Harmonization of three different accelerometers to classify the 24 h activity cycle.

Increasing interest in measuring key components of the 24 h activity cycle (24-HAC) [sleep, sedentary behavior (SED), light physical activity (LPA), and moderate to vigorous physical activity (MVPA)] has led to a need for better methods. Single wrist-worn accelerometers and different self-report instruments can assess the 24-HAC but may not accurately classify time spent in the different components or be subject to recall errors.Objective. To overcome these limitations, the current study harmonized output from multiple complimentary research grade accelerometers and assessed the feasibility and logistical challenges of this approach.Approach. Participants (n= 108) wore an: (a) ActiGraph GT9X on the wrist, (b) activPAL3 on the thigh, and (c) ActiGraph GT3X+ on the hip for 7-10 d to capture the 24-HAC. Participant compliance with the measurement protocol was compared across devices and an algorithm was developed to harmonize data from the accelerometers. The resulting 24-HAC estimates were described within and across days.Main results. Usable data for each device was obtained from 94.3% to 96.7% of participants and 89.4% provided usable data from all three devices. Compliance with wear instructions ranged from 70.7% of days for the GT3X+ to 93.2% of days for the activPAL3. Harmonized estimates indicated that, on average, university students spent 34% of the 24 h day sleeping, 41% sedentary, 21% in LPA, and 4% in MVPA. These behaviors varied substantially by time of day and day of the week.Significance. It is feasible to use three accelerometers in combination to derive a harmonized estimate the 24-HAC. The use of multiple accelerometers can minimize gaps in 24-HAC data however, factors such as additional research costs, and higher participant and investigator burden, should also be considered.

Tracking of Cardiorespiratory Fitness from Childhood to Mid-adulthood.

High cardiorespiratory fitness (CRF) in adulthood is important for survival from major chronic diseases and preserving good health. We examined how childhood CRF tracks, or persists, into adulthood. Among a cohort of 748 school children followed over 34 years, we found child CRF correlated with young- (r = 0.30) and mid-adulthood (r = 0.16) CRF.

Agreement between Fitbit and ActiGraph Estimates of Physical Activity in Young Children.

Physical activity (PA) estimates from the Fitbit Flex 2 were compared to those from the ActiGraph GT9X Link in 123 elementary school children. Steps and intensity-specific estimates of PA and 3-month PA change were calculated using two different ActiGraph cut-points (Evenson and Romanzini). Fitbit estimates were 35% higher for steps compared to the ActiGraph. Fitbit and ActiGraph intensity-specific estimates were closest for sedentary and light PA while estimates of moderate and vigorous PA varied substantially depending upon the ActiGraph cut-points used. Spearman correlations between device estimates were higher for steps (rs=.70) than for moderate (rs =.54 to .55) or vigorous (rs =.29 to .48) PA. There was low concordance between devices in assessing PA changes over time. Agreement between Fitbit Flex 2 and ActiGraph estimates may depend upon the cut-points used to classify PA intensity. However, there is fair to good agreement between devices in ranking children's steps and MVPA.

Childhood Factors Associated with Muscular Strength Trajectories between Childhood and Mid-Adulthood.

PURPOSE: To promote greater muscular strength across the life course and, in turn, help improve long-term health outcomes, strategies aimed at increasing muscular strength are required. To inform these strategies, this study identified childhood factors associated with muscular strength trajectories. METHODS: Prospective longitudinal study of 1280 Childhood Determinants of Adult Health participants who had a range of potentially modifiable factors (e.g., anthropometric measures, physical activity) and health and risk motivation items (e.g., attitudes, beliefs, and intentions on health-related actions) measured in childhood and had their muscular strength assessed up to three times between childhood and midlife. Associations between childhood factors and three predetermined life course muscular strength trajectories (identified previously using group-base trajectory modeling as follows: above average and increasing, average, and below average and decreasing) were examined using log multinomial regression. RESULTS: Greater physical fitness, physical activity, fat-free mass, enjoyment of physical activity, physical education, and school sports, and positive attitudes regarding the importance of exercising, staying fit, and body image were associated with a lower likelihood of being in the below average and decreasing muscular strength trajectory (relative risk range, 0.45-0.98). Greater physical fitness, physical activity, and fat-free mass, and attending an independent school were associated with a higher likelihood of being in the above average and increasing muscular strength trajectory (relative risk range, 1.03-1.93). CONCLUSIONS: In addition to providing health benefits in the short term, physical activity, physical fitness, positive health attitudes, and healthy weight in childhood may lead to better muscular strength in the long term.

