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Abstract

Objective Nowadays, there is growing interest in establishing daily activity wristband-based physical activity recommendations. Unfortunately, empirical studies examining the activity wristband-measured physical activity thresholds related to the daily physical activity recommendation in adolescents were not found. The main aim of the present study was to establish daily activity wristband-measured steps thresholds related to the recommendation of 60 minutes of moderate-to-vigorous physical activity daily in adolescents. The secondary aims of this study were twofold: (a) to establish daily activity wristband-measured total physical activity and moderate-to-vigorous physical activity thresholds; and (b) to examine the cross-validity of daily activity wristband-measured steps thresholds established in previous studies associated with the recommended 60 minutes per day of moderate-to-vigorous physical activity in adolescents. Methods Following a cross-sectional design, 85 Spanish adolescents (including 56 females; aged 12–18 years old) from a public high school wore an ActiGraph GT3X+ accelerometer and four activity wristbands (Xiaomi Mi Band 2, Fitbit Alta HR, Polar A360 and Garmin Vivofit 4; non-dominant hand; index tests) for a day. Results A total of 38.8% of the adolescents met the moderate-to-vigorous physical activity recommendation. The results showed that the validity of the daily total step-based thresholds tended to be higher (e.g., AUC = 0.83–0.91, P < 0.001) than those with total physical activity or moderate-to-vigorous physical activity (AUC = 0.66–0.88, P < 0.01). The results of the cross-validity showed that the 10,000 step-per-day threshold had a high agreement (e.g., Xiaomi, P = 0.80; k = 0.58; Garmin, P = 0.82; k = 0.63). Conclusions Activity wristband-measured total steps thresholds have a high validity for translating the daily moderate-to-vigorous physical activity recommendation, being more preferable than those with total physical activity or moderate-to-vigorous physical activity. A 10,000 step-per-day target seems to be a practical and adequate activity wristband-based threshold among adolescents. This knowledge may help policy makers to provide adequate daily activity wristband-measured step-based recommendations for adolescents.

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... Therefore, among the various consumer wearable activity devices available, activity wristbands have proven to be the most valued and utilized type of device by school-aged children [9,10]. ...
... In this regard, there are several interesting points to highlight. On one hand, there are many brands of physical activity wristbands, the most analyzed in research in recent years for validation in school populations have been the Xiaomi Mi Band, Fitbit Charge or Ace, and Garmin Vivofit [9,10,13], where it has been observed that they are valid for estimating step volume [14,15]. Thus, there is evidence that these models are valid for estimating steps; however, there is little evidence of whether they are suitable for measuring the level of physical activity [16]. ...
... It was not possible to compare overestimates or underestimates with the previous literature because of the lack of other studies evaluating the reliability or validity of this specific model of wristbands, although some studies have performed intra-device validation, as in the case of accelerometry [24,25]. It is interesting to highlight that, regarding PA, this wristband measures steps and minutes of MVPA, with encouraging data regarding its reliable measurement for young children [16,17]; although technical details and manufacturers' algorithms are sometimes kept confidential [9,17]. However, to our knowledge, this is the first study to evaluate intra-device variability in a wristband intended for children, a truly useful aspect when this device is being applied in a school setting and other environments where different participants are simultaneously engaged [18,19]. ...
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The main objective of this study was to evaluate the reliability of Garmin Vivofit® Jr. physical activity (PA) wristbands during daily life physical activities. Six wristbands were randomly selected from a stock of twenty-four. The wristbands were worn by a single four-year-old participant, with three on the right wrist area and three on the left wrist area. To assess device reliability under laboratory conditions on a treadmill (Powerjog, model JM200, SportEngineering Ltd., Birmingham, UK), the participant wore the six wristbands while performing five work conditions: sitting and standing (30 times per minute, controlled by a metronome), walking at 3 km/h, walking at 4 km/h, running at 5 km/h, and running at 6 km/h. Throughout the six minutes, variables related to physical activity provided by the device, step volume, and minutes of physical activity were recorded using the specific application of the wristband (Garmin International Inc., Olathe, KS, USA). The intraclass correlation coefficients (ICCs) were high for all six wristbands with each other, for both the number of steps taken (ICC = 0.991–0.998) and the number of minutes of PA (ICC = 0.892–0.977). The critical alpha value of the Cusum test was highest at.050 for all wristband associations. In conclusion, good reliability was found among the six wristbands, which could be adopted for field-based research to quantify physical activities.
... As regards the assessment of MVPA, all the previously studied activity wristbands (i.e., Fitbit Charge HR and Flex 2, and Xiaomi Mi Band) showed inadequate validity among primary schoolchildren (26,27,29). Despite the fact that activity wristbands could be not valid for estimating the exact values of PA levels (i.e., as a continuous variable), from a health promotion perspective, the main interest is knowing if activity wristbands are simply valid for classifying schoolchildren as meeting or not meeting the PA recommendations (i.e., as a dichotomous variable) (13). Furthermore, since different kinds of activity wristbands could be used in the same context due to economic constrains (e.g., monitoring or promoting PA in the physical education setting or large-scale research studies) (30,31), the agreement between activity wristbands (i.e., comparability) should be also studied (14). ...
... Particularly among primary schoolchildren, previous studies have found a high accuracy in the translation of the MVPA-based guidelines to about 10,000 (6) or 12,000 steps per day (7). Moreover, as shown in the results of the present study, because activity wristbands tend to have a much lower validity for estimating school children's MVPA than for steps (see discussion above), in order to correctly classify schoolchildren as meeting or not meeting the MVPA-based recommendations, activity wristband-based steps have shown to be considerably more valid than even with the activity wristband MVPA output (13). In this line, for instance, Casado-Robles et al. (11) in a systematic review about consumer-wearable activity tracker-based programs found that most of the studies with a goal-setting strategy set only a step-based goal (81%). ...
