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Accelerometer-determined physical activity among elementary school-aged children with autism spectrum disorders in Taiwan
Research in Autism Spectrum Disorders 5 (2011) 1042–1052
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Accelerometer-determined physical activity among elementary school-aged children with autism spectrum disorders in Taiwan Chien-Yu Pan a,*, Chia-Liang Tsai b, Kai-Wen Hsieh b, Chia-Hua Chu a, Ya-Lin Li a, Shih-Tse Huang a a b
Department of Physical Education, National Kaohsiung Normal University, No. 116, He-Ping First Road, Kaohsiung 802, Taiwan Institute of Physical Education, Health and Leisure Studies, National Cheng Kung University, Tainan 701, Taiwan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 November 2010 Accepted 29 November 2010 Available online 24 December 2010
To examine age-related physical activity (PA) patterns between- and within-day in elementary school-aged children with autism spectrum disorders (ASD). PA was recorded every 5-s by uniaxial accelerometry in 35 children (grades 1–2, n = 13; grades 3–4, n = 13; grades 5–6, n = 9) for up to five weekdays and two weekend days. Younger children were more active during weekend days compared with weekdays, while the opposite was observed in older children. Age variation also exists in children’s PA levels within a weekday, with this effect being most evident during recess and after school. Weekend days and free time within school days seem appropriate targets when promoting PA in older children with ASD. ß 2010 Elsevier Ltd. All rights reserved.
Keywords: Physical activity Accelerometry Autism Children
1. Introduction Regular physical activity (PA) is an important factor to promote and maintain a healthy lifestyle along the whole life cycle. Numerous studies have indicated that higher levels of PA are associated with reduced risk of obesity (Ekelund et al., 2004), prevention of clustering of cardiovascular disease risk factors (Andersen et al., 2006), enhanced motor skill proficiency (Houwen, Hartman, & Visscher, 2009), and less body fat and greater aerobic fitness (Dencker et al., 2008) in children. The significance of PA to the health of children has led to increased interest in monitoring compliance with PA guidelines in this population. The most consensus recommendation is that children should participate in at least 60 min of moderate PA (MPA) on most days of the week (U.S. Department of Health and Human Services (USDHHS) and Department of Agriculture, 2005), and accumulate 12,000 and 15,000 daily steps for ages 6–12 girls and boys, respectively (Tudor-Locke et al., 2004). In addition, current guidelines for physical education (PE) suggest that children should be active for at least 50% of PE class time, and schools should provide daily lessons for children in order for PE to meaningfully contribute toward the daily PA accumulation (USDHHS, 2000). Although the empirically tested PA guidelines do not exist for recess, researchers suggested that children should be physically active for 40% (Ridgers, Stratton, & Fairclough, 2005) or 50% (Stratton & Mullan, 2005) of recess time because they are exposed to these times on a daily basis for PA participation. These recommendations, though not specific to individuals with disabilities, may hold true for healthy individuals with mild or high-functioning autism spectrum disorders (ASD) who are often included into general school contexts. ASD is a developmental disorder characterized by difficulties in social interaction, language and communication, as well as by repetitive, restricted interest and behaviors (American Psychiatric Association, 1994). Various researchers have also noted differences of motor skills in school-aged children with ASD (Green et al., 2009; Ozonoff et al., 2008; Pan, Tsai, & Chu,
* Corresponding author. Tel.: +886 7 7172930x3531; fax: +886 7 7114633. E-mail address: [email protected] (C.-Y. Pan). 1750-9467/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.rasd.2010.11.010
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2009). These social and behavioral deficits and sometimes motor skill difficulties could limit opportunities for individuals with ASD to successfully participate in PA, and therefore, may put them at risk for being physically inactive. However, there is uncertainty regarding activity levels of children with ASD and the percentage who meet current PA recommendations in Taiwan. Since ASD is the second most common type among Taiwan elementary school-aged students with developmental disabilities and the prevalence rate of ASD diagnoses continues to rise (Taiwan Ministry of Education, 2009), accurate estimates of habitual PA levels in children with ASD, including proportions who meet stated recommendations about PA, will provide important baseline information and increase knowledge about variations in PA levels of this population. To understand PA behaviors, Deci and Ryan’s self-determination theory can be a useful theoretical framework for the study of PA in youths with ASD (Deci & Ryan, 1985, 2000). Self-determination theory includes both a psychological needs and a multidimensional motivation orientation for understanding human behaviors. That is, individuals are assumed to have three basic innate needs, and the satisfaction of those needs through social environments presumably influences motivation and ultimately leads to important cognitive, affective, and behavioral consequences. A recent study in adolescents with ASD examining their PA and self-determined motivation in PE found that external regulation was positively correlated with the percentage of time that adolescents with ASD spent in MPA and moderate-to-vigorous PA (MVPA), and this extrinsic motive was associated with their needs of being attached or related in the class (Pan, Tsai, Chu, & Hsieh, 2010). Furthermore, studies (Bass, Duchowny, & Llabre, 2009; Pan, 2010; Pitetti, Rendoff, Grover, & Beets, 2007; Wuang, Wang, Huang, & Su, 2010) suggest that children with ASD can be introduced to a PA training program and learn variety of skills under close supervision as well as structured teaching and various supports. Therefore, PA behaviors of children with ASD may be more affected by social and environmental constraints rather than the actual impairment. Previous studies in children without disabilities using objective measurements of PA have suggested that daily PA was significantly lower during weekend days compared with weekdays (Kristensen et al., 2008; Nyberg, Nordenfelt, Ekelund, & Marcus, 2009; Rowlands, Pilgrim, & Eston, 2008). In addition, PA has been suggested to decline by age at least after 9–10 years of age (Caspersen, Pereira, & Curran, 2000; Sallis, 2000), but it is still not clear at what age this decrease happens. In children, weekdays and weekend days are likely to provide different opportunities for being active, as well as various segmented time periods within a weekday (e.g., PE, recess, lunch break, after school). Assessing time in PA between days and within days is of interest to increase our understanding about variation in PA behavior of children with ASD. However, data regarding PA patterns in children with ASD are apparently lacking and there are few published PA studies that have included this population. A limited number of studies in youths with ASD have examined the influence of temporal sources of variation using accelerometry (Pan, 2008a, 2008b; Pan & Frey, 2006; Rosser-Sandt & Frey, 2005). Pan and Frey (2006) examined PA patterns (weekdays vs. weekend days; in school vs. after school) in 30 American youths with ASD aged 10–19, and found no differences in total PA or MVPA on between-day and within-day variability according to school level. PA declined with age in this group, and only 47% of youths with ASD accumulated recommended daily 60 min of MVPA. Rosser-Sandt and Frey (2005) compared PE, recess, after school, and daily MVPA of American children with (n = 15) and without (n = 13) ASD aged 5–12. There were no MVPA differences between weekdays and weekend days, and no significant differences existed between group PA levels at any setting. Children with ASD engaged in relatively similar MVPA in recess (58%), during PE (41%), and after school (29%) as compared to children without ASD. When time periods were compared, both groups spent more time in MVPA during recess and PE as compared to after school period. However, Pan (2008b) compared MVPA of children with (n = 24) and without (n = 24) ASD (aged 7–12) during inclusive PE and recess in Taiwan, and results were somewhat different from previous findings (Rosser-Sandt & Frey, 2005). Both children with and without ASD in this study (Pan, 2008b) spent a higher proportion of time in MVPA during PE (46% and 47%, respectively) than during recess (28% and 36%, respectively), although there were no significant differences existed between group PA levels at any setting. Furthermore, Pan (2008a) broke daily recess time into 7 blocks (3 morning recesses, lunch break, and 3 afternoon recesses) based on the educational system of Taiwan, and compared MVPA levels of children with and without ASD. Children with ASD were less active during overall recess (28%), lunchtime (17%), first (33%) and second (36%) morning recess compared to those without disabilities. All children in this study (Pan, 2008a) did not achieve 40% of recess time in PA. Differences in data reduction and analysis procedures from the aforementioned studies, combined with various age groups and diverse cultures, have made conclusions about variability in PA patterns of youths with ASD between and within days elusive. The patterns of PA in children with ASD across days and within days are not well examined in Taiwan. This knowledge is important when identifying possible arenas and settings when planning preventive initiatives aimed at increasing levels of PA in this population. Therefore, the aim of this study was to examine differences in patterns of objectively measured PA among weekdays and weekend days and among different time periods within a weekday and how these patterns are influenced by age in a sample of Taiwanese elementary school-aged children with ASD. The relative importance of each time period to total daily MVPA accumulation during weekdays as well as the percentage of children meeting PA guidelines was also evaluated. It was hypothesized that older children with ASD would be less active than younger children both between days and within days. 2. Methods 2.1. Participants and settings A convenience sample of 35 boys with ASD from 23 primary schools, aged 7–12 years, volunteered to participate. All children met the DSM-IV (American Psychiatric Association, 1994) criteria for autistic disorders and Asperger’s syndrome, as
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Table 1 Participant demographics.
