The Caltrac accelerometer as a physical activity monitor for school-age children

Sensor technology in eating disorders research: A systematic review

OBJECTIVE

Sensor technologies offer exciting potential to objectively measure psychopathological correlates of eating pathology and eating disorder (ED) research utilizing sensors has rapidly proliferated in the past several years. The aims of the present review are: (1) characterize the types of sensors that have been utilized in ED research, (2) identify the psychopathological factors relevant to EDs that have been assessed using sensors, (3) describe the data supporting the validity and reliability of these sensors, (4) discuss limitations associated with these sensors, and (5) identify gaps that persist within the ED literature with regard to use of sensor technologies.

METHOD

A systematic search was conducted of PubMed, PsycINFO, Web of Science, ProQuest, and "gray" literature sources. Eligible publications were empirical studies that utilized sensors to measure at least one psychological variable among clinical ED populations.

RESULTS

Sensors have been utilized with ED samples to measure eating behaviors, physical activity, sleep, autonomic nervous system activity, eyeblink startle response, visual attention, and visual-haptic object integration. The reliability and validity of these sensors varies widely and there are a number of significant gaps that remain in the literature with regard to the types of sensors utilized, context in which sensors have been used, and populations studied.

DISCUSSION

The existing literature utilizing sensors within ED research largely support the feasibility and acceptability of these tools. Sensors should continue to be utilized within the field, with a specific focus on examining the reliability and validity of these tools within ED samples and increasing the diversity of samples studied.

PUBLIC SIGNIFICANCE STATEMENT

Sensor technologies, such as those included in modern smartwatches, offer new opportunities to measure factors that may maintain or contribute to symptoms of eating disorders. This article describes the types of sensors that have been used in eating disorders research, challenges that may arise in using these sensors, and discusses new applications of these sensors that may be pursued in future research.

Impact of the COVID-19 pandemic on elementary schoolers' physical activity, sleep, screen time and diet: A quasi-experimental interrupted time series study

BACKGROUND

COVID-19 school closures pose a threat to children's wellbeing, but no COVID-19-related studies have assessed children's behaviours over multiple years .

OBJECTIVE

To examine children's obesogenic behaviours during spring and summer of the COVID-19 pandemic compared to previous data collected from the same children during the same calendar period in the 2 years prior.

METHODS

Physical activity and sleep data were collected via Fitbit Charge-2 in 231 children (7-12 years) over 6 weeks during spring and summer over 3 years. Parents reported their child's screen time and dietary intake via a survey on 2-3 random days/week.

RESULTS

Children's behaviours worsened at a greater rate following the pandemic onset compared to pre-pandemic trends. During pandemic spring, sedentary behaviour increased (+79 min; 95% CI = 60.6, 97.1) and MVPA decreased (-10 min, 95% CI = -18.2, -1.1) compared to change in previous springs (2018-2019). Sleep timing shifted later (+124 min; 95% CI = 112.9, 135.5). Screen time (+97 min, 95% CI = 79.0, 115.4) and dietary intake increased (healthy: +0.3 foods, 95% CI = 0.2, 0.5; unhealthy: +1.2 foods, 95% CI = 1.0, 1.5). Similar patterns were observed during summer.

CONCLUSIONS

Compared to pre-pandemic measures, children's PA, sedentary behaviour, sleep, screen time, and diet were adversely altered during the COVID-19 pandemic. This may ultimately exacerbate childhood obesity.

Dynamics of sleep, sedentary behavior, and moderate-to-vigorous physical activity on school versus nonschool days

STUDY OBJECTIVES

Studies examining time-use activity behaviors (sleep, sedentary behavior, and physical activity) on school days compared with nonschool days have examined these behaviors independently, ignoring their interrelated nature, limiting our ability to optimize the health benefits of these behaviors. This study examines the associations of school-day (vs. nonschool day) with time-use activity behaviors.

METHODS

Time series data (6,642 days) from Fitbits (Charge-2) were collected (n = 196, 53% female, 5-10 years). We used a variable-centered dynamic structural equation modeling approach to estimate day-to-day associations of time-use activity behaviors on school days for each child. We then used person-centered cluster analyses to group individuals based on these estimates.

RESULTS

Within-participant analysis showed that on school days (vs. nonschool days), children (1) slept less (β = -0.17, 95% CI = -0.21, -0.13), (2) were less sedentary (β = -0.05, 95% CI = -0.09, -0.02), and (3) had comparable moderate-to-vigorous physical activity (MVPA; β = -0.05, 95% CI = -0.11, 0.00). Between-participant analysis showed that, on school days, children with higher sleep carryover experienced greater decreases in sleep (β = 0.44, 95% CI = 0.08, 0.71), children with higher body mass index z-score decreased sedentary behavior more (β = -0.41, 95% CI = -0.64, -0.13), and children with lower MVPA increased MVPA more (β = -0.41, 95% CI -0.64, -0.13). Cluster analysis demonstrated four distinct patterns of connections between time-use activity behaviors and school (High Activity, Sleep Resilient, High Sedentary, and Dysregulated Sleep).

CONCLUSIONS

Using a combination of person-centered and more traditional variable-centered approaches, we identified patterns of interrelated behaviors that differed on school, and nonschool days. Findings can inform targeted intervention strategies tailored to children's specific behavior patterns.

Parental and Familial Factors Influencing Physical Activity Levels in Early Adolescence: A Prospective Study

Parental/familial factors are important determinants of the physical activity level (PAL) in children and adolescents, but studies rarely prospectively evaluate their relationships. This study aimed to evaluate the changes in physical activity levels among adolescents from Bosnia and Herzegovina over a two-year period and to determine parental/familial predictors of PAL in early adolescence. A total of 651 participants (50.3% females) were tested at baseline (beginning of high school education; 14 years old on average) and at follow-up (approximately 20 months later). The predictors included sociodemographic characteristics (age, gender) and parental/familial factors (socioeconomic status of the family, maternal and paternal education, conflict with parents, parental absence from home, parental questioning, and parental monitoring). Physical activity levels were evidenced by the Physical Activity Questionnaire for Adolescents (PAQ-A; criterion). Boys were more active than girls, both at baseline (t-test = 3.09, p < 0.001) and at follow-up (t-test = 3.4, p < 0.001). Physical activity level decreased over the observed two-year period (t-test = 16.89, p < 0.001), especially in boys, which is probably a consequence of drop-out from the sport in this period. Logistic regression evidenced parental education as a positive predictor of physical activity level at baseline (OR [95% CI]; 1.38 [1.15–170], 1.35 [1.10–1.65]), and at follow-up (1.35 [1.11–1.69], 1.29 [1.09–1.59], for maternal and paternal education, respectively). Parents with a higher level of education are probably more informed about the importance of physical activity on health status, and thus transfer this information to their children as well. The age from 14 to 16 years is likely a critical period for maintaining physical activity levels in boys, while further studies of a younger age are necessary to evaluate the dynamics of changes in physical activity levels for girls. For maintaining physical activity levels in adolescence, special attention should be paid to children whose parents are less educated, and to inform them of the benefits of an appropriate physical activity level and its necessity for maintaining proper health and growth.

