Long-term effects of the COVID-19 pandemic on children's physical activity and sedentary behavior.

Background: During the early months of the COVID-19 pandemic, decreases in physical activity (PA) and increases in sedentary behavior (SB) were reported among children in the United States (U.S.). This follow-up analysis examines 13-month effects of the COVID-19 pandemic on children's PA and SB one year into the pandemic. Methods: Parents of 5-13-year-old children in the U.S. (N = 71) reported on their child's PA and SB during the early COVID-19 period (April-May 2020) and again 12-14 months later (June-July 2021). Results: Paired t-tests showed significant within-subject reductions in SB minutes per day (M diff = -86.20, t = 3.26, p < 0.01) but no changes in PA minutes per day. Separate mixed-model repeated-measures analysis of covariance procedures found that within-subject changes in PA and SB did not differ by child sex or age. Conclusion: As COVID-19 restrictions lessened, there were more opportunities for children to reduce SB, but there were still barriers to engage in PA.

Investigating the day-level associations between affective variability and physical activity using ecological momentary assessment.

BACKGROUND: Understanding affect as a determinant of physical activity has gained increased attention in health behavior research. Fluctuations in affect intensity from moment-to-moment (i.e., affective variability) may interfere with cognitive and regulatory processes, making it difficult to engage in goal-directed behaviors such as physical activity. Preliminary evidence indicates that those with greater trait-level affective variability engage in lower levels of habitual physical activity. However, the extent to which daily fluctuations in affect variability are associated with same-day physical activity levels is unknown. This study used ecological momentary assessment (EMA) to investigate day-level associations between affective variability (i.e., within-subject variance) and physical activity. METHODS: Young adults (N = 231, M = 23.58 ± 3.02 years) provided three months of smartphone-based EMA and smartwatch-based activity data. Every two weeks, participants completed a 4-day EMA measurement burst (M = 5.17 ± 1.28 bursts per participant). Bursts consisted of hourly randomly-prompted EMA surveys assessing momentary positive-activated (happy, energetic), positive-deactivated (relaxed), negative-activated (tense, stressed), and negative-deactivated (sad, fatigued) affect. Participants continuously wore a smartwatch to measure physical activity across the three months. Mixed-effects location scale modeling examined the day-level associations of affective variability (i.e., positive-activated, positive-deactivated, negative-activated, and negative-deactivated) and physical activity, controlling for covariates such as mean levels of affect, between-subject effects of physical activity, time of day, day of week, day in study, and smartwatch wear time. RESULTS: There were 41,546 completed EMA surveys (M = 182.22 ± 69.82 per participant) included in the analyses. Above and beyond mean levels of affect, greater day-level variability in positive-activated affect was associated with greater physical activity on that same day compared to other days (τ = 0.01, p < .001), whereas greater day-level variability in negative-deactivated affect was associated with less physical activity on that same day compared to other days (τ = -0.01, p < .001). Day-level variability in positive-deactivated affect or negative-activated affect were not associated with day-level physical activity (ps > .05) CONCLUSIONS: Individuals were less active on days with greater variability in feeling sad and fatigued but more active on days with greater variability in feeling happy and energetic. Understanding the dynamic relationships of affective variability with day-level physical activity can strengthen physical activity interventions by considering how these processes differ within individuals and unfold within the context of daily life. Future research should examine causal pathways between affective variability and physical activity across the day.

A Systematic Review of the Associations of Adiposity and Cardiorespiratory Fitness With Arterial Structure and Function in Nonclinical Children and Adolescents.

PURPOSE: To summarize the evidence on associations of adiposity and cardiorespiratory fitness (CRF) with arterial structure and function in nonclinical children and adolescents. METHODS: Two researchers conducted a search in 5 electronic databases in April 2022 to find studies in nonclinical youth (age 5-17.9 y) reporting multivariable associations. Studies were eligible if adiposity and/or CRF were used as the predictor and arterial structure and/or function was the outcome. The Quality Assessment Tool for Quantitative Studies was used to assess methodological quality for experimental studies, and a modified version was used for observational studies. RESULTS: Ninety-nine studies (72.7% cross-sectional) were included. Ninety-four assessed associations between adiposity and arterial outcomes, most using overall body proportion (n = 71), abdominal (n = 52), or whole-body adiposity (n = 40). Most evidence was inconsistent or nonsignificant, but 59 studies suggested higher abdominal adiposity and worse body proportion were associated with adverse arterial outcomes. Twenty-one assessed associations between CRF and arterial outcomes, with findings inconsistent. Most evidence was rated weak in quality. CONCLUSION: While high adiposity may contribute to poor arterial outcomes, evidence is limited regarding CRF. Future studies should disentangle these associations by studying youth with healthy adiposity but poor CRF, or vice versa, using longitudinal or experimental study designs.