Muscular strength measured across the life-course and the metabolic syndrome.

BACKGROUND AND AIMS: Low muscular strength associates with the metabolic syndrome (MetS). However, how muscular strength measured at different life stages contribute to the development of MetS is unknown. This study compared the contribution of muscular strength measured in youth, young- and mid-adulthood with MetS in midlife. METHODS AND RESULTS: Prospective longitudinal study of 267 Childhood Determinants of Adult Health Study participants who between 1985 and 2019 had measures of muscular strength (dominant grip strength) at three life stages (youth = 9-15 years, young adulthood = 26-36 years, mid-adulthood = 36-49 years) and had their MetS status assessed in mid-adulthood. Bayesian relevant life-course exposure models quantified associations between muscular strength at each life stage with MetS and estimated the maximum accumulated effect of lifelong muscular strength. The contribution of muscular strength at each life stage with MetS was equal (youth = 38%, young adulthood = 28%, mid-adulthood = 34%). A one standard deviation increase in cumulative muscular strength was associated with 46% reduced odds of MetS. Of all MetS components, muscular strength was most strongly negatively associated with high waist circumference. CONCLUSION: A life-course approach demonstrated reduced odds of MetS in midlife was associated with cumulatively high muscular strength since youth. This supports efforts to promote physical fitness throughout life.

Scaling the Virtual Fitness Buddy Ecosystem as a School-Based Physical Activity Intervention for Children.

Childhood obesity is a growing concern as it can lead to lifelong health problems that carry over into adulthood. A substantial contributing factor to obesity is the physical activity (PA) habits that are formed in early childhood, as these habits tend to sustain throughout adulthood. To aid children in forming healthy PA habits, we designed a mixed reality system called the Virtual Fitness Buddy ecosystem, in which children can interact with a virtual pet agent. As a child exercises, their pet becomes slimmer, faster, and able to play more games with them. Our initial deployment of this project showed promise but was only designed for a short-term intervention lasting three days. More recently, we have scaled it from a pilot grade study to a 9-month intervention comprised of 422 children. Ultimately, our goal is to scale this project to be a nationwide primary prevention program to encourage moderate to vigorous PA in children. This article explores the challenges and lessons learned during the design and deployment of this system at scale in the field.

At-home testing to mitigate community transmission of SARS-CoV-2: protocol for a public health intervention with a nested prospective cohort study.

BACKGROUND: The COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to evolve as a global health crisis. Although highly effective vaccines have been developed, non-pharmaceutical interventions remain critical to controlling disease transmission. One such intervention-rapid, at-home antigen self-testing-can ease the burden associated with facility-based testing programs and improve testing access in high-risk communities. However, its impact on SARS-CoV-2 community transmission has yet to be definitively evaluated, and the socio-behavioral aspects of testing in underserved populations remain unknown. METHODS: As part of the Rapid Acceleration of Diagnostics-Underserved Populations (RADx-UP) program funded by the National Institutes of Health, we are implementing a public health intervention titled "Say Yes! COVID Test" (SYCT) involving at-home self-testing using a SARS-CoV-2 rapid antigen assay in North Carolina (Greenville, Pitt County) and Tennessee (Chattanooga City, Hamilton County). The intervention is supported by a multifaceted communication and community engagement strategy to ensure widespread awareness and uptake, particularly in marginalized communities. Participants receive test kits either through online orders or via local community distribution partners. To assess the impact of this intervention on SARS-CoV-2 transmission, we will conduct a non-randomized, ecological study using community-level outcomes. Specifically, we will evaluate trends in SARS-CoV-2 cases and hospitalizations, SARS-CoV-2 viral load in wastewater, and population mobility in each community before, during, and after the SYCT intervention. Individuals who choose to participate in SYCT will also have the option to enroll in an embedded prospective cohort substudy gathering participant-level data to evaluate behavioral determinants of at-home self-testing and socio-behavioral mechanisms of SARS-CoV-2 community transmission. DISCUSSION: This is the first large-scale, public health intervention implementing rapid, at-home SARS-CoV-2 self-testing in the United States. The program consists of a novel combination of an at-home testing program, a broad communications and community engagement strategy, an ecological study to assess impact, and a research substudy of the behavioral aspects of testing. The findings from the SYCT project will provide insights into innovative methods to mitigate viral transmission, advance the science of public health communications and community engagement, and evaluate emerging, novel assessments of community transmission of disease.