The impact of summer vacation on children's obesogenic behaviors and body mass index: a natural experiment

BACKGROUND

Children's BMI gain accelerates during summer. The Structured Days Hypothesis posits that the lack of the school day during summer vacation negatively impacts children's obesogenic behaviors (i.e., physical activity, screen time, diet, sleep). This natural experiment examined the impact of summer vacation on children's obesogenic behaviors and body mass index (BMI).

METHODS

Elementary-aged children (n = 285, 5-12 years, 48.7% male, 57.4% African American) attending a year-round (n = 97) and two match-paired traditional schools (n = 188) in the United States participated in this study. Rather than taking a long break from school during the summer like traditional schools, year-round schools take shorter and more frequent breaks from school. This difference in school calendars allowed for obesogenic behaviors to be collected during three conditions: Condition 1) all children attend school, Condition 2) year-round children attend school while traditional children were on summer vacation, and Condition 3) summer vacation for all children. Changes in BMI z-score were collected for the corresponding school years and summers. Multi-level mixed effects regressions estimated obesogenic behaviors and monthly zBMI changes. It was hypothesized that children would experience unhealthy changes in obesogenic behaviors when entering summer vacation because the absence of the school day (i.e., Condition 1 vs. 2 for traditional school children and 2 vs. 3 for year-round school children).

RESULTS

From Condition 1 to 2 traditional school children experienced greater unhealthy changes in daily minutes sedentary (∆ = 24.2, 95CI = 10.2, 38.2), screen time minutes (∆ = 33.7, 95CI = 17.2, 50.3), sleep midpoint time (∆ = 73:43, 95CI = 65:33, 81:53), and sleep efficiency percentage (-∆ = 0.7, 95CI = -1.1, - 0.3) when compared to year-round school children. Alternatively, from Condition 2 to 3 year-round school children experienced greater unhealthy changes in daily minutes sedentary (∆ = 54.5, 95CI = 38.0, 70.9), light physical activity minutes (∆ = - 42.2, 95CI = -56.2, - 28.3) MVPA minutes (∆ = - 11.4, 95CI = -3.7, - 19.1), screen time minutes (∆ = 46.5, 95CI = 30.0, 63.0), and sleep midpoint time (∆ = 95:54, 95CI = 85:26, 106:22) when compared to traditional school children. Monthly zBMI gain accelerated during summer for traditional (∆ = 0.033 95CI = 0.019, 0.047) but not year-round school children (∆ = 0.004, 95CI = -0.014, 0.023).

CONCLUSIONS

This study suggests that the lack of the school day during summer vacation negatively impacts sedentary behaviors, sleep timing, and screen time. Changes in sedentary behaviors, screen time, and sleep midpoint may contribute to accelerated summer BMI gain. Providing structured programming during summer vacation may positively impact these behaviors, and in turn, mitigate accelerated summer BMI gain.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03397940 . Registered January 12th 2018.

The Use of Inertial Measurement Units for the Study of Free Living Environment Activity Assessment: A Literature Review

This article presents an overview of fifty-eight articles dedicated to the evaluation of physical activity in free-living conditions using wearable motion sensors. This review provides a comprehensive summary of the technical aspects linked to sensors (types, number, body positions, and technical characteristics) as well as a deep discussion on the protocols implemented in free-living conditions (environment, duration, instructions, activities, and annotation). Finally, it presents a description and a comparison of the main algorithms and processing tools used for assessing physical activity from raw signals.

The impact of summer programming on the obesogenic behaviors of children: behavioral outcomes from a quasi-experimental pilot trial

BACKGROUND

Children from low-income families experience accelerated BMI gain and learning loss during summer. Healthy Summer Learners (HSL) addresses accelerated BMI gain and academic learning loss during summer by providing academic- and health-focused programming. This manuscript reports the effects of HSL on underlying obesogenic behaviors (i.e., physical activity, screen time, sleep, diet) that lead to accelerated summer BMI gain, a necessary first step to informing a future randomized controlled trial of HSL.

METHODS

In the summer of 2018 and 2019 using a quasi-experimental study design, 180 children (90 per summer, 7.9 years [SD = 1.0], 94% non-Hispanic Black, 40% male) at two schools (i.e., one per summer) who were struggling academically (25-75% on a standardized reading test) were provided a free, school-based 6-week health- and academic-focused summer program (i.e., HSL, n = 60), a 4- to 6-week academic-focused summer program (i.e., 21st Century Summer Learning program (21C), n = 60), or no summer program (n = 60). Children wore the Fitbit Charge 2™ over a 10-week period during the summers (June-Aug) of 2018-2019. Differences within (within child days attend vs. not attend) and between (differences between groups attend vs. not attend) were evaluated using mixed effects linear regression.

RESULTS

Regression estimates indicated that, on days attending, HSL children experienced a greater reduction in sedentary minutes (- 58.6 [95% CI = - 92.7, - 24.4]) and a greater increase in moderate-to-vigorous physical activity (MVPA) (36.2 [95% CI = 25.1, 47.3]) and steps (2799.2 [95% CI = 2114.2, 3484.2]) compared to 21C children. However, both HSL and 21C children were more active (i.e., greater MVPA, total steps) and less sedentary (i.e., less sedentary minutes and total screen time) and displayed better sleeping patterns (i.e., earlier and less variability in sleep onset and offset) on days they attended than children in the control.

CONCLUSIONS

HSL produced greater changes in physical activity than 21C. However, attendance at either HSL or 21C leads to more healthy obesogenic behaviors. Based on the behavioral data in this pilot study, a larger trial may be warranted. These results must be considered along with the pending primary outcomes (i.e., academics and BMI z-score) of the HSL pilot to determine if a full-scale trial is warranted.

TRIAL REGISTRATION

NIH-NCT03321071. Registered 25 October 2017.

Association of six-minute walk distance with subsequent lower extremity events in peripheral artery disease

The prognostic significance of the six-minute walk distance for lower extremity events in people with peripheral artery disease (PAD) is unknown. This longitudinal study assessed whether a poorer six-minute walk distance at baseline was associated with higher rates of subsequent lower extremity atherosclerotic disease events in PAD. A total of 369 patients (mean age 69.4 ± 10.0 years; mean ankle–brachial index (ABI) 0.67 ± 0.17; 31% women; 30% black individuals) from Chicago-area medical centers with PAD were enrolled. Participants underwent baseline six-minute walk testing and returned for annual study visits. Lower extremity events consisted of one or more of the following: ABI decline greater than 15% or medical record adjudicated lower extremity revascularization, critical limb ischemia, or amputation. At a mean follow-up of 33.3 months, lower extremity events occurred in 66/123 (53.7%) people in the first (worst) tertile of six-minute walk performance, 55/124 (44.4%) in the second tertile, and 56/122 (45.9%) in the third (best) tertile. After adjusting for age, sex, race, ABI, comorbidities, and other confounders, participants in the first (worst) tertile of six-minute walk distance at baseline had higher rates of lower extremity events during follow-up, compared to those in the best tertile at baseline (HR = 1.74, 95% CI 1.17–2.60, p = 0.0067). Among people with PAD, a poorer six-minute walk distance was associated with higher rates of subsequent lower extremity PAD-related events after adjusting for confounders. Further study is needed to determine whether interventions that improve six-minute walk distance can reduce lower extremity adverse events in people with PAD.