Associations between Amount of Recess, Physical Activity, and Cardiometabolic Traits in U.S. Children.

Introduction/purpose: In the United States, it is recommended that schools provide at least 20 minutes of daily recess, but the optimal amount for health benefits is unknown. We examined associations between amount of recess and health indicators using National Health and Nutrition Examination Survey data (NHANES; 2013-2016). Methods: For this cross-sectional analysis, parents/guardians of 6-11 year olds (n=738) reported recess provision which was classified as low (22.8%; approximately 10-15 min, 5 days per week), medium (54.9%; approximately 16-30 min, 5 days per week), or high (22.3%; approximately >30 min, 5 days per week). Outcomes measured included parent/guardian-reported and accelerometer-measured physical activity (PA), blood pressure, cholesterol, grip strength, bone mineral content, weight status, percent body fat, vitamin D level, and C-reactive protein level. Linear and logistic regression compared outcomes by level of recess provision accounting for the NHANES complex survey design. Results: The odds of meeting PA guidelines according to parent/guardian reports were 1.70 and 2.05 times higher in those with medium and high (respectively) versus low recess provision. Accelerometer-measured weekday activity was highest in those with high recess provision while weekend activity was highest in those with low recess provision (Cohen's d = 0.40-0.45). There were no other significant associations. Conclusion: At least 30 minutes of daily recess is associated with two-fold greater odds of achieving recommended PA levels according to parent/guardian reports; accelerometer data suggest this is through increased weekday activity. This finding suggests current national recess recommendations are insufficient for PA promotion. More detailed data on the frequency and duration of recess are needed to quantify optimal provision more precisely.

Effects of interrupting daily sedentary behavior on children's glucose metabolism: A 6-day randomized controlled trial.

BACKGROUND: Metabolic disease risk in youth is influenced by sedentary behaviors. Acute in-lab studies show that, during a single day, interrupting a sedentary period with short bouts of physical activity improves glucometabolic outcomes. OBJECTIVE: To determine if acutely improved glucose metabolism persists after multi-day interruptions of sitting with walking brief bouts. We hypothesized that children who underwent interrupting sitting on multiple days would demonstrate lower insulin area under the curve during an oral glucose tolerance test compared to uninterrupted sitting. METHODS: Healthy, normoglycemic children (N = 109) ages 7-11 years were randomized to one of two conditions: Control (3 h of daily Uninterrupted Sitting) or Interrupted Sitting (3-min of moderate-intensity walking every 30 min for 3 h daily); with dietary intake controlled through provision of foodstuffs for the entire experiment. Participants attended six consecutive daily visits at a research ambulatory unit. The primary outcome was insulin area under the curve during the oral glucose tolerance test on day 6 during interrupted or uninterrupted sitting; secondary outcomes included glucose and c-peptide area under the curve, energy intake at a buffet meal on day 6, and free-living activity. RESULTS: Among 93 children (42 uninterrupted sitting, 51 interrupted sitting), daily interrupted sitting resulted in 21% lower insulin (ß = 0.102 CI:0.032-0.172, p = 0.005) and a 10% lower C-peptide (ß = 0.043, CI:0.001-0.084, p = 0.045) area under the curve. Matsuda and Glucose Effectiveness Indices were also improved (p's < 0.05). There were no group differences in energy intake or expenditure. CONCLUSIONS: Sustained behavioral change by interrupting sedentary behaviors is a promising intervention strategy for improving metabolic risk in children.

Interventions to Reduce Sedentary Behavior in Cancer Patients and Survivors: a Systematic Review.