Age (years) Height (cm) Weight (kg) BMI (kg/m2) Diagnosis Asperger Mild autism Therapy Physical therapy Group therapy Occupational therapy Speech therapy Sensory integration therapy Medications Ritalin Concerta After school PA enrollment Tae Kwon Do Swimming Horse-back riding Tai Chi Fitness training Inline skating
Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
7.56 126.19 28.41 17.72
9.57 136.82 35.99 19.13
11.82 149.78 42.67 19.03
(0.76) (4.95) (5.73) (2.54)
(0.50) (5.88) (9.77) (4.65)
4 9
6 7
3 6
4 3 5 3 4
1 2 4 3 2
0 1 3 1 1
3 2
2 2
0 2
1 2 1 0 1 1
1 0 0 0 1 0
0 1 0 1 0 0
(0.36) (6.37) (7.56) (3.18)
Note. Group mean (SD); BMI = body mass index.
assessed by psychiatrists and physicians in the hospitals (Taiwan Executive Yuan Department of Health, 2009a). Diagnosis included 13 Asperger’s syndrome and 22 mild autistic disorders. Level of severity (mild, moderate, severe, and very severe) is based on functioning in the social adaptive skill areas and language comprehension and expression (Taiwan Executive Yuan Department of Health, 2009b). All participants resided in the same geographical area of high social and economic deprivation in a large urban city in Taiwan (n = 1,527,914) (Taiwan Kaohsiung City Government Department of Budget Accounting and Statistics, 2010). Participants were divided into three groups according to their grade levels: lower grade (grades 1–2, n = 13), middle grade (grades 3–4, n = 13), and upper grade (grades 5–6, n = 9) to address potential differences in developmental factor and PA opportunities. All children with ASD were enrolled in regular school and received most of their studies in regular classrooms while occasionally attended the resource room for special education services. Each school had 3 morning recesses, a lunch break, and 3 afternoon recesses during the whole-day (approximately 8 h a day) school days, and had 3 morning recesses and/or a lunch break during the half-day (approximately 4 h a day) school days. Days to attend school whole day or half day in a week vary and depend on the school district and children’s grade level. Usually, lower grade students take 1 whole day and 4 half days, while middle and upper grade students take 1 half day and 4 whole days during school days. Each morning and afternoon recess was scheduled for 10–20 min each day. In addition, the PE lesson was 40 min in duration, and students in lower grade and those in middle and upper grades were required to take 1 and 2 lessons each week, respectively. Furthermore, the average daily lunch break was 40 min and was held in the classroom; students were typically encouraged by class teacher to finish eating in approximately 20 min and to clean up and play for approximately the last 20 min (in the classroom or outside). These times are approximate; this schedule was not rigidly enforced, and students were free to play as long as they wished. Participant demographics are presented in Table 1. 2.2. Instrument PA was measured using the MTI accelerometer (Actigraph 7164, Manufacturing Technology Inc., Fort Walton Beach, FL, USA), a uniaxial accelerometer that measures vertical acceleration of human motion as well as step counts. The accelerometer has been used extensively and reported as a valid objective measure of PA in youths (Trost et al., 1998). It has also been used in research on youths with ASD (Pan, 2008b; Pan & Frey, 2006). Actigraph data are in counts per user-specified time intervals and represent the intensity of the activity during each time period. For the current study, accelerometers were programmed to collect data in 5-s intervals because children tend to do activities in short bursts and are more sporadic than adults (USDHHS, 2000). The output of the raw accelerometer counts was uploaded and then converts to calories to determine the time spent in MPA (3–5.99 METs), vigorous PA (VPA, 36 METs), and MVPA (33 METs). The age-specific count thresholds in 1-min epoch corresponding to these in intensity levels were used (Freedson, Melanson, & Sirard, 1998), and the appropriate age-specific count cutoffs were divided by 12 to accommodate the 5-s epoch length. Due to the differences in the monitoring length, the relative (percentage) time spent in total PA (counts per minute, CPM), MPA (MPA%), VPA (VPA%), MVPA (MVPA%) were calculated and used in the subsequent analyses.
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2.3. Procedures The study protocol was approved by the university review board for the protection of human subjects. Parental consent and student assent were obtained for all participants. The administration of accelerometers was conducted in collaboration with the schools and therefore the measurement period followed the school year, with the majority of measurements performed between the months of March and June. Before the start of the measurement, participants were instructed on accelerometer attachment (at the right waist), its removal (only during showering, bathing, swimming, or sleeping), and reattaching the accelerometer each morning upon awakening and dressing. They were also instructed to engage in their normal levels of PA and not to tamper with the accelerometer during the monitoring frame. Following a standardized protocol, the participant’s body mass (to the nearest 0.1 kg) and stature (to the nearest 0.5 cm) were directly measured without shoes using an automatic fitness measuring system (The Accuratus ACC-810, Taiwan). The accelerometers were initialized before placement on an elastic belt provided by the study and worn on each participant’s right waist. All participants wore the device during waking hours, except bathing or water activities, for 7 consecutive days (5 weekdays and 2 weekend days). They were given a brief log to record when they put on the Actigraph each morning and the time they removed it each evening. To ensure data completeness and quality, a research assistant collected the accelerometer just prior to the child’s bedtime every 2–3 days during the monitored days, and gave another initialized accelerometer for the following days. Data were immediately downloaded and checked (e.g., data sheets were reviewed, and missing and odd values were queried the next day). 2.4. Data reduction and statistical analysis Descriptive data were calculated for all variables by children’s grade level. Body mass index (BMI) was computed as kg/m2. For inclusion in the analyses, a child needed a minimum of 10 h wearing time each day for at least 4 weekdays and 1 weekend day. Intraclass correlation coefficients and 95% confidence intervals were calculated to investigate the intra- and interindividual variation in activity counts across different days of assessment (2 weekend days and 5 weekdays). All data from weekdays (school days) were divided into four time periods: PE, recess, lunch break, and after school, according to the child’s schedule reported by classroom teacher. To account for differences in the time-period length, the relative (percentage) time spent in each PA level was calculated and used in the subsequent analyses. Therefore, inferential statistics were undertaken on these variables: CPM, MPA%, VPA%, and MVPA%. Percentage of time for each time period spent in each PA level according to total monitoring time of the period was calculated by summing the minutes at that PA level for all sessions of that time period, and dividing the minutes of total monitoring time (actual registered time) of that period. Each PA level attributable to each time period represents the average of 4–5 valid days. Because PE was only offered on one or two of the data collection school days, PA levels attributable to PE represent the average of only those days. If there was a difference between monitoring length of specific time period across children’s grade levels, one-way ANCOVA controlling for the monitored length of that time period was used to examine the proportion of time for children’s PA levels at that time period. If there was no group difference between monitoring length of each time period, one-way ANOVAs were used to examine the proportion of time for children’s PA levels at each time period within the segmented school day. Next, the contribution of MVPA during each time period to daily total MVPA across children’s grade levels was also evaluated by a two-factor mixed-model ANOVA with repeated measures on time period of a school day. The percentage of time spent in MVPA was calculated by summing the MVPA minutes for all sessions of that time period, and dividing the minutes of total monitoring time that day. Tukey’s post hoc tests were undertaken if significant difference or interaction between factors were observed. Furthermore, all data were calculated separately for weekdays and weekend days. The dependent variables used for analysis were percentage of time spent in each PA level: CPM, MPA%, VPA%, and MVPA%. Children’s grade level differences in PA variables by day of week (weekday and weekend) were assessed with a two-factor mixed-model ANOVAs with repeated measures on day of week. Post hoc Tukey’s test was used where significant difference or interaction between factors were statistically significant. Finally, the proportion of children who achieved the recommended levels of daily average 60 min of MVPA was established based on two types of days across different grade levels. In addition, the proportions of boys meeting daily average 15,000 steps were also evaluated as indicative of meeting the BMI-referenced PA cut points (Tudor-Locke et al., 2004). All data were analyzed by SPSS version 13.0 for Windows (SPSS Inc., Chicago, IL), and an alpha level was set at .05. 3. Results Of the total 35 participants in the current study, all completed data collection requirements (e.g., provided at least 4 weekdays and 1 weekend day of at least 600 min per day recorded). Seventy-one percent (n = 25) of children had two valid weekend days and 94% (n = 33) had five valid weekdays, leading to a total of 233 valid PA registration days. Intraclass correlation coefficients demonstrated moderate to strong relationships between measured days on total PA: weekend days, R = .79, CI .52–.91 and weekdays R = .78, CI .64–.88.
