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A National Survey of Physical Activity and Sedentary Behavior of Chinese City Children and Youth Using Accelerometers Chao Wang a

a b

a

, Peijie Chen & Jie Zhuang

a

Shanghai University of Sport

b

Capital University of Physical Education and Sports Published online: 04 Dec 2013.

To cite this article: Chao Wang , Peijie Chen & Jie Zhuang (2013) A National Survey of Physical Activity and Sedentary Behavior of Chinese City Children and Youth Using Accelerometers, Research Quarterly for Exercise and Sport, 84:sup2, S12S28, DOI: 10.1080/02701367.2013.850993 To link to this article: http://dx.doi.org/10.1080/02701367.2013.850993

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Research Quarterly for Exercise and Sport, 84, S12–S28, 2013 Copyright q AAHPERD ISSN 0270-1367 print/ISSN 2168-3824 online DOI: 10.1080/02701367.2013.850993

A National Survey of Physical Activity and Sedentary Behavior of Chinese City Children and Youth Using Accelerometers

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Chao Wang Shanghai University of Sport Capital University of Physical Education and Sports

Peijie Chen and Jie Zhuang Shanghai University of Sport

Purpose: The purpose of this study was to objectively assess levels of physical activity (PA) and sedentary behavior (SB) of Chinese city children and youth aged 9 to 17 years old using accelerometers and to examine their differences by gender, age, grade, and weight status. Method: The PA and SB of 2,163 students in 4th grade through 11th grade (Mage ¼ 160.87 ^ 27.00 months [13.41 ^ 2.25 years], 50.21% boys) from 11 cities in China were measured by accelerometers. The amount of time spent in SB, light PA, moderate PA, vigorous PA, and moderate-to-vigorous PA (MVPA) was computed based on cutoff points developed specifically for the Chinese children and youth. The participants were classified into normal-weight, overweight, and obese groups based on their body mass index (BMI). Paired-sample t tests were conducted to examine the differences in PA and SB between weekdays and weekend days. Multivariate analysis of variance was used to test the differences in PA and SB variables by gender, age, grade, and weight status, respectively. Results: Chinese city children and youth spent an average of 28.26 ^ 17.66 min/day in MVPA and 521.50 ^ 110.02 min/day in SB. Only 9.4% of boys and 1.9% of girls met the recommendation of 60 min/day of MVPA. Chinese city children and youth were more active during weekdays than during weekend days, and boys were more active than girls; older children and youth spent more daily time in MVPA, but also spent more time being sedentary. No differences in PA and SB were found across different BMI categories. Conclusion: The findings warn of the insufficiency of PA and the excess of SB in Chinese city children and youth. Keywords: ActiGraph, MPA, MVPA, VPA

The benefits of physical activity (PA) in the health of children and youth have been well documented and include increased physical fitness (both cardiorespiratory fitness and muscular strength), reduced body fatness, favorable cardiovascular and metabolic disease risk profiles, and enhanced bone health (Dencker & Andersen, 2008; Janssen & Leblanc, 2010).

Correspondence should be addressed to Peijie Chen, Shanghai University of Sport, 399 Chang Hai Road, Shanghai 200438, P. R. China. E-mail: [email protected]

However, studies show that children and youth tend to have sedentary lifestyles and spend nearly 6 hr to 8 hr per day sitting (Pate, Mitchell, Byun, & Dowda, 2011). Physical inactivity has been identified as one of the major public health problems of the 21st century (Armstrong, 2012; Blair, 2009). Therefore, at least 60 min of moderate-to-vigorous PA (MVPA) per day is recommended specifically for children and youth for health-enhancing purposes (World Health Organization [WHO], 2010). Accurate estimation of PA levels at a population level could provide an important reference for policymakers to

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PA AND SEDENTARY BEHAVIOR OF CHINESE YOUTH

better understand the prevalence of PA and therefore to develop more specific intervention strategies. In the past, PA surveys among children and youth have largely relied on self-reports or proxy-reports, which have been demonstrated to have low validity and reliability (Chinapaw, Mokkink, van Poppel, van Mechelen, & Terwee, 2010). Since the late 1990s, the accelerometer has emerged as an objective measurement mean and is frequently used for the measurement of daily PA. Accelerometers enable measurement of the frequency, intensity, and duration of PA and are considered a valid, reliable, and feasible instrument to use in large-scale observational and intervention studies (Plasqui & Westerterp, 2007; Trost et al., 1998). In recent years, objective measures such as accelerometer have been applied to collect population data on PA of children and youth in large-scale studies in Western countries (Colley et al., 2011; Ruiz et al., 2011; Troiano et al., 2008). Based on accelerometer data, researchers found that 42% of children and 8% of adolescents in the United States met the recommended 60 min of MVPA per day (Troiano et al., 2008). Among children and youth in Canada, only 9% of boys and 4% of girls accumulated 60 min of MVPA per day for at least 6 days per week (Colley et al., 2011); and among European adolescents, compliance with the guideline of 60 min of MVPA per day was found for 56.8% for boys and 27.5% for girls aged 12 to 17 years old (Ruiz et al., 2011). In China, national data on PA prevalence in youth are rather limited, especially using objective measurement tools. The China Health and Nutrition Survey, a national survey, was conducted among nearly 2,700 youth aged 6 to 18 years old from eight provinces in China (Tudor-Locke, Ainsworth, Adair, Du, & Popkin, 2003). Using self-report measures of PA, the researchers found that while 72% of Chinese youth engaged in in-school MVPA for 90 to 110 min/week, only 8% of them participated in any MVPA outside of school (Tudor-Locke et al., 2003). To our knowledge, only one study with a limited number of participants (n ¼ 80) has been conducted to measure the PA patterns of Chinese children and youth using accelerometer (Yamauchi et al., 2007). The study showed that the PA level, which was calculated as total daily energy expenditure (kcal/day)/estimated basal metabolic rate (kcal/day), of 11- to 14-year-old youths was 1.48 to 1.57, and the steps of the studied sample ranged from 10,377 to 12,594 per day (Yamauchi et al., 2007). To date, no large-scale study has been conducted in China to collect objective information on PA and sedentary behavior (SB) among children and youth. As a key part of the Chinese City Children and Youth Physical Activity Study, the purpose of this study was to determine the levels of PA and SB of Chinese children and youth in 11 cities using accelerometers and to examine the differences in PA and SB by gender, age, grade, and weight status.

S13

METHOD Participants The study was performed during schooldays from April 2011 to May 2012 in 11 cities across China, including Chengdu, Fuyang, Ganzhou, Guangzhou, Shanghai, Shenyang, Tianjin, Tongzhou, Wenzhou, Xian, and Yingtan. Two or 3 public schools in each city were recruited to participate in the study by convenience. The aims and methods of the study were comprehensively introduced to all potential participants. Written informed assent was obtained from all participants and written informed consent was obtained from their parents or guardians. A total of 3,121 healthy children and youth (1,603 boys and 1,518 girls) in Grades 4 to 11 from 7 elementary schools, 11 middle schools, and 7 high schools volunteered to participate in the study. The methods and protocols were approved by the Ethics Advisory Committee of the Shanghai University of Sport. Of the total 3,121 participants, 42 were excluded because of accelerometer malfunction or loss, 54 for missing demographic or anthropometric data, and 14 for illness. One hundred and fourteen participants who were younger than 9 years old or older than 17 years old were excluded due to the limited number of participants in their corresponding age group. Among the rest of the 2,897 participants, 734 could not provide a sufficient number of valid wearing days. The final analytic sample consisted of 2,163 participants (1,086 boys and 1,077 girls) aged 9 to 17 years old with complete accelerometer, demographic, and anthropometric data, which resulted in a response rate of 69.3%. The participants were categorized into three grade groups—Grades 4 to 6, Grades 7 to 9, and Grades 10 to 11—which correspond to elementary schools, middle schools, and high schools in China, respectively. Measures Demographic Variables The participants reported their birth date and gender. Age in months was calculated as months between the birth date and measurement date. Grade was self-reported by participants. Anthropometric Variables Height and weight assessments were conducted in a private setting with participants dressed in light clothing. Height was measured to the nearest 0.1 cm using a freestanding portable stadiometer. Weight was measured to the nearest 0.1 kg with an electronic weighing scale (HN-358, Omron, Tokyo, Japan). Two measurements were taken and averaged for each anthropometric variable. Body mass index (BMI) was calculated as weight (kg) divided by height (m) squared. Participants were categorized into normal-weight,

S14

C. WANG ET AL.

overweight, or obese groups according to the age- and gender-specific BMI classification system that was developed for Chinese school-age children (Ji, 2005). Because this system was developed for overweight and obesity screening, only three weight categories (i.e., normal weight, overweight, and obesity) were used in this system.

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PA and Sedentary Behavior Measurements Objective assessments of PA and SB were obtained using the ActiGraph GT3Xþ or GT3X accelerometers (ActiGraph, LLC, Pensacola, FL). The sampling interval (epoch) in the present study was set at 60 s. Participants were instructed to wear the accelerometers for 7 consecutive days on the right hip and secured by an elastic belt, and were asked to wear the devices when they were awake and to take the devices off when swimming, bathing, and sleeping (Rowlands, 2007; Trost, Pate, Freedson, Sallis, & Taylor, 2000). The accelerometer data were downloaded onto a computer using ActiLife software 5.5.5 and were screened for data quality. When there was a recording of more than 20,000 counts per minute (CPM), it was considered a potential accelerometer malfunction and the corresponding data were excluded from the analysis. Accelerometer wearing time was calculated by subtracting nonwear time, which was defined as 20 min or more of consecutive zeros, from the total recorded time of a day. A valid day was defined as having 10 hr or more of accelerometer wearing time (Anderson, Hagstromer, & Yngve, 2005). The accelerometer data were included in the final analysis if they contained at least 2 valid weekdays and 1 valid weekend day. Three days of accelerometer-based data had been shown to produce a reliability coefficient of .7, which was thought to be acceptable and justified (Mattocks et al., 2008). The amount of time spent in SB and various intensities of PA (i.e., light PA [LPA], moderate PA [MPA], vigorous PA [VPA], and MVPA), was calculated based on valid accelerometer data. SB was defined as activity counts of less than 100 CPM, which is a widely adopted cutoff point for sedentary activity (Trost, Loprinzi, Moore, & Pfeiffer, 2011). MPA and VPA were defined using three types of accelerometer cutoff points: (a) the Chinese-specific cutoff points determined by our research group—and demonstrated to be more suitable for Chinese children and youth compared with previously developed cutoff points (for more details, see Z. Zhu, Chen, & Zhuang, this supplement)— which defined MPA as 2,800 to 3,999 CPM and VPA as $ 4,000 CPM; (b) the cutoff points calculated by Freedson’s age-specific Equation (Trost et al., 1998) using 3 metabolic equivalents (METs) and 6 METs to define MPA and VPA intensities, respectively (Trost et al., 2011); and (c) the cutoff points calculated by the same Freedson’s equation but using 4 METs and 7 METs to define MPA and VPA intensities, respectively (Trost et al., 2011). The