PURPOSE OF REVIEW: Sedentary behaviors (SB) after cancer diagnosis are associated with poor prognosis for certain cancers, and cancer patients and survivors report high levels of SB. Reducing SB may be a feasible and effective intervention strategy to improve outcomes. This systematic review aims to identify and evaluate the literature on interventions to reduce SB in cancer patients and survivors. RECENT FINDINGS: Studies were identified via database searches in December 2020. Two authors evaluated study eligibility. Data were extracted and checked, and risk of bias was assessed by the study team. Of 1401 records identified, nine studies involving 394 cancer patients or survivors were included in this review. Six were randomized trials, three were non-randomized intervention studies, and almost all (n = 8) focused on feasibility with small sample sizes. All studies were conducted within the previous 5 years in Canada, Australia, USA, and South Korea. Cancer types studied were breast (n = 3), prostate (n = 2), colorectal or peritoneal (n = 1), and mixed types (n = 3). Intervention duration of 12 weeks was most common (n = 7). Five studies had multiple intervention components, and six studies included wearable devices to measure and/or prompt behavior change. There was an overall trend where intervention groups reduced SB vs. control groups, often coupled with an increase in moderate-to-vigorous physical activity. This review suggests that there is some promise for intervention strategies to reduce SB in cancer patients and survivors. There is a need for more high-quality randomized controlled trials to understand how to best decrease SB in cancer patients and survivors.

Time-Varying Associations Between Device-Based and Ecological Momentary Assessment-Reported Sedentary Behaviors and the Concurrent Affective States Among Adolescents: Proof-of-Concept Study.

BACKGROUND: Previous studies on affective state-sedentary behavior (SB) associations have not accounted for their potentially time-varying nature and have used inconsistent SB measurement modalities. We investigated whether the strength of the associations between affective states and SB varied as a function of the time of day and by SB measurement modality (device-measured SB vs ecological momentary assessment-reported screen-based SB) in youth. OBJECTIVE: This study aimed to establish a proof of concept that SB-affective state associations may not be static during the day. In addition, we aimed to inform the methodology of future work, which may need to model associations as functions of the time of day and carefully consider how SB is operationalized or measured. METHODS: A total of 15 adolescents (age: mean 13.07, SD 1.03 years; 10/15, 67% female; 6/15, 40% Hispanic; 10/15, 67% healthy weight) wore thigh-mounted activPAL accelerometers and simultaneously reported their screen-based SBs and concurrent positive and negative affective states via ecological momentary assessment for 7 to 14 days (N=636 occasions). Time-varying effect models (varying slopes) examined how each measure of SB was associated with concurrent affective states from 7 AM to 8 PM. RESULTS: Time-varying effect model plots revealed that these associations varied in strength throughout the day. Specifically, device-based SB was related to greater concurrent negative affect only after approximately 5 PM and was unrelated to concurrent positive affect. Screen-based SB was related to greater concurrent negative affect only from 7 AM to approximately 9 AM. This was also related to greater concurrent positive affect from 7 AM to approximately 9:30 AM and from approximately 3 PM to approximately 7 PM. CONCLUSIONS: We provide preliminary evidence to suggest that future confirmatory studies investigating the SB-affective state relationship should consider the time-varying nature of these associations and SB measurement modality. There may be critical time windows when specific types of SBs co-occur with affect, suggesting that interventions may need tailoring to the time of day and type of SB if future studies using similar methodologies can replicate our findings.

Day-level associations of physical activity and sedentary time in mother-child dyads across three years: a multi-wave longitudinal study using accelerometers.

Understanding associations between mothers' and children's physical activity and sedentary behavior on more fine-grained timescales can provide insights into real-time intervention opportunities. This study examined the extent to which mothers' and their children's device-measured moderate-to-vigorous physical activity (MVPA) and sedentary time (SDT) were associated at the day level during non-school time. Mother-child dyads (N = 193; baseline Mean ages = 40.69 ± 6.11 [mother] and 9.57 ± 0.89 [child] years) provided 3,135 paired days of accelerometry data from six bi-annual waves across three years. Controlling for covariates, multilevel models revealed that mothers' and their children's MVPA and SDT were positively associated at the day level during non-school time, both on weekdays and weekends. During weekdays, the day-level association for SDT was stronger for older than younger children, and the day-level association for MVPA was stronger for boys than girls. Designing family-based interventions targeting school-age children and their mothers during non-school time across the week may be useful for promoting active lifestyles.

Understanding daily life experiences of women who smoke: The role of smoking-related weight control expectancies.