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3.1. Comparisons of physical activity levels during the segmented school day (weekday) Mean minutes and proportion of time for children’s PA levels over five school days are presented in Table 2. There were no grade level differences in total monitored length for each time period monitored (PE: F2,32 = 0.56, p = .58; recess: F2,32 = 2.92, p = .07; lunch break: F2,32 = 0.22, p = .81) except after school segment (F2,32 = 31.14, p < .01). Therefore, one-way ANCOVA controlling for monitored length was only used for after school time period to analyze group differences in after school PA during weekdays. Group differences in PA levels at each time period. As shown in Table 2, no differences on any PA variables among three grade levels of children with ASD were only observed in PE. All children were similarly active during PE. For recess, total PA and VPA were significantly higher in lower grade children as compared to middle grade children. In addition, lower grade children also engaged more percentage of time in MPA and MVPA than both middle and upper grade children. For lunch break, total PA was significantly higher in upper grade children than both middle and lower grade children, while PA intensity levels were similar for all children. For after school, total PA and each PA intensity level were significantly higher in lower grade children than those of children in middle and upper grades. Group differences in the contribution of MVPA for each time period to daily total MVPA. Results of two-way ANOVA with repeated measures on time period of day showed that there were no differences in the contribution of MVPA for each time period to daily total MVPA among three age groups of children with ASD (F2,32 = 1.59, p = .22). However, there were significant differences between the four time periods on the contribution of MVPA (F3,96 = 137.59, p < .01, partial h2 = 0.81, observed power = 1.00). After school MVPA significantly contributed to daily total MVPA more than PE (+22.69%), lunch break (+28.23%), and recess (+30.24%). The contribution of MVPA during PE was also significantly higher than recess (+7.56%) and lunch break (+5.55%). Furthermore, significant grade by time interaction effect was observed (F6,96 = 2.78, p < .05, partial Table 2 Physical activity, expressed in minutes and percentage of monitored length, within a school day and F-values of the proportion of time for children’s physical activity levels at each setting. Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
Minutes
Minutes
Minutes
Physical education Length 38.58 (11.84) Counts 39,216.88 (22,475.28) Steps 884.27 (487.05) MPA 6.91 (3.44) VPA 5.54 (3.67) MVPA 12.45 (5.86) Recess Length 13.09 (1.76) Counts 17,544.31 (9499.67) Steps 458.85 (227.75) MPA 3.13 (1.18) VPA 2.51 (1.47) MVPA 5.63 (2.09) Lunch break Length 40.38 (10.10) Counts 14,432.51 (9227.13) Steps 451.72 (299.54) MPA 4.28 (2.22) VPA 1.58 (1.40) MVPA 5.86 (3.38) After school Length 335.54 (51.00) Counts Steps MPA VPA MVPA
141,628.52 (30,820.89) 3115.53 (533.23) 33.56 (6.58) 17.08 (4.74) 50.63 (10.31)
%
1069.49 (668.99) 22.93 (14.15) 18.15 (7.65) 15.31 (11.14) 33.46 (16.29)
1304.70 (650.62) 32.51 (15.25) 23.60 (6.87) 18.53 (10.15) 42.06 (12.13)
349.13 (201.30) 10.93 (6.07) 10.48 (5.17) 3.75 (3.01) 14.23 (7.52)
35.85 (1.64) 42,213.69 (20,960.15) 1027.46 (555.39) 6.30 (2.56) 5.68 (3.62) 11.99 (5.62) 12.85 (1.38) 9817.18 (3787.53) 314.23 (135.28) 2.10 (0.93) 1.07 (0.61) 3.16 (1.25) 40.48 (8.03) 15,606.36 (6295.06) 508.52 (223.62) 3.96 (1.89) 1.40 (0.74) 5.36 (2.44)
%
1188.20 (592.00) 28.94 (15.90) 17.70 (7.29) 15.97 (10.03) 33.67 (15.81)
761.76 (271.43) 24.07 (8.52) 16.07 (5.67) 8.33 (4.59) 24.29 (8.00)
390.29 (160.57) 12.65 (5.38) 9.83 (4.54) 3.59 (2.16) 13.42 (6.29)
259.62 (10.00) 444.51 (181.24) 9.46 (3.69) 10.24 (2.47) 5.36 (2.30) 15.60 (4.60)
99,516.36 (34,915.81) 2769.64 (809.76) 22.61 (6.71) 9.64 (5.14) 32.25 (11.02)
385.01 (138.63) 10.71 (3.23) 8.74 (2.65) 3.74 (2.02) 12.48 (4.37)
35.83 (2.37) 36,088.09 (26,266.93) 821.38 (619.09) 5.32 (3.54) 4.32 (3.16) 9.71 (6.55) 11.20 (2.67) 11,933.83 (5081.34) 323.53 (134.72) 1.81 (0.61) 1.35 (0.71) 3.16 (1.68) 38.33 (5.00) 24,240.36 (11,825.07) 691.22 (302.01) 4.21 (1.78) 2.27 (1.43) 6.48 (3.10) 205.94 (44.26) 99,842.21 (63,860.07) 2467.81 (1684.96) 15.37 (8.58) 10.92 (9.67) 26.28 (17.85)
F
Post hoc
%
1020.36 (745.14) 23.36 (17.69)
0.19 0.58
14.97 (9.87) 12.24 (9.04) 27.41 (18.49)
0.45 0.38 0.46
1028.39 (287.61) 28.24 (9.38)
4.63* 1.72
15.97 (3.59) 11.52 (4.95) 27.49 (7.90)
7.11** 6.66** 11.96**
1 > 2, 3 1>2 1 > 2, 3
619.65 (245.07) 17.72 (6.10)
5.37*
3 > 1, 2
3.81*
3>1
10.82 (3.62) 5.76 (3.10) 16.58 (6.46)
0.13 1.95 0.59
501.30 (308.64) 12.53 (8.27)
5.12* 1.72
7.72 (4.20) 5.53 (4.65) 13.25 (8.70)
5.70** 4.63* 5.12*
1>2
1 > 2, 3
1 > 2, 3 1 > 2, 3 1 > 2, 3
Note. Values reported as mean (SD); MPA = moderate physical activity; VPA = vigorous physical activity; MVPA = moderate-to-vigorous physical activity. * p < .05. ** p < .01.