adoption of cutoff points calculated by Freedson’s equation was to facilitate comparisons to other studies. Because there is no consensus regarding the MET value defining MPA and VPA for children and youth (Trost et al., 2011), both 3 and 6 METs and 4 and 7 METs were adopted in Freedson’s equation to define MPA and VPA, respectively. Levels of PA and SB were reported as daily time (min/day) spent in LPA, MPA, VPA, MVPA, and SB averaged across all valid days. Adherence to PA recommendations was also reported and was calculated as the proportion of participants meeting the guideline of 60 min of MVPA per day recommended by the WHO (2010). PA and SB on weekdays and weekend days were reported as absolute values and relative values; absolute values were calculated as daily time averaged across valid weekdays and valid weekend days, respectively, and relative values were the percent of the PA and SB time relative to the daily wearing time. Data Collection Procedure Data collection was conducted from April 2011 to May 2012. Before the commencement of the study, the researchers obtained written informed assent/consent from all participants and their parents or guardians. Local helpers in each city were trained to conduct the anthropometric measurements in a standardized manner. Accelerometer distribution and collection in the 11 cities were conducted by the same researcher, who was also responsible for processing all accelerometer data to minimize city-specific error and inter-researcher bias. Body weight and height were measured in a private setting at school by local helpers with participants dressed in light clothing. After the weight and height were measured, all participants were given the accelerometers and were instructed to wear them for 7 consecutive days. The accelerometers were initialized beforehand using ActiLife software 5.5.5 to start collecting data at 0:00 a.m. on the day after they were distributed to the participants. The participants were asked to follow their normal daily routines during the monitoring period. Written instructions were also given to all participants and their parents/guardians to remind them to wear the accelerometer in order to increase compliance. Researchers collected the accelerometers after 8 days to assure 7 days of complete data collection. Statistical Analysis All analyses were conducted using the Statistical Package for the Social Sciences Version 18.0 (SPSS Inc., Chicago, IL). Descriptive statistics were used to determine means and standard deviations for age, height, weight, BMI, and minutes per day of SB, LPA, MPA, VPA, and MVPA. Independent-sample t tests were used to examine gender differences in age, height, weight, and BMI. A pairedsample t test was conducted to compare the differences of

PA AND SEDENTARY BEHAVIOR OF CHINESE YOUTH

49.05 ^ 13.54 kg. Overall, 79.0% of participants were categorized as normal-weight, 12.9% as overweight, and 8.1% as obese. A higher proportion of boys than girls was classified as overweight or obese (25.6% of boys vs. 16.4% of girls). Participants’ characteristics by grade/grade group were shown in Table 3. Gender differences for age in months existed in the Grades 4 to 6 and Grades10 to 11 groups, and gender differences for BMI only existed in the Grades 4 to 6 group.

PA and SB time between weekdays and weekend days. Multivariate analysis of variance (MANOVA) was used to test the differences in PA and SB variables by gender, age, grade/grade group, and weight status. Univariate post-hoc follow-up F tests were also used to analyze any significant main effects. The statistical significance level was set at p , .05. Due to the large sample size, effect size (ES) was also calculated to avoid the p value bias (W. Zhu, 2012). Small, medium, and large ESs (Cohen’s d) for independentsample t tests and the paired-sample t test were .2, .5, and .8, respectively (Cohen, 1992). Small, medium, and large ESs (partial h 2) for MANOVA were .01, .06, and .14, respectively (Cohen, 1992).

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Levels of PA and SB Determined by Chinese-Specific Cutoff Points Based on the Chinese-specific cutoff points, Chinese city children and youth spent an average of 521.50 ^ 110.02 min/ day being sedentary and 28.26 ^ 17.66 min/day in MVPA; only 5.6% of the participants (9.4% of boys and 1.9% of girls) met the recommendation of 60 min of MVPA per day (Table 4). Table 4 presents the PA and SB levels by age and gender. The MANOVA revealed a significant multivariate effect by gender, F(5, 10,815) ¼ 80.84, p , .01, partial h 2 ¼ .13. Univariate tests showed that there were significant differences between genders on MPA, F(1, 2,163) ¼ 146.20, p , .01, partial h 2 ¼ .06, VPA, F(1, 2,163) ¼ 308.03, p , .01, partial h 2 ¼ .13, and MVPA, F(1, 2,163) ¼ 277.63, p , .01, partial h 2 ¼ .11. Tukey’s honestly significant difference (HSD) tests showed that boys engaged in more MPA, VPA, and MVPA than did girls. The multivariate effect was also significant by age group, F(40, 10,815) ¼ 38.86, p , .01, partial h 2 ¼ .13. Univariate tests showed that there were significant differences across the age group levels on SB, F(8, 2,163) ¼ 66.193, p , .01, partial h 2 ¼ .20, LPA, F(8, 2,163) ¼ 116.47, p , .01, partial h 2 ¼ .30, MPA, F(8, 2,163) ¼ 4.74, p , .01, partial h 2 ¼ .17, VPA, F(8, 2,163) ¼ 13.06, p , .01, partial h 2 ¼ .05, and MVPA, F(8, 2,163) ¼ 8.96, p , .01, partial h 2 ¼ .03. Tukey’s HSD tests showed that

RESULTS Measurement Profile by City Table 1 shows basic information for the 11 data collection cities in this study. Compliance for wearing the accelerometer was computed as the percentage of participants who provided valid accelerometer data among the total sample. Overall compliance across the 11 cities was 69.30%. The city of Fuyang presented the lowest wearing compliance (42.57%), whereas the city of Yingtan demonstrated the highest wearing compliance (84.25%). Most of the accelerometer data (86.3%) were collected in the spring or fall. Two accelerometer models were used in this study, with 78.8% of the data collected from the GT3Xþ and 21.2% from the GT3X. Participants’ Characteristics Demographic and anthropometric characteristics of the participants by age are presented in Table 2. The participants’ mean age was 160.87 ^ 27.00 months (13.41 ^ 2.25 years), height was 156.55 ^ 11.72 cm, and weight was

TABLE 1 Measurement Profile of Accelerometer by City Accelerometer Models Cities Chengdu Fuyang Ganzhou Guangzhou Shanghai Shenyang Tianjin Tongzhou Wenzhou Xian Yingtan Total

Measured Sample

Valid Samples

Valid Ratio (%)

Measurement Season

GT3Xþ (%)

GT3X (%)

290 296 296 296 400 287 285 286 255 284 146 3,121

174 126 245 203 297 212 211 240 126 206 123 2,163

60.00 42.57 82.77 68.58 74.25 73.87 74.04 83.92 49.41 72.54 84.25 69.30

SU SP SP SP FA SP FA FA SP FA SU

64.9 100 98.0 100 70.7 72.6 65.9 71.7 99.2 68.0 67.5 78.8

35.1 0 2.0 0 29.3 27.4 34.1 28.3 0.8 32.0 32.5 21.2

Note. Valid ratio (%) ¼ measured samples/valid samples; SP ¼ spring; SU ¼ summer; FA ¼ fall.

Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All

9

b

a

40 88 128 99 152 251 142 145 287 134 136 270 186 176 362 164 133 297 134 76 210 107 101 208 80 70 150 1,086 1,077 2,163

Measured Sample

p , .05, effect size , .2. p , .05, .2 # effect size , .5. c p , .05, .5 # effect size , .8. d p , .05,.effect size $ .8.

Total

17

16

15

14

13

12

11

10

Gender

Age

Height (cm) 138.88 ^ 7.56 138.16 ^ 6.40 138.39 ^ 6.76 145.26 ^ 7.27b 142.91 ^ 7.31 143.84 ^ 7.37 148.10 ^ 7.39 149.19 ^ 7.74 148.65 ^ 7.57 155.30 ^ 8.34 154.89 ^ 5.86 155.10 ^ 7.19 161.46 ^ 8.53c 157.39 ^ 6.27 159.48 ^ 7.78 165.87 ^ 8.56d 158.36 ^ 5.78 162.51 ^ 8.32 170.07 ^ 6.64d 159.59 ^ 6.18 166.27 ^ 8.20 171.04 ^ 6.50d 160.03 ^ 5.77 165.70 ^ 8.25 172.13 ^ 5.98d 158.69 ^ 5.64 165.86 ^ 8.89 160.10 ^ 12.51c 152.96 ^ 9.63 156.55 ^ 11.72

Age in Months 115.54 ^ 3.09 116.02 ^ 2.72 115.87 ^ 2.84 127.20 ^ 3.43b 126.28 ^ 3.18 126.64 ^ 3.31 137.29 ^ 3.13 136.87 ^ 3.46 137.08 ^ 3.30 150.03 ^ 3.52 150.37 ^ 3.62 150.20 ^ 3.57 161.96 ^ 3.38 161.59 ^ 3.55 161.78 ^ 3.46 173.22 ^ 3.31 172.92 ^ 3.21 173.09 ^ 3.26 185.37 ^ 3.72 185.25 ^ 3.78 185.33 ^ 3.73 198.10 ^ 3.70 198.30 ^ 3.45 198.20 ^ 3.57 208.81 ^ 3.66 208.81 ^ 3.13 208.81 ^ 3.41 163.98 ^ 25.93b 157.72 ^ 27.70 160.87 ^ 27.00

33.19 ^ 9.19 31.74 ^ 6.79 32.19 ^ 7.61 41.37 ^ 10.26c 36.16 ^ 8.03 38.21 ^ 9.31 42.39 ^ 10.89 41.93 ^ 10.20 42.15 ^ 10.53 49.21 ^ 12.26b 45.92 ^ 8.37 47.56 ^ 10.59 52.72 ^ 14.93b 49.87 ^ 8.58 51.33 ^ 12.33 54.73 ^ 11.88b 50.42 ^ 9.38 52.80 ^ 11.02 59.83 ^ 12.68c 53.54 ^ 9.56 57.55 ^ 12.01 62.26 ^ 11.72c 55.90 ^ 10.17 59.17 ^ 11.42 63.82 ^ 12.85d 52.65 ^ 7.06 58.61 ^ 11.91 52.12 ^ 14.72b 45.96 ^ 11.44 49.05 ^ 13.54

Weight (kg)

2

17.02 ^ 3.46 16.51 ^ 2.68 16.67 ^ 2.94 19.42 ^ 3.68c 17.54 ^ 2.74 18.28 ^ 3.27 19.14 ^ 3.79 18.64 ^ 3.29 18.89 ^ 3.55 20.22 ^ 3.77b 19.07 ^ 2.89 19.64 ^ 3.40 19.97 ^ 4.23 20.07 ^ 2.87 20.02 ^ 3.62 19.75 ^ 3.20 20.04 ^ 3.18 19.88 ^ 3.19 20.60 ^ 3.78 20.92 ^ 2.88 20.72 ^ 3.48 21.23 ^ 3.56 21.78 ^ 3.46 21.50 ^ 3.51 21.47 ^ 3.84 20.91 ^ 2.59 21.21 ^ 3.32 20.01 ^ 3.84a 19.38 ^ 3.33 19.70 ^ 3.60

BMI (kg/m )

TABLE 2 Participants’ Characteristics by Gender and by Age (mean ^ SD)

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31 (77.5) 72 (81.8) 103 (80.5) 56 (56.6) 128 (84.2) 184 (73.3) 97 (68.3) 117 (80.7) 214 (74.6) 91 (67.9) 119 (87.5) 210 (77.8) 139 (74.7) 144 (81.8) 283 (78.2) 140 (85.4) 118 (88.7) 258 (86.9) 105 (78.4) 62 (81.6) 167 (79.5) 86 (80.4) 78 (77.2) 164 (78.8) 63 (78.8) 63 (90.0) 126 (84.0) 808 (74.4) 901 (83.7) 1709 (79.0)

Normal

6 (15.0) 13 (14.8) 19 (14.8) 25 (25.3) 15 (9.9) 40 (15.9) 26 (18.3) 13 (9.0) 39 (13.6) 27 (20.1) 7 (5.1) 34 (12.6) 24 (12.9) 25 (14.2) 49 (13.5) 14 (8.5) 9 (6.8) 23 (7.7) 20 (14.9) 12 (15.8) 32 (15.2) 11 (10.3) 16 (15.8) 27 (13) 10 (12.5) 6 (8.6) 16 (10.7) 163 (15.0) 116 (10.8) 279 (12.9)

Overweight

Weight Status (n [%])

3 (7.5) 3 (3.4) 6 (4.7) 18 (18.2) 9 (5.9) 27 (10.8) 19 (13.4) 15 (10.3) 34 (11.8) 16 (11.9) 10 (7.4) 26 (9.6) 23 (12.4) 7 (4.0) 30 (8.3) 10 (6.1) 6 (4.5) 16 (5.4) 9 (6.7) 2 (2.6) 11 (5.2) 10 (9.3) 7 (6.9) 17 (8.2) 7 (8.8) 1 (1.4) 8 (5.3) 115 (10.6) 60 (5.6) 175 (8.1)

Obese

S16 C. WANG ET AL.

b

a

p , .05, effect size , .2. p , .05, .2 # effect size , .5. c p , .05, .5 # effect size , .8. d p , .05,.effect size $ .8.