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Introduction The use of activity wristbands to monitor and promote schoolchildren's physical activity (PA) is increasingly widespread. However, their validity has not been sufficiently studied, especially among primary schoolchildren. Consequently, the main purpose was to examine the validity of the daily steps and moderate-to-vigorous PA (MVPA) scores estimated by the activity wristbands Fitbit Ace 2, Garmin Vivofit Jr 2, and the Xiaomi Mi Band 5 in primary schoolchildren under free-living conditions. Materials and methods An initial sample of 67 schoolchildren (final sample = 62; 50% females), aged 9–12 years old (mean = 10.4 ± 1.0 years), participated in the present study. Each participant wore three activity wristbands (Fitbit Ace 2, Garmin Vivofit Jr 2, and Xiaomi Mi Band 5) on his/her non-dominant wrist and a research-grade accelerometer (ActiGraph wGT3X-BT) on his/her hip as the reference standard (number of steps and time in MVPA) during the waking time of one day. Results Results showed that the validity of the daily step scores estimated by the Garmin Vivofit Jr 2 and Xiaomi Mi Band 5 were good and acceptable (e.g., MAPE = 9.6/11.3%, and lower 95% IC of ICC = 0.87/0.73), respectively, as well as correctly classified schoolchildren as meeting or not meeting the daily 10,000/12,000-step-based recommendations, obtaining excellent/good and good/acceptable results (e.g., Garmin Vivofit Jr 2, k = 0.75/0.62; Xiaomi Mi Band 5, k = 0.73/0.53), respectively. However, the Fitbit Ace 2 did not show an acceptable validity (e.g., daily steps: MAPE = 21.1%, and lower 95% IC of ICC = 0.00; step-based recommendations: k = 0.48/0.36). None of the three activity wristbands showed an adequate validity for estimating daily MVPA (e.g., MAPE = 36.6–90.3%, and lower 95% IC of ICC = 0.00–0.41) and the validity for the MVPA-based recommendation tended to be considerably lower (e.g., k = −0.03–0.54). Conclusions The activity wristband Garmin Vivofit Jr 2 obtained the best validity for monitoring primary schoolchildren's daily steps, offering a feasible alternative to the research-grade accelerometers. Furthermore, this activity wristband could be used during PA promotion programs to provide accurate feedback to primary schoolchildren to ensure their accomplishment with the PA recommendations.
... Smart wearable devices can collect accurate and comprehensive information about athletes' sports status, such as heart rate, stride frequency, stride length, etc., so as to customize the most suitable training plan for athletes. Moreover, smart wearable devices can also correct and guide athletes' technical movements through real-time feedback, which can help them improve the accuracy of their movements [11]. ...
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Sports characteristics and physiological signals serve as critical benchmarks for analyzing athletic performance and enhancing training methodologies. This study explores the design and development of an advanced smart wearable device system tailored for monitoring sports training. This system is engineered to track athletic performance in real-time by integrating embedded wearable devices with sophisticated software. It primarily encompasses the recognition of human movement states, detection of electrocardiogram (ECG) signals, and monitoring of respiratory signals, thereby facilitating comprehensive analysis of human physiological parameters and movement metrics. This, in turn, supports athletes in optimizing their training routines. Empirical results from the study indicate that the mean-square error for both ECG and respiratory signals recorded during testing approximated ±0.8Hz, falling within the predetermined error tolerance range. Additionally, analyses of joint angle variations during running activities confirmed the efficacy of the proposed smart wearable system in improving sports performance.
... The popularity of consumer-wearable activity trackers has surged in recent years, with global sales of wearable and smartphone devices exceeding 500 million and 13 billion worldwide, respectively (Laricchia, 2023a(Laricchia, , 2023b. Given this widespread adoption and their characteristics, stakeholders, including researchers, paediatrics, physical education teachers and parents, are increasingly interested in utilizing consumer-wearable activity trackers to monitor and promote healthy habits of PA in primary schoolchildren Mayorga-Vega et al., 2022). ...
Article
The purposes were to examine the criterion-related validity of the steps estimated by consumer-wearable activity trackers (wrist-worn activity trackers: Fitbit Ace 2, Garmin Vivofit Jr, and Xiomi Mi Band 5; smartphone applications: Pedometer, Pedometer Pacer Health, and Google Fit/Apple Health) and their comparability in primary schoolchildren under controlled conditions. An initial sample of 66 primary schoolchildren (final sample = 56; 46.4% females), aged 9-12 years old (mean = 10.4 ± 1.0 years), wore three wrist-worn activity trackers (Fitbit Ace 2, Garmin Vivofit Jr 2, and Xiaomi Mi Band 5) on their non-dominant wrist and had three applications in two smartphones (Pedometer, Pedometer Pacer Health, and Google Fit/Apple Health for Android/iOS installed in Samsung Galaxy S20+/iPhone 11 Pro Max) in simulated front trouser pockets. Primary schoolchildren’s steps estimated by the consumer-wearable activity trackers and the video-based counting independently by two researchers (gold standard) were recorded while they performed a 200-meter course in slow, normal and brisk pace walking, and running conditions. Results showed that the criterion-related validity of the step scores estimated by the three Samsung applications and the Garmin Vivofit Jr 2 were good-excellent in the four walking/running conditions (e.g., MAPE = 0.6-2.3%; lower 95% CI of the ICC = 0.81-0.99), as well as being comparable. However, the Apple applications, Fitbit Ace 2, and Xiaomi Mi Band 5 showed poor criterion-related validity and comparability on some walking/running conditions (e.g., lower 95% CI of the ICC < 0.70). Although, as in real life primary schoolchildren also place their smartphones in other parts (e.g., schoolbags, hands or even somewhere away from the body), the criterion-related validity of the Garmin Vivofit Jr 2 potentially would be considerably higher than that of the Samsung applications. The findings of the present study highlight the potential of the Garmin Vivofit Jr 2 for monitoring primary schoolchildren’s steps under controlled conditions.
... The popularity of consumer-wearable activity trackers has surged in recent years, with global sales of wearable and smartphone devices exceeding 500 million and 13 billion worldwide, respectively (Laricchia, 2023a(Laricchia, , 2023b. Given this widespread adoption and their characteristics, stakeholders, including researchers, paediatrics, physical education teachers and parents, are increasingly interested in utilizing consumer-wearable activity trackers to monitor and promote healthy habits of PA in primary schoolchildren Mayorga-Vega et al., 2022). ...