Muscular strength across the life course: The tracking and trajectory patterns of muscular strength between childhood and mid-adulthood in an Australian cohort.

OBJECTIVES: Low muscular strength is a risk factor for current and future adverse health outcomes. However, whether levels of muscular strength persist, or track, and if there are distinct muscular strength trajectories across the life course is unclear. This study aimed to explore muscular strength trajectories between childhood and mid-adulthood. DESIGN: Prospective longitudinal study. METHODS: Childhood Determinants of Adult Health Study participants had their muscular strength (right and left handgrip, shoulder extension and flexion, and leg strength measured by hand-held, shoulder and leg-back dynamometers, and a combined strength score) assessed in childhood, young adulthood and mid-adulthood. The tracking of muscular strength was quantified between childhood and mid-adulthood (n=385) and young- and mid-adulthood (n=822). Muscular strength trajectory patterns were identified for participants who had their muscular strength assessed at least twice across the life course (n=1280). RESULTS: Levels of muscular strength were persistent between childhood and mid-adulthood and between young- and mid-adulthood, with the highest tracking correlations observed for the combined strength score (childhood to mid-adulthood: r=0.47, p<0.001; young- to mid-adulthood: r=0.72, p<0.001). Three trajectories of combined muscular strength were identified across the life course; participants maintained average, above average, or below average levels of combined muscular strength. CONCLUSIONS: Weak children are likely to become weak adults in midlife unless strategies aimed at increasing muscular strength levels are introduced. Whether interventions aimed at increasing muscular strength could be implemented in childhood to help establish favourable muscular strength trajectories across the life course and in turn, better future health, warrant further attention.

The Association Between Grip Strength Measured in Childhood, Young- and Mid-adulthood and Prediabetes or Type 2 Diabetes in Mid-adulthood.

BACKGROUND: Although low child and adult grip strength is associated with adverse cardiometabolic health, how grip strength across the life course associates with type 2 diabetes is unknown. This study identified the relative contribution of grip strength measured at specific life stages (childhood, young adulthood, mid-adulthood) with prediabetes or type 2 diabetes in mid-adulthood. METHODS: Between 1985 and 2019, 263 participants had their grip strength measured using an isometric dynamometer in childhood (9-15 years), young adulthood (28-36 years) and mid-adulthood (38-49 years). In mid-adulthood, a fasting blood sample was collected and tested for glucose and glycated haemoglobin (HbA1c). Participants were categorized as having prediabetes or type 2 diabetes if fasting glucose levels were ≥ 5.6 mmol or if HbA1c levels were ≥ 5.7% (≥ 39 mmol/mol). A Bayesian relevant life course exposure model examined the association between lifelong grip strength and prediabetes or type 2 diabetes. RESULTS: Grip strength at each time point was equally associated with prediabetes or type 2 diabetes in mid-adulthood (childhood: 37%, young adulthood: 36%, mid-adulthood: 28%). A one standard deviation increase in cumulative grip strength was associated with 34% reduced odds of prediabetes or type 2 diabetes in mid-adulthood (OR 0.66, 95% credible interval 0.40, 0.98). CONCLUSIONS: Greater grip strength across the life course could protect against the development of prediabetes and type 2 diabetes. Strategies aimed at increasing muscular strength in childhood and maintaining behaviours to improve strength into adulthood could improve future cardiometabolic health. The Association Between Grip Strength Measured in Childhood, Young- and Mid-adulthood and Prediabetes or Type 2 Diabetes in Mid-adulthood.

Using virtual agents to increase physical activity in young children with the virtual fitness buddy ecosystem: Study protocol for a cluster randomized trial.

