The contribution and interplay of implicit and explicit processes on physical activity behavior: empirical testing of the physical activity adoption and maintenance (PAAM) model.

The adoption and maintenance of physical activity (PA) is an important health behavior. This paper presents the first comprehensive empirical test of the Physical Activity Adoption and Maintenance (PAAM) model, which proposes that a combination of explicit (e.g., intention) and implicit (e.g., habit,, affect) self-regulatory processes is involved in PA adoption and maintenance. Data were collected via online questionnaires in English, German, and Italian at two measurement points four weeks apart. The study included 422 participants (Mage= 25.3, SDage= 10.1; 74.2% women) from Germany, Switzerland, Italy, Canada, and the U.S. The study results largely supported the assumptions of the PAAM model, indicating that intentions and habits significantly mediate the effects of past PA on future PA. In addition, the effect of past PA on future PA was shown to be significant through a mediation chain involving affect and habit. Although the hypothesis that trait self-regulation moderates the intention-behavior relationship was not supported, a significant moderating effect of affect on the same relationship was observed. The results suggest that interventions targeting both explicit and implicit processes may be effective in promoting PA adoption and maintenance.

The Sport Experience Measure for Children and Youth (SEM:CY): A Rasch Validation Study.

This study employed Rasch analyses to validate a novel measure of sport experience: the Sport Experience Measure: Children and Youth (SEM:CY). Analyses were applied to self-reported data of n = 503 young people (age 9-18 years, M = 12.91, 50% female) in Canada who were engaging in sport during the previous 12 months. The revised measure, consisting of 24 items on a 3-point response scale, demonstrated good fit statistics (e.g., item fit residual: M = -0.50, SD = 0.94 and person fit residual: M = -0.62, SD = 2.33), an ability to reliably discriminate between levels of sport experience, and an absence of differential item functioning for various groups (males and females, older and younger individuals, solo and team sports, and those playing at various competitive levels, including recreation). The SEM:CY is a succinct tool that can serve as a valuable means to gauge the quality of an individual's sport experience, which can facilitate positive youth development and sustain participation across the life span.

Exercise identity and physical activity behavior during late adolescence: A four wave cross-lagged panel model.

Research has shown that physical activity behavior tends to decline across adolescence before stabilizing in adulthood. Identifying salient factors underlying these behavioral changes is therefore imperative for informing intervention development. This study explored the temporal nature of the relationship between exercise identity and physical activity behavior during the transition out of high school. An analysis of data from the Application of integrated Approaches to understanding Physical activity during the Transition to emerging adulthood (ADAPT) prospective cohort study was conducted, involving 1451 Canadian adolescents (Mage = 15.93 ± 0.53 years; 52.4% female). Participants completed the International Physical Activity Questionnaire-Short Form to report weekly moderate-to-vigorous physical activity and an abbreviated version of the Exercise Identity Scale yearly for four years beginning in Grade 11. A four-wave cross-lagged panel model was used to test bi-directional associations between exercise identity and physical activity behavior. Significant auto-regressive effects for exercise identity and physical activity were observed across all four time points. Significant positive cross-lagged paths were observed for exercise identity predicting future physical activity at all time points; however, none of the cross-lagged paths with physical activity predicting future exercise identity were significant. Collectively, these findings support existing theory that emphasizes the role that identity plays in physical activity behavior. Interventions seeking to attenuate the physical activity declines typically observed during the transition to emerging adulthood should therefore consider adopting behavior change techniques that target identity, as it appears to be an important psychological determinant underlying future physical activity engagement.

Relationship between Workload, Psychological State and Sleep in Female Soccer Athletes.

This study assessed the multifaceted relations between measures of workload, psychological state, and recovery throughout an entire soccer season. A prospective longitudinal study was utilized to measure workload (GPS training load, RPE), psychological state (mental stress, mental fatigue, and mood), and recovery (sleep duration, sleep quality, and soreness), across ninety observations. Separate linear-mixed effect models were used to assess outcomes of RPE, soreness, and sleep duration. A linear mixed-effects model explained 59% of the variance in RPE following each session. Specifically, each standard deviation increase in GPS load and mental stress in the morning prior to training increased RPE by 1.46(SE=0.08) and 0.29(SE= 0.07) respectively, following that day's training. Furthermore, a significant interaction was found between several predictor variables and chronological day in the season while predicting RPE. Specifically, for each standard deviation increase in GPS load, RPE went up by 0.055 per day across the season suggesting that load had a higher impact on RPE as the season progressed. In contrast, the interaction of day by mental stress, sleep duration, and soreness continued to be stronger as the season progressed. Each linear mixed-effect model predicted a larger amount of variance when accounting for individual variations in the random effects.