[()TD$FIG]
C.-Y. Pan et al. / Research in Autism Spectrum Disorders 5 (2011) 1042–1052
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Fig. 1. Percentage of time spent in MVPA for each time period according to daily total MVPA; asignificantly different from physical education (PE), recess, and lunch; bsignificantly different from recess and lunch; csignificantly different from recess and lunch; dsignificantly different from PE and lunch.
h2 = 0.15, observed power = 0.86). Further analysis according to grade by time revealed that for lower grade children, after school MVPA significantly contributed to daily MVPA as compared to PE (+29.99%), recess (+35.21%), and lunch break (+35.27%); PE MVPA was also significantly higher than recess (+5.23%) and lunch break (+5.29%). For middle grade children, after school MVPA significantly contributed higher daily MVPA as compared with PE (+22.07%), lunch break (+29.01%), and recess (+31.56%); PE MVPA was also significantly greater than recess (+9.49%) and lunch break (+6.95%). For upper grade children, MVPA during after school significantly contributed more daily MVPA than recess (+23.95%) and lunch break (+20.40%); recess was significantly lower than PE ( 7.95%) and lunch break ( 3.55%). No grade level differences were observed at any time periods (Fig. 1). 3.2. Comparisons of physical activity levels by weekday and weekend day The average registered time was 820.19 49.47 min on weekdays (F2,32 = 0.38, p = .69) and 733.04 77.19 min on weekend days (F2,32 = 0.27, p = .77). Proportions of children who accumulated at least 60 min of MVPA each day are: lower grade, weekdays = 100% (n = 13), weekend days = 84.62% (n = 11); middle grade, weekdays = 100% (n = 13), weekend days = 84.62% (n = 11); upper grade, weekdays = 100% (n = 9), weekend days = 33.33% (n = 3). None of children met 15,000 steps per day either during weekdays or weekend days, except one child in middle grade during weekend days. Table 3 displays the data stratified by weekdays versus weekend days. Results of the two-way ANOVAs with repeated measures on day of week indicate that there were significant differences between the three grade levels for all PA variables, regardless type of day (Table 4). Children in lower grade were more active overall than those in middle (+98.55) and upper (+112.50) grades and spent more percentage of time in MPA, VPA, and MVPA compared to middle (+2.58, +1.97, and +4.55, respectively) and upper (+5.20, +2.66, and +7.86, respectively) grade children. Middle grade children also engaged in significantly more percentage of time in MPA (+2.62) and MVPA (+3.30). In addition, results of the mixed two-way ANOVAs showed that there were no significant PA differences between weekdays versus weekend days, regardless of children’s grade levels. However, significant grade-by-day interactions were evident on all PA levels, indicating inconsistent directions of between-day differences within grade groups. Table 5 provides further analysis according to children’s grade level and day of week at each of significant PA levels. For weekday PA, total PA was significantly higher in the lower (+106.65) and upper grade children (+88.98) as compared to middle grade children. Percentage of time spent in various intensities of PA were significantly higher in lower grade children than middle (MPA%: +2.72; VPA%: +2.07; MVPA%: +4.79) and upper grade children (MPA%: +3.42; VPA%: +1.35; MVPA%: +4.76). For weekend PA, total PA was significantly higher (+207.32) in lower than upper grade children. Percentages of time spent in various intensities of PA were significantly higher in lower grade children than upper grade children (MPA%: +6.98; VPA%: +3.97; MVPA%: +10.95). Middle grade children also spent significantly higher percentage of time in MPA (+4.54) and MVPA (+6.63) as compared to upper grade children. PA differences on day of week within each grade level showed that lower grade children did not differ on any of PA levels between weekdays and weekend days. For middle grade children, total PA (+69.74) as well as percentage of time spent in MPA (+1.88) and MVPA (+2.65) were significantly higher on weekend days than during weekdays. However, upper grade children were more active during weekdays than during weekend days (CPM [+136.10]; MVPA% [+3.54]; VPA% [+1.85]). 4. Discussion The aim of this study was to characterize age differences in the patterns of PA of various intensities in 7–12-year-olds children with ASD between and within days. Lower grade children were the most active both on weekdays and weekend days compared with the other two groups. In accordance with literature (Lopes, Vasques, Maia, & Ferreira, 2007; Pan & Frey, 2006) that there was an apparent PA differences with increasing age. Irrespective of total PA, the decline occurred in all three PA intensities evaluated (MPA, VPA, and MVPA) both on weekdays and weekend days. Furthermore, results on between-day
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Weekday
Length Counts Steps MPA VPA MVPA
Weekend day
Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
Minutes
%
Minutes
%
Minutes
%
Minutes
%
Minutes
%
Minutes
%
447.69 (102.96) 10.57 (2.04) 10.46 (1.42) 5.45 (1.37) 15.91 (2.44)
829.03 (49.66) 282,423.61 (47,994.86) 8096.94 (1575.91) 64.08 (13.94) 28.11 (8.78) 92.19 (18.30)
341.04 (55.66) 9.79 (1.94) 7.74 (1.60) 3.39 (1.00) 11.12 (2.07)
819.53 (59.37) 350,414.42 (54,181.30) 8937.90 (1079.19) 57.57 (10.51) 33.36 (7.99) 90.93 (15.75)
430.02 (76.02) 10.94 (1.36) 7.04 (1.26) 4.11 (1.13) 11.15 (2.11)
720.35 (77.08) 363,706.94 (136,486.03) 7585.85 (2820.28) 89.65 (32.04) 45.43 (21.02) 135.09 (49.90)
501.24 (186.81) 10.49 (3.76) 12.33 (4.27) 6.23 (2.91) 18.56 (6.70)
740.31 (78.85) 305,759.64 (100,659.98) 8111.46 (4162.18) 73.70 (27.76) 31.96 (15.15) 105.66 (39.39)
410.78 (111.79) 10.78 (4.72) 9.89 (3.22) 4.35 (2.19) 14.24 (4.89)
740.89 (81.64) 219,522.57 (96,228.05) 5510.56 (3108.49) 40.09 (16.81) 16.96 (10.65) 57.05 (26.29)
293.92 (114.34) 7.27 (3.58) 5.35 (1.96) 2.26 (1.25) 7.61 (3.03)
811.81 (44.23) 362,370.42 (78,181.66) 8569.43 (1588.26) 84.84 (11.95) 44.15 (10.73) 128.99 (19.63)
Note. Values reported as mean (SD).
C.-Y. Pan et al. / Research in Autism Spectrum Disorders 5 (2011) 1042–1052
Table 3 Physical activity, expressed in minutes and percentage of monitored length, between an average weekday and weekend day in children with autism spectrum disorders.
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Table 4 Two-way ANOVA with repeated measures on day of week. Variables
p
Partial h2
Observed power
5.12 0.03 6.53
.01 .86 .00
.24 .00 .29
0.79 0.05 0.88
15.95 2.20 4.93
.00 .15 .01
.50 .06 .24
0.99 0.30 0.77
9.83 0.01 5.39
.00 .92 .01
.38 .00 .25
0.97 0.05 0.81
15.95 0.81 6.01
.00 .38 .00
.50 .03 .27
0.99 0.14 0.85
F
CPM Grade level (G)* Day of week (D) G D** MPA% Grade level (G)** Day of week (D) G D* VPA% Grade level (G)** Day of week (D) G D* MVPA% Grade level (G)** Day of week (D) G D**
Note. CPM = counts per minute; MPA% = daily average percentage of time spent in moderate physical activity; VPA% = daily average percentage of time spent in vigorous physical activity; MVPA% = daily average percentage of time spent in moderate-to-vigorous physical activity. * p < .05. ** p < .01.
differences in PA levels were inconsistent within grade levels. Upper grade children showed a higher PA levels on weekdays compared with weekend days, while both lower and middle grade children demonstrated a higher PA levels during weekend days than during weekdays. The within-day differences observed are unique in the current study as compared with previous accelerometer studies (Pan, 2008a, 2008b; Pan & Frey, 2006; Rosser-Sandt & Frey, 2005), highlighting particular time periods of the school day when grade level differences are most marked (e.g., recess and after school periods). In accordance with previous findings in youths with ASD (Pan & Frey, 2006) and those without a disability (Lopes et al., 2007), younger children were more active than older children. Part of the age differences in PA levels might be explained by more scheduled time spent at school with increasing age. It is possible that removal of the structured school environment at weekend days is detrimental to some children’s activity levels, with this effect being particularly noticeable in upper grade children. This is supported by assessment of activity levels during structured PE lessons demonstrating that upper grade children obtained the same amounts of MVPA in PE as middle and lower grade children. However, this is probably not the most important factor because our results also suggested a decline in PA by age during weekend days. It is possible that increased use of electronic recreation and increased sedentary behaviors with increasing age contribute. It is also possible that limited assess to PA facilities and programs, reduced outdoor spaces, and fierce academic competition reduce PA levels in this population. According to parent report, a higher proportion of lower grade children enrolled in after school organized PA than middle and upper grade children. Notably, in spite of spending more time on organized PA after school, lower grade children were still more active during recess than middle and upper grade children. These findings imply that increased opportunities for older children to be active in organized PA during free time are one avenue to increase their levels of PA. Altering weekend behavior or finding ways to be active while engaging in electronic recreation as well as reducing other time spent sedentary (e.g., increasing active transportation or staying busy with chores) may be another avenue to be effective in increasing PA of older children.