Smoking-related weight control expectancies are a motivational factor for maintaining cigarette use, particularly among women. Yet, less research has investigated the physiological and behavioral daily life weight-related experiences of women with smoking-related weight control expectancies. Increased research could contribute to understanding of maintenance factors for this group of smokers as well as unique intervention targets. Female smokers completed a baseline survey of smoking-related weight control expectancies and 35-days of ecological momentary assessment of physiological (i.e., smoking-related reduction in hunger, end-of-day perceived weight gain and bloating) and behavioral (i.e., daily exercise and sitting) weight-related experiences. Higher smoking-related weight control expectancies were associated with perceived smoking-related reductions in hunger and end-of-day perceived weight gain. Smoking-related weight control expectancies did not significantly associate with end-of-day bloating, daily exercise, or sitting. Given these findings, smoking-related weight control expectancies may maintain smoking in order to reduce hunger and to cope with perceived fluctuations in weight in daily life. It is critical for smoking cessation programs to assess smoking-related weight control expectancies and implement targeted treatments for these women.

Physical Activity and Sedentary Time Among Mothers of School-Aged Children: Differences in Accelerometer-Derived Pattern Metrics by Demographic, Employment, and Household Factors.

BACKGROUND: Dynamic patterns of how physical activity and sedentary time are accumulated across the day are associated with health outcomes, independent of total activity levels. Individual factors may influence activity patterns in mothers, but these associations are unknown. This study examined multivariable associations between demographic, employment, and household factors and day-level pattern metrics. METHODS: Mothers (N = 200) of school-aged children (ages 8-12 years) participated in 6 semi-annual 7-day assessments. Waist-worn Actigraph GT3X accelerometers assessed daily moderate-to-vigorous physical activity (MVPA; minutes, number of short bouts [<10 minutes], proportion of long bouts [≥20 minutes]) and sedentary time (minutes, number of breaks, proportion of long bouts [≥60 minutes], temporal dispersion). Multilevel models examined associations between individual characteristics and activity metrics. RESULTS: There were 4,930 day-level observations. Having a college degree was associated with fewer short MVPA bouts (B = -2.67), more sedentary minutes (B = 21.66), greater long sedentary bouts (odds ratio = 1.50), and having sedentary time less evenly distributed across the day (B = 0.01). Working full-time was associated with more short MVPA bouts (B = 1.39) and breaks in sedentary time (B = 2.08). Having at least 1 infant (<6 months old) in the same household was associated with fewer MVPA minutes (B = -0.11) and short MVPA bouts (B = -4.46), whereas having at least 1 young child (6 months-5 years old) in the same household was associated with fewer sedentary minutes (B = -11.85) and fewer long sedentary bouts (odds ratio = 0.70). CONCLUSIONS: Day-level pattern metrics show differences not captured when examining total volume alone. Results provide more nuanced information as to how activity is accumulated in terms of bouts and breaks, which can inform programs to increase MVPA and reduce sedentary time by elucidating subpopulations that should be targeted by health behavior interventions.

Momentary intentions and perceived behavioral control are within-person predictors of sedentary leisure time: preliminary findings from an ecological momentary assessment study in adolescents.

Previous studies among adolescents conceptualize behavioral cognitions [e.g., intentions and perceived behavioral control (PBC)] as stable trait-like factors despite evidence suggesting they vary momentarily. We examined whether intentions and PBC momentarily relate to subsequent sedentary time during non-school periods. Healthy adolescents (N = 15, ages 11-15) reported their intentions and PBC regarding sedentary leisure behaviors via ecological momentary assessment (EMA) up to seven times/day for 14 days. Sedentary time in the two hours following each EMA prompt was measured by ActivPAL accelerometers. When participants reported greater sedentary intentions (within-person ß = 1.1, 95% CI 0.2, 2.1, p = 0.0213) and sedentary PBC (within-person ß = 1.7, 95% CI 0.6, 2.8, p = 0.0029), they accumulated greater sedentary time. This demonstrates that sedentary intentions and PBC are acutely associated with sedentary time among adolescents. Our findings highlight the potential for implementing just-in-time activity interventions among adolescents during at-risk periods within the day, characterized by deviations from one's usual intentions and PBC levels.

Patterns of Objectively Measured Sedentary Time and Emotional Disorder Symptoms Among Youth.