Independent and Joint Associations of Physical Activity and Sleep on Mental Health Among a Global Sample of 200,743 Adults.

BACKGROUND: Previous research has demonstrated that both sleep and physical activity (PA) are independently associated with various indicators of mental health among adults. However, their joint contribution to mental health has received limited attention. The present study used cross-sectional data from the Mental Health Million Project to examine the independent and joint effects of sleep and PA on mental health among a global sample of adults, and whether these effects differ among individuals receiving mental health treatment. METHOD: The sample included 200,743 participants (33.1% young adults, 45.6% middle-aged adults, 21.3% older adults; 57.6% females, 0.9% other) from 213 countries, territories, and archipelagos worldwide that completed a comprehensive 47-item assessment of mental health including both problems (i.e., ill-being) and assets (i.e., well-being): the Mental Health Quotient. Participants also reported their weekly frequency of PA and adequate sleep, and mental health treatment status. A series of generalized linear mixed models were computed. RESULTS: Independent dose-response associations were observed, whereby greater amounts of PA and adequate sleep were each associated with better mental health. In addition, a synergistic interaction was observed in which the positive correlation of PA with mental health was strengthened with greater frequency of adequate sleep. These benefits were less pronounced among adults receiving mental health treatment. CONCLUSION: While findings suggest sleep can help to offset the negative influence of a physically inactive lifestyle (and vice versa), our results point to a "more is better" approach for both behaviors when it comes to promoting mental health.

Trends in adherence to the 24-h movement guidelines among US adolescents from 2011 to 2019: Evidence from repeated cross-sectional cycles of the Youth Risk Behavior Surveillance System.

BACKGROUND: Adherence to the 24-h movement guidelines is associated with various health benefits, but given the novelty of these integrative recommendations, little is known about year-to-year trends in guideline adherence in adolescents. This study investigated trends of adherence to the 24-h movement guidelines among US adolescents. METHODS: Data from 2011 to 2019 cycles of the Youth Risk Behavior Surveillance System were used, which included 62 589 US adolescents aged 14-17 years (female: unweighted sample size = 31 876, 51%; weighted% = 50.1%). Participants self-reported their demographic information (i.e., sex, age, race/ethnicity), physical activity, screen time and sleep duration. Meeting the 24-h movement guidelines was operationalized as simultaneously engaging in 60 min or more of moderate-to-vigorous physical activity, no more than 2 h of screen time, and 8-10 h of sleep per day. Trend analysis was used to examine the secular changes in adherence to the integrated guidelines from 2011 to 2019. RESULTS: Downward trends in adherence to the 24-h movement guidelines were observed among adolescents from 2011 (3.6%) to 2019 (2.6%). After stratification by sex, age, and race/ethnicity, similar downward trends in the guideline adherence were observed in females and Black/African American adolescents. The lowest prevalence of meeting the individual guidelines was for the PA guidelines (25.6%). Movement guideline adherence was consistently lowest among females, older adolescents, and those who identified as Black/African American. CONCLUSIONS: Adherence to the 24-h movement guidelines has declined among US adolescents over the past decade. Interventions should prioritize an integrative approach that could increase concurrent adherence to each of the 24-h movement guideline, particularly among female, older and minority adolescents.

Associations Between Intersecting Sociodemographic Characteristics and Device-Measured Physical Activity Among Children and Adolescents Living in the United States.