10– 11

7–9

Grade by School Level 4–6

11

10

9

8

7

6

Boys Girls All Boys Girls All Boys Girls All

Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All

4

5

Gender

Grade

303 402 705 538 481 1,019 245 194 439

61 169 230 170 152 322 72 81 153 219 186 405 139 152 291 180 143 323 125 66 191 120 128 248

Measured Sample

146.08 ^ 7.96a 144.66 ^ 8.55 145.27 ^ 8.33 162.49 ^ 8.99c 157.11 ^ 6.24 159.95 ^ 8.26 172.20 ^ 5.97d 159.89 ^ 5.78 166.76 ^ 8.49

140.48 ^ 7.74 139.99 ^ 7.00 140.12 ^ 7.19 147.03 ^ 7.20 146.25 ^ 8.02 146.66 ^ 7.59 148.58 ^ 7.78b 151.41 ^ 6.71 150.08 ^ 7.35 157.91 ^ 8.36b 154.84 ^ 6.22 156.50 ^ 7.60 165.37 ^ 7.75d 158.47 ^ 5.95 161.77 ^ 7.68 165.83 ^ 8.22d 158.64 ^ 5.69 162.65 ^ 8.04 172.05 ^ 6.35d 160.62 ^ 6.50 168.10 ^ 8.39 172.37 ^ 5.56d 159.51 ^ 5.36 165.73 ^ 8.43

119.49 ^ 6.90 120.84 ^ 6.07 120.48 ^ 6.31 132.97 ^ 6.55 131.69 ^ 5.71 132.37 ^ 6.19 140.70 ^ 6.09 140.69 ^ 6.16 140.70 ^ 6.11 156.90 ^ 8.59b 154.70 ^ 7.62 155.89 ^ 8.22 168.96 ^ 8.83b 166.88 ^ 7.80 167.87 ^ 8.36 175.61 ^ 9.76 174.65 ^ 9.05 175.18 ^ 9.45 192.53 ^ 7.69b 195.69 ^ 8.13 193.62 ^ 7.97 204.50 ^ 6.13 203.11 ^ 6.40 203.78 ^ 6.30 132.10 ^ 9.61b 128.94 ^ 9.68 130.30 ^ 9.77 166.28 ^ 12.19a 164.48 ^ 11.64 165.43 ^ 11.96 198.39 ^ 9.19b 200.59 ^ 7.85 199.36 ^ 8.68

Height (cm)

Age in Months

41.12 ^ 10.88b 37.66 ^ 9.33 39.15 ^ 10.17 53.15 ^ 13.14b 49.20 ^ 9.17 51.29 ^ 11.61 63.46 ^ 12.44c 55.10 ^ 9.29 59.77 ^ 11.89

36.81 ^ 10.95b 33.45 ^ 7.14 34.34 ^ 8.43 41.36 ^ 10.39b 38.50 ^ 9.15 40.01 ^ 9.91 44.22 ^ 10.95 44.86 ^ 8.95 44.56 ^ 9.91 49.52 ^ 12.14b 46.42 ^ 8.82 48.10 ^ 10.84 57.97 ^ 15.32c 51.26 ^ 8.76 54.47 ^ 12.77 53.83 ^ 11.09b 50.64 ^ 9.21 52.42 ^ 10.41 62.84 ^ 12.89b 56.99 ^ 9.77 60.82 ^ 12.20 64.11 ^ 11.97d 54.12 ^ 8.91 58.96 ^ 11.61

Weight (kg)

197 (65.0) 335 (83.3) 532 (75.5) 422 (78.4) 409 (85.0) 831 (81.6) 189 (77.1) 157 (80.9) 346 (78.8)

38 (62.3) 142 (84.0) 180 (78.3) 114 (67.1) 127 (83.6) 241 (74.8) 45 (62.5) 66 (81.5) 111 (72.5) 165 (75.3) 159 (85.5) 324 (80.0) 97 (69.8) 127 (83.6) 224 (77.0) 160 (88.9) 123 (86.0) 283 (87.6) 93 (74.4) 52 (78.8) 145 (75.9) 96 (80.0) 105 (82.0) 201 (81.0)

18.39 ^ 4.07b 16.94 ^ 2.60 17.32 ^ 3.11 18.94 ^ 3.60b 17.81 ^ 2.99 18.41 ^ 3.37 19.85 ^ 3.75 19.43 ^ 2.91 19.63 ^ 3.33 19.70 ^ 3.78 19.28 ^ 3.03 19.51 ^ 3.46 20.99 ^ 4.27 20.36 ^ 2.94 20.66 ^ 3.65 19.43 ^ 2.98 20.06 ^ 3.11 19.71 ^ 3.05 21.18 ^ 3.94 22.02 ^ 2.95 21.47 ^ 3.64 21.54 ^ 3.71 21.25 ^ 3.18 21.40 ^ 3.44 19.04 ^ 3.75b 17.77 ^ 2.96 18.32 ^ 3.38 19.95 ^ 3.72 19.85 ^ 3.06 19.90 ^ 3.42 21.36 ^ 3.82 21.51 ^ 3.12 21.43 ^ 3.53

Normal

2

BMI (kg/m )

TABLE 3 Participants’ Characteristics by Gender and by Grade (mean ^ SD)

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65 (21.5) 40 (10.0) 105 (14.9) 66 (12.3) 48 (10.0) 114 (11.2) 32 (13.1) 28 (14.4) 60 (13.7)

13 (21.3) 23 (13.6) 36 (15.7) 36 (21.2) 11 (7.2) 47 (14.6) 16 (22.2) 6 (7.4) 22 (14.4) 36 (16.4) 16 (8.6) 52 (12.8) 16 (11.5) 16 (10.5) 32 (11.0) 14 (7.8) 16 (11.2) 30 (9.3) 19 (15.2) 9 (13.6) 28 (14.7) 13 (10.8) 19 (14.8) 32 (12.9)

Overweight

Weight Status (n [%])

41 (13.5) 27 (6.7) 68 (9.6) 50 (9.3) 24 (5.0) 74 (7.3) 24 (9.8) 9 (4.6) 33 (7.5)

10 (16.4) 4 (2.4) 14 (6.1) 20 (11.8) 14 (9.2) 34 (10.6) 11 (15.3) 9 (11.1) 20 (13.1) 18 (8.2) 11 (5.9) 29 (7.2) 26 (18.7) 9 (5.9) 35 (12) 6 (3.3) 4 (2.8) 10 (3.1) 13 (10.4) 5 (7.6) 18 (9.4) 11 (9.2) 4 (3.1) 15 (6.0)

Obese

PA AND SEDENTARY BEHAVIOR OF CHINESE YOUTH

S17

S18

C. WANG ET AL. TABLE 4 Levels of PA and SB by Gender and by Age Determined by Chinese-Specific Cutoff Points (mean ^ SD, min/day)

Age

Gender

9

Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All

10

11

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12

13

14

15

16

17

Total

Sedentary

LPA

MPA

VPA

MVPA

Meeting MVPA Recommendation (%)

419.13 ^ 61.95 442.80 ^ 61.12 435.40 ^ 62.12 413.41 ^ 89.39 474.92 ^ 96.16 450.66 ^ 98.10 452.77 ^ 99.39 495.44 ^ 94.34 474.33 ^ 99.03 519.25 ^ 110.11 553.64 ^ 90.81 536.57 ^ 102.12 526.91 ^ 117.99 543.71 ^ 97.63 535.08 ^ 108.75 511.32 ^ 90.35 544.78 ^ 77.19 526.30 ^ 86.20 533.77 ^ 94.49 561.03 ^ 92.60 543.63 ^ 94.50 596.11 ^ 109.29 597.22 ^ 117.60 596.65 ^ 113.13 607.67 ^ 101.29 589.38 ^ 100.00 599.13 ^ 100.77 513.21 ^ 115.66 529.85 ^ 103.40 521.50 ^ 110.02

332.70 ^ 46.80 344.38 ^ 58.41 340.73 ^ 55.13 354.13 ^ 59.90 342.58 ^ 74.26 347.14 ^ 69.06 336.76 ^ 60.67 323.49 ^ 78.79 330.05 ^ 70.60 308.70 ^ 87.08 261.80 ^ 67.47 285.08 ^ 81.15 298.90 ^ 81.77 274.57 ^ 76.63 287.07 ^ 80.14 255.21 ^ 73.84 236.76 ^ 62.18 246.95 ^ 69.36 242.97 ^ 71.24 226.40 ^ 60.22 236.97 ^ 67.79 225.85 ^ 67.00 216.87 ^ 53.63 221.49 ^ 60.90 201.64 ^ 47.74 210.26 ^ 54.98 205.66 ^ 51.25 283.48 ^ 84.72 277.19 ^ 83.10 280.35 ^ 83.96

23.40 ^ 12.86 15.83 ^ 8.21 18.19 ^ 10.46 21.22 ^ 10.73 15.59 ^ 7.93 17.81 ^ 9.52 22.11 ^ 9.88 14.86 ^ 8.18 18.45 ^ 9.75 18.06 ^ 9.18 13.45 ^ 9.11 15.74 ^ 9.42 21.79 ^ 10.56 14.34 ^ 9.34 18.16 ^ 10.64 19.92 ^ 9.95 16.57 ^ 11.18 18.42 ^ 10.63 19.34 ^ 11.22 16.24 ^ 9.19 18.22 ^ 10.61 22.88 ^ 11.14 19.69 ^ 8.83 21.33 ^ 10.18 21.40 ^ 11.52 17.21 ^ 10.00 19.45 ^ 11.00 20.87 ^ 10.62 15.69 ^ 9.25 18.29 ^ 10.29

