Comparing the Actical and ActiGraph Approach to Measuring Young Children's Physical Activity Levels and Sedentary Time.

Young children's activity and sedentary time were simultaneously measured via the Actical method (i.e., Actical accelerometer and specific cut-points) and the ActiGraph method (i.e., ActiGraph accelerometer and specific cut-points) at both 15-s and 60-s epochs to explore possible differences between these 2 measurement approaches. For 7 consecutive days, participants (n = 23) wore both the Actical and ActiGraph side-by-side on an elastic neoprene belt. Device-specific cut-points were applied. Paired sample t tests were conducted to determine the differences in participants' daily average activity levels and sedentary time (min/h) measured by the 2 devices at 15-s and 60-s time sampling intervals. Bland-Altman plots were used to examine agreement between Actical and ActiGraph accelerometers. Regardless of epoch length, Actical accelerometers reported significantly higher rates of sedentary time (15 s: 42.7 min/h vs 33.5 min/h; 60 s: 39.4 min/h vs 27.1 min/h). ActiGraph accelerometers captured significantly higher rates of moderate-to-vigorous physical activity (15 s: 9.2 min/h vs 2.6 min/h; 60 s: 8.0 min/h vs 1.27 min/h) and total physical activity (15 s: 31.7 min/h vs 22.3 min/h; 60 s: = 39.4 min/h vs 25.2 min/h) in comparison with Actical accelerometers. These results highlight the present accelerometry-related issues with interpretation of datasets derived from different monitors.

Sedentary Time and Screen-Based Sedentary Behaviors of Children With a Chronic Disease.

The objectives of this study were to (i) assess sedentary time and prevalence of screen-based sedentary behaviors of children with a chronic disease and (ii) compare sedentary time and prevalence of screen-based sedentary behaviors to age- and sex-matched healthy controls. Sixty-five children (aged 6-18 years) with a chronic disease participated: survivors of a brain tumor, hemophilia, type 1 diabetes mellitus, juvenile idiopathic arthritis, cystic fibrosis, and Crohn's disease. Twenty-nine of these participants were compared with age- and sex-matched healthy controls. Sedentary time was measured objectively by an ActiGraph GT1M or GT3× accelerometer worn for 7 consecutive days and defined as less than 100 counts per min. A questionnaire was used to assess screen-based sedentary behaviors. Children with a chronic disease engaged in an average of 10.2 ± 1.4 hr of sedentary time per day, which comprised 76.5 ± 7.1% of average daily monitoring time. There were no differences between children with a chronic disease and controls in sedentary time (adjusted for wear time, p = .06) or in the prevalence of TV watching, and computer or video game usage for varying durations (p = .78, p = .39 and, p = .32 respectively). Children with a chronic disease, though relatively healthy, accumulate high levels of sedentary time, similar to those of their healthy peers.

Physical Activity Trajectories in Early Childhood: Investigating Personal, Environmental, and Participation Factors.

INTRODUCTION/PURPOSE: To determine personal, environmental, and participation factors that predict children's physical activity (PA) trajectories from preschool through to school years. METHODS: Two hundred seventy-nine children (4.5 ± 0.9 yr, 52% boys) were included in this study. Physical activity was collected via accelerometry at six different timepoints over 6.3 ± 0.6 yr. Time-stable variables were collected at baseline and included child's sex and ethnicity. Time-dependent variables were collected at six timepoints (age, years) and included household income (CAD), parental total PA, parental influence on PA, and parent-reported child's quality of life, child's sleep, and child's amount of weekend outdoor PA. Group-based trajectory modeling was applied to identify trajectories of moderate-to-vigorous PA (MVPA) and total PA (TPA). Multivariable regression analysis identified personal, environmental, and participation factors associated with trajectory membership. RESULTS: Three trajectories were identified for each of MVPA and TPA. Group 3 in MVPA and TPA expressed the most PA over time, with increased activity from timepoints 1 to 3, and then declining from timepoints 4 to 6. For the group 3 MVPA trajectory, male sex (ß estimate, 3.437; P = 0.001) and quality of life (ß estimate, 0.513; P < 0.001) were the only significant correlates for group membership. For the group 3 TPA trajectory, male sex (ß estimate, 1.970; P = 0.035), greater household income (ß estimate, 94.615; P < 0.001), and greater parental total PA (ß estimate, 0.574; P = 0.023) increased the probability of belonging to this trajectory group. CONCLUSIONS: These findings suggest a need for interventions and public health campaigns to increase opportunities for PA engagement in girls starting in the early years. Policies and programs to address financial inequities, positive parental modeling, and improving quality of life are also warranted.