BACKGROUND: Despite robust evidence demonstrating sociodemographic characteristics may underly some of the disparities in physical activity observed among children and adolescents, the often-overlooked nexus of potential interactions between these characteristics warrants further exploration. This study explored the intersectionality of gender, race/ethnicity, parental education, and household income in relation to device-measured physical activity volume and intensity in a nationally representative sample of US children and adolescents. METHODS: Cross-sectional data from 3 cycles of the US National Health and Nutrition Survey (2011-2012; 2012 National Youth Fitness Survey; and 2013-2014) were used. A total of 6116 participants (49% female) between 3 and 17 years of age wore an accelerometer on their nondominant wrist for 7 days. Monitor-independent movement summary units were used to represent physical activity volume and intensity. A Social Jeopardy Index was created to represent increasing levels of intersecting social disadvantages based on combinations of gender, race/ethnicity, parental education, and household income-to-poverty ratio tertiles. Generalized linear regression models were computed. RESULTS: The results showed social disadvantages become increasingly evident among children and adolescents during the most intense 60 minutes of daily physical activity (B = -48.69 [9.94] SE, P < .001), but disparities in total volume were not observed (B = 34.01 [44.96] SE, P = .45). CONCLUSIONS: Findings suggest that patterns of physical activity behavior may differ based on intersecting sociodemographic characteristics-more socially disadvantaged children and adolescents appear to accumulate activity at lighter intensities. Collecting contextual information about device-measured physical activity represents an important next step for gaining insight into these sociodemographic differences.

The golden ratio in baseball: the influence of historical eras on winning percentages in major league baseball.

Introduction: The golden section or golden ratio (61.8% or 0.618) is a mathematical phenomenon that appears in art, literature, music and nature with such ubiquity that it is thought to be a fundamental principle of aesthetic organisation. The golden ratio also manifests in sport, particularly as the proportion of wins to losses required to win a Major League Baseball championship. This study extends early work on the golden ratio in baseball by incorporating more than three decades of additional data. Methods: This study involved a historically contextualized examination of how winning percentages have changed across the seven historical eras of modern baseball, including analyses of the relative contribution of offensive and defensive statistics to championship winning teams. Data was extracted from Baseball Reference and included statistics for 398 championship winning teams from both the American and National Leagues between 1901 and 2019. Pearson correlation coefficients were computed for winning percentage with indicators of offensive and defensive performance during each era. Main and interaction effects of Era and League on winning percentage were examined using factorial ANOVA, with follow-up analyses examining whether the golden ratio was included in each factor's 95% confidence interval. Results: Our findings suggest that winning percentages for championship teams were closest to the golden ratio during eras where the relative contribution of offense and defense was most closely balanced: the Integration Era (1942-1960) and the Expansion Era (1961-1976). Discussion: Previous scholarship theorizes that the golden ratio represents an aesthetic ideal or a Gestalt archetype. If this aesthetic theory is applied to sporting competition, these results suggest that baseball may be most aesthetically appealing to fans when offense and defense is balanced in such a way as to ensure that championship teams win 61.8% of their games.

Characteristics of 24-hour movement behaviours and their associations with mental health in children and adolescents.

Background: Time-use estimates are typically used to describe 24-hour movement behaviours. However, these behaviours can additionally be characterised by other easily measured metrics. These include sleep quality (e.g., sleep efficiency), 24-hour rest-activity rhythmicity (e.g., between-day rhythm variability), and directly measured acceleration metrics (e.g., intensity gradient). Associations between these characteristics and youth mental health are unclear. This study aimed to [1] compare 24-hour movement behaviour characteristics by sex and age groups, [2] determine which movement behaviour characteristics were most strongly associated with mental health outcomes, and [3] investigate the optimal time-use behaviour compositions for different mental health outcomes. Methods: Three-hundred-and-one children and adolescents (age 9-13 y; 60% girls) wore accelerometers for 24-hours/day over 7-days. Overall mental health, externalising, and internalising problems were self-reported using the Strengths and Difficulties Questionnaire. 24-hour movement behaviour characteristics were categorised as time-use estimates, sleep quality, 24-hour activity rhythmicity, and directly measured acceleration. Linear mixed models and compositional data analysis were used to analyse the data in alignment with the study aims. Results: Time-use estimates, directly measured accelerations, and 24-hour rest-activity rhythm metrics indicated that children were significantly more physically active (p = .01-<0.001) than adolescents. Children were also less sedentary (p < .01), slept longer (p = .02-0.01), and had lower sleep efficiency. Boys were significantly more active than girls (p < .001) who in turn accrued more time in sleep (p = .02). The timing of peak activity was significantly later among adolescents (p = .047). Overall mental health and externalising problems were significantly associated with sleep, sedentary time, sleep efficiency, amplitude, and inter-daily stability (p = .04-0.01). The optimal time-use compositions were specific to overall mental health and externalising problems and were characterised by more sleep, light and vigorous physical activity, and less sedentary time and moderate physical activity than the sample's mean time-use composition. Conclusions: Extracting and examining multiple movement behaviour characteristics from 24-hour accelerometer data can provide a more rounded picture of the interplay between different elements of movement behaviours and their relationships with mental health than single characteristics alone, such as time-use estimates. Applying multiple movement behaviour characteristics to the translation of research findings may enhance the impact of the data for research users. Supplementary Information: The online version contains supplementary material available at 10.1186/s44167-023-00021-9.