Article
The purposes were to examine the criterion-related validity of the steps estimated by consumer-wearable activity trackers (wrist-worn activity trackers: Fitbit Ace 2, Garmin Vivofit Jr, and Xiomi Mi Band 5; smartphone applications: Pedometer, Pedometer Pacer Health, and Google Fit/Apple Health) and their comparability in primary schoolchildren under controlled conditions. An initial sample of 66 primary schoolchildren (final sample = 56; 46.4% females), aged 9-12 years old (mean = 10.4 ± 1.0 years), wore three wrist-worn activity trackers (Fitbit Ace 2, Garmin Vivofit Jr 2, and Xiaomi Mi Band 5) on their non-dominant wrist and had three applications in two smartphones (Pedometer, Pedometer Pacer Health, and Google Fit/Apple Health for Android/iOS installed in Samsung Galaxy S20+/iPhone 11 Pro Max) in simu-lated front trouser pockets. Primary schoolchildren’s steps esti-mated by the consumer-wearable activity trackers and the video-based counting independently by two researchers (gold standard) were recorded while they performed a 200-meter course in slow, normal and brisk pace walking, and running conditions. Results showed that the criterion-related validity of the step scores esti-mated by the three Samsung applications and the Garmin Vivofit Jr 2 were good-excellent in the four walking/running conditions (e.g., MAPE = 0.6 - 2.3%; lower 95% CI of the ICC = 0.81 - 0.99), as well as being comparable. However, the Apple applica-tions, Fitbit Ace 2, and Xiaomi Mi Band 5 showed poor criterion-related validity and comparability on some walking/running con-ditions (e.g., lower 95% CI of the ICC < 0.70). Although, as in real life primary schoolchildren also place their smartphones in other parts (e.g., schoolbags, hands or even somewhere away from the body), the criterion-related validity of the Garmin Vivofit Jr 2 potentially would be considerably higher than that of the Samsung applications. The findings of the present study highlight the potential of the Garmin Vivofit Jr 2 for monitoring primary schoolchildren’s steps under controlled conditions.
... Wearable consumer activity trackers have become very popular over the past few years. These devices provide near-continuous information about physical activity, heart rate, and sleep [14]. ...
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Moderate-to-vigorous physical activity (MVPA) is essential for disease prevention and health promotion. Emerging evidence suggests other intensities of physical activity (PA), including light-intensity activity (LPA), may also be important, but there has been no rigorous evaluation of the evidence. The purpose of this systematic review was to examine the relationships between objectively measured PA (total and all intensities) and health indicators in school-aged children and youth. Online databases were searched for peer-reviewed studies that met the a priori inclusion criteria: population (apparently healthy, aged 5-17 years), intervention/exposure/comparator (volumes, durations, frequencies, intensities, and patterns of objectively measured PA), and outcome (body composition, cardiometabolic biomarkers, physical fitness, behavioural conduct/pro-social behaviour, cognition/academic achievement, quality of life/well-being, harms, bone health, motor skill development, psychological distress, self-esteem). Heterogeneity among studies precluded meta-analyses; narrative synthesis was conducted. A total of 162 studies were included (204 171 participants from 31 countries). Overall, total PA was favourably associated with physical, psychological/social, and cognitive health indicators. Relationships were more consistent and robust for higher (e.g., MVPA) versus lower (e.g., LPA) intensity PA. All patterns of activity (sporadic, bouts, continuous) provided benefit. LPA was favourably associated with cardiometabolic biomarkers; data were scarce for other outcomes. These findings continue to support the importance of at least 60 min/day of MVPA for disease prevention and health promotion in children and youth, but also highlight the potential benefits of LPA and total PA. All intensities of PA should be considered in future work aimed at better elucidating the health benefits of PA in children and youth.
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Incomplete reporting has been identified as a major source of avoidable waste in biomedical research. Essential information is often not provided in study reports, impeding the identification, critical appraisal, and replication of studies. To improve the quality of reporting of diagnostic accuracy studies, the Standards for Reporting of Diagnostic Accuracy Studies (STARD) statement was developed. Here we present STARD 2015, an updated list of 30 essential items that should be included in every report of a diagnostic accuracy study. This update incorporates recent evidence about sources of bias and variability in diagnostic accuracy and is intended to facilitate the use of STARD. As such, STARD 2015 may help to improve completeness and transparency in reporting of diagnostic accuracy studies.
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The purpose of this study was to establish step-count guidelines for sixth-grade students and assess the ability of step-counts to discriminate between students achieving and not achieving 60-minutes of moderate to vigorous physical activity daily. 201 sixth-grade students completed the study. They wore a pedometer and an accelerometer at the waist level for one full day. ROC curves were used to establish step-count guidelines and determine the diagnostic accuracy of step-counts. Sixth grade students need 12,118 steps/day to reach adequate daily levels of physical activity. The AUC indicated good diagnostic accuracy of step-counts. Suggested step-count guidelines can be a useful tool for identifying children who need to increase their daily levels of physical activity. The step-count cutoff proposed in this study is adequate for discriminating between sixth grade students reaching and not reaching recommended levels of physical activity.
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Abstract Activity monitors are frequently used to assess activity in many settings. But as technology advances, so do the mechanisms used to estimate activity causing a continuous need to validate newly developed monitors. The purpose of this study was to examine the step count validity of the Yamax Digiwalker SW-701 pedometer (YX), Omron HJ-720 T pedometer (OP), Polar Active accelerometer (PAC) and Actigraph gt3x+ accelerometer (AG) under controlled and free-living conditions. Participants completed five stages of treadmill walking (n = 43) and a subset of these completed a 3-day free-living wear period (n = 37). Manually counted (MC) steps provided a criterion measure for treadmill walking, whereas the comparative measure during free-living was the YX. During treadmill walking, the OP was the most accurate monitor across all speeds (±1.1% of MC steps), while the PAC underestimated steps by 6.7-16.0% per stage. During free-living, the OP and AG counted 97.5% and 98.5% of YX steps, respectively. The PAC overestimated steps by 44.0%, or 5,265 steps per day. The Omron pedometer seems to provide the most reliable and valid estimate of steps taken, as it was the best performer under lab-based conditions and provided comparable results to the YX in free-living. Future studies should consider these monitors in additional populations and settings.
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Background A recent review concludes that the agreement of data across ActiGraph accelerometer models for children and youth still is uncertain. The aim of this study was to evaluate the agreement of three generations of ActiGraph accelerometers in children in a free-living condition. Methods Sixteen 9-year-olds wore the ActiGraph AM7164, GT1M and GT3X+ simultaneously for three consecutive days. We compared mean counts per minute (mcpm) and time spent at different intensities from the three generations of monitors, and the agreement of outputs were evaluated by intra-class correlation coefficients (ICC) and Bland-Altman plots. Results The ICC for mcpm was 0.985 (95% CI = 0.898, 0.996). We found a relative difference of 11.6% and 9.8% between the AM7164 and the GT1M and AM7164 and the GT3X+, respectively. The relative difference between mcpm assessed by the GT1M and GT3X+ was 1.7%. The inter-generation differences varied in magnitude and direction across intensity levels, with the largest difference found in the highest intensities. Conclusion We found that the ActiGraph model AM7164 yields higher outputs of mean physical activity intensity (mcpm) than the models GT1M and GT3X+ in children in free-living conditions. The generations GT1M and GT3X+ provided comparable outputs. The differences between the old and the newer monitors were more complex when investigating time spent at different intensities. Comparisons of data assessed by the AM7164 with data assessed by newer generations ActiGraphs should be done with caution.