The health outcomes and physical activity in preschoolers (HOPP) study: rationale and design.

BACKGROUND: The early years are the period of growth for which we know the least about the impact of physical activity. In contrast, we know that more than 90 % of school-aged Canadian children, for example, are not meeting physical activity recommendations. Such an activity crisis is a major contributor to recent trends in childhood obesity, to which preschoolers are not immune. The World Health Organization estimated that more than 42 million children under the age of 5 years were overweight world-wide in 2010. If an activity crisis exists during the preschool years, we should also be concerned about its broader impact on health. Unfortunately, the relationship between physical activity and health during the early years is poorly understood. The goal of the Health Outcomes and Physical activity in Preschoolers (HOPP) study is to describe how the prevalence and patterns of physical activity in preschoolers are associated with indices of health. METHODS: The HOPP study is a prospective cohort study. We aim to recruit 400 3- to 5-year-old children (equal number of boys and girls) and test them once per year for 3 years. Each annual assessment involves 2 laboratory visits and 7 consecutive days of physical activity monitoring with protocols developed in our pilot work. At visit 1, we assess body composition, aerobic fitness, short-term muscle power, motor skills, and have the parents complete a series of questionnaires related to their child's physical activity, health-related quality of life and general behaviour. Over 7 consecutive days each child wears an accelerometer on his/her waist to objectively monitor physical activity. The accelerometer is programmed to record movement every 3 s, which is needed to accurately capture the intensity of physical activity. At visit 2, we assess vascular structure and function using ultrasound. To assess the associations between physical activity and health outcomes, our primary analysis will involve mixed-effects models for longitudinal analyses. DISCUSSION: The HOPP study addresses a significant gap in health research and our findings will hold the potential to shape public health policy for active living during the early years.

Preschool to School-Age Physical Activity Trajectories and School-Age Physical Literacy: A Longitudinal Analysis.

PURPOSE: The associations between longitudinal physical activity (PA) patterns across childhood and physical literacy have not been studied. The purpose of this study was to identify PA trajectories from preschool to school-age, and to determine if trajectory group membership was associated with school-age physical literacy. METHODS: Participants (n = 279, 4.5 [0.9] y old, 48% girls) enrolled in this study and completed annual assessments of PA with accelerometry over 6 timepoints. Physical literacy was assessed at timepoint 6 (10.8 [1.0] y old). Group-based trajectory analysis was applied to identify trajectories of total volume of PA and of moderate to vigorous PA and to estimate group differences in physical literacy. RESULTS: Three trajectories of total volume of PA and of moderate to vigorous PA were identified. Groups 1 (lowest PA) included 40% to 53% of the sample, groups 2 included 39% to 44% of the sample, and groups 3 (highest PA) included 8% to 16% of the sample. All trajectories declined from timepoint 1 to timepoint 6. School-age physical literacy was lowest in trajectory groups with the lowest total volume of PA or moderate to vigorous PA over time (P < .05). CONCLUSIONS: PA should be promoted across early and middle childhood, as it may play a formative role in the development of school-age physical literacy.

Motor Competence, Physical Activity, and Fitness across Early Childhood.