Towards the development of a quality youth sport experience measure: Understanding participant and stakeholder perspectives.

Quality sport experiences may be a key underlying mechanism through which continued sport participation may facilitate positive youth development. However, what constitutes a quality sport experience for youth is poorly understood due to a lack of comprehensiveness among existing measures. This study aimed to identify the salient factors that constitute quality sport experience for youth by capturing athletes and stakeholder perspectives with a broader goal of developing a more robust quality sport experiences measure. A total of 53 youth athletes and stakeholders (i.e., parents, coaches, and sport administrators) completed semi-structured interviews or focus groups about what they felt were important aspects of a quality sport experience for youth. Inductive content analysis of the data identified four themes representing important indicators for a quality sport experience for youth: fun and enjoyment, opportunity for sport skill development and progress, social support and sense of belonging, and open and effective communication. These higher order themes were found among each of the groups that have important interpersonal relationships with athletes, as well as among athletes themselves. Each of these themes were also related to one another. Collectively, findings outline a framework to understand what constitutes a quality sport experience for youth. The Quality Sport Experience Framework for Youth will help in the development of a quantitative tool to assess this construct and enable researchers to examine how these experiences contribute to continued engagement in sport and positive developmental outcomes among youth sport participants.

Associations between collagen X biomarker and linear growth velocity in a pediatric chronic kidney disease cohort.

BACKGROUND: Collagen X biomarker (CXM) is a novel biomarker of linear growth velocity. We investigated whether CXM correlated with measured growth velocity in children with impaired kidney function. METHODS: We used data from children aged 2 through 16 years old enrolled in the Chronic Kidney Disease in Children (CKiD) study. We assessed the association between CXM level and growth velocity based on height measurements obtained at study visits using linear regression models constructed separately by sex, with and without adjustment for CKD covariates. Linear mixed-effects models were used to capture the between-individual and within-individual CXM changes over time associated with concomitant changes in growth velocity from baseline through follow-up. RESULTS: A total of 967 serum samples from 209 participants were assayed for CXM. CXM correlated more strongly in females compared to male participants. After adjustment for growth velocity and CKD covariates, only proteinuria in male participants affected CXM levels. Finally, we quantified the between- and within-participant associations between CXM level and growth velocity. A between-participant increase of 24% and 15% in CXM level in females and males, respectively, correlated with a 1 cm/year higher growth velocity. Within an individual participant, on average, 28% and 13% increases in CXM values in females and males, respectively, correlated with a 1 cm/year change in measured growth. CONCLUSIONS: CXM measurement is potentially a valuable aid for monitoring growth in pediatric CKD. However, future research, including studies of CXM metabolism, is needed to clarify whether CXM can be a surrogate of growth in children with CKD. A higher resolution version of the Graphical abstract is available as Supplementary information.

24-hour movement guideline adherence and mental health: A cross-sectional study of emerging adults with chronic health conditions and disabilities.

BACKGROUND: Recent work has shown that individuals with chronic health conditions and disabilities (CCD) meet the 24-h movement guidelines at lower rates than population norms; however, the evidence base remains limited across different stages of the lifespan and very few studies have examined associations with mental health outcomes. OBJECTIVE: This study examined 24-h movement guideline adherence among emerging adults with CCD compared to those without and associations between guideline adherence and indicators of mental health. METHODS: This cross-sectional study used data from the 2020 cycle of the Canadian Campus Wellbeing Survey. A total of 17,874 emerging adults enrolled at 20 post-secondary institutions (mean age = 21.6 ± 2.94 years; 65.2% female), including 3336 who identified with a CCD, self-reported their movement behaviors (physical activity, sedentary behaviors, sleep) and completed measures of psychological distress and mental well-being. Logistic regressions models were computed to examine differences in guideline adherence. Propensity score weighted linear regression models were computed to examine associations between guideline adherence and indicators of mental health. RESULTS: Emerging adults with CCD had significantly lower odds of meeting the 24-h movement guidelines than their peers, and disparities in guideline adherence were most pronounced among those with multimorbidity, developmental, and physical disabilities. Guideline adherence was associated with significantly more favorable scores for psychological distress and mental well-being among those with and without CCD. CONCLUSIONS: Findings suggest emerging adults with CCD engage in less healthy movement behavior patterns than their peers, yet they appear to experience similar mental health benefits when they do meet the 24-h movement guidelines.