BACKGROUND: Designing and implementing a truly self-determined physical activity (PA) intervention has required excessive amounts of labor and expenses that, until recently, have made it prohibitively costly to implement in the field at scale. METHODS: Guided by self-determination theory, and harnessing the power of consumer-grade interactive technologies, we developed the Virtual Fitness Buddy (VFB) Ecosystem. Designed to foster intrinsic motivation toward adopting PA as a lifestyle change in 6-10-year-old children, the Ecosystem features a mixed-reality kiosk which houses a personalized virtual pet for each user. Each time a child visits the kiosk, the pet (a mid-sized dog) automatically detects its owner based on the data from a child's Fitbit, assists the child in setting daily PA goals and provides tailored feedback on the child's PA progress. The pet alerts parents in real-time by sending text messages and relaying the parents' response to the child, so that parents and children can remain connected about the child's PA progress even when they are physically apart. We aim to implement the kiosk in 12 after-school sites, plus use 12 additional sites as controls, where children can still set and view progress toward their PA goals without access to a virtual pet. CONCLUSION: The VFB Ecosystem represents a new generation of technology-mediated health interventions for children to promote sustainable PA lifestyle changes. Because the VFB Ecosystem is a cost- and labor-effective solution that integrates consumer-grade technology with low barriers for continued use, it has the potential for rapid diffusion and widespread public health impact.

Using Virtual Agents and Activity Monitors to Autonomously Track and Assess Self-Determined Physical Activity Among Young Children: A 6-Week Feasibility Field Study.

The majority of youth fail to get the recommended amount of physical activity (PA), and there is a precipitous decline in PA among children as they get older. Guided by self-determination theory and social cognitive theory, we designed an interactive, mixed reality PA intervention for 6-10-year-old children. Capitalizing on the features of consumer-grade interactive communication technologies, the intervention features a kiosk-based system that houses a virtual agent programmed to encourage children to set self-determined PA goals. This intervention aims to resolve many practical challenges in designing and administering a personalized, intrinsically motivated PA intervention for this age group. We pilot tested the feasibility of this kiosk across 6 weeks with n = 42 child/parent dyads. The kiosk tracked and logged children's daily PA and engagement with the intervention without having to rely on human reporting, provided tailored evaluation and feedback whenever children requested it, informed parents about their child's PA progress, and employed a virtual agent (a dog) to offer social support to children. The virtual agent prompted users to set PA goals, and as children met these goals over time, their personalized dog became happier, more fit, and better at tricks. Each time a child engaged with the kiosk the system automatically sent a text message to his/her parent with details about the child's PA progress. The current study demonstrated the kiosk's feasibility in the field over 6 weeks, illustrating the potential of using interactive technologies as tools for disseminating self-sufficient, and truly self-determined health interventions for children at scale.

Factors Associated with Persistently High Muscular Power from Childhood to Adulthood.

PURPOSE: Child and adult muscular power have been shown to associate with contemporary cardiometabolic health. Muscular power typically persists (tracks) between childhood and adulthood. Few studies span childhood to adulthood, so we aimed to identify modifiable and environmental factors associated with the persistence or change in muscular power across the life course. METHODS: Prospective study examining 1938 participants who had their muscular power (standing long jump distance) measured in 1985 as children 7-15 yr old and again 20 yr later in adulthood (26-36 yr old). A selection of objectively measured anthropometric characteristics (adiposity and fat-free mass), cardiorespiratory fitness (CRF), self-reported physical activity, dietary (quality and fruit, vegetable, and protein intake), and sociodemographic data were available at both time points. Muscular power was separated into thirds, and participants were reported as having persistently low, decreasing, persistently moderate, increasing, or persistently high muscular power. RESULTS: Higher adiposity, lower physical activity, diet quality and socioeconomic status (SES) across the life course, and lower adult CRF were associated with persistently low muscular power. Lower adult protein intake and an increase in adiposity over time were associated with decreasing muscular power. An increase in fat-free mass was associated with a reduced probability of decreasing or persistently high muscular power and an increased probability of increasing muscular power. Higher adult fruit intake was associated with increasing muscular power. Lower adiposity across the life course, higher adult CRF and SES, and higher child protein intake were associated with persistently high muscular power. CONCLUSION: Healthy weight, good CRF, greater protein intake, and high SES are important correlates of high muscular power maintained from childhood to adulthood.

Sex-Specific Muscular Mediation of the Relationship Between Physical Activity and Cortical Bone in Young Adults.