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This study examined the effect of different epoch lengths (from 3 to 60 s) on (a) moderate to vigorous physical activity (MVPA), (b) 10 minutes bouts of MVPA and (c) compliance with World Health Organization (WHO) guidelines, as measured with an ActiGraph accelerometer. A sample of 401 adolescents (14.48±0.69 years) wore a GT3X accelerometer to measure physical activity (PA) for 7 consecutive days. Data, originally collected in 1-s epoch(s), were then reintegrated into epochs of 3-, 5-, 10-, 15-, 30-, 45- and 60-s. The results showed a significant epoch effect (P=0.000) for time spent in MVPA, 10-min bouts of MVPA and the extent of compliance with guidelines percentage of compliance of guidelines. Bland-Altman analysis showed good agreement between 5- and 10-, 5- and 15-, and 10- and 15-s data, both for MVPA and 10-min bouts of MVPA. Epidemiological studies should take into account the sampling interval to offer accurate conclusions with regard to levels of MVPA and the extent to which adolescents comply with guidelines. Shorter epochs, such as 5-, 10- or 15-s are proposed for comparative studies carried out with adolescents in this area.
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Abstract The objective of this study was to develop count cut-points for three different accelerometer models: ActiGraph GT3X, RT3 and Actical to accurately classify physical activity intensity levels in adolescents. Seventy-nine adolescents (10-15 years) participated in this study. Accelerometers and oxygen consumption ([Formula: see text]) data were collected at rest and during 11 physical activities of different intensities. Accelerometers were worn on the waist and [Formula: see text] was measured by a portable metabolic system: Cosmed K4b2. Receiver operating characteristic (ROC) curves were used to determine cut-points. Cut-points for sedentary (SED), moderate-to-vigorous (MVPA) and vigorous-intensity physical activity (VPA) were 46, 607 and 818 counts·15s(-1) to the vertical axis of ActiGraph; 180, 757 and 1112 counts·15s(-1) to the vector magnitude of ActiGraph; 17, 441 and 873 counts·15s(-1) for Actical; and 5.6, 20.4 and 32.2 counts·s(-1) for RT3, respectively. For all three accelerometer models, there was an almost perfect discrimination of SED and MVPA (ROC >0.97) and an excellent discrimination of VPA (ROC>0.90) observed. Areas under the ROC curves indicated better discrimination of MVPA by ActiGraph (AUC=0.994) and Actical (AUC=0.993) when compared to RT3 (AUC=0.983). The cut-points developed in this study for the ActiGraph (vector magnitude), RT3 and Actical accelerometer models can be used to monitor physical activity level of adolescents.
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Objectives: The physical activity (PA) levels of Spanish adolescents must be determined to assess how the lack of PA may affect the increasing prevalence of obesity. Thus, to assess PA in this age range valid measurement instruments are essential. The aim of this study was to evaluate the validity of four easily applied questionnaires (the enKid and FITNESSGRAM questions, the Patient-Centered Assessment and Counselling (PACE) questionnaire, and an activity rating) to assess PA in Spanish adolescents by using an accelerometer as the criterion instrument. Methods: A total of 232 adolescents (113 girls) completed the questionnaires and wore an ActiGraph accelerometer for 7 consecutive days. Spearman's correlation coefficient (rho) was used to compare the questionnaires and total PA, moderate PA, vigorous PA and moderate-to-vigorous PA (MVPA) assessed by the accelerometer. Results: All the questionnaires showed moderate correlations when compared against total PA (rho ¼ 0.36-0.43) and MVPA (rho ¼ 0.34-0.46) obtained by the accelerometer in the total sample. Higher correlations were found when comparing the questionnaires against vigorous PA (rho ¼ 0.42-0.51) than against moderate PA (rho ¼ 0.15-0.17). The FITNESSGRAM question and the PACE questionnaire obtained weak correlations in girls and the enKid question and activity rating were moderately correlated for boys and girls. Conclusions: The four questionnaires evaluated showed acceptable validity in the assessment of PA in the Spanish adolescent population.
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Physical activity is defined as any bodily movement produced by skeletal muscles that results in energy expenditure. The doubly labeled water method for the measurement of total energy expenditure (TEE), in combination with resting energy expenditure, is the reference for physical activity under free-living conditions. To compare the physical activity level (PAL) within and between species, TEE is divided by resting energy expenditure resulting in a figure without dimension. The PAL for sustainable lifestyles ranges between a minimum of 1.1–1.2 and a maximum of 2.0–2.5. The average PAL increases from 1.4 at age 1 year to 1.7–1.8 at reproductive age and declines again to 1.4 at age 90 year. Exercise training increases PAL in young adults when energy balance is maintained by increasing energy intake. Professional endurance athletes can reach PAL values around 4.0. Most of the variation in PAL between subjects can be ascribed to predisposition. A higher weight implicates higher movement costs and less body movement but not necessarily a lower PAL. Changes in physical activity primarily affect body composition and to a lesser extent body weight. Modern man has a similar PAL as a wild mammal of a similar body size.