Development and evaluation of the IPLAY program: A protocol for a mixed-methods feasibility study targeting newcomer youth.

BACKGROUND: Physical Literacy (PL) is a synthesis construct that ties together movement competencies with affective, motivational, and knowledge-based elements. It is considered foundational to the development of physical activity-related outcomes. Many diverse organizations and programs have embraced the concept and are implementing programs targeting each of those core elements. However, research has lagged behind its interest and adoption. Among the more prominent gaps is the design and evaluation of programs that aim to increase PL within special populations such as new immigrants or refugee youth. METHODS: The Immigrant-focused Physical Literacy for Youth (IPLAY) program is a co-developed evidence-informed 8-week PL program designed for new immigrant and refugee youths who have recently settled in Calgary, Alberta, Canada. This study aims to use a convergent parallel mixed-methods approach to collect, analyse, and interpret quantitative and qualitative data in the evaluation and iteration of the IPLAY program. DISCUSSION: PL programs can be used as a tool to build confidence and physical competencies among newcomer youth. Furthermore, academic-community collaborations in the design and delivery of PL programs can help improve the access and interest for PL programs among newcomer youth. These partnerships are critical and timely considering the recent and upcoming waves of immigration to "arrival cities" across Canada.

Comprehensive Associations between Acidosis and the Skeleton in Patients with Kidney Disease.

SIGNIFICANCE STATEMENT: Renal osteodystrophy (ROD) contributes substantially to morbidity in CKD, including increased fracture risk. Metabolic acidosis (MA) contributes to the development of ROD, but an up-to-date skeletal phenotype in CKD-associated acidosis has not been described. We comprehensively studied associations between acidosis and bone in patients with CKD using advanced methods to image the skeleton and analyze bone-tissue, along with biochemical testing. Cross-sectionally, acidosis was associated with higher markers of bone remodeling and female-specific impairments in cortical and trabecular bone quality. Prospectively, acidosis was associated with cortical expansion and trabecular microarchitectural deterioration. At the bone-tissue level, acidosis was associated with deficits in bone mineral content. Future work investigating acidosis correction on bone quality is warranted. BACKGROUND: Renal osteodystrophy is a state of impaired bone quality and strength. Metabolic acidosis (MA) is associated with alterations in bone quality including remodeling, microarchitecture, and mineralization. No studies in patients with CKD have provided a comprehensive multimodal skeletal phenotype of MA. We aim to describe the structure and makeup of bone in patients with MA in the setting of CKD using biochemistry, noninvasive imaging, and histomorphometry. METHODS: The retrospective cross-sectional analyses included 180 patients with CKD. MA was defined as bicarbonate ≤22 mEq/L. We evaluated circulating bone turnover markers and skeletal imaging with dual energy x-ray absorptiometry and high-resolution peripheral computed tomography. A subset of 54 participants had follow-up. We assessed associations between baseline and change in bicarbonate with change in bone outcomes. Histomorphometry, microCT, and quantitative backscatter electron microscopy assessed bone biopsy outcomes in 22 participants. RESULTS: The mean age was 68±10 years, 54% of participants were male, and 55% were White. At baseline, acidotic subjects had higher markers of bone turnover, lower areal bone mineral density at the radius by dual energy x-ray absorptiometry, and lower cortical and trabecular volumetric bone mineral density and impaired trabecular microarchitecture. Over time, acidosis was associated with opposing cortical and trabecular effects: cortical expansion but trabecular deterioration. Bone-tissue analyses showed reduced tissue mineral density with increased heterogeneity of calcium distribution in acidotic participants. CONCLUSIONS: MA is associated with multiple impairments in bone quality. Future work should examine whether correction of acidosis improves bone quality and strength in patients with CKD.

Interactive Associations between Physical Activity and Sleep Duration in Relation to Adolescent Academic Achievement.