Physical activity patterns in children with cerebral palsy and typically developing peers

Objective: To compare physical activity level between children with cerebral palsy and typically developing peers using accelerometer and activity diary.Method: Twenty children with spastic cerebral palsy Level I and II according to Gross Motor Function Classification System, and 20 healthy age- and sex-matched typically developing peers were included. An activity diary was logged, and each child wore an accelerometer for 4 days, 2 weekdays and 2 weekend days.Results: Total and physical activity energy expenditure assessed using either accelerometer or activity diary was markedly lower in children with spastic cerebral palsy compared to typically developing peers. Moderate and vigorous physical activities and daily total energy expenditure assessed using activity diary were significantly lower in children with cerebral palsy than those of typically developing peers (p < .05). There was a significant relationship between accelerometer and activity diary in total energy expenditure for children with cerebral palsy (r = 0.752, p < .001) and typically developing peers (r = 0.732, p < .001) and a moderate significant relationship in physical activity energy expenditure for children with cerebral palsy (r = 0.463, p = .040).Conclusion: In this study, children with cerebral palsy had lower physical activity levels than their typically developing peers. The activity diary provided detailed information about physical activities and was correlated with accelerometer data. The activity diary could be a valid measure of physical activity levels in children with cerebral palsy.

Changes in children's sleep and physical activity during a 1-week versus a 3-week break from school: a natural experiment

Study Objectives

To examine changes in elementary aged children's sleep and physical activity during a 1-week and a 3-week school break.

Methods

Sleep and physical activity of elementary children (n = 154, age = 5-9 years, 44.8% female, 65.5% African American) were collected over 7 weeks that included a 1-week break in two schools and a 3-week break in a single school. Mixed regression models estimated sleep and physical activity changes within and between groups (i.e. 1-week vs. 3-weeks) during school and school break weeks.

Results

Compared to school weeks, bed times shifted 72.7 (95% CI = 57.5, 87.9) and 75.4 (95% CI = 58.1, 92.7) minutes later on weekdays during the 1-week and 3-week break, respectively. Wake times shifted 111.6 (95% CI = 94.3, 128.9) and 99.8 (95% CI = 80.5, 119.1) minutes later on weekdays during 1-week and 3-week breaks. On weekdays during the 3-week break, children engaged in 33.1 (95% CI = 14.1, 52.2) more sedentary minutes and -12.2 (-20.2, -4.2) fewer moderate-to-vigorous physical activity minutes/day. No statistically significant changes in children's sedentary, light, or moderate-to-vigorous physical activity (MVPA) minutes were observed on weekdays during the 1-week break. Between-group differences in the change in time sedentary (32.1-95% CI = 5.8, 58.4), and moderate-to-vigorous (-13.0-95% CI = -23.9, -2.0) physical activity were observed.

Conclusions

Children's sleep shifted later on both 1-week and 3-week breaks. Children's activity changed minimally on weekdays during a 1-week school break and more during a 3-week school break. Displaced sleep and reductions in activity are intervention targets for mitigating unhealthy weight gain during extended breaks from school.

The Intention to be Physically Active in Sedentary Obese Children: A Longitudinal Study

Obese children are usually less active than their normal-weight counterparts, although the reasons for this remain unclear. The objective of the present study was to determine how a long-term program (3 years of intervention and 6 months of follow-up detraining) of physical exercise with or without a low calorie diet influenced sedentary obese children’s intention to be physically active. The participants were 27 children, ages from 8 to 11 years, who formed two groups according to the program that they followed. One group followed an exercise program (three 90-min sessions per week), and the other this same exercise program together with a hypocaloric diet. The intention to be physically active was assessed via the Measurement of Intention to be Physically Active (MIFA) questionnaire. The subjects’ scores at different times of the program (baseline, Year 3, and detraining) were compared using a repeated-measures ANOVA, and a post-hoc Tukey’s test was applied to confirm the differences. After both the intervention and detraining, both groups showed greater intention to be physically active. This suggests the suitability of long-term physical exercise to generate greater intention to be physically active and thus establish healthy life habits including increased levels of physical activity.

A validation study concerning the effects of interview content, retention interval, and grade on children's recall accuracy for dietary intake and/or physical activity

BACKGROUND

Practitioners and researchers are interested in assessing children's dietary intake and physical activity together to maximize resources and minimize subject burden.

OBJECTIVE

Our aim was to investigate differences in dietary and/or physical activity recall accuracy by content (diet only; physical activity only; diet and physical activity), retention interval (same-day recalls in the afternoon; previous-day recalls in the morning), and grade (third; fifth).

DESIGN

Children (n=144; 66% African American, 13% white, 12% Hispanic, 9% other; 50% girls) from four schools were randomly selected for interviews about one of three contents. Each content group was equally divided by retention interval, each equally divided by grade, each equally divided by sex. Information concerning diet and physical activity at school was validated with school-provided breakfast and lunch observations, and accelerometry, respectively. Dietary accuracy measures were food-item omission and intrusion rates, and kilocalorie correspondence rate and inflation ratio. Physical activity accuracy measures were absolute and arithmetic differences for moderate to vigorous physical activity minutes.

STATISTICAL ANALYSES PERFORMED

For each accuracy measure, linear models determined effects of content, retention interval, grade, and their two-way and three-way interactions; ethnicity and sex were control variables.

RESULTS

Content was significant within four interactions: intrusion rate (content×retention-interval×grade; P=0.0004), correspondence rate (content×grade; P=0.0004), inflation ratio (content×grade; P=0.0104), and arithmetic difference (content×retention-interval×grade; P=0.0070). Retention interval was significant for correspondence rate (P=0.0004), inflation ratio (P=0.0014), and three interactions: omission rate (retention-interval×grade; P=0.0095), intrusion rate, and arithmetic difference (both already mentioned). Grade was significant for absolute difference (P=0.0233) and five interactions mentioned. Content effects depended on other factors. Grade effects were mixed. Dietary accuracy was better with same-day than previous-day retention interval.

CONCLUSIONS

Results do not support integrating dietary intake and physical activity in children's recalls, but do support using shorter rather than longer retention intervals to yield more accurate dietary recalls. Additional validation studies need to clarify age effects and identify evidence-based practices to improve children's accuracy for recalling dietary intake and/or physical activity.