OBJECTIVE: We examined the within-person longitudinal and bidirectional associations between patterns of sedentary time accumulation [alpha (sedentary bout duration/length), sedentary breaks (number of breaks in sedentary bouts)], and symptoms of major depressive disorder and generalized anxiety disorder. METHODS: Children [N = 167, 10.1(0.9) years old, 54.5% female, 59.3% Hispanic, 35.9% overweight/obese at baseline] participated in a 3-year longitudinal study that consisted of assessments of sedentary time, and depressive and anxiety symptoms. At each assessment, participants wore accelerometers and completed the Revised Child Anxiety and Depression Scale. Separate random intercept cross-lagged panel models estimated the within-person longitudinal and bidirectional associations between alpha, sedentary breaks, and symptoms of major depressive disorder and generalized anxiety disorder across chronological age intervals. RESULTS: Having greater than one's own usual depressive symptoms at age 11 was associated with fewer sedentary breaks 1 year later. Having greater than one's own usual generalized anxiety symptoms at age 11 was associated with longer sedentary bouts and fewer sedentary breaks 1 year later. In contrast, having greater than one's own usual sedentary breaks at age 10 was associated with fewer generalized anxiety symptoms 1 year later. All other associations, including at younger ages, were null. CONCLUSION: Deviations from one's usual levels of depressive or anxiety symptoms may be important for how sedentary time is subsequently accumulated. Intraindividual processes appear to be at play, therefore more within-person research is needed. Intervention strategies for promoting a healthier accumulation of sedentary time may consider targeting occasions when depressive and anxiety symptoms are greater than usual.

Associations among affect, diet, and activity and binge-eating severity using ecological momentary assessment in a non-clinical sample of middle-aged fathers.

PURPOSE: Knowledge of within-day factors associated with binge-eating severity among middle-aged fathers is limited. The purpose of the current report was to examine within-day associations of affect, diet, and activity in relation to binge-eating severity using ecological momentary assessment (EMA) in men. METHODS: Twenty-three middle-aged fathers completed 8 days of EMA and wore accelerometers to objectively assess activity. Generalized estimating equations assessed relationships among affect, diet, and activity and binge-eating severity. RESULTS: When positive affect was above average, men reported greater binge-eating severity in the next 2 h. Oppositely, when negative affect was above average, men reported less binge-eating severity in the next 2 h. At times when men reported consumption of sweets and fast food, they reported higher binge-eating severity during the same 2-h window. Men with greater average levels of light activity reported less overall binge-eating severity. CONCLUSIONS: Findings show that affect, unhealthy food intake, and light activity could be targeted among middle-aged fathers to reduce binge-eating severity and prevent eating disorders. LEVEL OF EVIDENCE: Level III: Evidence obtained from cohort or case-control analytic studies.

The Acute Relationship between Affective States and Stress Biomarkers in Ethnic Minority Youths.

Background: Whether affective states acutely predict the hypothalamic-pituitary-adrenal (HPA) axis activities and whether energy balance-related behaviors moderate the affect-HPA axis relationship in obese youths are not well-understood. Methods: 87 mostly obese (94.3% obese) minority adolescents (mean: 16.3 ± 1.2 years old; 56.8% Latino and 43.2% African American) participated in a randomized crossover trial in an observation laboratory, where they received either high-sugar/low-fiber (HSLF) or low-sugar/high-fiber (LSHF) meals first and then crossed over in the next visit 2-4 weeks later. During each visit, they rated five affective states and provided a saliva sample every 30 min for the first 5 h and wore a waist-worn accelerometer. The association between the affect ratings and cortisol levels in the subsequent 30 min and the moderation effect of energy balance-related behavior were examined using multilevel models. Results: Within-person negative affect (ß = 0.02, p = 0.0343) and feeling of panic (ß = 0.007, p = 0.004) were acutely related to the subsequent cortisol level only during the HSLF condition. The time spent in moderate-to-vigorous physical activity did not moderate the acute relationship between affect and the subsequent cortisol level. Conclusions: Negative affect could be acutely related to heightened HPA axis activities in youths, but only when they were exposed to meals with high sugar and low fiber content. These results suggest that the meals' sugar and fiber content may modulate HPA axis reactivity to negative affect in youths.

US Population-referenced Percentiles for Wrist-Worn Accelerometer-derived Activity.