OBJECTIVES: To examine if the associations between motor competence and physical activity and musculoskeletal fitness change over time, whether motor competence is associated with longitudinal trajectories of physical activity and fitness, and mediating pathways among these constructs across early childhood. METHODS: Four hundred and eighteen children 3 to 5 yr of age (210 boys; age, 4.5 ± 1.0 yr) were recruited and completed three annual assessments as part of the Health Outcomes and Physical activity in Preschoolers study. Motor competence was assessed using the Bruininks-Oseretsky Test of Motor Proficiency Second Edition-Short Form. Musculoskeletal fitness (short-term muscle power) was evaluated using a modified 10-s Wingate protocol on a cycle ergometer. Physical activity was measured over 7 d using accelerometers. RESULTS: At baseline, the cross-sectional relationship between motor competence and vigorous physical activity was not significant; however, a significant, weak positive association emerged across time. Results from longitudinal mixed-effect models found motor competence to be a significant positive predictor of musculoskeletal fitness and vigorous physical activity and to be associated with steeper increases in physical activity across time. Motor competence was independently associated with musculoskeletal fitness and physical activity during this early childhood period. CONCLUSIONS: Motor competence is an important independent predictor of physical activity and musculoskeletal fitness levels across early childhood. Motor competence may be an important target for early interventions to improve both physical activity and fitness in the early years.

Associations between carotid artery longitudinal wall motion and arterial stiffness indicators in young children.

BACKGROUND AND AIMS: Carotid artery longitudinal wall motion (CALM) is associated with established indicators of arterial stiffness in healthy adults and in adults with cardiovascular disease risk factors. CALM assessment may be more feasible for incorporation into routine clinical examination than traditional assessments of arterial stiffness; however, the relationship between CALM and arterial stiffness in children has not been established. METHODS: Data were collected from a subset of children participating in the Health Outcomes and Physical activity in Preschoolers study. CALM was characterized by segmental longitudinal wall displacement, velocity, and acceleration. Arterial stiffness was measured using whole-body pulse wave velocity (PWV) and carotid artery ß-stiffness index. Associations between CALM and arterial stiffness and the influence of age, sex, and height on those associations were determined. RESULTS: One hundred and ninety-one children (ages 5.0-8.0 years) were included in the analyses. Systolic retrograde (r = -0.20, p = 0.01) and maximum (r = -0.15, p = 0.04) CALM displacements were weakly correlated with PWV while systolic anterograde and diastolic CALM displacements and wall velocities and accelerations were not correlated with PWV (r = -0.12 to -0.03, p = 0.10 to 0.64). There were no significant correlations between any CALM outcome and ß-stiffness index (r = -0.12 to 0.10; p > 0.05). Associations were attenuated after adjusting for age, sex, and height. CONCLUSIONS: Higher arterial stiffness, measured by PWV, but not ß-stiffness, is weakly associated with less longitudinal movement of the common carotid artery in young, healthy children indicating CALM measurement is not a strong candidate for clinical assessment of arterial stiffness in children.

Retrograde shift in carotid artery longitudinal wall motion after one-year follow-up in children.

BACKGROUND AND AIMS: Cross-sectional studies suggest that arterial stiffness increases during childhood; however, this evidence stems from pressure-dependent arterial distension, while longitudinal movement of the arterial wall has not been explored. Carotid artery longitudinal wall motion (CALM) has been identified as a novel biomarker of vascular health in adults and may provide complementary biaxial wall information to vascular changes during childhood development. Accordingly, the purpose of this study was to assess how CALM changes and tracks over a one-year period in young children. METHODS: Children were recruited from the Health Outcomes and Physical activity in Preschoolers study (n = 114; 65 girls; age: 5.8 ±â€¯0.9 years-old). CALM was measured at the left common carotid artery using ultrasound with speckle tracking. RESULTS: There were increases in CALM magnitudes over one-year follow-up, including systolic retrograde, diastolic, maximum, and total radial-axial displacement (all p < 0.01), with no differences between boys and girls. With the exception of systolic anterograde displacement, all CALM variables tracked better in girls than in boys, both individually (Spearman's ρ ranges: 0.49-0.61 vs. 0.25-0.47), as well as when split into tertile groups (Cohen's weighted κ ranges: 0.43-0.60 vs. 0.16-0.44), indicating overall moderate tracking (κ > 0.40) in the entire cohort. CONCLUSIONS: CALM displacements change rapidly during childhood and track into pre-pubescence in a sex-specific manner. These findings suggest that CALM is influenced by individual factors that track consistently, and that similar to arterial stiffness, it may be valuable to examine the age-associated changes in CALM magnitudes to infer changes in child vascular health over time.