Relationship Between Break-Time Physical Activity, Age, and Sex in a Rural Primary Schools, Wales, UK

The aim of this study was to examine the physical activity during the break-times of primary school children in rural areas, and its relationship with age and sex. 380 children (192 boys and 188 girls; age=9.5±1.1 years) participated in the study. Break-time physical activity in the morning and lunch breaks was measured by accelerometry. An ANOVA was used to determine differences by sex in each age group, together with the respective confidence intervals and effect sizes. The results showed that 8-year-olds performed more physical exercise than 11-year-olds during the two breaks (p=0.005). For the boys, the 8-year-olds did more physical activity than the 10-year-olds, while, for the girls, those aged 8 and 9 years did more PA than girls aged 11 years (p<0.001). The only difference between boys and girls was for the 10-year-olds (p=0.043), with the boys doing more physical activity. Teachers might find it useful to take these findings into account to design physical activity programmes aimed at increasing the playground physical activity of older children.

Effects of a long-term physical exercise program with and without diet on obese boys after six-month detraining

BACKGROUND

Most studies on physical fitness and detraining have been conducted on normal-weight children. Their results indicate that any gains regress to the untrained control values during the detraining period. It, therefore, seems necessary to determine how detraining affects the different fitness parameters in obese children. The aim of the present study was to evaluate the effects of detraining (6 months) on kinanthropometry and the components of physical fitness after an intervention (31 months) consisting of a program of exercise and/or diet for obese boys.

METHODS

The participants were 18 boys, aged between 8 and 11 years, divided into E and E+D groups according to the program they followed. The E group followed a physical exercise program (three 90-minute sessions/ week), and the E+D group the same physical exercise program plus a low calorie diet. Physical fitness was assessed by the European physical fitness test battery including flamingo balance, plate tapping, sit-andreach, standing broad jump, hand-grip strength, sit-ups, bent-arm hang, 10 × 5-metre shuttle run, and 20-metre endurance shuttle run. The Kruskal-Wallis test was applied to reveal overall intergroup differences (E and E+D groups), and measurements showing significant differences were further analysed for differences between individual groups by the Mann-Whitney U test.

RESULTS

In both groups, changes were observed in various physical fitness parameters, especially limb speed (E group, P=0.001; E+D group, P=0.002), agility (E group, P<0.001; E+D group, P<0.001), and aerobic fitness (E group, P=0.009; E+D group, P=0.002).

CONCLUSION

Detraining after a long-term intervention based on the combination of exercise program and exercise program plus diet in obese boys does not affect the changes attained during the intervention.

Does school-based physical activity decrease overweight and obesity in children aged 6-9 years? A two-year non-randomized longitudinal intervention study in the Czech Republic

Background

Globally, efforts aimed at the prevention of childhood obesity have led to the implementation of a range of school-based interventions. This study assessed whether augmenting physical activity (PA) within the school setting resulted in increased daily PA and decreased overweight/obesity levels in 6-9-year-old children.

Methods

Across the first to third primary school years, PA of 84 girls and 92 boys was objectively monitored five times (each for seven successive days) using Yamax pedometer (step counts) and Caltrac accelerometer (activity energy expenditure AEE - kcal/kg per day). Four schools were selected to participate in the research (2 intervention, 2 controls), comprising intervention (43 girls, 45 boys) and control children (41 girls, 47 boys). The study was non-randomized and the intervention schools were selected on the basis of existing PA-conducive environment. Analyses of variance (ANOVA) for repeated measures examined the PA programme and gender effects on the step counts and AEE. Logistic regression (Enter method) determined the obesity and overweight occurrence prospect over the course of implementation of the PA intervention.

Results

There was a significant increase of school-based PA during schooldays in intervention children (from ≈ 1718 to ≈ 3247 steps per day; and from 2.1 to ≈ 3.6 Kcal/Kg per day) in comparison with the control children. Increased school-based PA of intervention children during schooldays contributed to them achieving >10,500 steps and >10.5 Kcal/Kg per school day across the 2 years of the study, and resulted in a stop of the decline in PA levels that is known to be associated with the increasing age of children. Increased school-based PA had also positive impact on leisure time PA of schooldays and on PA at weekends of intervention children. One year after the start of the PA intervention, the odds of being overweight or obese in the intervention children was almost three times lower than that of control children (p < 0.005), and these odds steadily decreased with the duration of the intervention.

Conclusions

The findings suggest that school-based PA (Physical Education lessons, PA during short breaks and longer recesses, PA at after-school nursery) in compatible active environments (child-friendly gym and school playground, corridors with movement and playing around corners and for games) has a vital role in obesity and overweight reduction among younger pupils.

Convergent Validity and Test–Retest Reliability of the Oxford Physical Activity Questionnaire for Secondary School Students

The purpose of this study was to examine the convergent validity and test–retest reliability of the Oxford Physical Activity Questionnaire (OPAQ), a self-administered questionnaire designed to assess the activity patterns of adolescents. The test–retest reliability of the OPAQ was assessed by administering the questionnaire on two occasions separated by 1 week (N = 87, mean age = 13.1 ± .9). Intraclass correlation (ICC) was used to examine the test–retest reliability of the OPAQ. The convergent validity of the OPAQ was evaluated using Caltrac accelerometers worn consecutively for 4 days (N = 51, mean age = 12.6 ± .5). Spearman's rank-order correlation was used to examine the convergent validity of the questionnaire. ICCs ranged from .76 to .91 and reliability was higher for males (r = .89) than females (r = .78). Correlations between self-reported physical activity and Caltrac accelerometer counts were related to vigorous physical activity (r = .33, p = .01) and moderate to vigorous activity (r = .32, p = .02). The OPAQ has excellent test–retest reliability and acceptable validity in comparison to other measures of youth physical activity.

HR index--a simple method for the prediction of oxygen uptake

PURPOSE

Energy expenditure measured in METs is widely used in cardiovascular medicine, exercise physiology, and nutrition assessment. However, measurement of METs requires complex equipment to determine oxygen uptake. A simple method to predict oxygen uptake on the basis of HR measurements without requirement for gas analysis, movement-recording devices, or exercise equipment (treadmills, cycle ergometers) would enable a simple prediction of energy expenditure. The purpose of this study was to determine whether HR can be used to accurately predict oxygen uptake.

METHODS

Published studies that reported a measured resting HR (HR(rest)), a measured activity HR (HR(absolute)), and a measured oxygen uptake (mL O(2)·kg(-1)·min(-1)) associated with the HR(absolute) were identified. A total of 220 data sets were extracted from 60 published exercise studies (total subject cohort = 11,257) involving a diverse range of age, pathophysiology, and the presence/absence of β-blocker therapy. Net HR (HR(net) = HR(absolute) - HR(rest)) and HR index (HR(index) = HR(absolute)/HR(rest)) were calculated from the HR data. A regression analysis of oxygen uptake (expressed as METs) was performed against HR(absolute), HR(net), and HR(index).

RESULTS

Statistical models for the relationship between METs and the different HR parameters (HR(absolute), HR(net), and HR(index)) were developed. A comparison between regression analyses for the models and the actual data extracted from the published studies demonstrated that the best fit model was the regression equation describing the relationship between HR(index) and METs. Subgroup analyses of clinical state (normal, pathology), testing device (cycle ergometer, treadmill), test protocol (maximal, submaximal), gender, and the effect of β-blockade were all consistent with combined data analysis, demonstrating the robustness of the equation.