PURPOSE: This study aimed to present age- and sex-specific percentiles for daily wrist-worn movement metrics in US youth and adults. This metric represents a summary of all recorded movement, regardless of the purpose, context, or intensity. METHODS: Wrist-worn accelerometer data from the combined 2011-2014 National Health and Nutrition Examination Survey cycles and the 2012 National Health and Nutrition Examination Survey National Youth Fitness Survey were used for this analysis. Monitor-Independent Movement Summary units (MIMS-units) from raw triaxial accelerometer data were used. We removed the partial first and last assessment days and days with ≥5% nonwear time. Participants with ≥1 valid day were included. Mean MIMS-units were calculated across all valid days. Percentile tables and smoothed curves of daily MIMS-units were calculated for each age and sex using the Generalized Additive Models for Location Shape and Scale. RESULTS: The analytical sample included 14,705 participants age ≥3 yr. The MIMS-unit activity among youth was similar for both sexes, whereas adult females generally had higher MIMS-unit activity than did males. Median daily MIMS-units peaked at age 6 yr for both sexes (males, 20,613; females, 20,706). Lowest activity was observed for males and females 80+ yr of age: 8799 and 9503, respectively. CONCLUSIONS: Population referenced MIMS-unit percentiles for US youth and adults are a novel means of characterizing total activity volume. By using MIMS-units, we provide a standardized reference that can be applied across various wrist-worn accelerometer devices. Further work is needed to link these metrics to activity intensity categories and health outcomes.

Cross-Sectional and Longitudinal Associations between Non-School Time Physical Activity, Sedentary Time, and Adiposity among Boys and Girls: An Isotemporal Substitution Approach.

This study investigated the cross-sectional and longitudinal associations of the substitution of non-school time light physical activity (LPA), moderate-to-vigorous physical activity (MVPA), and sedentary time (ST) with adiposity in boys and girls. Boys (n = 65, baseline Mage= 9.93 ± 0.86 years) and girls (n = 77, baseline Mage = 10.17 ± 0.95 years) wore waist-worn accelerometers (ActiGraph GT3X) at baseline and at a 30-month follow-up, from which non-school time LPA, MVPA, ST, and total device wear were quantified. Body mass index (BMI) and waist-to-height-ratio (WHR) were measured at baseline and follow-up. Body fat percent (BF%) was obtained at follow-up only. Isotemporal substitution models assessed the cross-sectional and longitudinal associations of reallocating non-school time activity with BMI, WHR and BF%. In boys, replacing 30 min/day of LPA with MVPA was cross-sectionally (ß = -8.26, p < 0.05) associated with a lower BF%. Replacing 30 min/day of ST with MVPA was cross-sectionally (ß = -6.02, p < 0.05) associated with a lower BF% in boys. Longitudinally in boys, replacing 30 min of change in LPA with MVPA (ß = -7.42, p < 0.10) and replacing 30 min of change in MVPA with ST (ß = 5.78, p < 0.10) over 30 months was marginally associated with less BF%. Associations were null in girls (p > 0.05). These results may support targeting activity reallocation during non-school time for the purposes of adiposity improvement in boys. A multi-behavioral approach may be more appropriate for girls, as non-school time activity may not be driving adiposity status.

Associations of Mothers' and Children's Stress With Children's Device-Measured Physical Activity and Sedentary Behavior Trajectories Across 3 Years.

BACKGROUND: Psychological stress has adverse effects on health-related behaviors, yet longitudinal research is lacking. Research examined how children's and mothers' perceived stress are associated with children's physical activity and sedentary behavior trajectories across 3 years. METHODS: Mothers and their children (N = 186 dyads; 8-12 y at baseline, 57% Hispanic) completed 6 assessments across 3 years. Children and mothers self-reported perceived stress using the Stress in Children Scale and Perceived Stress Scale, respectively. Children's moderate to vigorous physical activity (MVPA) and sedentary behavior were assessed using accelerometers. Mixed models examined interactions of mothers' and children's perceived stress by time elapsed in the study on children's MVPA and sedentary behavior. RESULTS: The perceived stress × time elapsed interactions were significant for children's MVPA and sedentary behavior (Ps < .05). Higher average perceived stress in mothers was associated with greater decreases in children's MVPA and increases in children's sedentary behavior. The child stress × time elapsed interactions was significant for children's MVPA (P < .05) but not sedentary behavior. Higher average perceived stress in children was associated with smaller decreases in children's MVPA. CONCLUSION: Interventions to promote physical activity and reduce screen time in children should mitigate the effects of psychological stress, especially among mothers, on these behaviors.

Age-varying Bi-directional Associations Between Momentary Affect and Movement Behaviors in Children: Evidence From a Multi-wave Ecological Momentary Assessment Study.