Muscle mass is a commonly cited mediator of the relationship between physical activity (PA) and bone, representing the mechanical forces generated during PA. However, neuromuscular properties (eg, peak force) also account for unique portions of variance in skeletal outcomes. We used serial multiple mediation to explore the intermediary role of muscle mass and force in the relationships between cortical bone and moderate-to-vigorous intensity PA (MVPA). In a cross-sectional sample of young adults (n = 147, 19.7 ± 0.7 years old, 52.4% female) cortical diaphyseal bone was assessed via peripheral quantitative computed tomography at the mid-tibia. Peak isokinetic torque in knee extension was assessed via Biodex dynamometer. Thigh fat-free soft tissue (FFST) mass, assessed via dual-energy X-ray absorptiometry, represented the muscular aspect of tibial mechanical forces. Habitual MVPA was assessed objectively over 7 days using Actigraph GT3X+ accelerometers. Participants exceeded MVPA guidelines (89.14 ± 27.29 min/day), with males performing 44.5% more vigorous-intensity activity relative to females (p < 0.05). Males had greater knee extension torque and thigh FFST mass compared to females (55.3%, and 34.2%, respectively, all p < 0.05). In combined-sex models, controlling for tibia length and age, MVPA was associated with strength strain index (pSSI) through two indirect pathways: (i) thigh FFST mass (b = 1.11 ± 0.37; 95% CI, 0.47 to 1.93), and (i) thigh FFST mass and knee extensor torque in sequence (b = 0.30 ± 0.16; 95% CI, 0.09 to 0.73). However, in sex-specific models MVPA was associated with pSSI indirectly through its relationship with knee extensor torque in males (b = 0.78 ± 0.48; 95% CI, 0.04 to 2.02) and thigh FFST mass in females (b = 1.12 ± 0.50; 95% CI, 0.37 to 2.46). Bootstrapped CIs confirmed these mediation pathways. The relationship between MVPA and cortical structure appears to be mediated by muscle in young adults, with potential sex-differences in the muscular pathway. If confirmed, these findings may highlight novel avenues for the promotion of bone strength in young adults. © 2019 American Society for Bone and Mineral Research.

International Waist Circumference Percentile Cutoffs for Central Obesity in Children and Adolescents Aged 6 to 18 Years.

CONTEXT: No universal waist circumference (WC) percentile cutoffs used have been proposed for screening central obesity in children and adolescents. OBJECTIVE: To develop international WC percentile cutoffs for children and adolescents with normal weight based on data from 8 countries in different global regions and to examine the relation with cardiovascular risk. DESIGN AND SETTING: We used pooled data on WC in 113,453 children and adolescents (males 50.2%) aged 4 to 20 years from 8 countries in different regions (Bulgaria, China, Iran, Korea, Malaysia, Poland, Seychelles, and Switzerland). We calculated WC percentile cutoffs in samples including or excluding children with obesity, overweight, or underweight. WC percentiles were generated using the general additive model for location, scale, and shape (GAMLSS). We also estimated the predictive power of the WC 90th percentile cutoffs to predict cardiovascular risk using receiver operator characteristics curve analysis based on data from 3 countries that had available data (China, Iran, and Korea). We also examined which WC percentiles linked with WC cutoffs for central obesity in adults (at age of 18 years). MAIN OUTCOME MEASURE: WC measured based on recommendation by the World Health Organization. RESULTS: We validated the performance of the age- and sex-specific 90th percentile WC cutoffs calculated in children and adolescents (6-18 years of age) with normal weight (excluding youth with obesity, overweight, or underweight) by linking the percentile with cardiovascular risk (area under the curve [AUC]: 0.69 for boys; 0.63 for girls). In addition, WC percentile among normal weight children linked relatively well with established WC cutoffs for central obesity in adults (eg, AUC in US adolescents: 0.71 for boys; 0.68 for girls). CONCLUSION: The international WC cutoffs developed in this study could be useful to screen central obesity in children and adolescents aged 6 to 18 years and allow direct comparison of WC distributions between populations and over time.

Factors associated with muscular fitness phenotypes in Australian children: A cross-sectional study.