CONCLUSIONS

HR(index) can be used to predict energy expenditure with the equation METs = 6HR(index) - 5.

Effects of Exercise and/or Diet Programs on Kinanthropometric and Metabolic Parameters in Obese Children: a Pilot Study

This study was aimed at determining the effects of implementing a medium-term (six-month) exercise and/or a diet program on the kinanthropometric and metabolic parameters of obese children. The participants were 42 subjects (27 boys, 15 girls), whose ages were between 8 and 11, divided into three groups according to the program they followed. The E group followed a physical exercise program (three 90-minute sessions per week), the D group a low calorie diet, and the E+D group both interventions. A repeated-measure ANOVA was used to compare measurements of the participants' kinanthropometric and metabolic parameters at different times of the program, with the means being compared using the Tukey post-hoc test. It was found that medium-term intervention based on the combination of exercise and low calorie diet improved the obese children's kinanthropometric and metabolic parameters, especially those related to the lipid profile. Also, this combined program was more effective in controlling weight than the exercise or low calorie diet interventions alone.

Transient and steady state estimation of human oxygen uptake based on noninvasive portable sensor measurements

The main motivation of this study is to establish an ambulatory cardio-respiratory analysis system for the monitoring and evaluation of exercise and regular daily physical activity. We explored the estimation of oxygen uptake by using noninvasive portable sensors. These sensors are easy to use but may suffer from malfunctions under free living environments. A promising solution is to combine sensors with different measuring mechanisms to improve both reliability and accuracy of the estimation results. For this purpose, we selected a wireless heart rate sensor and a tri-axial accelerometer to form a complementary sensor platform. We analyzed the relationship between oxygen uptake measured by gas analysis and data collected from the simple portable sensors using multivariable nonlinear modeling approaches. It was observed that the resulting nonlinear multivariable model could not only achieve a better estimate compared with single input single output models, but also had greater potential to improve reliability.

Review of prediction models to estimate activity-related energy expenditure in children and adolescents

Purpose. To critically review the validity of accelerometry-based prediction models to estimate activity energy expenditure (AEE) in children and adolescents. Methods. The CINAHL, EMBASE, PsycINFO, and PubMed/MEDLINE databases were searched. Inclusion criteria were development or validation of an accelerometer-based prediction model for the estimation of AEE in healthy children or adolescents (6–18 years), criterion measure: indirect calorimetry, or doubly labelled water, and language: Dutch, English or German. Results. Nine studies were included. Median methodological quality was 5.5 ± 2.0 IR (out of a maximum 10 points). Prediction models combining heart rate and counts explained 86–91% of the variance in measured AEE. A prediction model based on a triaxial accelerometer explained 90%. Models derived during free-living explained up to 45%. Conclusions. Accelerometry-based prediction models may provide an accurate estimate of AEE in children on a group level. Best results are retrieved when the model combines accelerometer counts with heart rate or when a triaxial accelerometer is used. Future development of AEE prediction models applicable to free-living scenarios is needed.

Reliability and validity of the Activity Questionnaire for Adults and Adolescents (AQuAA)

BACKGROUND

Accurate measures of physical activity are highly needed. We evaluated the test-retest reliability and construct validity of the self-report Activity Questionnaire for Adults and Adolescents (AQuAA). The AQuAA is a commonly used questionnaire in Dutch youth.

METHODS

In the test-retest reliability study, 53 adolescents and 58 adults completed the AQuAA twice, with an interval of two weeks. In the validity study, 33 adolescents and 47 adults wore an accelerometer (Actigraph) during two weeks, and subsequently completed the AQuAA.

RESULTS

In adolescents the test-retest reliability was fair to moderate (intraclass correlations (ICCs) ranging from 0.30 to 0.59). In adults the test-retest reliability was fair to moderate for the time spent on sedentary, light and moderate intensity activities (ICCs ranging from 0.49 to 0.60), but poor for time spent on vigorous activities (ICC = -0.005). The correlations between the AQuAA and Actigraph were low and nonsignificant. Compared with the Actigraph, time spent on all physical activities was significantly higher according to the questionnaire (except for light intensity activities in adolescents), while time spent on sedentary behaviours was significantly lower.

CONCLUSION

Reliability of the AQuAA is fair to moderate. The validity of the AQuAA compared to an accelerometer is poor. Both adolescents and adults underestimate the time spent on sedentary behaviours and overestimate the time spent on physical activities.

Changes in physical activity in pre-schoolers and first-grade children: longitudinal study in the Czech Republic

BACKGROUND

The transition from kindergarten to first year at school is associated with a variety of psychosocial changes in children. The aim of this longitudinal study was to identify the changes in children's physical activity (PA) upon entry to first year at school; and to identify the days of the school week that exhibit low PA.

METHODS

We monitored the PA levels of 176 children twice: initially in kindergarten and again in first-year classes at school. The age (mean +/- standard deviation) of children at kindergarten was 5.7 +/- 0.5 years and 6.7 +/- 0.5 years at the first year of elementary school. We evaluated PA employing the activity energy expenditure (AEE - kcal/kg/day) from Caltrac accelerometer and daily amount of steps (STEPS) from Yamax pedometer. Participants were monitored over 7 days to include a weekend.

RESULTS

The mean AEE was 11.5 in pre-school girls and 12.9 kcal/kg/day in boys; and STEPS were 9923 steps/day in girls and 11 864 in boys on weekdays. At weekends, it was 11.5 kcal/kg/day in girls and 12.7 kcal/kg/day in boys and 10 606 steps/day in girls and 11 182 steps/day in boys. The mean AEE and STEPS in first-grade girls and boys was 9.9 and 9.8 kcal/kg/day respectively, and 7911 and 8252 steps/day respectively on weekdays, and 8.8 and 9.0 kcal/kg/day and 6872 and 7194 steps/day respectively at weekends. First-grade school children had significantly lower PA than pre-school children on weekdays (P < 0.0001) and at weekends (P < 0.0001). Decline in PA on weekdays was during time spent at school (P < 0.0001) and not during after-school children's leisure time.

CONCLUSION

The parts of the week when first-grade school children show low PA are the times spent in lessons and in after-school nursery and at weekends. PA needs to be promoted using intervention programmes mainly during the after-school nursery programmes and at weekends.

Measuring distance walked and step count in children with cerebral palsy: an evaluation of two portable activity monitors

Assessing clinical outcomes in the context of activity and participation is essential to reflect functional changes in the home and community for children with cerebral palsy (CP). However, no activity monitor has been investigated for measurement of the distance walked and step count in children with CP who have atypical gait. Twenty typically developing children and twenty children with CP, aged 4-16 years, were recruited to evaluate two portable activity monitors, AMP 331 (AMP) and Dynaport Minimod (Minimod), under three walking conditions (continuous walking, structured activity lap walking and stair climbing). Measurements of the activity monitors were compared to known walking distances and video recordings for step count. The devices performed differently under different walking conditions. The Minimod gave more accurate measurement of continuous walking over level ground. On the other hand, the AMP performed better in detecting the walks in a structured activity lap and during stair ascent and descent. Researchers and clinicians need to consider different characteristics of the monitoring devices and walking conditions, and choose an appropriate device that is most reflective of what they want to measure.