Physical Activity and Trajectories of Cardiovascular Health Indicators During Early Childhood.

OBJECTIVES: Cardiovascular disease prevention should begin in childhood. However, the influence of physical activity on cardiovascular health in early childhood is unknown. Our purpose in this study was to determine the effect of physical activity on trajectories of cardiovascular health indicators during early childhood. METHODS: This prospective, observational cohort study (Health Outcomes and Physical Activity in Preschoolers) enrolled 418 3- to 5-year-olds with annual assessments for 3 years. Total physical activity (TPA) and moderate-to-vigorous physical activity (MVPA) were measured over 7 days via accelerometry. Cardiovascular health indicators included cardiovascular fitness (exercise time on a maximal treadmill test [treadmill time] and 1-minute heart rate recovery), resting arterial stiffness (whole-body pulse wave velocity and carotid ß stiffness index), and seated systolic blood pressure. Data were analyzed by using linear mixed-effects modeling; effects are reported as unstandardized estimates (Est). RESULTS: There were main effects of TPA and MVPA on treadmill time (Est = 0.004 [P = .005] and 0.008 [P = .001], respectively) and heart rate recovery (Est = 0.05 [P < .001] and 0.08 [P < .001], respectively). There was a main effect of TPA on pulse wave velocity (Est = -0.001; P = .02) and an MVPA × time interaction (Est = -0.002; P = .01). For carotid ß stiffness index, the effect of a TPA × time interaction was not significant (Est = -0.002; P = .051); however, there was a significant MVPA × time interaction (Est = -0.003; P = .03). MVPA was associated with a slower rate of change in systolic blood pressure for girls (Est = 0.06; P = .009). CONCLUSIONS: Children who engage in higher levels of physical activity during early childhood have better cardiovascular health indicators, with more intense physical activity (ie, MVPA) attenuating the stiffening of arteries.

Automated ultrasound edge-tracking software comparable to established semi-automated reference software for carotid intima-media thickness analysis.

Many commercial ultrasound systems are now including automated analysis packages for the determination of carotid intima-media thickness (cIMT); however, details regarding their algorithms and methodology are not published. Few studies have compared their accuracy and reliability with previously established automated software, and those that have were in asymptomatic adults. Therefore, this study compared cIMT measures from a fully automated ultrasound edge-tracking software (EchoPAC PC, Version 110.0.2; GE Medical Systems, Horten, Norway) to an established semi-automated reference software (Artery Measurement System (AMS) II, Version 1.141; Gothenburg, Sweden) in 30 healthy preschool children (ages 3-5 years) and 27 adults with coronary artery disease (CAD; ages 48-81 years). For both groups, Bland-Altman plots revealed good agreement with a negligible mean cIMT difference of -0·03 mm. Software differences were statistically, but not clinically, significant for preschool images (P = 0·001) and were not significant for CAD images (P = 0·09). Intra- and interoperator repeatability was high and comparable between software for preschool images (ICC, 0·90-0·96; CV, 1·3-2·5%), but slightly higher with the automated ultrasound than the semi-automated reference software for CAD images (ICC, 0·98-0·99; CV, 1·4-2·0% versus ICC, 0·84-0·89; CV, 5·6-6·8%). These findings suggest that the automated ultrasound software produces valid cIMT values in healthy preschool children and adults with CAD. Automated ultrasound software may be useful for ensuring consistency among multisite research initiatives or large cohort studies involving repeated cIMT measures, particularly in adults with documented CAD.

Validity of field assessments to predict peak muscle power in preschoolers.