Table 5 Simple main effect of grade level by day of week at each of the various intensities of PA in children with autism spectrum disorders. CPM F Grade (G) At WD At WK Day At G1 At G2 At G3
6.26** 5.44** 1.14 6.30* 10.08*
MPA%
VPA%
MVPA%
Post hoc
F
Post hoc
F
Post hoc
F
Post hoc
G1, G3 > G2 G1 > G3
18.03** 11.16**
G1 > G2, G3 G1, G2 > G3
10.14** 7.84**
G1 > G2, G3 G1 > G3
18.79** 11.36**
G1 > G2, G3 G1, G2 > G3
WD < WK WD > WK
2.70 14.39** 4.46
WD < WK
1.13 3.09 14.23**
WD > WK
2.23 9.48* 10.31*
WD < WK WD > WK
Note. CPM = counts per minute; MPA% = daily average percentage of time spent in moderate physical activity; VPA% = daily average percentage of time spent in vigorous physical activity; MVPA% = daily average percentage of time spent in moderate-to-vigorous physical activity; WD = weekday; WK = weekend day; G1 = lower grade; G2 = middle grade; G3 = upper grade. * p < .05. ** p < .01.
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Previous studies examining differences in the amount of PA between weekdays and weekend days are not conclusive. For example, one study suggested that young children spend more time in MVPA during weekend days compared with weekdays, while the opposite was observed in adolescents (Trost, Pate, Freedson, Sallis, & Taylor, 2000). Others have shown that time spent in MVPA was greater during weekdays compared with weekend days in primary school children (Gavarry, Giacomoni, Bernard, Seymat, & Falgairette, 2003; Nyberg et al., 2009; Rowlands et al., 2008), while no clear difference was indicated in high school students (Gavarry et al., 2003). For youths with ASD, Pan and Frey (2006) have shown that no clear PA difference was observed during weekdays compared with weekend days in primary, middle, and high school students with ASD. Our results suggest that type of day may significantly influence PA behavior in ASD children with different age. Younger children were more active on weekend days than weekdays, while older children were more active on weekdays than weekend days. Consistent with some (Trost et al., 2000), but not all (Gavarry et al., 2003; Nyberg et al., 2009; Rowlands et al., 2008) previous research. Although weekend days likely offer more free time than school days, surprisingly small proportions of upper grade children in the current study were able to reach the current recommendation for healthenhancing PA in youths. Since weekend days had the greatest potential for increased PA and parents and significant others are primarily responsible for ensuring that children are sufficiently physically active, family involved interventions may be a prerequisite to increase PA in this age group. Our data suggest that within-day differences in PA levels exist and do not show a consistent pattern between different grade levels. Grade variation exists in children’s activity levels within school days, with this effect being most evident during children’s free time (e.g., recess and after school). Therefore, the free time of the data collection may contribute to the higher levels of activity seen on school days and weekend days in younger children. It is a concern that children in the current study did not achieve 50% of PE class time in MVPA, and the majority of middle and upper grade children did not achieve 40% of recess time in MVPA. PE teachers might take into consideration the PE contents they offer to provide students with substantial amounts of PA. Playground environment at school and accessibility to game equipment during free time should be conducive for PA (e.g., larger space, more equipments, playground facilities, and adult supervision and support). It is also clear that the majority of children are unable to accumulate 60 min of MVPA during school time alone. After school PA seems to contribute, perhaps more than expected, to the total amount of time spent at MVPA, and subsequently, for achieving the daily 60-min MVPA recommendation. Given that school time offers less potential time for PA compared with after school, PA-promoting efforts including increased opportunities for being active after school seem warranted to support larger proportions of school-age youths to meet the current recommendations. Few studies have focused attention on the contribution of the various segmented school time periods within a weekday (e.g., PE, recess, lunch break, after school) to total daily MVPA. Inconsistent with pervious study (Rosser-Sandt & Frey, 2005), time engaged in MVPA at recess in the current study contributed the least to total daily MVPA, suggesting that elementary school playgrounds in Taiwan should provide an ideal setting for promoting PA of children with ASD. Strategies to enhance children’s PA at school recess time include: (a) reduced or eliminated recess time for the sake of academic time or behavior problems, (b) modified game strategies taught during PE that can be played at recess that focus on inclusion, low organization, and maximize activity, (c) appropriately designed school playgrounds and the availability of equipment, and (d) adult-assisted social context with varying levels of support in recess (e.g., verbal or physical prompts to engage in MVPA). Nevertheless, our results support the idea that appropriate engagement in MVPA after school can make a significant contribution to total daily PA levels (Tudor-Locke, Lee, Morgan, Beighile, & Pangrazi, 2006; Wickel & Eisenmann, 2007) and has the potential to impact future practice after schools and possibly increase the physical fitness components (Dencker et al., 2008) and movement skills (Houwen et al., 2009) of school children with ASD. Future studies examining the effect of the recess and after school environment on PA and the exact activities that children chose to participate at recess and after school are needed because they may provide educators with important strategies to employ during the segmented school day. Our findings are encouraging in light of the current recommendations for 60 min of MVPA in youths, consistent with other studies that have reported that the majority of elementary school-aged children exceed the current recommendations (Lopes et al., 2007; Pan & Frey, 2006; Rosser-Sandt & Frey, 2005). Considerably fewer achieved the target if only daily step counts are included. Therefore, a paradigm shift re-examining the current daily step recommendation for children perhaps should take into consideration of PA intensity. Although a national recommendation on children’s PA in Taiwan has not yet established, however, it has been suggested by the Taiwan’s Ministry of Education that elementary school-aged children should exercise three times for at least 30 min that raise the heart rate to 130 beats per minute each week. In addition, children should also be physically active for at least 30 min each day to accumulate at least 210 min of overall PA each week (Taiwan Ministry of Education, 2004). As compared with the US, this may be not comprehensive. For young children, PA can be carried out as part of active play, and not regular exercise. Emphasizing the accumulating of intermittent PA in short bouts (e.g., 5 or 10 min in one shot) and more occur over the day could be more practical approach in children (Lopes et al., 2007; Rowlands et al., 2008). The following limitations should be considered when interpreting our results. First, data from this study are from 35 children with ASD in a relatively small region in the Southern of Taiwan; therefore, the findings are not fully generalizable to the ASD population in Taiwan. Second, because the aim of the current study was to assess habitual PA levels, it is likely that the most physically active children with ASD chose to participate. Third, it might also be that all children with ASD were from middle income families and parents in this urban community were more aware of the health benefits of PA and therefore encourage their children to be physically active. Future studies should extend the assessment of the PA patterns in children
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with ASD to larger samples across more than one location. Longitudinal measurements of PA are also needed to provide reliable results about the daily variation in PA of children with ASD. More research is also needed to understand the reasons for decreasing levels of PA during free time and weekend days for older children with ASD. Further study and more precise descriptions of the PA environment and personal correlates may also help to explain PA behaviors of this population. In conclusion, differences in PA patterns between weekdays and weekend days seem inconsistent across different grade levels; that is, younger children were more active at weekend days, while older children were more active during weekdays. Furthermore, older children were less active than younger children both between and within days, with this effect being most evident during children’s free time. The amount of PA accumulated during school time seemed not to be enough to achieve the current recommendations for health-enhancing PA in all children with ASD. Overall, weekend days and free time within school days seem appropriate targets when promoting PA in older children with ASD. Acknowledgments The authors wish to thank the National Science Council, Taiwan for financial support (NSC 99-2410-H-017-036, MY2), all the children who participated in this study, parents of children for their supports, and research assistants who helped with data collection and other contributions. References American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: American Psychiatric Association. Andersen, L. B., Harro, M., Sardinha, L. B., Froberg, K., Ekelund, U., Brage, S., et al. (2006). Physical activity and clustered cardiovascular risk in children: A crosssectional study. Lancet, 368, 299–304. Bass, M. M., Duchowny, C. 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Contents lists available at ScienceDirect
Research in Autism Spectrum Disorders Journal homepage: http://ees.elsevier.com/RASD/default.asp
Accelerometer-determined physical activity among elementary school-aged children with autism spectrum disorders in Taiwan Chien-Yu Pan a,*, Chia-Liang Tsai b, Kai-Wen Hsieh b, Chia-Hua Chu a, Ya-Lin Li a, Shih-Tse Huang a a b
Department of Physical Education, National Kaohsiung Normal University, No. 116, He-Ping First Road, Kaohsiung 802, Taiwan Institute of Physical Education, Health and Leisure Studies, National Cheng Kung University, Tainan 701, Taiwan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 21 November 2010 Accepted 29 November 2010 Available online 24 December 2010
To examine age-related physical activity (PA) patterns between- and within-day in elementary school-aged children with autism spectrum disorders (ASD). PA was recorded every 5-s by uniaxial accelerometry in 35 children (grades 1–2, n = 13; grades 3–4, n = 13; grades 5–6, n = 9) for up to five weekdays and two weekend days. Younger children were more active during weekend days compared with weekdays, while the opposite was observed in older children. Age variation also exists in children’s PA levels within a weekday, with this effect being most evident during recess and after school. Weekend days and free time within school days seem appropriate targets when promoting PA in older children with ASD. ß 2010 Elsevier Ltd. All rights reserved.