Physical activity during daily life and functional decline in peripheral arterial disease

BACKGROUND

Few modifiable behaviors have been identified that are associated with slower rates of functional decline in persons with lower-extremity peripheral arterial disease. We determined whether higher levels of physical activity during daily life are associated with less functional decline in persons with peripheral arterial disease.

METHODS AND RESULTS

The study population included 203 peripheral arterial disease participants who underwent vertical accelerometer-measured physical activity continuously over 7 days and were followed up annually for up to 4 years (mean, 33.6 months). Outcomes were average annual changes in 6-minute walk performance, usual-paced and fast-paced 4-m walking velocity, and the short performance physical battery. Analyses were adjusted for age, sex, race, comorbidities, body mass index, ankle brachial index, smoking, and walking exercise frequency. Higher baseline physical activity levels measured by a vertical accelerometer were associated with significantly less average annual decline in 6-minute walk performance (P for trend=0.010), fast-paced 4-m walking velocity (P for trend=0.002), and the short performance physical battery (P for trend=0.001). Compared with the lowest baseline quartile, those in the highest baseline quartile of physical activity had less annual decline in 6-minute walk performance (-50.82 versus -107.0 ft/y; P=0.019), fast-paced 4-m walking speed (-0.0034 versus -0.111 m . s(-1) . y(-1); P=0.002), and the short performance physical battery (-0.074 versus -0.829; P=0.005).

CONCLUSIONS

Higher physical activity levels during daily life are associated with less functional decline among people with peripheral arterial disease. These findings may be particularly important for the large number of peripheral arterial disease persons without access to supervised walking exercise programs.

Effects of average childhood dairy intake on adolescent bone health

OBJECTIVE

To evaluate the effects of usual childhood dairy intake on adolescent bone health.

STUDY DESIGN

Dietary data collected in the Framingham Children's Study over 12 years were used to evaluate usual dairy consumption and adolescent bone health. Each child's average Food Pyramid servings were estimated from yearly sets of 3-day diet records. Bone mineral content (BMC) and area (BA) for total body and 6 regions (arms, legs, trunk, ribs, pelvis, and spine) at ages 15 to 17 years were the primary outcomes. Analysis of covariance was used to adjust for potential confounding by sex and physical activity, as well as age, height, body mass index and percent body fat at the time of the bone scan.

RESULTS

Consuming >or= 2 servings/day of dairy (versus less) was associated with significantly higher mean BMC and BA. Higher intakes of meats/other proteins (>or= 4 servings per/day) were also associated with higher mean BMC and BA values. Children with higher intakes of both dairy and meats/other proteins had the highest adjusted BMC (3090.1 g), and children consuming less of each had the lowest BMC (2740.2 g).

CONCLUSIONS

These prospective data provide evidence for a beneficial effect of childhood dairy consumption on adolescent bone health.

Application of cross-sectional time series modeling for the prediction of energy expenditure from heart rate and accelerometry

Accurate estimation of energy expenditure (EE) in children and adolescents is required for a better understanding of physiological, behavioral, and environmental factors affecting energy balance. Cross-sectional time series (CSTS) models, which account for correlation structure of repeated observations on the same individual, may be advantageous for prediction of EE. CSTS models for prediction of minute-by-minute EE and, hence, total EE (TEE) from heart rate (HR), physical activity (PA) measured by accelerometry, and observable subject variables were developed in 109 children and adolescents by use of Actiheart and 24-h room respiration calorimetry. CSTS models based on HR, PA, time-invariant covariates, and interactions were developed. These dynamic models involve lagged and lead values of HR and lagged values of PA for better description of the series of minute-by-minute EE. CSTS models with random intercepts and random slopes were investigated. For comparison, likelihood ratio tests were used. Log likelihood increased substantially when random slopes for HR and PA were added. The population-specific model uses HR and 1- and 2-min lagged and lead values of HR, HR(2), and PA and 1- and 2-min lagged values of PA, PA(2), age, age(2), sex, weight, height, minimum HR, sitting HR, HR x height, HR x weight, HR x age, PA x weight, and PA x sex interactions (P < 0.001). Prediction error for TEE was 0.9 +/- 10.3% (mean +/- SD). Errors were not correlated with age, weight, height, or body mass index. CSTS modeling provides a useful predictive model for EE and, hence, TEE in children and adolescents on the basis of HR and PA and other observable explanatory subject characteristics of age, sex, weight, and height.

Active transportation to school over 2 years in relation to weight status and physical activity

OBJECTIVE

To prospectively examine potential benefits of active commuting to school on measures of weight status and physical activity in a sample of youth.

RESEARCH METHODS AND PROCEDURES

A cohort of students from seven elementary schools was measured four times--in the fall and spring of fourth grade (N = 1083) and fifth grade (N = 924). Participants were classified as active (walking, biking, or skateboarding to school almost every day for baseline analyses or at least 2 d/wk for analyses of consistent active commuting) or non-active commuters to school. Accelerometers were used to measure physical activity. Height, weight, and skinfolds were objectively assessed.

RESULTS

Boys who actively commuted to school had lower BMI (p < 0.01) and skinfolds (p < 0.05) than non-active commuters to school in the fourth grade. Active commuting to school over 2 years was not associated with BMI change or overweight status.

DISCUSSION

Walking and cycling to school may contribute to preventing excessive weight gain, or leaner children may walk or cycle to school.

Physical activity during daily life and mortality in patients with peripheral arterial disease

BACKGROUND

We determined whether patients with lower-extremity peripheral arterial disease (PAD) who are more physically active during daily life have lower mortality rates than PAD patients who are less active.

METHODS AND RESULTS

Participants were 460 men and women with PAD (mean age 71.9+/-8.4 years) followed up for 57 months (interquartile range 36.6 to 61.9 months). At baseline, participants were interviewed about their physical activity. Vertical accelerometers measured physical activity continuously over 7 days in 225 participants. Analyses were adjusted for age, sex, race, body mass index, hypertension, smoking, comorbidities, total cholesterol, HDL cholesterol, leg symptoms, and ankle-brachial index. At 57-month follow-up, 134 participants (29%) had died, including 75 participants (33%) who wore accelerometers. Higher baseline physical activity levels measured by vertical accelerometer were associated with lower all-cause mortality (P(trend)=0.003). Relative to PAD participants in the highest quartile of accelerometer-measured physical activity, those in the lowest quartile had higher total mortality (hazard ratio 3.48, 95% confidence interval 1.23 to 9.87, P=0.019). Similar results were observed for the combined outcome of cardiovascular events or cardiovascular mortality (P(trend)=0.005). Higher numbers of stair flights climbed during 1 week were associated with lower total mortality (P(trend)=0.035).