BACKGROUND: The bi-directional associations between affective states and movement behaviors (e.g., physical activity, sedentary behavior) have been observed in children. It is unclear if the strength of these bi-directional associations varies with age as children transition from childhood to adolescence. PURPOSE: This multi-wave ecological momentary assessment (EMA) study investigates the acute time-varying associations between affect and movement behaviors among youth. METHODS: Children (N = 195, baseline mean age = 10.72, range = 8-12 years, mean BMI-z = 0.49, 51% female) participated in a six-wave EMA study across three years. Each EMA survey captured momentary positive and negative affect. Time spent in moderate-to-vigorous physical activity (MVPA) and sedentary time in the 15-min window before and after each EMA survey was calculated using accelerometry data. Time-varying effect models (TVEM) examined the acute bi-directional associations between momentary positive/negative affect and MVPA/sedentary time across ages 8 to 14. RESULTS: Children provided 14,246 valid activity-matched EMA surveys across all waves. TVEM plots revealed that the directionality and the strength (time-varying slopes) of associations between momentary affect and activity levels vary across ages. Positive affect was associated with higher MVPA levels and lower sedentary time at younger ages, whereas negative affect linked to lower MVPA levels and more sedentary time at older ages. CONCLUSIONS: The acute associations between momentary affect and (in)activity levels may vary as a function of children's age. Applying TVEM to intensive longitudinal data could provide valuable information for developing age-tailored interventions that promote healthy lifestyles among children and adolescents.

Examining the same-day relationship between morning cortisol after awakening, perceived stress in the morning, and physical activity in youth.

Most children in the United States currently do not meet physical activity (PA) guidelines, and perceived stress is a known barrier against PA. However, most studies have solely focused on the between-subject (BS) association of stress and PA, whereas the within-subject (WS) relationship remains under-studied in children. This limits our understanding of day-level psychosocial factors that influence children's PA engagement. This study assessed the same-day associations of the Morning Cortisol after Awakening (MCA) and morning perceived stress with moderate-to-vigorous physical activity (MVPA) in children using Ecological Momentary Assessment (EMA) methodologies. The analytic sample consisted of 143 children from Los Angeles in the Mothers and Their Children's Health (MATCH) study. Children collected four saliva samples and wore accelerometers to assess MVPA minutes across four days (two weekdays and two weekend days) during each data collection wave. On weekend days, they also answered a mobile phone EMA survey on perceived stress within 1 h of awakening. Data from four assessment waves, each approximately six months apart, were combined and analyzed cross-sectionally. Multilevel modeling, which adjusts for the nested data structure, was used to test the same-day associations of MCA and weekend morning perceived stress with MVPA. On weekend days when morning perceived stress was higher than usual, participants engaged in more MVPA on the same day (ß = 0.79, SE = 0.32, p = 0.02), but no association was found between MCA and MVPA. These findings elucidate same-day factors that predict MVPA in children and inform future WS studies on stress and PA.HighlightIt is unknown how stress influences children's daily activity levels. We tested if two types of stress (self-reported and saliva-measured) are related to children's daily activity. We found that self-reported stress is associated with physical activity, but saliva-measured stress is not.

Longitudinal associations of maternal stress and child stress with child body mass index trajectory.

BACKGROUND: Although exposure to stress is common among children and their parents, longitudinal research on the effects of perceived stress on child obesity risk is lacking. This study examined the 3-year longitudinal associations of children and mothers' perceived stress with children's body mass index (BMI). METHODS: A sample of 199 mothers and their children (8-12 years at baseline, 56% Hispanic) completed six semi-annual assessments across 3 years with questionnaire-based self-report measures of perceived stress and measured height/weight. Parallel process latent growth curve modelling specified regressions of latent intercept and slope of children's BMI on latent intercepts and slopes for mothers' and children's perceived stress. RESULTS: Greater child self-reported perceived stress at baseline predicted greater increase in children's BMI across the six assessments whereas mother self-reported perceived stress at baseline was unrelated to change in child BMI. Baseline child BMI was unrelated to change in children or mothers' perceived stress across the six assessment waves. CONCLUSION: Children's own perceptions of stress may play a larger contributing role in BMI progression during middle childhood than their mother's perceived stress levels. These findings underscore the importance of focusing on children's stress-coping strategies for promoting a healthy weight.