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Background An evidence-based steps/day translation of U.S. federal guidelines for youth to engage in ≥60 minutes/day of moderate-to-vigorous physical activity (MVPA) would help health researchers, practitioners, and lay professionals charged with increasing youth’s physical activity (PA). The purpose of this study was to determine the number of free-living steps/day (both raw and adjusted to a pedometer scale) that correctly classified children (6–11 years) and adolescents (12–17 years) as meeting the 60-minute MVPA guideline using the 2005–2006 National Health and Nutrition Examination Survey (NHANES) accelerometer data, and to evaluate the 12,000 steps/day recommendation recently adopted by the President’s Challenge Physical Activity and Fitness Awards Program. Methods Analyses were conducted among children (n = 915) and adolescents (n = 1,302) in 2011 and 2012. Receiver Operating Characteristic (ROC) curve plots and classification statistics revealed candidate steps/day cut points that discriminated meeting/not meeting the MVPA threshold by age group, gender and different accelerometer activity cut points. The Evenson and two Freedson age-specific (3 and 4 METs) cut points were used to define minimum MVPA, and optimal steps/day were examined for raw steps and adjusted to a pedometer-scale to facilitate translation to lay populations. Results For boys and girls (6–11 years) with ≥ 60 minutes/day of MVPA, a range of 11,500–13,500 uncensored steps/day for children was the optimal range that balanced classification errors. For adolescent boys and girls (12–17) with ≥60 minutes/day of MVPA, 11,500–14,000 uncensored steps/day was optimal. Translation to a pedometer-scaling reduced these minimum values by 2,500 step/day to 9,000 steps/day. Area under the curve was ≥84% in all analyses. Conclusions No single study has definitively identified a precise and unyielding steps/day value for youth. Considering the other evidence to date, we propose a reasonable ‘rule of thumb’ value of ≥ 11,500 accelerometer-determined steps/day for both children and adolescents (and both genders), accepting that more is better. For practical applications, 9,000 steps/day appears to be a more pedometer-friendly value.
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There is a lack of robust evidence to support a daily step count target that equates to current physical activity guidelines in children and youth. This information would be useful to researchers and practitioners who are using pedometers to monitor physical activity. Accelerometer and pedometer data collected on children and youth age 6-19 yr in the Canadian Health Measures Survey were used in this analysis (n = 1613). Correlation analyses of daily step counts and minutes of moderate-to-vigorous physical activity (MVPA) by age and sex were completed. The daily step count equivalent to 60 min of MVPA was derived using linear regression by age and sex. Cross-validation, including receiver operating curve analysis, was completed to compare the new cut points to one currently used as a proxy estimate of 60 min of daily MVPA (13,500 steps per day) as well as a range of possible step count targets between 8000 and 15,000 steps per day. Daily step counts were correlated with daily minutes of MVPA (r = 0.81, P < 0.0001). The step count equivalents to 60 min of MVPA ranged between 11,290 and 12,512 steps per day (R range = 0.59-0.74). A step count target of 12,000 steps per day resulted in closer population estimates of meeting the physical activity guideline (as measured as minutes of MVPA by accelerometer) as well as improved balance between sensitivity and specificity when compared with any cut point between 8000 and 15,000 steps per day, including the currently used daily step count target of 13,500 steps per day. We propose that 12,000 steps per day be used as a target to determine whether children and youth age 6-19 yr are meeting the current physical activity guideline of 60 min of daily MVPA.
Article
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Worldwide, public health physical activity guidelines include special emphasis on populations of children (typically 6-11 years) and adolescents (typically 12-19 years). Existing guidelines are commonly expressed in terms of frequency, time, and intensity of behaviour. However, the simple step output from both accelerometers and pedometers is gaining increased credibility in research and practice as a reasonable approximation of daily ambulatory physical activity volume. Therefore, the purpose of this article is to review existing child and adolescent objectively monitored step-defined physical activity literature to provide researchers, practitioners, and lay people who use accelerometers and pedometers with evidence-based translations of these public health guidelines in terms of steps/day. In terms of normative data (i.e., expected values), the updated international literature indicates that we can expect 1) among children, boys to average 12,000 to 16,000 steps/day and girls to average 10,000 to 13,000 steps/day; and, 2) adolescents to steadily decrease steps/day until approximately 8,000-9,000 steps/day are observed in 18-year olds. Controlled studies of cadence show that continuous MVPA walking produces 3,300-3,500 steps in 30 minutes or 6,600-7,000 steps in 60 minutes in 10-15 year olds. Limited evidence suggests that a total daily physical activity volume of 10,000-14,000 steps/day is associated with 60-100 minutes of MVPA in preschool children (approximately 4-6 years of age). Across studies, 60 minutes of MVPA in primary/elementary school children appears to be achieved, on average, within a total volume of 13,000 to 15,000 steps/day in boys and 11,000 to 12,000 steps/day in girls. For adolescents (both boys and girls), 10,000 to 11,700 may be associated with 60 minutes of MVPA. Translations of time- and intensity-based guidelines may be higher than existing normative data (e.g., in adolescents) and therefore will be more difficult to achieve (but not impossible nor contraindicated). Recommendations are preliminary and further research is needed to confirm and extend values for measured cadences, associated speeds, and MET values in young people; continue to accumulate normative data (expected values) for both steps/day and MVPA across ages and populations; and, conduct longitudinal and intervention studies in children and adolescents required to inform the shape of step-defined physical activity dose-response curves associated with various health parameters.
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Steps/day guidelines for children aged 12 years and under are 12,000 to 16,000. There are limited reports in the literature on how many steps/day adolescents need to meet the 60-minutes/day moderate-to-vigorous physical activity (MVPA) recommendation. This study aimed to determine the steps/day that correctly classifies adolescents as meeting the 60-minute recommendation using objective measures. This analysis used data from 40 overweight (BMI M=31.5, SD=5.3) adolescents enrolled between 2005 and 2006 in a study to lose weight. Participants were aged 11 to 16 years (M=13.2, SD=1.2), 70.0% girls, and 52.6% non-Hispanic white, 23.7% Hispanic, and 23.7% other race/ethnicity. Participants wore an Actigraph accelerometer for up to 7 days that measured accelerations and step counts simultaneously. The age-adjusted Freedson equation was used to estimate physical activity-intensity minutes. Two criteria were used to define MVPA (3/6 and 4/7 METs). Analyses were conducted between 2008 and 2009. Based on accelerometer data, approximately 48% and 10% of adolescents met the MVPA recommendation depending on the MVPA criteria. Adolescents who met phyiscial activity recommendation had higher MVPA min/day (p<0.001) and higher step counts (p<0.001), after adjusting for gender, age, and ethnicity. Receiver operating characteristic (ROC) curve analyses found that 9930 steps produced 0.84 sensitivity and 0.81 specificity (area under the curve [AUC] =0.89) and 11,714 steps produced 0.75 and 0.81 specificity (AUC=0.94) for meeting the recommendation using the 3/6 and 4/7 criteria, respectively. Depending on the MVPA criteria used, these data suggest that overweight adolescents are likely to meet national MVPA recommendations if they accumulate between 10,000 and 11,700 steps per day.