CONCLUSIONS

PAD patients with higher physical activity during daily life have reduced mortality and cardiovascular events compared with PAD patients with the lowest physical activity, independent of confounders. Further study is needed to determine whether interventions that increase physical activity during daily life are associated with improved survival in patients with PAD.

Clinimetric review of motion sensors in children and adolescents

BACKGROUND AND OBJECTIVES

To review the clinimetric quality of motion sensors used to assess physical activity in healthy children and adolescents (2-18 years).

METHODS

A systematic literature search was performed in PubMed, Embase, and SpycINFO. The clinimetric quality of two pedometers (Digi-Walker, Pedoboy), four one-dimensional accelerometers (LSI, Caltrac, Actiwatch, CSA/ActiGraph), and three three-dimensional accelerometers (Tritrac-R3D, RT3, Tracmor2) was evaluated and compared using a 20-item checklist.

RESULTS

Overall, the quality of the studies (n = 35), and therefore the level of evidence for the reproducibility, validity, and feasibility of the motion sensors was modest (mean = 6.4 +/- 1.6 out of 14 points). There was strong evidence for a good reproducibility of the Caltrac in adolescents (12-18 years), a poor reproducibility of the Digi-Walker in children (8-12 years), a good validity of the CSA/ActiGraph in children and adolescents (8-18 years), and a good validity of the Tritrac-R3D in children (8-12 years).

CONCLUSIONS

The CSA/ActiGraph and the Caltrac are the only motion sensors in which the reproducibility, validity, and feasibility have been examined in different age groups. Further studies of the reproducibility of motion sensors in preschool children, improvement of the quality of clinimetric studies, and evaluation of the acceptability of motion sensors are warranted.

Low dairy intake in early childhood predicts excess body fat gain

OBJECTIVE

To estimate the effect of dairy intake in early childhood on the acquisition of body fat throughout childhood.

RESEARCH METHODS AND PROCEDURES

Ninety-nine of the original 106 families enrolled in the Framingham Children's Study with a child age to 6 years at baseline were followed into adolescence through yearly clinic visits and periodic data collection throughout each year. Dairy intake for these analyses was derived from a mean of 15 days of diet records per subject collected before age 6. A trained examiner took two measurements each year of height, weight, and triceps, subscapular, suprailiac, and abdominal skinfolds using a standardized protocol. Yearly change in body fat was estimated as the slope of these anthropometry measures from ages 5 to 13 years. Early adolescent body fat was estimated as the mean of all available measurements from 10 to 13 years of age.

RESULTS

Children in the lowest sex-specific tertile of dairy intake during preschool (i.e., <1.25 servings per day for girls and <1.70 servings per day for boys) had significantly greater gains in body fat during childhood. These children with low dairy intakes gained more than 3 additional mm of subcutaneous fat per year in the sum of four skinfold measures. By the time of early adolescence, those in the lowest tertile of dairy intake had a BMI that was approximately two units higher and an extra 25 mm of subcutaneous fat.

DISCUSSION

Suboptimal dairy intakes during preschool in this cohort were associated with greater gains in body fat throughout childhood.

Calibration of Accelerometer Output for Children

Understanding the determinants of physical activity behavior in children and youths is essential to the design and implementation of intervention studies to increase physical activity. Objective methods to assess physical activity behavior using various types of motion detectors have been recommended as an alternative to self-report for this population because they are not subject to many of the sources of error associated with children's recall required for self-report measures. This paper reviews the calibration of four different accelerometers used most frequently to assess physical activity and sedentary behavior in children. These accelerometers are the ActiGraph, Actical, Actiwatch, and the RT3 Triaxial Research Tracker. Studies are reviewed that describe the regression modeling approaches used to calibrate these devices using directly measured energy expenditure as the criterion. Point estimates of energy expenditure or count ranges corresponding to different activity intensities from several studies are presented. For a given accelerometer, the count cut points defining the boundaries for 3 and 6 METs vary substantially among the studies reviewed even though most studies include walking, running and free-living activities in the testing protocol. Alternative data processing using the raw acceleration signal is recommended as a possible alternative approach where the actual acceleration pattern is used to characterize activity behavior. Important considerations for defining best practices for accelerometer calibration in children and youths are presented.

The reliability and validity of two Ambulatory Monitoring actigraphs

Evidence for the reliability and validity of two models of Ambulatory Monitoring, Inc. actigraphs was obtained by testing four instruments of each kind 10 times each on a precision pendulum. Correlation and coefficient of variation methods were used to analyze the data. Reliability coefficients of .98 were obtained for both models. Coefficient of variation methods yielded reliability coefficients of 92% for the MotionLogger model and 97% for the BuzzBee model. Validity coefficients of.99 were obtained for both models. However, MotionLogger means were found to differ by up to 36% from one instrument to another, whereas BuzzBee means differed by 10% at most. Issues of standardization and measurement units were discussed.

Utility of a step activity monitor for the measurement of daily ambulatory activity in children

OBJECTIVES

To evaluate the reliability and validity of the StepWatch Activity Monitor (SAM) as a reliable and valid measurement tool for assessing ambulatory activity in able-bodied children and to assess the ambulatory activity of able-bodied children.

DESIGN

Descriptive study.

SETTING

General community.

PARTICIPANTS

Ninety-seven able-bodied children, aged 6 to 20 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Anthropometric parameters, calibration of a step activity monitor to ensure accuracy, and 3 days of simultaneous heart rate and step activity monitoring.

RESULTS

The SAM had an accuracy of 99.87% compared with the observer-counted steps and was shown to be valid and reliable when compared with heart rate monitoring. The subjects in all age groups (6-10 y, 11-15 y, 16-20 y) spent most of their active time at low step rate but took the fewest steps at this rate. Although the least amount of time was spent at high step rate, it accounted for the most steps. The 6- to 10-year-old group took more total steps per day than any of the other groups. Boys spent significantly more time at high step rate than girls in all age groups (mean for boys, 66+/-4 min/d; girls, 47+/-4 min/d).

CONCLUSIONS

The SAM is an accurate, valid, and useful tool for measuring continuous, time-based step activity during real-world community activity for children and adolescents.

Uptime in children with cerebral palsy

Quantitative evaluation of function, in children with physical disabilities, has to date been mainly focused on laboratory-based measures. However, the measurement of activity in the community may have a more direct relationship with physical function, health, and well-being. We assessed the utility of a remote activity monitor, the Uptimer (National Aging Research Institute of Melbourne, Melbourne, Australia), to measure one aspect of physical function, time spent in the upright position, in a consecutive cohort of 300 children with cerebral palsy who attended an orthopedic outpatient department. The Uptimer was found to be a valid and reliable tool to measure the amount of time children spent on their feet each day. Uptime was closely related to the severity of cerebral palsy and had excellent correlations with validated instruments including the Pediatric Orthopaedic Data Collection Instrument (PODCI), the Child Health Questionnaire (CHQ), and the Functional Mobility Scale (FMS). Uptime complements any quantitative functional assessment of impairments in children with cerebral palsy.