PURPOSE: The present study aimed to examine independent and interactive associations between physical activity and sleep duration with adolescent academic achievement. METHODS: This cross-sectional study used data from the 2019 cycle of the US-based Youth Risk Behavior Surveillance System. A total of 13,677 American adolescents in grades 9 through 12 (MAGE = 16.06 ± 1.24 years; 50.9% female) self-reported their sleep and physical activity behavior as well as their grades. Linear regression models fit with cubic splines were computed to capture potential non-linear associations. RESULTS: Findings for the independent effect models revealed significant curvilinear relationships between physical activity and sleep with academic achievement wherein optimal grades were associated with 7-9 h/night of sleep and 5-7 days/week of physical activity. A significant physical activity by sleep interaction was also observed for academic achievement, which demonstrated that the association between sleep duration and academic achievement is not uniform across levels of physical activity engagement, and tradeoffs may exist. CONCLUSIONS: Overall, the results help to identify different combinations of physical activity and sleep behavior associated with optimal academic achievement and suggest that a one-size-fits-all approach to physical activity and sleep recommendations may not be adequate for promoting academic achievement during adolescence.

Seeking justice, equity, diversity and inclusion in pediatric nephrology.

Inequity, racism, and health care disparities negatively impact the well-being of children with kidney disease. This review defines social determinants of health and describes how they impact pediatric nephrology care; outlines the specific impact of systemic biases and racism on chronic kidney disease care and transplant outcomes; characterizes and critiques the diversity of the current pediatric nephrology workforce; and aims to provide strategies to acknowledge and dismantle bias, address barriers to care, improve diversity in recruitment, and strengthen the pediatric nephrology community. By recognizing historical and current realities and limitations, we can move forward with strategies to address racism and bias in our field and clinical practices, thereby cultivating inclusive training and practice environments.

Being physically active with epilepsy: Insights from young people and their parents.

INTRODUCTION: Researchers have called for innovative tailored interventions to address specific challenges to physical activity (PA) engagement for young people with epilepsy (YPE). Working with YPE and their parents, this study aimed to identify barriers and facilitators to adoption and maintenance of PA among YPE prior to and during the COVID-19 pandemic. METHODS: Ten YPE (all female) and their 13 caregivers, and five additional caregivers to males (N = 18; 72% mothers), completed virtual focus group sessions prior to and during the COVID-19 pandemic. Trained Child Life specialists asked questions about barriers and facilitators of PA engagement experienced by YWE, which included a specific focus on the impact of epilepsy. RESULTS: Thematic analysis of the data identified both epilepsy-specific and generic themes that impact PA participation among YPE. These included: (i) epilepsy experience/impact and accommodation; (ii) safety precautions; (iii) concern about seizures; (iv) social connections and acceptance; (v) parent and family support; (vi) intrapersonal self-regulation and motivation; (vii) health benefits; and (viii) key factors in common with all youth. CONCLUSION: This study provides valuable insight into diverse social-ecological health factors that impact PA participation among YPE from two key stakeholder perspectives (YPE and their caregivers). By understanding these lived experiences, providers can better tailor individual support for YPE and their families to foster and maintain a healthy active lifestyle.

Healthier movement behavior profiles are associated with higher psychological wellbeing among emerging adults attending post-secondary education.

BACKGROUND: Emerging adulthood is a stressful time fraught with new challenges while attending higher education. Identifying protective factors to help reduce the psychological burden that many will experience during this period is therefore important. This study aimed to identify whether emerging adults attending post-secondary education can be classified into distinct profiles based on their 24-h movement behaviors, evaluate correlates of profile membership, and examine relationships between profile membership and indicators of mental health. METHODS: This cross-sectional study used data from Cycle 1 of the Canadian Campus Wellbeing Survey. Emerging adults (N = 15,080; 67.6 % female; mean age = 20.78 ± 2.00) from 20 post-secondary institutions in Canada self-reported their movement behaviors - moderate-to-vigorous physical activity (MVPA), recreational screen time (ST) and sleep - and completed measures of psychological distress and mental wellbeing. Latent profile analysis was employed. RESULTS: Five profiles were identified: low ST with very high (12.6 %), high (24.4 %) and low MVPA (51.2 %) as well as high ST with high (2.3 %) and low MVPA (9.4 %). Profiles had similar sleep patterns and were thus characterized by differences in MVPA and ST. Several socio-demographic variables were associated with profile membership. Profiles characterized by healthier combinations of MVPA, ST and sleep generally reported more favorable scores for indicators of mental health. LIMITATIONS: Cross-sectional data limits causal inference, whereas self-reports may be biased. CONCLUSIONS: Campus-based interventions should focus on getting students to engage in a healthy balance of physical activity and recreational screen use as it has the potential to reduce the mental health burden on emerging adults attending post-secondary education.