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To develop an internationally acceptable definition of child overweight and obesity, specifying the measurement, the reference population, and the age and sex specific cut off points. International survey of six large nationally representative cross sectional growth studies. Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States. 97 876 males and 94 851 females from birth to 25 years of age. Body mass index (weight/height(2)). For each of the surveys, centile curves were drawn that at age 18 years passed through the widely used cut off points of 25 and 30 kg/m(2) for adult overweight and obesity. The resulting curves were averaged to provide age and sex specific cut off points from 2-18 years. The proposed cut off points, which are less arbitrary and more internationally based than current alternatives, should help to provide internationally comparable prevalence rates of overweight and obesity in children.
Article
This paper analyses the state of the art on accuracy and metrological characteristics of wrist-worn and chest-strap wearable devices, in comparison with reference instruments. Basing on literature available results, neither a standard protocol for validation nor fixed metrological characteristics can be identified. Wearable devices are validated without standard procedures (test protocol, population characteristics and metrological parameters), which turns into irregular results, barely comparable each other. Therefore, it would be extremely interesting to conduct a pilot study to identify standard characteristics to evaluate accuracy, compliant to the guidelines for the expression of uncertainty in measurement and recognized by organizations promoting public health (e.g. the Food and Drug Administration in the United States). This way, it would be possible to start establishing a database of wearable devices’ metrological properties, useful not only for research, but also for caregivers and sportsmen, in different application fields (e.g. sport, medicine, Active and Assisted Living, etc.). The paper is freely downloadable at https://authors.elsevier.com/a/1asw3xsQaBzwg (link valid for 50 days!)
Article
Objective: In this study we aimed to examine the reliability and validity of the wristband activity monitor against the accelerometer for children.. Methods: A total of 99 children (mean age = 13.0 ± 2.5 y) wore the two monitors in a free-living context for 7 days. Reliability was measured by intraclass correlation to evaluate consistency over time. Repeated-measures analyses of variance was used to detect differences across days. Spearman's correlation coefficient (rho), median of absolute percentage error, and Bland-Altman analyses were performed to assess the validity of the wristband against the ActiGraph accelerometer. The optimal number of repeated measures for the wristband was calculated by using the Spearman-Brown prophecy formula. Results: The wristband had high reliability for all variables, although physical activity data were different across 7 days. A strong correlation for steps (rho: 0.72, P < 0.001), and moderate correlations for time spent on total physical activity (rho: 0.63, P < 0.001) and physical activity energy expenditure (rho: 0.57, P < 0.001) were observed between the wristband and the accelerometer. For different intensities of physical activity, weak to moderate correlations were found (rho: 0.38 to 0.55, P < 0.001). Conclusion: The wristband activity monitor seems to be reliable and valid for measurement of overall children's physical activity, providing a feasible objective method of physical activity surveillance in children.
Article
Purpose: Activity trackers are useful tools for physical activity promotion in adolescents, but robust validity evaluations have not been done under free-living conditions. This study evaluated the validity of the Garmin Vívofit 1 (G1) and Garmin Vívofit 3 (G3) in different settings and contexts. Methods: The participants (girls: 52%, age: 15.9 [1.9] y) wore the G1 and G3 on their nondominant wrist and the Yamax pedometer on their right hip for a period of 1 week. Validity was examined in 4 discrete segments (before school, in school, after school, and whole day). The criterion method was the Yamax pedometer. Results: Both the G1 and G3 could be considered equivalent to the Yamax pedometer regarding the before school, in school, and whole day segments. The G1 showed wider limits of agreement than G3. Conclusions: The G1 and G3 trackers exhibited acceptable validity for 3 of the 4 segments (before school, in school, and whole day measurements). The results were less accurate during the after-school segment. The evidence that the validity of the monitors varied depending on the setting and context is an important consideration for research on adolescent activity patterns.
Article
The purpose of this study was to compare the accuracy of commercially-available physical activity devices when walking and running at various treadmill speeds using CTA 2056: Physical Activity Monitoring for Fitness Wearables: Step Counting, standard by the Consumer Technology Association (CTA). Twenty participants (10 males and 10 females) completed self-paced walking and running protocols on the treadmill for five minutes each. Eight devices (Apple iWatch series 1, Fitbit Surge, Garmin 235, Moto 360, Polar A360, Suunto Spartan Sport, Suunto Spartan Trainer, and TomTom Spark 3) were tested two at a time, one per wrist. Manual step counts were obtained from video to serve as the benchmark. The mean absolute percent error (MAPE) was calculated during walking and running. During walking, three devices: Fitbit Surge (11.20%), Suunto Sport (22.93%), and TomTom (10.11%) and during running, one device, Polar (10.66%), exceeded the CTA suggestion of a MAPE < 10%. The Moto 360 had the lowest MAPE of all devices for both walking and running. The devices tested had higher step accuracy with running than walking, except for the Polar. Overall, the Apple iWatch series 1, Moto 360, Garmin, and Suunto Spartan Trainer met the CTA standard for both walking and running.
Article
Background: Increasing physical activity levels is a high priority to optimize long-term health in children with congenital heart disease (CHD). Commercial activity trackers have been validated in adults and are increasingly used to measure and promote physical activity in pediatric populations, but they have not been validated in children. Methods: In 30 children with CHD aged 10-18 years, we assessed the validity of physical activity form the wrist-based Fitbit Charge HR (Fitbit, San Francisco, CA) against hip-based ActiGraph (ActiGraph LLC, Pensacola, FL) accelerometers under free living conditions for 7 days. We assessed the association between devices using intraclass correlation coefficients (ICCs) and Bland-Altman plots. Receiver operating curves were used to identify Fitbit step cut points. Results: There was a strong association between the 2 devices for daily steps across 138 analyzed person-days (ICC?= 0.855; P < 0.001), but poorer agreement for time spent in physical activity intensities (ICCs < 0.7). Daily Fitbit steps of ? 12,500 identified meeting physical activity guidelines defined as ? 60 minutes of moderate-to-vigorous physical activity per day. Fitbit devices recorded more steps than accelerometers (-2242 steps per day, 95% limits of agreement of?-7738 to 3253). Between-device differences were greater in boys vs girls. Fitbit devices were worn for longer than accelerometers (-36?minutes per day, 95% limits of agreement,?-334 to 261), but overall differences in wear time explained little of the variance in step differences (7%, P?= 0.048). Conclusions: Commercial activity trackers provide opportunities to remotely monitor physical activity in children with CHD, but absolute values might differ from accelerometers. These findings are important because of the increasing emphasis on physical activity promotion and monitoring in children with cardiovascular risk factors.