Prevalence of Exercise-Induced Arterial Hypoxemia in Healthy Women

PURPOSE

Exercise-induced arterial hypoxemia (EIAH) is reported to occur in approximately 50% of highly trained male endurance athletes. Few studies have examined EIAH in women and the prevalence remains unclear. It has been reported that some female subjects who develop EIAH possess maximal oxygen consumption (VO2max) values that are within 15% of their predicted value. This is unique to women, where EIAH has generally been reported in men who have a high VO2max. The primary objective of this investigation was to determine the prevalence of EIAH in a large female population with a wide range of VO2max values. It was hypothesized that EIAH would occur with a greater prevalence and at relatively lower predicted VO2max than that previously reported in males.

METHODS

Young women (N = 52; 26.5 +/- 4.9 yr) performed a cycle test to exhaustion to determine VO2max, and oxyhemoglobin saturation (SaO2) was monitored via pulse oximetry. All subjects were tested during the early follicular phase of their menstrual cycle. A >/= 4% drop in SaO2 represented EIAH.

RESULTS

Values for VO2max were variable (VO2max range: 28.0-61.3 mL x kg(-1) x min(-1)). EIAH was present in 67% of the women with N = 19 displaying mild EIAH (92-94%SaO2) and N = 16 displaying moderate EIAH (87-91%SaO2).

CONCLUSION

It appears that the prevalence of EIAH in women is slightly greater than the 50% prevalence value that is typically reported for highly fit men.

Estimating human energy expenditure: a review of techniques with particular reference to doubly labelled water

This review includes an historical overview of the techniques for measuring energy expenditure (EE). Following this overview, the "gold standard" method of measuring EE, the doubly labelled water (DLW) method, is emphasised. Other methods, such as direct calorimetry, indirect calorimetry systems, heart rate and EE relationships, questionnaires and activity recall, motion sensors, combined heart rate and motion sensors for the estimation of EE are then highlighted in relation to their validation against the DLW method. The major advantages and disadvantages for each method are then considered. The preferred method to determine EE is likely to depend principally on factors such as the number of study participants to be monitored, the time period of measurements and the finances available. Small study participant numbers over a short period may be measured accurately by means of indirect calorimetric methods (stationary and portable systems). For periods over 3-4 days, EE should ideally be measured using the DLW method. However, the use of motion sensors is very promising in the measurement of EE, and has a number of advantages over the DLW method. Furthermore, if used correctly, both heart rate and questionnaire methods may provide valuable estimates of EE. Additional studies are needed to examine the possibility of improving the accuracy of measurement by combining two or more techniques. Such information, if confirmed by scientific rigour, may lead to an improvement in the estimation of EE and population-based physical activity levels. The accurate measurement of physical activity and EE is critical from both a research and health prospective. A consideration of the relevant techniques used for the estimation of EE may also help improve the quality of these frequently reported measurements.

Validity of uniaxial accelerometry during activities of daily living in children

The purpose of this study was to examine the validity of treadmill-based equations of two commonly used uniaxial accelerometers to estimate energy expenditure (EE) during activities of daily living in children. Twelve subjects with mean (SD) age11.4 (0.4) years engaged in a choreographed routine consisting of three activities (sweeping, bowling, and basketball) of 4min duration while wearing a Manufacturing Technology, Inc. (MTI) accelerometer, Caltrac accelerometer, and a portable gas analyzer (Cosmed K4b(2)). The equations of Trost et al. and Sallis et al. were used to convert activity counts to estimations of EE for the MTI and Caltrac, respectively. Correlation coefficients between Caltrac predictions of EE and measured EE from indirect calorimetry ranged from r=0.22 to 0.72 for individual activities. Correlations between MTI EE predictions and indirect calorimetry ranged from r=0.50 to 0.68 for individual activities. When the activities were pooled the correlations between EE from uniaxial accelerometers and EE from indirect calorimetry were moderately strong (MTI, r=0.78 and Caltrac, r=0.82). Inter-accelerometer (counts min(-1)) correlations were 0.08, -0.54, 0.63, and 0.79 for sweeping, bowling, basketball, and pooled data, respectively. The overall mean difference, or bias, and 95% confidence intervals (CI) for each uniaxial accelerometer compared to indirect calorimetry were as follows: Caltrac, bias = 2.80 (2.36, 3.24) kcal min(-1); MTI, bias = 0.88 (0.23, 1.53) kcal min(-1). Both accelerometers significantly underestimated measured EE ( P<0.05). Uniaxial accelerometers provide potential for the measurement of physical activity (PA) and EE in children. Future studies refining accelerometry predictions of PA and EE are warranted.

Physical activity and health related physical fitness in children with juvenile idiopathic arthritis

OBJECTIVE

To obtain insight into the interaction between daily physical activity and components of health related physical fitness in children with juvenile idiopathic arthritis.

METHODS

Forty five patients (10 male/35 female; mean (SD) age 8.9 (2.2) years) participated in the study. Body mass, height, skinfold thickness, number of swollen joints, and joint range of motion were determined. The maximal oxygen consumption (VO(2peak)) was assessed during a graded maximal bicycle exercise test. Daily physical activity levels were measured with a Caltrac activity monitor and a parental physical activity rating (PAL) on a five point Likert scale.

RESULTS

Partial correlation coefficients (to control for age) between physical activity and indices of health related physical fitness showed significant relationships between Caltrac motion counts and absolute VO(2peak) (r=0.31) and relative VO(2peak) (r=0.34), but not with the indices of body composition. There was also a significant correlation between PAL and relative VO(2peak) (r=0.33).

CONCLUSIONS

Physical activity was significantly related to cardiorespiratory fitness but not to body composition in children with juvenile idiopathic arthritis. A longitudinal follow up should show whether an active lifestyle protects for loss of aerobic fitness in this patient group.

Does early physical activity predict body fat change throughout childhood?

BACKGROUND

Declining levels of physical activity in the population at large may be responsible in part for the rising rates of childhood obesity. Studies to date, however, have not consistently demonstrated such a protective effect. We used longitudinal data from the Framingham Children's Study (FCS) to address this important question.

METHODS

We used 8 years of activity monitoring (Caltrac electronic motion sensors) and repeated anthropometry measures for 103 children to examine the effect of activity on body fat change from preschool to early adolescence. Longitudinal data analysis methods were employed to account for the use of repeated measures on these children.

RESULTS

Children in the highest tertile of average daily activity from ages 4 to 11 years had consistently smaller gains in BMI, triceps, and sum of five skinfolds throughout childhood. By early adolescence (age 11), the sum of five skinfolds was 95.1, 94.5, and 74.1 for the low, middle, and high tertiles of activity, respectively (P for trend = 0.045). This protective effect of activity was evident for both girls and boys.

CONCLUSION

This longitudinal study adds strong support for the hypothesis that higher levels of physical activity during childhood lead to the acquisition of less body fat by the time of early adolescence.