To help inform strategies aimed at increasing muscular fitness levels, we examined factors associated with childhood muscular fitness (strength and power) that preceded the recently observed secular decline. Data were available from a nationally representative sample of Australian children aged 7-15 years in 1985 (n = 8469). Muscular fitness measures included strength (right and left grip, shoulder extension and flexion, and leg strength) and power (standing long jump distance). Anthropometric (adiposity, fat-free mass), cardiorespiratory fitness (CRF), flexibility, speed capability, physical activity (individual and parental), dietary quality and intake (fruit, vegetable, protein) and sociodemographic (area-level socioeconomic status (SES), school type) data were available. Statistical analyses included sex-stratified linear regression. Of all examined factors, measures of adiposity, fat-free mass, CRF, flexibility and speed capability were associated with muscular fitness at levels that met Cohen's threshold for important effects (r-squared = 0.02 to 0.28). These findings highlight the multifactorial relationship between muscular fitness and its determinants. Collectively, these factors were powerful in explaining muscular strength (females: r-squared = 0.32; males: r-squared = 0.41) and muscular power (females: r-squared = 0.36; males: r-squared = 0.42). These findings highlight modifiable and environmental factors that could be targeted to increase childhood muscular fitness.

Exercise effects on arterial stiffness and heart health in children with excess weight: The SMART RCT.

INTRODUCTION: Childhood obesity and inactivity are associated with cardiovascular risk. Evidence is limited for exercise effects on arterial health in children. METHODS: One hundred and seventy-five inactive children with overweight or obesity (8-11 years, ≥85th percentile BMI, 61% female, 87% Black, 73% with obesity) were randomized to an 8-month daily after-school aerobic exercise program (40 min/day, n = 90) or a sedentary control condition (n = 85). Carotid-femoral pulse wave velocity (PWV, primary outcome, arterial stiffness), fitness, adiposity, blood pressure (BP), glucose, insulin resistance, lipids, and C-reactive protein were measured at baseline and posttest (8 months). Adiposity, fitness, and BP were measured again at follow-up, 8-12 months later. Intent-to-treat analyses were conducted using mixed models. RESULTS: The study had 89% retention, with attendance of 59% in exercise and 64% in the control condition, and vigorous exercise participation (average heart rate 161 ± 7 beats/min). Compared with controls, the exercise group had twice the improvement in fitness (VÈ®2 peak, 2.7 (95% CI 1.8, 3.6) vs. 1.3 (0.4, 2.3) mL/kg/min) and adiposity (-1.8 (-2.4, -1.1) vs. -0.8 (-1.5, -0.1)%), each p = 0.04, and a large improvement in HDL-cholesterol (0.13 (0.075, 0.186) vs. -0.028 (-0.083, 0.023) mmol/L, p < 0.0001). There was no group × time effect on other outcomes at 8 months, or on any outcomes at follow-up. The change in PWV at 8 months correlated with changes in insulin and insulin resistance (both r = 0.32), diastolic BP (r = 0.24), BMI (r = 0.22), and adiposity (r = 0.18). CONCLUSIONS: Eight months of aerobic exercise training improved fitness, adiposity, and HDL-cholesterol levels, but did not reduce arterial stiffness in children with excess weight. PWV improved as a function of insulin resistance, BP, BMI, and adiposity. Weight loss may be required to improve arterial stiffness. Exercise benefits waned after discontinuing the program.

Relationships between Post-Concussion Sleep and Symptom Recovery: A Preliminary Study.

Post-concussion sleep disturbances can be debilitating and may influence days to symptom recovery; however, evidence is minimal. The purpose of this study was to explore relationships between days to symptom recovery and aspects of sleep, as measured by actigraphy and subjective sleep questionnaires in a concussed sample. Thirty-one college students were physician-diagnosed with a concussion and asked to complete a daily sleep symptom checklist. Participants (n = 14) were excluded based on lack of compliance/early termination (22.6%), recorded <5 nights of data (12.9%), and protracted recoveries (3.2%). Final concussed sample included 17 college-aged students (varsity student-athletes, n = 5; university students, n = 12). A wrist-worn ActiGraph GT9X Link was provided during initial evaluation (within 72 h post-injury) and worn continuously until symptom recovery (follow-up evaluation; 14.3 ± 5.9 days post-injury). The Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) also were completed at follow-up. Pearson's correlations were conducted to determine relationships between days to symptom recovery and actigraphy sleep outcomes (sleep onset latency, wake after sleep onset (WASOnorm), total sleep time, sleep efficiency (SE), and number of awakenings) across recovery stages (2-3 days post-injury, mid-point, and end). Spearman's rho correlations were used to determine relationships between subjective sleep (PSQI global), sleepiness (ESS total), and sleep cluster symptom severity and days to symptom recovery. At recovery mid-point, individuals who were awake longer throughout the night (24.1 ± 9.0%) and/or were less efficient at sleeping (73.7 ± 9.7%) took longer to recover (WASOnorm: r = 0.58, p = 0.015; SE: r = -0.51, p = 0.035). Poorer post-concussion sleep quality (based on PSQI) was correlated with longer recovery (rs = 0.70, p = 0.001). Post-concussion sleep-wake disturbances at recovery mid-point and overall poorer sleep quality may be associated with longer symptom recovery. Our findings provide preliminary guidance on identifying those who may be at risk for longer recoveries based on poorer sleep post-injury.