Field-based fitness assessments are time- and cost-efficient. However, no studies to date have reported the predictive value of field-based musculoskeletal fitness assessments in preschoolers. The purpose of this study was to determine the validity of 2 field assessments to predict peak muscle power in preschool-aged children. Four-hundred and nineteen 3- to 5-year olds participated (208 girls, 211 boys; mean age: 4.5 ± 0.9 years). Peak power (PP) was evaluated using a modified 10-s Wingate protocol as the criterion standard. Standing long-jump was measured in inches to the back of the heel using a 2-footed takeoff and landing. Shuttle-run time was measured using a shuttle-run protocol, which required children to sprint 50 feet (15.2 m), pick up a small block, and sprint back, with time measured to the closest tenth of a second. Regression modelling was used to calculate the predictive power of each field-based measurement, adjusting for weight (kg), age, and sex. Both standing long-jump distance and shuttle-run time were significantly correlated with PP (r = 0.636, p < 0.001, and r = -0.684, p < 0.001, respectively). Linear regression analysis determined that a child's PP can be predicted from the child's weight, age, and sex and either standing long-jump or shuttle-run time (adjusted R2 = 0.79, p < 0.001, and 0.81, p < 0.001, respectively). The standing long-jump and the Bruininks Oseretsky Test of Motor Proficiency 2nd Edition shuttle-run are both significant predictors of peak muscle power in preschool children. Either measure can be used as a cost- and time-efficient estimate of musculoskeletal fitness in preschoolers.

Tracking of physical activity and fitness during the early years.

The early years are characterized by rapid physical growth and the development of behaviours such as physical activity. The objectives of this study were to assess the 12-month changes in and the tracking of physical activity and fitness in 400 preschoolers (201 boys, 4.5 ± 0.9 years of age). Physical activity data, expressed as minutes per day and as the percentage of time spent at various intensities while wearing an accelerometer, were collected in 3-s epochs for 7 days. Short-term muscle power, assessed with a 10-s modified Wingate Anaerobic Test, was expressed as absolute (W) and relative (W/kg) peak power (PP) and mean power (MP). Aerobic fitness, assessed with the Bruce Protocol progressive treadmill test, was expressed as maximal treadmill time and heart rate recovery (HRR). Light physical activity decreased by 3.2 min/day (p < 0.05), whereas vigorous physical activity increased by 3.7 min/day (p < 0.001), from year 1 to year 2. Physical activity exhibited moderate tracking on the basis of Spearman correlations (r = 0.45-0.59, p < 0.001) and fair tracking on the basis of κ statistics (κ = 0.26-0.38). PP and MP increased from year 1 (PP, 94.1 ± 37.3 W; MP, 84.1 ± 30.9 W) to year 2 (PP, 125.6 ± 36.2 W; MP, 112.3 ± 32.2 W) (p < 0.001) and tracked moderately to substantially (PP, r = 0.89, κ = 0.61; MP, r = 0.86, κ = 0.56). Time to exhaustion on the treadmill increased from 9.4 ± 2.3 min to 11.8 ± 2.3 min (p < 0.001) and tracked strongly (r = 0.82, κ = 0.56). HRR was unchanged at 65 ± 14 beats/min (p = 0.297) and tracked fairly (r = 0.52, κ = 0.23). The findings indicate that fitness tracks better than physical activity over a 12-month period during the early years.

Step count targets corresponding to new physical activity guidelines for the early years.

