subcomponents include (1) school days: in-school, (2) school days: out-of-school, and (3) nonschool days. How subcomponents include: (1) functional, (2) transportation, (3) organized, and (4) free play. Setting subcomponents include: (1) natural areas, (2) schools, (3) home, (4) recreational facilities, (5) shops and services, and (6) travel infrastructure. CONCLUSIONS: The Y-PATHS is a comprehensive classification framework that can help researchers, practitioners, and policymakers to better understand youth physical activity. Specifically, Y-PATHS can help to identify the domains of youth physical activity for surveillance and research and to inform the planning/evaluation of more comprehensive physical activity programming.

Heat-Moderating Effects of Bus Stop Shelters and Tree Shade on Public Transport Ridership.

Rising temperatures threaten the resilience of public transit systems. We determined whether bus stop shelters and tree canopy surrounding bus stops moderated the effect of warm season temperatures on ridership in Austin, Texas, and whether shelters and trees were equitably distributed. For bus stops (n = 2271) of Capital Metropolitan Transportation Authority, boardings per bus were measured 1 April-30 September 2019. Air temperature data originated from the Camp Mabry weather station. Tree canopy was calculated by classification of high-resolution aerial imagery from the National Agriculture Imagery Program. Data on race, ethnicity, poverty level, median age, and bus commuters within census tracts of bus stops originated from the 2014-2018 American Community Survey. Using multilevel negative binomial regression models, we found that shelters did not moderate the effect of high temperatures on ridership (p > 0.05). During high temperatures, each one-percent increase in tree canopy was associated with a lesser decrease (1.6%) in ridership compared to if there were no trees (1.7%) (p < 0.001). In general, shelters and trees were equitably distributed. Insignificant or modest effects of shelters and trees on ridership during high temperatures may be attributed to the transit dependency of riders. For climate change adaptation, we recommend tree planting at bus stops to protect from ridership losses and unhealthy exposure to extreme heat.

Effects of trees, gardens, and nature trails on heat index and child health: design and methods of the Green Schoolyards Project.

BACKGROUND: Latinx children in the United States are at high risk for nature-deficit disorder, heat-related illness, and physical inactivity. We developed the Green Schoolyards Project to investigate how green features-trees, gardens, and nature trails-in school parks impact heat index (i.e., air temperature and relative humidity) within parks, and physical activity levels and socioemotional well-being of these children. Herein, we present novel methods for a) observing children's interaction with green features and b) measuring heat index and children's behaviors in a natural setting, and a selection of baseline results. METHODS: During two September weeks (high temperature) and one November week (moderate temperature) in 2019, we examined three joint-use elementary school parks in Central Texas, United States, serving predominantly low-income Latinx families. To develop thermal profiles for each park, we installed 10 air temperature/relative humidity sensors per park, selecting sites based on land cover, land use, and even spatial coverage. We measured green features within a geographic information system. In a cross-sectional study, we used an adapted version of System for Observing Play and Recreation in Communities (SOPARC) to assess children's physical activity levels and interactions with green features. In a cohort study, we equipped 30 3rd and 30 4th grade students per school during recess with accelerometers and Global Positioning System devices, and surveyed these students regarding their connection to nature. Baseline analyses included inverse distance weighting for thermal profiles and summing observed counts of children interacting with trees. RESULTS: In September 2019, average daily heat index ranged 2.0 °F among park sites, and maximum daily heat index ranged from 103.4 °F (air temperature = 33.8 °C; relative humidity = 55.2%) under tree canopy to 114.1 °F (air temperature = 37.9 °C; relative humidity = 45.2%) on an unshaded playground. 10.8% more girls and 25.4% more boys interacted with trees in September than in November. CONCLUSIONS: We found extreme heat conditions at select sites within parks, and children positioning themselves under trees during periods of high heat index. These methods can be used by public health researchers and practitioners to inform the redesign of greenspaces in the face of climate change and health inequities.

Transit environments for physical activity: Relationship between micro-scale built environment features surrounding light rail stations and ridership in Houston, Texas.

INTRODUCTION: Health professionals promote transport-related physical activity because travelers oftentimes walk or bike to and from transit stops or stations. Although previous studies have examined the associations between macro-scale built environment features surrounding light rail transit (LRT) stations (e.g., density) and LRT ridership, this study examined the associations between numerous micro-scale features (e.g., street-level noise pollution) and ridership. METHODS: This analysis originated from the Houston Travel-Related Activity in Neighborhoods (TRAIN) Study, a project evaluating how an LRT extension impacted adult physical activity in Houston, Texas. In 2014, researchers used the Analytic Audit Tool to quantify 58 micro-scale built environment features within six categories: Land Use Environment, Transportation Environment, Facilities, Aesthetics, Signage, and Social Environment. Feature data were obtained from 590 street segments within 0.25 miles of 22 LRT stations. For each station, separate composite indices were created per category by averaging the computed feature scores (1-7) within each category, with higher scores signifying more physical activity-promoting features. Station-level LRT ridership data were obtained from monthly ridership reports for the 12 months following station opening. Linear mixed models were constructed to examine the associations of the six built environment categories with ridership, adjusting for season, weekday vs. weekend day, and station as a random intercept. RESULTS: Holding all other variables constant, every one-unit increase in composite index scores for Transportation Environment and Social Environment was associated with an increase in daily ridership by 425 and 488 riders, respectively (p < 0.05). Every one-unit increase in composite index score for Signage was associated with a decrease of 722 riders daily (p < 0.05). The relations of Land Use Environment, Facilities, and Aesthetics with ridership were statistically null (p > 0.05). CONCLUSIONS: Enhancements to the Transportation Environment and Social Environment may slightly increase overall LRT ridership, and consequently, utilitarian physical activity.

Physical Activity in the Summer Heat: How Hot Weather Moderates the Relationship Between Built Environment Features and Outdoor Physical Activity of Adults.

BACKGROUND: Research has not yet examined how hot weather moderates the relationship between the built environment and outdoor physical activity levels. The authors posited that hot days will increase the magnitude of the expected directional effect of built environment features on physical activity. METHODS: This longitudinal study included 134 US adults from the Three city Heat and Electrical failure AdapTation study. Adults self-reported physical activity for multiple summer days (nstudy-days = 742) in 2016. Hot days were defined as ≥90th percentile of daily maximum heat index. Built environment features included density, safety, trees, hilliness, connectivity, access to parks, and access to shops + services. Separate growth curve models with interaction terms (ie, hot day × built environment feature) were run for daily minutes of outdoor physical activity (ie, any activity and recommended activity). RESULTS: Neither hot days nor built environment features impacted outdoor physical activity significantly, and hot days did not moderate the relationship between built environment features and physical activity (P > .05). CONCLUSIONS: With adults failing to modify behavior on hot days, cities may be placing adults at increased risk of exertional heat illness. The authors recommend incorporating the risk of exertional heat illness in health impact assessments and deploying heat management strategies.