Keywords: Physical activity Accelerometry Autism Children
1. Introduction Regular physical activity (PA) is an important factor to promote and maintain a healthy lifestyle along the whole life cycle. Numerous studies have indicated that higher levels of PA are associated with reduced risk of obesity (Ekelund et al., 2004), prevention of clustering of cardiovascular disease risk factors (Andersen et al., 2006), enhanced motor skill proficiency (Houwen, Hartman, & Visscher, 2009), and less body fat and greater aerobic fitness (Dencker et al., 2008) in children. The significance of PA to the health of children has led to increased interest in monitoring compliance with PA guidelines in this population. The most consensus recommendation is that children should participate in at least 60 min of moderate PA (MPA) on most days of the week (U.S. Department of Health and Human Services (USDHHS) and Department of Agriculture, 2005), and accumulate 12,000 and 15,000 daily steps for ages 6–12 girls and boys, respectively (Tudor-Locke et al., 2004). In addition, current guidelines for physical education (PE) suggest that children should be active for at least 50% of PE class time, and schools should provide daily lessons for children in order for PE to meaningfully contribute toward the daily PA accumulation (USDHHS, 2000). Although the empirically tested PA guidelines do not exist for recess, researchers suggested that children should be physically active for 40% (Ridgers, Stratton, & Fairclough, 2005) or 50% (Stratton & Mullan, 2005) of recess time because they are exposed to these times on a daily basis for PA participation. These recommendations, though not specific to individuals with disabilities, may hold true for healthy individuals with mild or high-functioning autism spectrum disorders (ASD) who are often included into general school contexts. ASD is a developmental disorder characterized by difficulties in social interaction, language and communication, as well as by repetitive, restricted interest and behaviors (American Psychiatric Association, 1994). Various researchers have also noted differences of motor skills in school-aged children with ASD (Green et al., 2009; Ozonoff et al., 2008; Pan, Tsai, & Chu,
* Corresponding author. Tel.: +886 7 7172930x3531; fax: +886 7 7114633. E-mail address: [email protected] (C.-Y. Pan). 1750-9467/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.rasd.2010.11.010
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2009). These social and behavioral deficits and sometimes motor skill difficulties could limit opportunities for individuals with ASD to successfully participate in PA, and therefore, may put them at risk for being physically inactive. However, there is uncertainty regarding activity levels of children with ASD and the percentage who meet current PA recommendations in Taiwan. Since ASD is the second most common type among Taiwan elementary school-aged students with developmental disabilities and the prevalence rate of ASD diagnoses continues to rise (Taiwan Ministry of Education, 2009), accurate estimates of habitual PA levels in children with ASD, including proportions who meet stated recommendations about PA, will provide important baseline information and increase knowledge about variations in PA levels of this population. To understand PA behaviors, Deci and Ryan’s self-determination theory can be a useful theoretical framework for the study of PA in youths with ASD (Deci & Ryan, 1985, 2000). Self-determination theory includes both a psychological needs and a multidimensional motivation orientation for understanding human behaviors. That is, individuals are assumed to have three basic innate needs, and the satisfaction of those needs through social environments presumably influences motivation and ultimately leads to important cognitive, affective, and behavioral consequences. A recent study in adolescents with ASD examining their PA and self-determined motivation in PE found that external regulation was positively correlated with the percentage of time that adolescents with ASD spent in MPA and moderate-to-vigorous PA (MVPA), and this extrinsic motive was associated with their needs of being attached or related in the class (Pan, Tsai, Chu, & Hsieh, 2010). Furthermore, studies (Bass, Duchowny, & Llabre, 2009; Pan, 2010; Pitetti, Rendoff, Grover, & Beets, 2007; Wuang, Wang, Huang, & Su, 2010) suggest that children with ASD can be introduced to a PA training program and learn variety of skills under close supervision as well as structured teaching and various supports. Therefore, PA behaviors of children with ASD may be more affected by social and environmental constraints rather than the actual impairment. Previous studies in children without disabilities using objective measurements of PA have suggested that daily PA was significantly lower during weekend days compared with weekdays (Kristensen et al., 2008; Nyberg, Nordenfelt, Ekelund, & Marcus, 2009; Rowlands, Pilgrim, & Eston, 2008). In addition, PA has been suggested to decline by age at least after 9–10 years of age (Caspersen, Pereira, & Curran, 2000; Sallis, 2000), but it is still not clear at what age this decrease happens. In children, weekdays and weekend days are likely to provide different opportunities for being active, as well as various segmented time periods within a weekday (e.g., PE, recess, lunch break, after school). Assessing time in PA between days and within days is of interest to increase our understanding about variation in PA behavior of children with ASD. However, data regarding PA patterns in children with ASD are apparently lacking and there are few published PA studies that have included this population. A limited number of studies in youths with ASD have examined the influence of temporal sources of variation using accelerometry (Pan, 2008a, 2008b; Pan & Frey, 2006; Rosser-Sandt & Frey, 2005). Pan and Frey (2006) examined PA patterns (weekdays vs. weekend days; in school vs. after school) in 30 American youths with ASD aged 10–19, and found no differences in total PA or MVPA on between-day and within-day variability according to school level. PA declined with age in this group, and only 47% of youths with ASD accumulated recommended daily 60 min of MVPA. Rosser-Sandt and Frey (2005) compared PE, recess, after school, and daily MVPA of American children with (n = 15) and without (n = 13) ASD aged 5–12. There were no MVPA differences between weekdays and weekend days, and no significant differences existed between group PA levels at any setting. Children with ASD engaged in relatively similar MVPA in recess (58%), during PE (41%), and after school (29%) as compared to children without ASD. When time periods were compared, both groups spent more time in MVPA during recess and PE as compared to after school period. However, Pan (2008b) compared MVPA of children with (n = 24) and without (n = 24) ASD (aged 7–12) during inclusive PE and recess in Taiwan, and results were somewhat different from previous findings (Rosser-Sandt & Frey, 2005). Both children with and without ASD in this study (Pan, 2008b) spent a higher proportion of time in MVPA during PE (46% and 47%, respectively) than during recess (28% and 36%, respectively), although there were no significant differences existed between group PA levels at any setting. Furthermore, Pan (2008a) broke daily recess time into 7 blocks (3 morning recesses, lunch break, and 3 afternoon recesses) based on the educational system of Taiwan, and compared MVPA levels of children with and without ASD. Children with ASD were less active during overall recess (28%), lunchtime (17%), first (33%) and second (36%) morning recess compared to those without disabilities. All children in this study (Pan, 2008a) did not achieve 40% of recess time in PA. Differences in data reduction and analysis procedures from the aforementioned studies, combined with various age groups and diverse cultures, have made conclusions about variability in PA patterns of youths with ASD between and within days elusive. The patterns of PA in children with ASD across days and within days are not well examined in Taiwan. This knowledge is important when identifying possible arenas and settings when planning preventive initiatives aimed at increasing levels of PA in this population. Therefore, the aim of this study was to examine differences in patterns of objectively measured PA among weekdays and weekend days and among different time periods within a weekday and how these patterns are influenced by age in a sample of Taiwanese elementary school-aged children with ASD. The relative importance of each time period to total daily MVPA accumulation during weekdays as well as the percentage of children meeting PA guidelines was also evaluated. It was hypothesized that older children with ASD would be less active than younger children both between days and within days. 2. Methods 2.1. Participants and settings A convenience sample of 35 boys with ASD from 23 primary schools, aged 7–12 years, volunteered to participate. All children met the DSM-IV (American Psychiatric Association, 1994) criteria for autistic disorders and Asperger’s syndrome, as
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Table 1 Participant demographics.