Article
Incomplete reporting has been identified as a major source of avoidable waste in biomedical research. Essential information is often not provided in study reports, impeding the identification, critical appraisal, and replication of studies. To improve the quality of reporting of diagnostic accuracy studies, the Standards for Reporting Diagnostic Accuracy (STARD) statement was developed. Here we present STARD 2015, an updated list of 30 essential items that should be included in every report of a diagnostic accuracy study. This update incorporates recent evidence about sources of bias and variability in diagnostic accuracy and is intended to facilitate the use of STARD. As such, STARD 2015 may help to improve completeness and transparency in reporting of diagnostic accuracy studies.
Article
Objectives: The purpose of this brief review was to describe the missingness, from both attrition and non-compliance, during physical activity randomized controlled trials among children which have used accelerometers to measure physical activity. Design: Systematic review. Methods: Using a previously published search strategy, an updated search of the literature was performed in the MEDLINE database for articles published from 1996 to February 2015 identifying physical activity RCTs in children (ages 2-18) measuring physical activity using accelerometers. Rates of attrition and non-compliance were extracted from identified articles. Twenty-three independent studies provided complete attrition and non-compliance data and were included. Results: The mean attrition rate was 11.5% (SD 10.1%, range 0-30.9%). The mean accelerometer non-compliance rate at baseline was 22.7% (SD 16.4%, range 1.7-67.8%) and 29.6% (SD 19.4%, range 3.3-70.1%) at follow-up. The mean total study missingness was 37.4% (SD 20.2%, range 3.3-75.4%) and ranged from 3.3% to 75.4%. There was large variation in how missingness was accounted for between studies. There were no statistically significant differences in missingness between study characteristics including sample size, participant age, intervention setting, duration of follow-up, whether physical activity was the primary outcome, and weartime compliance criteria. Conclusions: Missingness is common among randomized controlled trials using accelerometry in children and is currently handled inconsistently. Researchers must plan for high levels of missingness in study design and account for missingness in reporting and analyses of trial outcomes.
Article
Purpose: This study aimed to (i) explore children's compliance to wearing wrist and hip-mounted accelerometers, (ii) compare children's physical activity (PA) derived from wrist and hip raw accelerations, and (iii) examine differences in raw and counts PA measured by hip-worn accelerometry. Methods: One hundred and twenty nine 9-10 y old children wore a wrist-mounted GENEActiv accelerometer (GAwrist) and a hip-mounted ActiGraph GT3X+ accelerometer (AGhip) for 7 d. Both devices measured raw accelerations and the AGhip also provided counts-based data. Results: More children wore the GAwrist than the AGhip regardless of wear time criteria applied (p<.001 - .035). Raw data signal vector magnitude (SVM; r = .68), moderate PA (MPA; r = .81), vigorous PA (VPA; r = .85), and moderate-to-vigorous PA (MVPA; r = .83) were strongly associated between devices (p<.001). GAwrist SVM (p = .001), MPA (p = .037), VPA (p = .002), and MVPA (p = .016) were significantly greater than AGhip. According to GAwrist raw data, 86.9% of children engaged in at least 60 min MVPA[BULLET OPERATOR]d, compared to 19% for AGhip. ActiGraph MPA (raw) was 42.00 ± 1.61 min[BULLET OPERATOR]d compared to 35.05 ± 0.99 min[BULLET OPERATOR]d (counts) (p=.02). Actigraph VPA was 7.59 ± 0.46 min[BULLET OPERATOR]d (raw) and 37.06 ± 1.85 min[BULLET OPERATOR]d (counts; p=.19). Conclusion: In children accelerometer wrist placement promotes superior compliance than the hip. Raw accelerations were significantly higher for GAwrist compared to AGhip, possibly due to placement location and technical differences between devices. AGhip PA calculated from raw accelerations and counts differed substantially, demonstrating that PA outcomes derived from cutpoints for raw output and counts cannot be directly compared.
Article
There is a need to examine step-counting accuracy of activity monitors during different types of movements. The purpose of this study was to compare activity monitor (AM) and manually counted steps during treadmill and simulated free-living activities and to compare the AM steps to the StepWatch (SW) in a natural setting. Fifteen participants performed lab-based treadmill (2.4, 4.8, 7.2 and 9.7 km/h) and simulated free-living activities (e.g., cleaning room) while wearing an activPAL, Omron® HJ720-ITC, Yamax® Digi-walker SW-200, two Actigraph GT3Xs (one in 'low frequency extension' (AGLFE) and one in 'normal frequency' mode), an Actigraph 7164, and a SW. Participants also wore monitors for one-day in their free-living environment. Linear mixed models identified differences between AM steps and the criterion in the lab/free-living settings. Most monitors performed poorly during treadmill walking at 2.4 km/h. Cleaning a room had the largest errors of all simulated free-living activities. The accuracy was highest for forward/rhythmic movements for all monitors. In the free-living environment, the AGLFE had the largest discrepancy with the SW. This study highlights the need to verify step-counting accuracy of AMs with activities that include different movement types/directions. This is important to understand the origin of errors in step-counting during free-living conditions.
Article
Background: The aim of this systematic review was to identify the most optimal step-count cutoff for children and adolescents (5-19 years) among guidelines currently available in the literature. Methods: The databases searched were PubMed, SportDiscus, Science Direct, Web of Science and LILACS. Studies were categorized into Health Cohort studies or Physical Activity (PA) Cohort studies according to the reference standard used. The quality of the studies was assessed using the QUADAS-2 instrument. Results: Six Health and 3 PA Cohort studies were included in the final pool of papers after Full Text reading. With the exception of a single study, studies demonstrated a high risk of methodological bias in at least one of the QUADAS-2 domains. Guidelines ranged from 10,000 to 16,000 steps/day for the Health studies (5-16 years), and from 9,000 to 14,000 steps/day for PA studies (6-19 years). Due to the high risk of methodological bias, none of the Health Cohort guidelines were endorsed. The PA Cohort study with the lowest risk of methodological bias suggested 12,000 steps/day for children and adolescents irrespective of gender. Conclusion: PA Cohort studies demonstrated lower risk of methodological bias than Health Cohort studies. The optimal youth step-count guideline of 12,000 steps/day was endorsed.