10.81 ^ 6.36 6.68 ^ 5.02 7.97 ^ 5.78 9.19 ^ 8.73 6.20 ^ 4.43 7.38 ^ 6.62 10.66 ^ 8.00 5.67 ^ 4.84 8.14 ^ 7.05 10.25 ^ 8.16 5.76 ^ 5.67 7.99 ^ 7.36 13.92 ^ 10.75 6.35 ^ 5.73 10.24 ^ 9.46 14.64 ^ 10.24 6.70 ^ 5.62 11.09 ^ 9.35 14.25 ^ 12.44 7.78 ^ 8.49 11.91 ^ 11.58 18.46 ^ 13.88 8.31 ^ 9.09 13.53 ^ 12.83 17.10 ^ 14.15 7.47 ^ 7.63 12.61 ^ 12.51 13.33 ^ 10.98 6.59 ^ 6.19 9.97 ^ 9.54

34.21 ^ 18.21 22.50 ^ 12.28 26.16 ^ 15.32 30.41 ^ 18.27 21.79 ^ 11.51 25.19 ^ 15.12 32.77 ^ 16.34 20.53 ^ 11.87 26.59 ^ 15.50 28.31 ^ 15.94 19.21 ^ 13.47 23.73 ^ 15.41 35.70 ^ 18.76 20.69 ^ 13.31 28.40 ^ 17.96 34.56 ^ 17.12 23.26 ^ 14.85 29.50 ^ 17.07 33.59 ^ 20.93 24.02 ^ 15.04 30.13 ^ 19.52 41.34 ^ 22.82 28.01 ^ 15.25 34.87 ^ 20.58 38.50 ^ 22.13 24.69 ^ 15.81 32.05 ^ 20.57 34.20 ^ 19.10 22.28 ^ 13.69 28.26 ^ 17.66

12.5 1.1 3.9 9.1 1.3 2.8 9.9 0.7 4.9 3.7 2.2 3.0 14.0 2.8 6.6 12.8 3.0 4.4 12.7 2.6 7.6 17.8 3.0 8.2 26.3 2.9 12.0 9.4 1.9 5.6

participants aged 16 to 17 years old spent more time in MVPA and SB but spent less time in LPA compared with the younger participants. Similar results were observed when data were broken down by grade—participants in higher grades/ grade groups engaged in more MVPA and SB, but less LPA, compared with those in lower grades/grade groups (Table 5).

PA and SB Across Weight Status Determined by Chinese-Specific Cutoff Points As shown in Table 8, when stratified by weight status, the multivariate effect was not significant for all PA and SB variables by weight status, F(10, 10,815) ¼ 5.10, p , .01, partial h 2 ¼ .09.

PA Levels Determined by Freedson’s Cutoff Points PA and SB Between Weekdays and Weekend Days Determined by Chinese-Specific Cutoff Points The results of PA and SB time on weekdays and weekend days by age and by grade are presented in Tables 6 and 7, respectively. Overall, children and youth were more active during weekdays than during weekend days regarding the higher absolute and relative values of MPA, VPA, and MVPA observed for the whole sample (all p , .05, ES . .20). On the other hand, children and youth had more sedentary time on weekdays than on weekend days (535.27 ^ 116.04 min/day vs. 483.46 ^ 134.98 min/day, p , .05, ES ¼ .46).

PA levels determined by Freedson’s cutoff points are shown in Table 9 (presented by age) and Table 10 (presented by grade). MANOVA revealed a significant multivariate effect by age, F(40, 10,815) ¼ 71.90, p , .01, partial h 2 ¼ .21.Univariate tests showed that there were significant differences across the age group levels on SB, F(8, 2,163) ¼ 133.79, p , .01, partial h 2 ¼ .33, LPA, F(8, 2,163) ¼ 165.79, p , .01, partial h 2 ¼ .38, MPA, F(8, 2,163) ¼ 144.46, p , .01, partial h 2 ¼ .35, VPA, F(8, 2,163) ¼ 38.29, p , .01, partial h 2 ¼ .13, and MVPA, F(8, 2,163) ¼ 140.69, p , .01, partial h 2 ¼ .34. Tukey’s HSD tests showed that older participants spent more time in SB and less time in LPA, MPA, VPA, and

PA AND SEDENTARY BEHAVIOR OF CHINESE YOUTH

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TABLE 5 Levels of PA and SB by Gender and by Grade Determined by Chinese-Specific Cutoff Points (mean ^ SD, min/day)

Grade

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4

Gender

Boys Girls All 5 Boys Girls All 6 Boys Girls All 7 Boys Girls All 8 Boys Girls All 9 Boys Girls All 10 Boys Girls All 11 Boys Girls All Grade by School Level 4–6 Boys Girls All 7–9 Boys Girls All 10– 11 Boys Girls All

Sedentary

LPA

MPA

VPA

MVPA

Meeting MVPA Recommendation (%)

404.89 ^ 75.97 458.66 ^ 86.84 444.40 ^ 87.24 431.43 ^ 102.23 484.98 ^ 97.45 456.71 ^ 103.38 471.89 ^ 61.50 494.19 ^ 69.33 483.70 ^ 66.49 536.77 ^ 124.90 566.55 ^ 104.91 550.45 ^ 116.96 514.54 ^ 86.42 533.52 ^ 74.19 524.46 ^ 80.68 507.05 ^ 83.26 537.26 ^ 75.60 520.43 ^ 81.24 571.81 ^ 109.79 617.78 ^ 131.17 587.70 ^ 119.30 612.60 ^ 102.34 588.38 ^ 95.04 600.10 ^ 99.18

347.67 ^ 55.09 349.49 ^ 64.62 349.01 ^ 62.12 351.58 ^ 57.00 342.27 ^ 79.06 347.19 ^ 68.36 309.51 ^ 59.51 280.67 ^ 56.03 294.24 ^ 59.28 309.34 ^ 87.18 272.17 ^ 71.35 292.27 ^ 82.32 276.78 ^ 74.25 269.18 ^ 75.26 272.81 ^ 74.75 243.18 ^ 72.46 223.23 ^ 55.40 234.35 ^ 66.11 244.59 ^ 68.88 218.70 ^ 47.82 235.64 ^ 63.49 200.25 ^ 50.61 209.47 ^ 54.73 205.01 ^ 52.87

22.61 ^ 11.49 14.88 ^ 7.47 16.93 ^ 9.34 22.70 ^ 10.83 16.35 ^ 8.44 19.70 ^ 10.26 19.80 ^ 8.07 15.63 ^ 8.59 17.59 ^ 8.58 20.58 ^ 10.83 13.54 ^ 9.73 17.35 ^ 10.91 21.04 ^ 9.87 16.27 ^ 9.66 18.55 ^ 10.03 19.25 ^ 10.11 14.46 ^ 9.96 17.13 ^ 10.31 18.41 ^ 10.46 18.33 ^ 10.07 18.38 ^ 10.30 23.38 ^ 11.72 18.48 ^ 9.27 20.85 ^ 10.79

9.81 ^ 5.96 6.10 ^ 4.40 7.08 ^ 5.12 10.29 ^ 8.72 6.51 ^ 5.18 8.51 ^ 7.50 9.18 ^ 7.19 6.18 ^ 6.03 7.59 ^ 6.75 12.75 ^ 9.57 6.05 ^ 5.52 9.67 ^ 8.63 14.89 ^ 11.63 6.43 ^ 5.51 10.47 ^ 9.90 14.25 ^ 10.99 6.55 ^ 6.20 10.84 ^ 9.94 12.41 ^ 11.39 7.92 ^ 8.50 10.86 ^ 10.68 20.71 ^ 14.54 7.93 ^ 8.94 14.11 ^ 13.56

32.42 ^ 16.42 20.97 ^ 10.97 24.01 ^ 13.59 32.99 ^ 18.12 22.86 ^ 12.57 28.21 ^ 16.52 28.98 ^ 13.91 21.81 ^ 13.28 25.18 ^ 14.01 33.32 ^ 18.54 19.60 ^ 13.88 27.02 ^ 17.90 35.93 ^ 18.74 22.70 ^ 13.08 29.02 ^ 17.32 33.50 ^ 18.29 21.01 ^ 14.48 27.97 ^ 17.81 30.82 ^ 19.70 26.24 ^ 15.89 29.24 ^ 18.56 44.09 ^ 22.97 26.41 ^ 15.56 34.96 ^ 21.38

6.6 0.6 2.2 8.2 1.3 5.0 6.9 1.2 3.9 8.7 2.7 5.9 8.6 1.3 4.8 7.8 2.1 5.3 8.0 4.5 6.8 20.0 2.3 10.9

435.70 ^ 91.65 475.77 ^ 88.98 458.55 ^ 92.23 521.08 ^ 103.63 547.41 ^ 88.87 533.51 ^ 97.79 591.79 ^ 107.94 598.38 ^ 109.24 594.71 ^ 108.44

340.80 ^ 59.68 332.89 ^ 73.69 336.29 ^ 68.09 278.79 ^ 84.02 256.68 ^ 71.61 268.35 ^ 79.14 222.87 ^ 64.45 212.61 ^ 52.54 218.34 ^ 59.64

21.99 ^ 10.42 15.59 ^ 8.08 18.34 ^ 9.69 20.25 ^ 10.36 14.68 ^ 9.82 17.62 ^ 10.48 20.84 ^ 11.35 18.43 ^ 9.52 19.78 ^ 10.64

9.93 ^ 7.87 6.27 ^ 5.05 7.84 ^ 6.66 13.80 ^ 10.63 6.32 ^ 5.72 10.27 ^ 9.43 16.48 ^ 13.65 7.92 ^ 8.77 12.70 ^ 12.48

31.92 ^ 16.90 21.85 ^ 12.08 26.18 ^ 15.18 34.06 ^ 18.51 21.00 ^ 13.85 27.89 ^ 17.71 37.32 ^ 22.33 26.35 ^ 15.63 32.47 ^ 20.38

7.6 1.0 3.8 8.4 2.1 5.4 13.9 3.1 9.1

MVPA compared with their younger counterparts. Similar results were also observed by grade/grade group, with participants in higher grades/grade groups being more sedentary and less active compared with those in lower grades/grade groups.

DISCUSSION This study was the first large-scale study to objectively assess PA and SB of Chinese city children and youth. We found that children and youth in Chinese cities were physically inactive and tended to have a sedentary lifestyle. Based on the results derived by the Chinese-specific cutoff points, Chinese city children and youth were more active during weekdays than weekend days, boys were more active than girls, and older children and youth spent more daily time in MVPA but also more time being sedentary; no differences in PA and SB were found across different BMI categories.