Age (years) Height (cm) Weight (kg) BMI (kg/m2) Diagnosis Asperger Mild autism Therapy Physical therapy Group therapy Occupational therapy Speech therapy Sensory integration therapy Medications Ritalin Concerta After school PA enrollment Tae Kwon Do Swimming Horse-back riding Tai Chi Fitness training Inline skating
Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
7.56 126.19 28.41 17.72
9.57 136.82 35.99 19.13
11.82 149.78 42.67 19.03
(0.76) (4.95) (5.73) (2.54)
(0.50) (5.88) (9.77) (4.65)
4 9
6 7
3 6
4 3 5 3 4
1 2 4 3 2
0 1 3 1 1
3 2
2 2
0 2
1 2 1 0 1 1
1 0 0 0 1 0
0 1 0 1 0 0
(0.36) (6.37) (7.56) (3.18)
Note. Group mean (SD); BMI = body mass index.
assessed by psychiatrists and physicians in the hospitals (Taiwan Executive Yuan Department of Health, 2009a). Diagnosis included 13 Asperger’s syndrome and 22 mild autistic disorders. Level of severity (mild, moderate, severe, and very severe) is based on functioning in the social adaptive skill areas and language comprehension and expression (Taiwan Executive Yuan Department of Health, 2009b). All participants resided in the same geographical area of high social and economic deprivation in a large urban city in Taiwan (n = 1,527,914) (Taiwan Kaohsiung City Government Department of Budget Accounting and Statistics, 2010). Participants were divided into three groups according to their grade levels: lower grade (grades 1–2, n = 13), middle grade (grades 3–4, n = 13), and upper grade (grades 5–6, n = 9) to address potential differences in developmental factor and PA opportunities. All children with ASD were enrolled in regular school and received most of their studies in regular classrooms while occasionally attended the resource room for special education services. Each school had 3 morning recesses, a lunch break, and 3 afternoon recesses during the whole-day (approximately 8 h a day) school days, and had 3 morning recesses and/or a lunch break during the half-day (approximately 4 h a day) school days. Days to attend school whole day or half day in a week vary and depend on the school district and children’s grade level. Usually, lower grade students take 1 whole day and 4 half days, while middle and upper grade students take 1 half day and 4 whole days during school days. Each morning and afternoon recess was scheduled for 10–20 min each day. In addition, the PE lesson was 40 min in duration, and students in lower grade and those in middle and upper grades were required to take 1 and 2 lessons each week, respectively. Furthermore, the average daily lunch break was 40 min and was held in the classroom; students were typically encouraged by class teacher to finish eating in approximately 20 min and to clean up and play for approximately the last 20 min (in the classroom or outside). These times are approximate; this schedule was not rigidly enforced, and students were free to play as long as they wished. Participant demographics are presented in Table 1. 2.2. Instrument PA was measured using the MTI accelerometer (Actigraph 7164, Manufacturing Technology Inc., Fort Walton Beach, FL, USA), a uniaxial accelerometer that measures vertical acceleration of human motion as well as step counts. The accelerometer has been used extensively and reported as a valid objective measure of PA in youths (Trost et al., 1998). It has also been used in research on youths with ASD (Pan, 2008b; Pan & Frey, 2006). Actigraph data are in counts per user-specified time intervals and represent the intensity of the activity during each time period. For the current study, accelerometers were programmed to collect data in 5-s intervals because children tend to do activities in short bursts and are more sporadic than adults (USDHHS, 2000). The output of the raw accelerometer counts was uploaded and then converts to calories to determine the time spent in MPA (3–5.99 METs), vigorous PA (VPA, 36 METs), and MVPA (33 METs). The age-specific count thresholds in 1-min epoch corresponding to these in intensity levels were used (Freedson, Melanson, & Sirard, 1998), and the appropriate age-specific count cutoffs were divided by 12 to accommodate the 5-s epoch length. Due to the differences in the monitoring length, the relative (percentage) time spent in total PA (counts per minute, CPM), MPA (MPA%), VPA (VPA%), MVPA (MVPA%) were calculated and used in the subsequent analyses.
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2.3. Procedures The study protocol was approved by the university review board for the protection of human subjects. Parental consent and student assent were obtained for all participants. The administration of accelerometers was conducted in collaboration with the schools and therefore the measurement period followed the school year, with the majority of measurements performed between the months of March and June. Before the start of the measurement, participants were instructed on accelerometer attachment (at the right waist), its removal (only during showering, bathing, swimming, or sleeping), and reattaching the accelerometer each morning upon awakening and dressing. They were also instructed to engage in their normal levels of PA and not to tamper with the accelerometer during the monitoring frame. Following a standardized protocol, the participant’s body mass (to the nearest 0.1 kg) and stature (to the nearest 0.5 cm) were directly measured without shoes using an automatic fitness measuring system (The Accuratus ACC-810, Taiwan). The accelerometers were initialized before placement on an elastic belt provided by the study and worn on each participant’s right waist. All participants wore the device during waking hours, except bathing or water activities, for 7 consecutive days (5 weekdays and 2 weekend days). They were given a brief log to record when they put on the Actigraph each morning and the time they removed it each evening. To ensure data completeness and quality, a research assistant collected the accelerometer just prior to the child’s bedtime every 2–3 days during the monitored days, and gave another initialized accelerometer for the following days. Data were immediately downloaded and checked (e.g., data sheets were reviewed, and missing and odd values were queried the next day). 2.4. Data reduction and statistical analysis Descriptive data were calculated for all variables by children’s grade level. Body mass index (BMI) was computed as kg/m2. For inclusion in the analyses, a child needed a minimum of 10 h wearing time each day for at least 4 weekdays and 1 weekend day. Intraclass correlation coefficients and 95% confidence intervals were calculated to investigate the intra- and interindividual variation in activity counts across different days of assessment (2 weekend days and 5 weekdays). All data from weekdays (school days) were divided into four time periods: PE, recess, lunch break, and after school, according to the child’s schedule reported by classroom teacher. To account for differences in the time-period length, the relative (percentage) time spent in each PA level was calculated and used in the subsequent analyses. Therefore, inferential statistics were undertaken on these variables: CPM, MPA%, VPA%, and MVPA%. Percentage of time for each time period spent in each PA level according to total monitoring time of the period was calculated by summing the minutes at that PA level for all sessions of that time period, and dividing the minutes of total monitoring time (actual registered time) of that period. Each PA level attributable to each time period represents the average of 4–5 valid days. Because PE was only offered on one or two of the data collection school days, PA levels attributable to PE represent the average of only those days. If there was a difference between monitoring length of specific time period across children’s grade levels, one-way ANCOVA controlling for the monitored length of that time period was used to examine the proportion of time for children’s PA levels at that time period. If there was no group difference between monitoring length of each time period, one-way ANOVAs were used to examine the proportion of time for children’s PA levels at each time period within the segmented school day. Next, the contribution of MVPA during each time period to daily total MVPA across children’s grade levels was also evaluated by a two-factor mixed-model ANOVA with repeated measures on time period of a school day. The percentage of time spent in MVPA was calculated by summing the MVPA minutes for all sessions of that time period, and dividing the minutes of total monitoring time that day. Tukey’s post hoc tests were undertaken if significant difference or interaction between factors were observed. Furthermore, all data were calculated separately for weekdays and weekend days. The dependent variables used for analysis were percentage of time spent in each PA level: CPM, MPA%, VPA%, and MVPA%. Children’s grade level differences in PA variables by day of week (weekday and weekend) were assessed with a two-factor mixed-model ANOVAs with repeated measures on day of week. Post hoc Tukey’s test was used where significant difference or interaction between factors were statistically significant. Finally, the proportion of children who achieved the recommended levels of daily average 60 min of MVPA was established based on two types of days across different grade levels. In addition, the proportions of boys meeting daily average 15,000 steps were also evaluated as indicative of meeting the BMI-referenced PA cut points (Tudor-Locke et al., 2004). All data were analyzed by SPSS version 13.0 for Windows (SPSS Inc., Chicago, IL), and an alpha level was set at .05. 3. Results Of the total 35 participants in the current study, all completed data collection requirements (e.g., provided at least 4 weekdays and 1 weekend day of at least 600 min per day recorded). Seventy-one percent (n = 25) of children had two valid weekend days and 94% (n = 33) had five valid weekdays, leading to a total of 233 valid PA registration days. Intraclass correlation coefficients demonstrated moderate to strong relationships between measured days on total PA: weekend days, R = .79, CI .52–.91 and weekdays R = .78, CI .64–.88.