The association between muscular power from childhood to adulthood and adult measures of glucose homeostasis.

This study aimed to assess whether the longitudinal association between childhood muscular fitness and adult measures of glucose homeostasis persist despite changes in muscular fitness across the life course. This prospective longitudinal study included 586 participants who had their muscular power (standing long jump distance), cardiorespiratory fitness (CRF), and waist circumference measured as children (aged 9, 12, 15 years) and again 20 years later as adults. In adulthood, these participants also provided a fasting blood sample which was tested for glucose and insulin. Glucose homeostasis measures including insulin resistance (HOMA2-IR) and beta cell function (HOMA2-ß) were estimated. Child and adult muscular power levels were separated into thirds, and tracking groups (persistently low, decreasing, persistently moderate, increasing, and persistently high) were created. Sex-stratified multivariable linear regression models were used to examine the association between muscular power tracking groups and adult measures of glucose homeostasis. Compared with males with persistently high muscular power, males with increasing and persistently low muscular power had higher fasting insulin (increasing: ß = 1.12 mU/L, P = .04; persistently low: ß = 2.12 mU/L, P = .001) and HOMA2-ß (increasing: ß = 8.50%, P = .03; persistently low: ß = 11.27%, P = .01) independent of CRF and males with persistently low muscular power had greater fasting insulin (ß = 1.22 mU/L, P = .02) and HOMA2-IR (ß = 0.14, P = .02) independent of waist circumference. Non-significant associations were present for females. For males, maintaining persistently high muscular power between childhood and adulthood could lead to a healthier adult glucose homeostasis profile.

Mortality Risk Reductions for Replacing Sedentary Time With Physical Activities.

INTRODUCTION: Excess sitting is a risk factor for early mortality. This may be resulting, at least in part, from the displacement of physical activity with sedentary behaviors. The purpose of this observational study was to examine the mortality risk reductions associated with replacing 30minutes/day sitting for an equivalent duration of light or moderate to vigorous physical activity (MVPA). METHODS: Participants included 37,924 men and 54,617 women in the Cancer Prevention Study-II Nutrition Cohort, of which 14,415 men and 13,358 women died during follow-up (1999-2014). An isotemporal substitution approach to the Cox proportional hazards regression model was used to estimate adjusted hazard ratios and 95% CIs for mortality associated with the substitution of 30minutes/day self-reported sitting for light physical activity or MVPA. Analyses were conducted in 2018. RESULTS: Among the least active participants (≤17minutes/day MVPA), the replacement of 30minutes/day sitting with light physical activity was associated with a 14% mortality risk reduction (hazard ratio=0.86, 95% CI=0.81, 0.89) and replacement with MVPA was associated with a 45% mortality risk reduction (hazard ratio=0.55, 95% CI=0.47, 0.62). Similar associations were seen among moderately active participants (light physical activity replacement, hazard ratio=0.94, 95% CI=0.91, 0.97; MVPA replacement, hazard ratio=0.83, 95% CI=0.76, 0.88). However, for the most active (MVPA >38 minutes/day), substitution of sitting time with light physical activity or MVPA was not associated with a reduction in mortality risk (hazard ratio=1.00, 95% CI=0.97, 1.03, and hazard ratio=0.99, 95% CI=0.95, 1.02, respectively). CONCLUSIONS: These findings suggest that the replacement of modest amounts of sitting time with even light physical activity may have the potential to reduce the risk of premature death among less active adults.