Article
Background: Anecdotal evidence suggests that the sensitivity and specificity of a diagnostic test may vary with disease prevalence. Our objective was to investigate the associations between disease prevalence and test sensitivity and specificity using studies of diagnostic accuracy. Methods: We used data from 23 meta-analyses, each of which included 10-39 studies (416 total). The median prevalence per review ranged from 1% to 77%. We evaluated the effects of prevalence on sensitivity and specificity using a bivariate random-effects model for each meta-analysis, with prevalence as a covariate. We estimated the overall effect of prevalence by pooling the effects using the inverse variance method. Results: Within a given review, a change in prevalence from the lowest to highest value resulted in a corresponding change in sensitivity or specificity from 0 to 40 percentage points. This effect was statistically significant (p < 0.05) for either sensitivity or specificity in 8 meta-analyses (35%). Overall, specificity tended to be lower with higher disease prevalence; there was no such systematic effect for sensitivity. Interpretation: The sensitivity and specificity of a test often vary with disease prevalence; this effect is likely to be the result of mechanisms, such as patient spectrum, that affect prevalence, sensitivity and specificity. Because it may be difficult to identify such mechanisms, clinicians should use prevalence as a guide when selecting studies that most closely match their situation.
Article
Objective To develop an internationally acceptable definition of child overweight and obesity, specifying the measurement, the reference population, and the age and sex specific cut off points. Design International survey of six large nationally representative cross sectional growth studies. Setting Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States Subjects 97 876 males and 94 851 females from birth to 25 years of age Main outcome measure Body mass index (weight/height2). Results For each of the surveys, centile curves were drawn that at age 18 years passed through the widely used cut off points of 25 and 30 kg/m2 for adult overweight and obesity. The resulting curves were averaged to provide age and sex specific cut off points from 2-18 years. Conclusions The proposed cut off points, which are less arbitrary and more internationally based than current alternatives, should help to provide internationally comparable prevalence rates of overweight and obesity in children.
Article
The absence of comparative validity studies has prevented researchers from reaching consensus regarding the application of intensity-related accelerometer cut points for children and adolescents. This study aimed to evaluate the classification accuracy of five sets of independently developed ActiGraph cut points using energy expenditure, measured by indirect calorimetry, as a criterion reference standard. A total of 206 participants between the ages of 5 and 15 yr completed 12 standardized activity trials. Trials consisted of sedentary activities (lying down, writing, computer game), lifestyle activities (sweeping, laundry, throw and catch, aerobics, basketball), and ambulatory activities (comfortable walk, brisk walk, brisk treadmill walk, running). During each trial, participants wore an ActiGraph GT1M, and V˙O2 was measured breath-by-breath using the Oxycon Mobile portable metabolic system. Physical activity intensity was estimated using five independently developed cut points: Freedson/Trost (FT), Puyau (PU), Treuth (TR), Mattocks (MT), and Evenson (EV). Classification accuracy was evaluated via weighted κ statistics and area under the receiver operating characteristic curve (ROC-AUC). Across all four intensity levels, the EV (κ=0.68) and FT (κ=0.66) cut points exhibited significantly better agreement than TR (κ=0.62), MT (κ=0.54), and PU (κ=0.36). The EV and FT cut points exhibited significantly better classification accuracy for moderate- to vigorous-intensity physical activity (ROC-AUC=0.90) than TR, PU, or MT cut points (ROC-AUC=0.77-0.85). Only the EV cut points provided acceptable classification accuracy for all four levels of physical activity intensity and performed well among children of all ages. The widely applied sedentary cut point of 100 counts per minute exhibited excellent classification accuracy (ROC-AUC=0.90). On the basis of these findings, we recommend that researchers use the EV ActiGraph cut points to estimate time spent in sedentary, light-, moderate-, and vigorous-intensity activity in children and adolescents.
Article
The 2005–2006 National Health and Nutrition Examination Survey collected accelerometer-defined step data in addition to activity counts. The accelerometer used (ActiGraph AM-7164) is known to detect more low-force steps than research-quality pedometers. This study extends similar research focused on adults in National Health and Nutrition Examination Survey. Its purpose is to provide the descriptive epidemiology of accelerometer-determined steps per day in US children (6–11 yr) and youth (12–19 yr), with and without censoring steps detected at G500 activity counts per minute, in an attempt to interpret these data against existing pedometer-based scales. The analysis sample represents 2610 children and youth who had at least one valid day (i.e., at least 10 h) of monitoring. Means (SE) for steps per day were computed using all detected steps (i.e., uncensored) and again after disregarding those steps below 500 activity counts per minute (i.e., censored). US children average approximately 13,000 (boys) and 12,000 (girls) uncensored accelerometer-determined steps per day. Comparable values for male and female youth are 11,000 and 9000 uncensored accelerometer-determined steps per day, respectively. Censoring low-force steps reduces uncensored values by approximately 2600 steps per day overall, shifts distributions to the left, and shows that almost 42% of US male children and almost 21% of female children are sedentary as interpreted against expected values for steps per day in childhood using a pedometer-based scale. Regardless of censoring or not, across age, the US data show a peak value at 6 yr followed by generally consistent declines in steps per day values throughout childhood and into youth.
Article
A calibration study was conducted to determine the threshold counts for two commonly used accelerometers, the ActiGraph and the Actical, to classify activities by intensity in children 5 to 8 years of age. Thirty-three children wore both accelerometers and a COSMED portable metabolic system during 15 min of rest and then performed up to nine different activities for 7 min each, on two separate days in the laboratory. Oxygen consumption was measured on a breath-by-breath basis, and accelerometer data were collected in 15-s epochs. Using receiver operating characteristic curve (ROC) analysis, cutpoints that maximised both sensitivity and specificity were determined for sedentary, moderate and vigorous activities. For both accelerometers, discrimination of sedentary behaviour was almost perfect, with the area under the ROC curve at or exceeding 0.98. For both the ActiGraph and Actical, the discrimination of moderate (0.85 and 0.86, respectively) and vigorous activity (0.83 and 0.86, respectively) was acceptable, but not as precise as for sedentary behaviour. This calibration study, using indirect calorimetry, suggests that the two accelerometers can be used to distinguish differing levels of physical activity intensity as well as inactivity among children 5 to 8 years of age.
How many daily steps are really enough for adolescents? A cross-validation study
  • Parra Saldías
New Zealand: International Society for the Advancement of Kinanthropometry
  • A Stewart
  • M Marfell-Jones
  • T Olds
  • De Ridder
Stewart A, Marfell-Jones M, Olds T, De Ridder J. International standards for anthropometric assessment. New Zealand: International Society for the Advancement of Kinanthropometry; 2011.