PURPOSE: New physical activity guidelines recommend that children age 3­4 yr should accumulate at least 180 min of physical activity at any intensity spread throughout the day, including progression toward at least 60 min of energetic play by 5 yr of age. Step count targets corresponding to these recommendations will help practitioners and researchers monitor physical activity. METHODS: One hundred thirty-three preschoolers were instructed to wear accelerometers for seven consecutive days. Activity and step count data were recorded in 3-s epochs. Step count targets equivalent to physical activity recommendations were derived using prediction equations from regression analyses. Receiver operating curve analyses were conducted to compare the sensitivity and specificity of the derived thresholds as well as a range of other targets. RESULTS: The daily step count target derived for 180 min of physical activity of any intensity was 6013 +/- 88, whereas the target for 180 min of physical activity of any intensity including at least 60 min of moderate-to-vigorous physical activity was 6191 +/- 103. The smallest discrepancy between days meeting physical activity guidelines and step count targets was found with a 6000-step-per-day target. Receiver operating curves confirmed a balanced sensitivity and specificity of this target. CONCLUSIONS: On the basis of our data, we suggest that a new step count target of 6000 steps per day should be used to determine whether 3- to 5-yr-old children are meeting physical activity recommendations.

Short-term muscle power and speed in preschoolers exhibit stronger tracking than physical activity.

The purpose of this study was to examine the tracking of short-term muscle power, speed, and physical activity over a 15-month period in a sample of healthy Canadian preschool-aged children. Seventeen preschoolers (age, 4.4 ± 0.8 years) completed exercise testing and physical activity monitoring at baseline and follow-up separated by 14.6 ± 4.1 months. Short-term muscle power was measured using a modified 10-s Wingate test with peak power and mean power normalized to body mass. Speed was assessed with a 25-m dash. Physical activity was measured by accelerometry (Actigraph GT1M) using a 3-s epoch over 7 consecutive days. Total physical activity and moderate-to-vigorous physical activity, expressed as a percentage of accelerometer wear time, were examined. Tracking of the variables between year 1 and year 2 was analyzed using Spearman rank order correlations and Kappa statistics. Paired t-tests were used to assess differences in performance and physical activity between year 1 and year 2. Total physical activity was not significantly different at year 2 (p > 0.05) and showed fair tracking (r = 0.51, p = 0.05; ĸ = 0.30). Moderate-to-vigorous physical activity was increased at year 2 (p = 0.03) and exhibited poor tracking (r = 0.29, p = 0.28; ĸ = 0.00). Short-term muscle power and speed was increased at year 2 (p < 0.0001) and exhibited significant tracking: peak power (r = 0.72, p = 0.001; ĸ = 0.46), mean power (r = 0.83, p = 0.00004; ĸ = 0.82), and 25-m dash (r = 0.82, p = 0.0001; ĸ = 0.47). Moderate-to-vigorous physical activity increased in this sample of boys and girls during the preschool years, and short-term muscle power and speed exhibited stronger tracking than physical activity.

Noninvasive measures of vascular health are reliable in preschool-aged children.

Measures of vascular health are known to be important predictors of cardiovascular disease in adulthood. The reliability of commonly used measures of vascular health has been demonstrated in school-aged children, adolescents, and adults; however, their reliability in preschool-aged children remains to be determined. Twenty 2- to 6-year-old children participated in 2 identical testing sessions on different days. Following 10 min of supine rest, carotid artery blood pressures and common carotid artery images were assessed simultaneously for 10 heart cycles, using applanation tonometry and B-mode ultrasound, respectively, while electrocardiogram (ECG) and infrared measures of arterial pressure waves at the dorsalis pedis were recorded continuously. Brachial artery blood pressures were determined using an automated oscillometric device. Carotid artery diameters and intima-media thickness (IMT) were analyzed using a semiautomated detection software program. Carotid compliance, distensibility, and stiffness index were calculated from carotid diameters and carotid blood pressures. Whole-body pulse-wave velocity (PWV) was determined from the time delay between the R spike of the ECG and the foot of the dorsalis pedis arterial pressure wave. Reliability of all measures was assessed using the coefficient of variation (CV) and the intraclass correlation coefficient (ICC). The most reliable measures were carotid artery IMT and PWV with CVs of 2.6% and 3.5% and ICCs of 0.86 and 0.76, respectively. The lower reliability of carotid compliance and distensibility (ICC≤0.63) is likely attributable to the variability of blood pressure measurements. This study confirms that vascular measurements demonstrate substantial reliability in preschool-aged children as young as 2 years.