Because of the growing awareness of the health benefits of regular PA, public health recommendations for PA have been established. The WHO has recommended at least 60 min of MVPA per day for children and adolescents (WHO, 2010). Our study found that only 5.6% of Chinese city children and youth (9.4% of boys and 1.9% of girls) met the recommendation of 60 min of MVPA per day. They were sedentary nearly 8.7 hr a day and spent less than 0.5 hr in MVPA per day. These findings call for an urgent need to develop effective PA promotion programs for Chinese city children and youth, especially girls whose PA participation rate was extremely low. Although we were interested in comparing the prevalence of PA determined in the current study with existing data from other countries and districts, inconsistencies regarding accelerometers used, measurement protocols, and ways of analyzing and reporting data impeded such comparisons. There was also no consensus on the count cutoff points used to define different PA intensities. There were several proposed count cutoff points,

S20

C. WANG ET AL. TABLE 6 Weekday and Weekend Day Patterns of PA and SB by Age Determined by Chinese-Specific Cutoff Points (mean ^ SD) Absolute Values (min/day)

Age 9

10

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11

12

13

14

15

16

17

Total

Variables

Weekday

Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA

452.51 ^ 72.79 340.10 ^ 58.74 19.12 ^ 11.11b 8.49 ^ 5.96b 27.61 ^ 16.07b 460.44 ^ 100.38b 346.70 ^ 73.09 19.02 ^ 10.45b 8.14 ^ 7.09b 27.17 ^ 16.53b 485.27 ^ 106.96b 332.31 ^ 73.66 19.29 ^ 10.34b 8.70 ^ 7.46b 27.99 ^ 16.33b 558.01 ^ 109.41c 281.79 ^ 85.49a 16.82 ^ 9.80b 8.52 ^ 7.50b 25.35 ^ 15.65b 548.30 ^ 117.04b 286.77 ^ 83.57 19.59 ^ 11.22b 11.38 ^ 10.60b 30.97 ^ 19.24b 542.24 ^ 94.89c 243.69 ^ 71.99a 19.47 ^ 11.35b 11.99 ^ 10.26b 31.46 ^ 18.35b 556.89 ^ 101.21b 239.56 ^ 69.82a 19.01 ^ 10.48b 12.56 ^ 12.23b 31.57 ^ 19.65b 607.17 ^ 117.37b 222.45 ^ 62.02 22.18 ^ 10.63b 14.45 ^ 12.99b 36.64 ^ 21.12b 610.69 ^ 103.14b 208.96 ^ 61.15 21.13 ^ 12.13b 13.54 ^ 13.28a 34.67 ^ 22.04b 535.27 ^ 116.04b 280.22 ^ 86.78 19.39 ^ 10.86b 10.76 ^ 10.14b 30.16 ^ 18.57b c

Relative Values (%)

Weekend Day

Weekday

Weekend Day

391.34 ^ 79.17 338.71 ^ 78.91 15.64 ^ 13.65 6.77 ^ 8.95 22.41 ^ 20.60 423.83 ^ 128.74 346.99 ^ 93.61 14.80 ^ 11.37 5.50 ^ 6.88 20.30 ^ 16.40 445.13 ^ 122.17 324.65 ^ 94.12 16.13 ^ 14.44 6.74 ^ 9.19 22.87 ^ 21.87 476.15 ^ 131.42 294.51 ^ 95.58 12.87 ^ 13.09 6.57 ^ 9.97 19.45 ^ 21.25 497.66 ^ 136.35 289.28 ^ 101.52 14.49 ^ 14.33 7.10 ^ 9.89 21.59 ^ 21.95 483.59 ^ 105.95 254.00 ^ 90.30 15.48 ^ 12.97 8.58 ^ 10.28 24.06 ^ 20.65 510.63 ^ 113.80 230.32 ^ 80.08 16.38 ^ 14.46 10.48 ^ 13.11 26.86 ^ 24.12 571.57 ^ 136.19 218.77 ^ 78.45 19.09 ^ 13.13 11.24 ^ 14.07 30.33 ^ 23.76 553.60 ^ 163.04 214.74 ^ 101.73 16.97 ^ 15.39 11.49 ^ 15.29 28.46 ^ 27.81 483.46 ^ 134.98 281.73 ^ 102.29 15.54 ^ 13.70 8.02 ^ 10.96 23.56 ^ 22.12

55.1 ^ 7.1 41.5 ^ 6.4b 2.4 ^ 1.4a 1.0 ^ 0.7 3.4 ^ 2.0a 55.0 ^ 8.9a 41.7 ^ 8.2b 2.3 ^ 1.3b 1.0 ^ 0.9b 3.3 ^ 2.1b 57.2 ^ 9.1 39.5 ^ 8.2a 2.3 ^ 1.3a 1.1 ^ 0.9a 3.4 ^ 2.1a 64.5 ^ 9.5b 32.5 ^ 8.7b 2.0 ^ 1.1b 1.0 ^ 0.9a 2.9 ^ 1.8b 63.2 ^ 9.6a 33.2 ^ 8.9b 2.3 ^ 1.3b 1.3 ^ 1.3b 3.6 ^ 2.3b 66.4 ^ 9.0b 29.8 ^ 8.1b 2.4 ^ 1.4b 1.5 ^ 1.3b 3.9 ^ 2.3b 67.2 ^ 8.5 29.0 ^ 7.9a 2.3 ^ 1.3 1.5 ^ 1.5 3.8 ^ 2.4a 69.9 ^ 7.4 25.8 ^ 6.9a 2.6 ^ 1.3a 1.7 ^ 1.5b 4.3 ^ 2.5b 71.5 ^ 7.0 24.5 ^ 6.6a 2.5 ^ 1.4 1.6 ^ 1.5 4.0 ^ 2.5 63.2 ^ 10.3a 33.2 ^ 9.8b 2.3 ^ 1.3b 1.3 ^ 1.2b 3.6 ^ 2.2b

52.2 ^ 9.7 44.9 ^ 8.6 2.1 ^ 1.7 0.9 ^ 1.2 2.9 ^ 2.6 53.2 ^ 11.2 44.1 ^ 10.4 1.9 ^ 1.5 0.7 ^ 0.9 2.7 ^ 2.2 56.1 ^ 11.6 41.0 ^ 10.4 2.0 ^ 1.8 0.9 ^ 1.2 2.9 ^ 2.8 60.1 ^ 11.9 37.5 ^ 11.0 1.6 ^ 1.7 0.8 ^ 1.2 2.4 ^ 2.7 61.4 ^ 12.3 35.9 ^ 11.4 1.8 ^ 1.9 0.9 ^ 1.4 2.7 ^ 3.0 63.6 ^ 11.5 33.2 ^ 10.9 2.0 ^ 1.7 1.1 ^ 1.4 3.2 ^ 2.7 66.4 ^ 10.4 30.1 ^ 9.7 2.2 ^ 1.9 1.4 ^ 1.7 3.5 ^ 3.1 69.4 ^ 10.4 26.9 ^ 9.8 2.3 ^ 1.6 1.4 ^ 1.7 3.7 ^ 2.9 69.0 ^ 16.4 27.4 ^ 14.6 2.2 ^ 2.1 1.5 ^ 2.1 3.6 ^ 3.8 61.1 ^ 13.0 35.9 ^ 12.3 2.0 ^ 1.8 1.0 ^ 1.4 3.0 ^ 2.9

Note. Relative Values (%) ¼ PA or SB time (min/day)/accelerometer wearing time (min/day). a p , .05, effect size , .2. b p , .05, .2 # effect size , .5. c p , .05, .5 # effect size , .8.

b

PA AND SEDENTARY BEHAVIOR OF CHINESE YOUTH

S21

TABLE 7 Weekday and Weekend Day Patterns of PA and SB by Grade Determined by Chinese-Specific Cutoff Points (mean ^ SD) Absolute Values (min/day) Grade 4

5

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6

7

8

9

10

11

Grade by School Level 4–6

7–9

10 – 11

Variables

Weekday

Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA Sedentary LPA MPA VPA MVPA

Relative Values (%)

Weekend Day

Weekday

459.58 ^ 95.37 346.84 ^ 65.79 17.92 ^ 10.18b 7.72 ^ 5.49b 25.64 ^ 14.77b 463.45 ^ 105.47b 348.28 ^ 72.30 20.43 ^ 10.86b 8.99 ^ 7.70b 29.41 ^ 17.23b 496.21 ^ 75.02b 300.89 ^ 61.01b 19.25 ^ 9.55b 8.51 ^ 7.75b 27.75 ^ 15.72b 571.86 ^ 122.47c 288.24 ^ 86.56a 18.53 ^ 11.29b 10.56 ^ 9.15b 29.10 ^ 18.47b 539.67 ^ 89.27b 272.41 ^ 77.08 19.90 ^ 10.64b 11.72 ^ 11.37b 31.63 ^ 19.07b 535.20 ^ 92.60c 231.78 ^ 70.66a 17.95 ^ 10.63b 11.38 ^ 10.49b 29.33 ^ 18.25b 597.97 ^ 126.14b 239.48 ^ 67.01b 19.51 ^ 10.57b 11.71 ^ 11.09b 31.22 ^ 18.80b 609.73 ^ 101.90b 207.86 ^ 58.33 22.11 ^ 11.76b 14.95 ^ 14.01b 37.06 ^ 22.58b 469.30 ^ 97.21b 337.53 ^ 70.49a 19.35 ^ 10.41b 8.47 ^ 7.08b 27.82 ^ 16.20b 551.05 ^ 105.94c 265.83 ^ 82.62a 18.74 ^ 10.92b 11.15 ^ 10.25b 29.89 ^ 18.59b 604.61 ^ 113.10b 221.61 ^ 64.13 20.98 ^ 11.32b 13.54 ^ 12.91b 34.52 ^ 21.20b

c

Weekend Day

405.29 ^ 106.10 354.06 ^ 85.57 14.43 ^ 11.82 5.64 ^ 7.43 20.07 ^ 17.50 438.36 ^ 133.73 342.10 ^ 92.13 17.61 ^ 14.45 7.27 ^ 9.52 24.89 ^ 21.98 449.83 ^ 104.75 278.18 ^ 84.68 13.35 ^ 12.55 5.30 ^ 7.15 18.66 ^ 18.43 490.80 ^ 144.98 303.98 ^ 102.73 14.30 ^ 14.87 7.29 ^ 10.36 21.59 ^ 22.96 480.03 ^ 114.32 274.53 ^ 99.72 15.12 ^ 13.77 7.33 ^ 10.29 22.45 ^ 21.35 482.22 ^ 96.08 240.00 ^ 73.27 14.76 ^ 12.63 9.25 ^ 11.33 24.01 ^ 21.37 563.58 ^ 133.43 223.55 ^ 76.25 15.64 ^ 13.00 8.65 ^ 11.44 24.29 ^ 22.25 567.22 ^ 149.79 209.74 ^ 91.33 18.70 ^ 14.16 12.77 ^ 15.69 31.47 ^ 26.22

b

55.0 ^ 8.3 41.8 ^ 7.4b 2.2 ^ 1.3b 0.9 ^ 0.7b 3.1 ^ 1.9b 54.8 ^ 8.8 41.6 ^ 8.0a 2.5 ^ 1.4a 1.1 ^ 1.0a 3.6 ^ 2.2a 60.2 ^ 7.0 36.5 ^ 6.6 2.3 ^ 1.1b 1.0 ^ 0.9b 3.4 ^ 1.9b 64.2 ^ 9.7b 32.5 ^ 8.9b 2.1 ^ 1.3b 1.2 ^ 1.1b 3.3 ^ 2.1b 64 ^ 8.8a 32.2 ^ 8,0b 2.4 ^ 1.3b 1.4 ^ 1.4b 3.8 ^ 2.3b 67.2 ^ 9.2b 29.1 ^ 8.5b 2.3 ^ 1.3b 1.4 ^ 1.3a 3.7 ^ 2.3b 68.6 ^ 7.9 27.8 ^ 7.5 2.3 ^ 1.2b 1.4 ^ 1.3b 3.6 ^ 2.2b 71.3 ^ 7 24.4 ^ 6.5a 2.6 ^ 1.4a 1.7 ^ 1.6 4.3 ^ 2.6a