Understanding Changes in Adolescent Physical Activity Behaviors and Cognitions Prior to and During the COVID-19 Pandemic.

Despite accumulating evidence that has found significant negative declines in physical activity (PA) as a result of the COVID-19 pandemic, little work has sought to understand how PA cognitions have changed during this period and in relation to behavior change during the pandemic. The purpose of the current study was to investigate the changes in adolescents' PA behaviors and cognitions associated with COVID-19 and prospective predictors of PA using the Multi-Process Action Control (M-PAC) framework. Adolescents were recruited from a large school board and a total of 588 participants (Mage = 15.87 ± 0.43 years, 60% female) completed data collection in both Fall 2019 and 2020-prior to and during the COVID-19 pandemic. Participants completed self-reported measures of moderate-to-vigorous PA (MVPA), participation in organized activities, and variables derived from the M-PAC framework. Mixed effects models were computed to examine longitudinal changes in MVPA and cognitions as well as whether cognitions prior to COVID-19 predict MVPA during COVID-19. A generalized estimating equations model was computed to examine longitudinal changes for participation in organized activities. Findings indicated that MVPA (B = -56.41, p < 0.01) and participation in organized activities (OR = 0.33, p < 0.01) significantly decreased during the COVID-19 pandemic. Correspondingly, there were significant decreases in intentions (B = -0.34), identity (B = -0.19), and habit (B = -0.20), though there were increases in behavioral regulation (B = 0.18). No significant changes were found in affective attitudes, instrumental attitudes, perceived opportunity, and perceived capability. Among the baseline M-PAC cognitions, habit (B = 46.28) was the lone significant predictor of MVPA during COVID-19. Overall results suggest that adolescents' PA behaviors and cognitions were negatively impacted by the COVID-19 pandemic, along with promising evidence that restrictions prompted adaptive utilization of behavioral regulation skills. Moreover, habit appears to play a salient role in predicting PA behaviors during uncertain times involving major life disruptions. These findings highlight the need to dedicate additional attention to PA promotion as COVID-19 moves toward an endemic phase, and that interventions targeting habit formation may be critical for helping adolescents better sustain healthy active lifestyles during major life changes.

Longitudinal Associations between Low Serum Bicarbonate and Linear Growth in Children with CKD.

Background: Poor linear growth is a consequence of chronic kidney disease (CKD) that has been linked to adverse outcomes. Metabolic acidosis (MA) has been identified as a risk factor for growth failure. We investigated the longitudinal relationship between MA and linear growth in children with CKD and examined whether treatment of MA modified linear growth. Methods: To describe longitudinal associations between MA and linear growth, we used serum bicarbonate levels, height measurements, and standard deviation (z scores) of children enrolled in the prospective cohort study Chronic Kidney Disease in Children. Analyses were adjusted for covariates recognized as correlating with poor growth, including demographic characteristics, glomerular filtration rate (GFR), proteinuria, calcium, phosphate, parathyroid hormone, and CKD duration. CKD diagnoses were analyzed by disease categories, nonglomerular or glomerular. Results: The study population included 1082 children with CKD: 808 with nonglomerular etiologies and 274 with glomerular etiologies. Baseline serum bicarbonate levels ≤22 mEq/L were associated with worse height z scores in all children. Longitudinally, serum bicarbonate levels ≤18 and 19-22 mEq/L were associated with worse height z scores in children with nonglomerular CKD causes, with adjusted mean values of -0.39 (95% CI, -0.58 to -0.2) and -0.17 (95% CI, -0.28 to -0.05), respectively. Children with nonglomerular disease and more severe GFR impairment had a higher risk for worse height z score. A significant association was not found in children with glomerular diseases. We also investigated the potential effect of treatment of MA on height in children with a history of alkali therapy use, finding that only persistent users had a significant positive association between their height z score and higher serum bicarbonate levels. Conclusions: We observed a longitudinal association between MA and lower height z score. Additionally, persistent alkali therapy use was associated with better height z scores. Future clinical trials of alkali therapy need to evaluate this relationship prospectively.