51.9 ^ 10.2 45.5 ^ 9.5 1.9 ^ 1.5 0.7 ^ 1.0 2.6 ^ 2.3 54.1 ^ 11.2 42.8 ^ 10.1 2.2 ^ 1.9 0.9 ^ 1.2 3.2 ^ 2.9 60.2 ^ 11.8 37.3 ^ 10.6 1.8 ^ 1.8 0.7 ^ 1.1 2.5 ^ 2.7 59.9 ^ 12.5 37.5 ^ 11.6 1.8 ^ 1.9 0.9 ^ 1.3 2.6 ^ 2.9 61.8 ^ 12.3 35.2 ^ 11.6 2.0 ^ 1.9 1.0 ^ 1.5 2.9 ^ 3.0 64.6 ^ 10.0 32.2 ^ 9.4 2.0 ^ 1.7 1.2 ^ 1.5 3.2 ^ 2.8 69.2 ^ 9.6 27.7 ^ 9.1 1.9 ^ 1.6 1.1 ^ 1.4 3.0 ^ 2.8 69.7 ^ 14.3 26.3 ^ 12.8 2.3 ^ 1.9 1.6 ^ 2.0 3.9 ^ 3.4

430.06 ^ 120.42 332.13 ^ 92.93 15.65 ^ 13.34 6.31 ^ 8.43 21.96 ^ 20.02 485.00 ^ 122.51 275.29 ^ 97.17 14.68 ^ 13.87 7.92 ^ 10.68 22.60 ^ 22.01 565.64 ^ 142.75 215.75 ^ 85.28 17.37 ^ 13.74 10.98 ^ 14.14 28.35 ^ 24.80

56.1 ^ 8.6a 40.6 ^ 7.8a 2.4 ^ 1.3a 1.0 ^ 0.9b 3.4 ^ 2.0b 65.1 ^ 9.4b 31.3 ^ 8.7b 2.2 ^ 1.3b 1.3 ^ 1.3b 3.6 ^ 2.2b 70.1 ^ 7.5 25.7 ^ 7.1a 2.5 ^ 1.3a 1.6 ^ 1.5a 4.0 ^ 2.5b

54.7 ^ 11.4 42.5 ^ 10.4 2.0 ^ 1.8 0.8 ^ 1.1 2.8 ^ 2.7 61.9 ^ 11.8 35.2 ^ 11.2 1.9 ^ 1.8 1.0 ^ 1.4 2.9 ^ 2.9 69.5 ^ 12.4 26.9 ^ 11.3 2.2 ^ 1.8 1.4 ^ 1.8 3.5 ^ 3.2

Note. Relative Values (%) ¼ PA or SB time (min/day)/accelerometer wearing time (min/day). a p , .05, effect size , .2. b p , .05, .2 # effect size , .5. c p , .05, .5 # effect size , .8.

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C. WANG ET AL.

but their validation studies had either included a limited number of children with a large age span or included a reasonably large population but with a narrow age span (Trost et al., 2011). The Chinese-specific cutoff points used in the present study were developed by Z. Zhu and colleagues (this supplement) using the Cosmed K4b2 portable metabolic unit during treadmill activities, gymnastics, and table tennis exercises in an independent sample of 367 Chinese children and youth aged 9 to 17 years old. These cutoff points were demonstrated to be more suitable for Chinese children and youth (see more details in the article by Z. Zhu et al. in this supplement). Large differences in PA time and prevalence determined by the Chinese-specific cutoff points and Freedson’s cutoff points were observed in the present study. For instance, average MVPA time and PA prevalence determined by the Chinese-specific cutoff points were 28 min/day and 5.6%, respectively, whereas the Freedson’s cutoff points using 4 METs to define MPA generated a value of 39 min/day and 17% and the Freedson’s cutoff points using 3 METs to define MPA generated a value of 77 min/ day and 61%. These findings indicated that the amount of PA measured by accelerometer was sensitive to the cutoff points chosen to define activity intensity, which was consistent with another study’s conclusion (Apete, Zitouni, Hubert, & Guinhouya, 2012). The results from studies using different cutoff points would therefore not be comparable. Freedson’s cutoff points were used in this study to calculate the MVPA time in order to compare the results with other studies that adopted similar methods. With MPA intensity defined as 4 METs, American cross-sectional data from the 2003– 2004 and 2005 –2006 National Health and Nutrition Examination Survey showed that 12- to 15-yearolds spent 33 min/day in MVPA and 16- to 19-year-olds spent 26 min/day in MVPA (Belcher et al., 2010). In our study, when the same cutoff points for MPA were adopted students in Grades 7 through 9, aged approximately 12 to 15 years old, spent 32.68 ^ 20.81 min/day in MVPA, while students in Grades 10 through 11, aged approximately 16 to 17 years old, spent 27.70 ^ 19.14 min/day in MVPA. These findings are similar to the PA status of American youth. When 3 METs was adopted as the MPA threshold, much higher PA levels of children and youth were observed in various studies. French primary school students accumulated 83 ^ 23 min of MVPA every day and middle school students accumulated 60 ^ 20 min of MVPA every day (Blaes, Baquet, Van Praagh, & Berthoin, 2011). Longitudinal descriptive analyses of the 1,032 participants in the United States showed that children aged 9 years engaged in MVPA for approximately 3 hr per day on both weekends and weekdays, and by age 15, adolescents were only engaging in MVPA for 50 min per weekday and 36 min per weekend day (Nader, Bradley, Houts, McRitchie, & O’Brien, 2008). Data from Denmark, Portugal, Estonia, and Norway showed that at age 9, boys spent 192 ^ 66 min/day in MVPA and girls

spent 160 ^ 54 min/day in MVPA, while at age 15, boys accumulated only 99 ^ 45 min of MVPA per day and girls accumulated 73 ^ 32 min of MVPA per day (Riddoch et al., 2004). Although we found that Chinese city children and youth demonstrated a similar PA level compared with Western counterparts when the same cutoff points were used, their activity levels were far lower with the use of the Chinese-specific cutoff points, which may be more suitable for Chinese city children and youth. Most existing studies defined SB as activity counts of less than 100 CPM (Trost et al., 2011). Ekelund et al. (2012) pooled data from 14 studies from 1998 to 2009 that included 20,871 children (aged 4 to 18 years old) from the International Children’s Accelerometry Database. The results showed that children spent 354 ^ 96 min/day being sedentary. A study aimed to objectively assess levels of sedentary time, LPA, MPA, and VPA among 10- to 12-year-olds across five European countries found that girls spent 500 min/day and boys spent 474 min/day being sedentary (Verloigne et al., 2012). Another European study showed 12- to 17-year-old adolescents spent most of their registered time in SB (9 hr/day, or 71% of the registered time; Ruiz et al., 2011). American cross-sectional data from the 2003–2004 and 2005–2006 National Health and Nutrition Examination Survey showed that 6- to 11-year-olds accumulated 221.7 min of SB per day, 12- to 15-year-olds accumulated 269.0 min of SB per day, and 16- to 19-year-olds accumulated 273.0 min of SB per day (Belcher et al., 2010). Canadian children and youth spend 8.6 hr per day (62% of their waking hours) in sedentary pursuits (Colley et al., 2011). Notably, our study found that Chinese children and youth spent nearly 8.7 hr being sedentary, especially those age 16 to 17 years old and in Grade 10 through 11, whose sedentary time was nearly 10 hr per day. Differences in MVPA between weekdays and weekend days were clear. Several studies using objective measures of PA in youth have documented marked differences in weekday and weekend day PA behavior (Blaes et al., 2011; Generelo, Zaragoza, Julian, Abarca-Sos, & Murillo, 2011; Steele et al., 2010). Differences in PA and SB were also observed in the present study. Children and youth spent more time in both MVPA and SB on weekdays than on weekend days. Because a difference of wearing time between weekdays and weekend days may exist, a relative percentage might be more appropriate than absolute minutes to reflect the difference of PA levels between weekdays and weekend days. The results were similar when relative values (percent of PA and SB relative to wearing time) were used. High levels of both MVPA and SB on weekdays observed in the present study may be due to prolonged class time on weekdays, which may lead to higher sedentary time (Steele et al., 2010), and due to structured activities organized by school on weekdays, which may result in more MVPA time. Studies that used Freedson’s age-specific equation to calculate MVPA time have shown lower PA levels of older children compared with their younger counterparts (Chung,

9.8 9.2 7.0 1.9 2.6 0 5.6 6.5 4.6 35.04 ^ 19.05 33.44 ^ 19.55 29.35 ^ 18.20 22.16 ^ 13.95 22.45 ^ 12.20 23.87 ^ 12.53 28.25 ^ 17.76 28.87 ^ 17.71 27.47 ^ 16.64 13.96 ^ 11.24 12.11 ^ 10.14 10.59 ^ 9.77 6.55 ^ 6.27 6.69 ^ 5.85 7.04 ^ 5.57 10.05 ^ 9.70 9.86 ^ 9.01 9.37 ^ 8.71 276.93 ^ 83.91 303.41 ^ 82.77 301.25 ^ 86.83 275.17 ^ 82.01 277.21 ^ 85.75 307.46 ^ 89.54 276.00 ^ 82.89 292.52 ^ 84.86 303.38 ^ 87.56 Total

Girls

Normal Overweight Obese Normal Overweight Obese Normal Overweight Obese Boys

521.14 ^ 112.66 497.68 ^ 130.28 479.51 ^ 106.82 533.01 ^ 103.38 526.06 ^ 106.89 489.74 ^ 88.70 527.40 ^ 108.00 509.48 ^ 121.71 483.02 ^ 100.83

21.08 ^ 10.42 21.32 ^ 11.67 18.77 ^ 10.37 15.61 ^ 9.43 15.76 ^ 7.95 16.82 ^ 8.90 18.20 ^ 10.27 19.01 ^ 10.63 18.10 ^ 9.91

MVPA VPA MPA LPA Sedentary Weight Status Gender

TABLE 8 Weight Status Difference in SB and PA Determined by Chinese-Specific Cutoff Points (mean ^ SD, min/day)

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Meeting MVPA Recommendation (%)

PA AND SEDENTARY BEHAVIOR OF CHINESE YOUTH

S23

Skinner, Steiner, & Perrin, 2012; Troiano et al., 2008). Using Freedson’s age-specific cutoff points to calculate PA time, we similarly found that MVPA decreased by age/ grade. However, when using the Chinese-specific cutoff points, we observed that MVPA increased by age/grade. Considering that the MVPA cutoff points calculated by Freedson’s age-specific equation increased with increasing age, whereas the Chinese-specific cutoff points adopted a single value (2,800 CPM) to define MVPA for all age groups, the discrepancy of age/grade difference in MVPA determined by the two cutoff points may be due to the different cutoff point algorithm rather than the actual difference. This was partly supported by Ruiz et al.’s (2011) study, which failed to find the age difference in PA when adopting a single cutoff point (i.e., 2,000 CPM) to define the MVPA of children aged 12 to 17 years old. Gender was the most studied variable in PA pattern differences. Most studies revealed that boys were more active and less sedentary than girls. For example, European girls spent significantly more time in SB and significantly less time in LPA and MVPA compared with European boys (Verloigne et al., 2012). Six- to 19-year-old girls spent less time in MVPA than did boys in the United States (Belcher et al., 2010). There was a consistent conclusion that the proportion of adolescent boys who met the PA recommendations was higher than the percentage of girls who met the recommendations (Ruiz et al., 2011; Troiano et al., 2008). The current study also confirmed gender differences in both MVPA and percentage of participants of meeting the recommendations. But the results showed no differences in SB and LPA between genders, which is inconsistent with another study that found girls participated in more low- and moderate-intensity activities while boys participated in more high-intensity activities (Odunaiya, Ayodele, & Oguntibeju, 2010). Indeed, the difference in VPA between boys and girls increased with the increase in grade, which indicated the possible impact of puberty. Thompson and colleagues found that gender differences in PA disappeared when aligned with physical maturity (Thompson, BaxterJones, Mirwald, & Bailey, 2003). This finding supported the notion that maturity differences between genders (i.e., on average, girls mature earlier than boys) may be one reason why research consistently shows that girls are less active than boys of the same chronological age. Maturity status was not investigated within this study, and further research is needed to substantiate this claim. In the past 10 years, the prevalence of obesity among Chinese children and youth has increased at an alarming rate. Lack of PA has been hypothesized to be an important contributing factor in the development and/or maintenance of childhood obesity. However, findings regarding the relationship between PA and obesity are mixed. Researchers have found that obese children exhibit significantly less time in daily total PA, MPA, and VPA (Trost, Kerr, Ward, & Pate, 2001). A study among 3,147 U.S. students demonstrated that

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TABLE 9 PA Levels by Age Determined by Freedson’s Cutoff Points (mean ^ SD, min/day) Age Freedson’s thresholds (4, 7 METs) 9

10

11

12

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13

14

15

16

17

Total

Freedson’s thresholds (3, 6 METs) 9

10

11

12

13

14

15

16

17

Total

Gender

LPA

MPA

VPA

MVPA

Meeting MVPA Recommendation (%)

Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All

300.91 ^ 45.97 313.15 ^ 53.23 309.33 ^ 51.21 324.91 ^ 54.24 317.90 ^ 69.25 320.67 ^ 63.73 312.54 ^ 57.47 303.94 ^ 73.10 308.19 ^ 65.86 295.67 ^ 84.97 251.05 ^ 64.51 273.20 ^ 78.47 289.69 ^ 79.55 267.21 ^ 74.95 278.76 ^ 78.06 251.05 ^ 73.08 232.85 ^ 61.43 242.90 ^ 68.60 242.45 ^ 72.58 226.12 ^ 61.21 236.54 ^ 68.98 229.53 ^ 55.61 220.91 ^ 42.01 223.86 ^ 49.59 210.41 ^ 32.38 217.72 ^ 33.58 213.29 ^ 33.10 261.95 ^ 88.22 255.64 ^ 83.87 258.81 ^ 86.12

65.05 ^ 25.60 51.89 ^ 18.78 56.00 ^ 21.92 58.41 ^ 21.31 46.36 ^ 16.74 51.11 ^ 19.55 54.04 ^ 20.19 38.98 ^ 19.03 46.43 ^ 20.98 39.02 ^ 18.72 29.26 ^ 17.31 34.10 ^ 18.64 42.51 ^ 19.70 27.25 ^ 15.57 35.09 ^ 19.36 35.99 ^ 17.56 26.40 ^ 16.40 31.69 ^ 17.68 32.35 ^ 20.22 22.80 ^ 14.15 28.89 ^ 18.79 34.74 ^ 20.47 23.01 ^ 13.74 29.04 ^ 18.45 28.56 ^ 18.70 16.36 ^ 12.76 22.87 ^ 17.26 41.83 ^ 22.12 32.27 ^ 19.35 37.07 ^ 21.32

6.41 ^ 4.10 3.78 ^ 3.13 4.61 ^ 3.66 4.10 ^ 4.41 2.76 ^ 2.14 3.29 ^ 3.29 4.00 ^ 4.02 2.05 ^ 1.97 3.01 ^ 3.30 2.95 ^ 2.94 1.59 ^ 1.90 2.26 ^ 2.56 3.37 ^ 4.10 1.30 ^ 1.29 2.36 ^ 3.24 3.20 ^ 3.85 1.26 ^ 1.33 2.33 ^ 3.14 1.73 ^ 2.23 1.45 ^ 2.49 1.63 ^ 2.32 2.11 ^ 2.26 0.63 ^ 1.06 1.39 ^ 1.93 0.98 ^ 1.53 0.41 ^ 1.03 0.72 ^ 1.35 3.05 ^ 3.63 1.73 ^ 2.07 2.39 ^ 3.03

71.47 ^ 28.47 55.67 ^ 20.86 60.61 ^ 24.52 62.51 ^ 24.46 49.12 ^ 18.07 54.40 ^ 21.79 58.04 ^ 22.64 41.03 ^ 20.19 49.45 ^ 23.04 41.96 ^ 20.44 30.85 ^ 18.33 36.36 ^ 20.15 45.88 ^ 21.67 28.55 ^ 15.95 37.45 ^ 20.96 39.19 ^ 18.80 27.66 ^ 16.77 34.03 ^ 18.79 34.08 ^ 21.34 24.25 ^ 15.21 30.52 ^ 19.88 36.85 ^ 21.56 23.63 ^ 14.36 30.43 ^ 19.53 29.55 ^ 19.50 16.77 ^ 12.94 23.59 ^ 17.89 44.89 ^ 24.17 34.00 ^ 20.60 39.46 ^ 23.11

60.0 35.2 43.0 48.5 23.7 33.5 37.3 15.2 26.1 16.4 5.9 11.1 24.2 5.7 15.2 14.0 6.8 10.8 10.4 3.9 8.1 9.3 2.0 5.8 7.5 1.4 4.7 22.6 11.3 17.0

Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All Boys Girls All

240.88 ^ 41.78 252.55 ^ 44.46 248.90 ^ 43.82 265.08 ^ 44.69 264.01 ^ 60.43 264.43 ^ 54.67 261.21 ^ 50.02 258.86 ^ 62.87 260.02 ^ 56.78 258.00 ^ 76.21 219.82 ^ 57.92 238.77 ^ 70.15 252.41 ^ 70.12 236.41 ^ 67.01 244.63 ^ 68.99 219.94 ^ 66.87 203.88 ^ 55.17 212.75 ^ 62.32 215.40 ^ 67.18 200.53 ^ 56.88 210.02 ^ 63.91 202.75 ^ 51.61 193.63 ^ 37.13 198.83 ^ 45.34 186.48 ^ 27.61 193.71 ^ 30.05 189.32 ^ 28.97 224.11 ^ 77.34 218.53 ^ 72.31 221.33 ^ 74.91

113.66 ^ 30.82 106.01 ^ 29.31 108.40 ^ 29.88 110.40 ^ 28.14 94.90 ^ 25.83 101.01 ^ 27.77 98.02 ^ 26.75 80.11 ^ 31.65 88.97 ^ 30.62 71.40 ^ 26.23 57.58 ^ 24.44 64.43 ^ 26.23 73.87 ^ 28.43 55.54 ^ 22.51 64.96 ^ 27.27 62.20 ^ 25.61 53.52 ^ 23.43 58.31 ^ 24.99 55.46 ^ 25.03 46.69 ^ 18.84 52.29 ^ 23.32 58.09 ^ 24.43 49.25 ^ 17.71 53.80 ^ 21.84 49.90 ^ 23.94 39.74 ^ 19.10 45.16 ^ 22.33 74.16 ^ 32.90 66.29 ^ 31.91 70.24 ^ 32.64

17.84 ^ 10.82 10.26 ^ 7.08 12.63 ^ 9.10 11.94 ^ 10.03 8.10 ^ 5.67 9.62 ^ 7.90 11.36 ^ 8.36 5.99 ^ 5.23 8.65 ^ 7.44 8.24 ^ 7.01 4.50 ^ 4.88 6.36 ^ 6.30 9.29 ^ 8.30 3.80 ^ 3.72 6.62 ^ 7.04 8.10 ^ 7.02 3.12 ^ 3.07 5.87 ^ 6.12 5.66 ^ 6.18 3.15 ^ 4.75 4.76 ^ 5.82 5.54 ^ 5.17 1.67 ^ 2.33 3.66 ^ 4.48 3.58 ^ 4.22 1.04 ^ 1.70 2.39 ^ 3.52 8.57 ^ 8.08 4.81 ^ 5.25 6.70 ^ 7.07

131.50 ^ 38.06 116.27 ^ 34.11 121.03 ^ 35.95 122.34 ^ 33.87 103.00 ^ 28.77 110.63 ^ 32.24 109.38 ^ 31.45 86.11 ^ 34.82 97.62 ^ 35.13 79.63 ^ 30.41 62.08 ^ 27.29 70.79 ^ 30.14 83.16 ^ 32.25 59.35 ^ 23.76 71.58 ^ 30.80 70.29 ^ 28.17 56.64 ^ 24.60 64.18 ^ 27.44 61.13 ^ 28.36 49.84 ^ 20.93 57.04 ^ 26.43 63.63 ^ 27.57 50.92 ^ 19.05 57.46 ^ 24.60 53.48 ^ 26.57 40.79 ^ 19.69 47.56 ^ 24.38 82.73 ^ 37.73 71.10 ^ 35.37 76.94 ^ 37.02

97.5 97.7 97.7 98.0 93.4 95.2 95.8 74.5 85.0 69.4 45.6 57.4 71.0 40.9 56.4 58.5 39.8 50.2 43.3 25.0 36.7 54.2 28.7 41.8 38.8 14.3 27.3 68.1 53.9 61.1

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S25

TABLE 10 PA Levels by Grade Determined by Freedson’s Cutoff Points (mean ^ SD, min/day)

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Grade

Gender

LPA

Freedson’s thresholds (4, 7 METs) 4 Boys 316.24 ^ 53.74 Girls 321.56 ^ 59.54 All 320.15 ^ 57.99 5 Boys 324.59 ^ 53.46 Girls 319.08 ^ 74.58 All 321.99 ^ 64.26 6 Boys 289.24 ^ 55.17 Girls 263.76 ^ 50.69 All 275.75 ^ 54.19 7 Boys 298.53 ^ 84.84 Girls 263.60 ^ 69.87 All 282.49 ^ 80.15 8 Boys 269.50 ^ 74.27 Girls 263.11 ^ 72.97 All 266.16 ^ 73.54 9 Boys 237.17 ^ 71.30 Girls 217.22 ^ 54.23 All 228.34 ^ 64.97 10 Boys 218.26 ^ 75.42 Girls 179.59 ^ 46.09 All 204.90 ^ 69.13 11 Boys 207.45 ^ 39.50 Girls 188.97 ^ 40.79 All 201.35 ^ 43.35 Grade by School Level 4–6 Boys 314.51 ^ 55.67 Girls 308.98 ^ 67.90 All 311.35 ^ 62.95 7–9 Boys 270.50 ^ 82.02 Girls 249.66 ^ 69.81 All 260.66 ^ 77.17 10–11 Boys 212.19 ^ 73.02 Girls 183.94 ^ 47.97 All 202.13 ^ 63.77 Freedson’s thresholds (3, 6 METs) 4 Boys 254.84 ^ 47.25 Girls 263.42 ^ 50.86 All 261.14 ^ 49.97 5 Boys 268.53 ^ 47.33 Girls 268.49 ^ 66.53 All 268.51 ^ 57.11 6 Boys 243.26 ^ 45.64 Girls 225.46 ^ 42.40 All 233.84 ^ 44.70 7 Boys 260.40 ^ 75.15 Girls 231.72 ^ 62.40 All 247.23 ^ 70.96 8 Boys 236.63 ^ 66.40 Girls 232.67 ^ 65.82 All 234.56 ^ 66.02 9 Boys 207.27 ^ 65.90 Girls 191.04 ^ 49.36 All 200.09 ^ 59.61 10 Boys 221.88 ^ 71.71 Girls 196.28 ^ 44.41 All 213.19 ^ 66.24 11 Boys 182.11 ^ 34.24 Girls 188.97 ^ 40.79 All 185.75 ^ 38.23

MPA

VPA

MVPA

Meeting MVPA Recommendation (%)

62.40 ^ 22.63 47.91 ^ 17.58 51.75 ^ 20.05 57.99 ^ 21.64 45.26 ^ 18.92 51.98 ^ 21.34 47.03 ^ 16.79 37.68 ^ 18.26 42.08 ^ 18.14 41.90 ^ 20.54 27.60 ^ 16.24 35.34 ^ 19.98 38.69 ^ 18.18 28.00 ^ 15.39 33.11 ^ 17.59 34.50 ^ 17.95 23.22 ^ 15.60 29.50 ^ 17.83 26.94 ^ 17.73 21.65 ^ 14.28 25.11 ^ 16.77 35.41 ^ 20.69 45.21 ^ 18.50 27.56 ^ 18.98

5.36 ^ 3.69 3.14 ^ 2.59 3.73 ^ 3.08 4.18 ^ 4.47 2.73 ^ 2.37 3.50 ^ 3.70 3.14 ^ 3.53 1.82 ^ 2.06 2.44 ^ 2.92 3.26 ^ 3.04 1.50 ^ 1.58 2.45 ^ 2.63 3.23 ^ 4.97 1.21 ^ 1.31 2.18 ^ 3.70 2.75 ^ 2.87 1.17 ^ 1.17 2.05 ^ 2.41 1.55 ^ 2.26 1.24 ^ 2.67 1.44 ^ 2.41 1.64 ^ 2.21 1.29 ^ 2.01 1.03 ^ 1.79

67.76 ^ 25.11 51.05 ^ 19.16 55.48 ^ 22.12 62.17 ^ 24.69 47.99 ^ 20.56 55.48 ^ 23.87 50.16 ^ 18.85 39.50 ^ 19.36 44.52 ^ 19.79 45.16 ^ 22.24 29.10 ^ 16.99 37.79 ^ 21.52 41.93 ^ 20.09 29.21 ^ 15.66 35.28 ^ 18.98 37.25 ^ 19.18 24.39 ^ 15.97 31.56 ^ 18.92 28.49 ^ 18.96 22.89 ^ 15.51 26.55 ^ 18.00 37.05 ^ 21.82 46.50 ^ 19.45 28.59 ^ 19.97

54.1 26.0 43.0 48.2 25.7 33.5 19.4 11.1 26.1 21.9 4.3 11.1 20.1 6.6 15.2 11.7 4.9 10.8 6.4 4.5 8.1 9.2 1.6 5.8

56.27 ^ 21.44 44.85 ^ 18.58 49.76 ^ 20.63 38.60 ^ 19.33 26.42 ^ 15.89 32.85 ^ 18.79 31.09 ^ 19.66 20.69 ^ 13.85 26.49 ^ 18.07

4.17 ^ 4.17 2.72 ^ 2.45 3.34 ^ 3.38 3.08 ^ 3.59 1.31 ^ 1.39 2.25 ^ 2.91 1.59 ^ 2.23 0.73 ^ 1.79 1.21 ^ 2.09

60.44 ^ 24.24 47.57 ^ 20.15 53.10 ^ 22.89 41.68 ^ 20.94 27.73 ^ 16.39 35.10 ^ 20.16 32.68 ^ 20.81 21.42 ^ 14.58 27.70 ^ 19.14

42.6 22.9 31.3 18.0 5.2 12.0 7.8 2.6 5.5

114.15 ^ 27.73 100.62 ^ 28.41 104.21 ^ 28.80 106.24 ^ 27.16 90.63 ^ 29.74 98.87 ^ 29.42 86.76 ^ 26.24 71.88 ^ 26.88 78.88 ^ 27.52 74.13 ^ 29.22 56.78 ^ 22.91 66.16 ^ 27.86 66.37 ^ 25.24 56.47 ^ 23.93 61.20 ^ 25.02 59.80 ^ 23.44 47.49 ^ 20.78 54.35 ^ 23.09 49.58 ^ 22.80 46.57 ^ 19.19 48.54 ^ 21.62 57.07 ^ 25.61 45.21 ^ 18.50 50.95 ^ 22.96

15.01 ^ 9.59 8.57 ^ 6.03 10.28 ^ 7.67 11.99 ^ 9.63 7.96 ^ 6.31 10.09 ^ 8.47 9.39 ^ 8.01 5.92 ^ 5.83 7.55 ^ 7.13 9.16 ^ 7.46 4.20 ^ 4.17 6.89 ^ 6.64 8.43 ^ 8.44 3.17 ^ 2.98 5.68 ^ 6.74 7.36 ^ 6.63 3.09 ^ 3.20 5.47 ^ 5.78 4.29 ^ 5.37 2.64 ^ 4.89 3.72 ^ 5.26 5.32 ^ 5.16 1.29 ^ 2.01 3.24 ^ 4.36

129.15 ^ 33.89 109.20 ^ 32.15 114.49 ^ 33.72 118.23 ^ 32.93 98.59 ^ 33.53 108.96 ^ 34.58 96.14 ^ 30.02 77.79 ^ 30.20 86.43 ^ 31.40 83.30 ^ 33.32 60.98 ^ 25.06 73.05 ^ 31.79 74.80 ^ 28.88 59.64 ^ 24.85 66.88 ^ 27.86 67.15 ^ 26.49 50.57 ^ 22.29 59.81 ^ 26.03 53.87 ^ 25.96 49.20 ^ 21.19 52.26 ^ 24.46 62.39 ^ 28.55 46.50 ^ 19.45 54.19 ^ 25.51

98.4 96.4 97.7 97.6 87.5 95.2 88.9 66.7 85.0 70.8 45.2 57.4 64.0 39.5 56.4 54.4 30.1 50.2 40.0 28.8 36.7 48.3 19.5 41.8 (continued)

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C. WANG ET AL.

TABLE 10 (Continued) Grade

Gender

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Grade by School Level 4–6 Boys Girls All 7–9 Boys Girls All 10–11 Boys Girls All

LPA

MPA

VPA

MVPA

Meeting MVPA Recommendation (%)

259.77 ^ 47.96 257.69 ^ 58.11 258.58 ^ 53.95 236.48 ^ 73.43 219.93 ^ 62.75 228.67 ^ 69.06 214.83 ^ 69.73 196.94 ^ 44.19 203.48 ^ 60.48

103.20 ^ 28.66 91.05 ^ 30.47 96.27 ^ 30.29 67.33 ^ 27.05 53.92 ^ 22.97 61.00 ^ 26.07 53.25 ^ 24.46 45.67 ^ 18.70 49.90 ^ 22.39

11.98 ^ 9.42 7.80 ^ 6.16 9.60 ^ 8.00 8.37 ^ 7.49 3.55 ^ 3.58 6.09 ^ 6.44 4.79 ^ 5.28 1.75 ^ 3.34 3.45 ^ 4.77

115.18 ^ 34.32 98.86 ^ 34.25 105.87 ^ 35.20 75.70 ^ 30.78 57.46 ^ 24.57 67.09 ^ 29.45 58.04 ^ 27.54 47.42 ^ 20.05 53.35 ^ 25.05

95.7 87.1 90.8 63.6 38.9 51.9 44.1 22.7 34.6

overweight/obese children were less active than nonoverweight children (Chung et al., 2012). On the contrary, there are also studies that have shown no differences in MVPA or sedentary time between BMI categories (Ruiz et al., 2011; Spinks, Macpherson, Bain, & McClure, 2007; Trost et al., 2001). In the present study, we did not observe differences in PA and SB across BMI categories. Strengths and Limitations The major strength of this study is that it is the first study to use an objective monitoring device to assess PA and SB in a large sample of Chinese city children and youth. To measure children and youth PA using objective measures is important because young children often have difficulty recalling their past behavior accurately. In addition, we adopted the cutoff points specifically developed for Chinese children and youth as one of the definitions to determine the intensity of PA, which may be more appropriate for the studied population. Meanwhile, there were a few limitations to this study. First, the participants in each city were recruited by convenience and were therefore not a random or representative sample. Second, the epoch was set at 60 s. A validation study with the ActiGraph showed that minutes of high activity were substantially underestimated when using longer epoch time (i.e., 60-s epoch time) due to the nature of short bursts of PA in this population (Edwardson & Gorely, 2010). Third, accelerometers are not sensitive to detect movements such as cycling, skating, and climbing stairs. The PA level of Chinese city children and youth—a large portion of whom use bicycles as their main commuting mode—might be underestimated by accelerometry. Last, the compliance rate for providing valid accelerometer data in the current study (69.3%) was relatively low compared with other large-scale studies using accelerometers that were conducted in Canada (76.3%; Colley et al., 2011) and Europe (88.0%; Ruiz et al., 2011), especially when considering that the inclusion criteria for the number of days of wearing the accelerometer was 3 in the current study

in contrast to 4 in those studies. Efforts should be made in future studies to improve the compliance rate among Chinese children and youth.

CONCLUSION Large proportions of Chinese city children and youth did not meet PA recommendations and spent a large portion of time being sedentary. Chinese city children and youth were more active during weekdays than during weekend days, boys were more active than girls, and older children and youth spent more daily time in MVPA but also more time being sedentary; no differences in PA or SB were found across different BMI categories. Intervention strategies are warranted to promote PA participation and to decrease SB in Chinese city children and youth, especially during weekends and among girls.

WHAT DOES THIS ARTICLE ADD? Due to the significant impact of PA and SB on the health of children and youth, an accurate understanding of the prevalence of such behaviors is of great importance to researchers and policymakers. Objective measures of PA and SB (e.g., accelerometers and pedometers, which are considered valid and reliable instruments and suitable in large-scale studies) have been applied in large-scale studies among youth in Western countries, such as the United States and Canada. However, population-based PA assessments among Chinese children and youth have relied on selfreports or proxy-reports (Tudor-Locke et al., 2003). Data of objectively measured PA and SB among the young Chinese population are lacking. The present study addressed this knowledge gap by providing objective information about patterns of PA and SB in a large sample of Chinese children and youth from 11 cities using accelerometry. Accelerometer cutoff points for defining intensities of PA used in this study were developed specifically for Chinese children and youth and therefore enable us to provide a more precise

PA AND SEDENTARY BEHAVIOR OF CHINESE YOUTH

estimation of PA levels in the study population. This study helps to enhance our understanding of the sedentary lifestyle of Chinese city children and youth. The findings of this study will inform the development of intervention strategies by targeting youth who are at risk for physical inactivity and targeting the period when they are likely to be sedentary.

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