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3.1. Comparisons of physical activity levels during the segmented school day (weekday) Mean minutes and proportion of time for children’s PA levels over five school days are presented in Table 2. There were no grade level differences in total monitored length for each time period monitored (PE: F2,32 = 0.56, p = .58; recess: F2,32 = 2.92, p = .07; lunch break: F2,32 = 0.22, p = .81) except after school segment (F2,32 = 31.14, p < .01). Therefore, one-way ANCOVA controlling for monitored length was only used for after school time period to analyze group differences in after school PA during weekdays. Group differences in PA levels at each time period. As shown in Table 2, no differences on any PA variables among three grade levels of children with ASD were only observed in PE. All children were similarly active during PE. For recess, total PA and VPA were significantly higher in lower grade children as compared to middle grade children. In addition, lower grade children also engaged more percentage of time in MPA and MVPA than both middle and upper grade children. For lunch break, total PA was significantly higher in upper grade children than both middle and lower grade children, while PA intensity levels were similar for all children. For after school, total PA and each PA intensity level were significantly higher in lower grade children than those of children in middle and upper grades. Group differences in the contribution of MVPA for each time period to daily total MVPA. Results of two-way ANOVA with repeated measures on time period of day showed that there were no differences in the contribution of MVPA for each time period to daily total MVPA among three age groups of children with ASD (F2,32 = 1.59, p = .22). However, there were significant differences between the four time periods on the contribution of MVPA (F3,96 = 137.59, p < .01, partial h2 = 0.81, observed power = 1.00). After school MVPA significantly contributed to daily total MVPA more than PE (+22.69%), lunch break (+28.23%), and recess (+30.24%). The contribution of MVPA during PE was also significantly higher than recess (+7.56%) and lunch break (+5.55%). Furthermore, significant grade by time interaction effect was observed (F6,96 = 2.78, p < .05, partial Table 2 Physical activity, expressed in minutes and percentage of monitored length, within a school day and F-values of the proportion of time for children’s physical activity levels at each setting. Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
Minutes
Minutes
Minutes
Physical education Length 38.58 (11.84) Counts 39,216.88 (22,475.28) Steps 884.27 (487.05) MPA 6.91 (3.44) VPA 5.54 (3.67) MVPA 12.45 (5.86) Recess Length 13.09 (1.76) Counts 17,544.31 (9499.67) Steps 458.85 (227.75) MPA 3.13 (1.18) VPA 2.51 (1.47) MVPA 5.63 (2.09) Lunch break Length 40.38 (10.10) Counts 14,432.51 (9227.13) Steps 451.72 (299.54) MPA 4.28 (2.22) VPA 1.58 (1.40) MVPA 5.86 (3.38) After school Length 335.54 (51.00) Counts Steps MPA VPA MVPA
141,628.52 (30,820.89) 3115.53 (533.23) 33.56 (6.58) 17.08 (4.74) 50.63 (10.31)
%
1069.49 (668.99) 22.93 (14.15) 18.15 (7.65) 15.31 (11.14) 33.46 (16.29)
1304.70 (650.62) 32.51 (15.25) 23.60 (6.87) 18.53 (10.15) 42.06 (12.13)
349.13 (201.30) 10.93 (6.07) 10.48 (5.17) 3.75 (3.01) 14.23 (7.52)
35.85 (1.64) 42,213.69 (20,960.15) 1027.46 (555.39) 6.30 (2.56) 5.68 (3.62) 11.99 (5.62) 12.85 (1.38) 9817.18 (3787.53) 314.23 (135.28) 2.10 (0.93) 1.07 (0.61) 3.16 (1.25) 40.48 (8.03) 15,606.36 (6295.06) 508.52 (223.62) 3.96 (1.89) 1.40 (0.74) 5.36 (2.44)
%
1188.20 (592.00) 28.94 (15.90) 17.70 (7.29) 15.97 (10.03) 33.67 (15.81)
761.76 (271.43) 24.07 (8.52) 16.07 (5.67) 8.33 (4.59) 24.29 (8.00)
390.29 (160.57) 12.65 (5.38) 9.83 (4.54) 3.59 (2.16) 13.42 (6.29)
259.62 (10.00) 444.51 (181.24) 9.46 (3.69) 10.24 (2.47) 5.36 (2.30) 15.60 (4.60)
99,516.36 (34,915.81) 2769.64 (809.76) 22.61 (6.71) 9.64 (5.14) 32.25 (11.02)
385.01 (138.63) 10.71 (3.23) 8.74 (2.65) 3.74 (2.02) 12.48 (4.37)
35.83 (2.37) 36,088.09 (26,266.93) 821.38 (619.09) 5.32 (3.54) 4.32 (3.16) 9.71 (6.55) 11.20 (2.67) 11,933.83 (5081.34) 323.53 (134.72) 1.81 (0.61) 1.35 (0.71) 3.16 (1.68) 38.33 (5.00) 24,240.36 (11,825.07) 691.22 (302.01) 4.21 (1.78) 2.27 (1.43) 6.48 (3.10) 205.94 (44.26) 99,842.21 (63,860.07) 2467.81 (1684.96) 15.37 (8.58) 10.92 (9.67) 26.28 (17.85)
F
Post hoc
%
1020.36 (745.14) 23.36 (17.69)
0.19 0.58
14.97 (9.87) 12.24 (9.04) 27.41 (18.49)
0.45 0.38 0.46
1028.39 (287.61) 28.24 (9.38)
4.63* 1.72
15.97 (3.59) 11.52 (4.95) 27.49 (7.90)
7.11** 6.66** 11.96**
1 > 2, 3 1>2 1 > 2, 3
619.65 (245.07) 17.72 (6.10)
5.37*
3 > 1, 2
3.81*
3>1
10.82 (3.62) 5.76 (3.10) 16.58 (6.46)
0.13 1.95 0.59
501.30 (308.64) 12.53 (8.27)
5.12* 1.72
7.72 (4.20) 5.53 (4.65) 13.25 (8.70)
5.70** 4.63* 5.12*
1>2
1 > 2, 3
1 > 2, 3 1 > 2, 3 1 > 2, 3
Note. Values reported as mean (SD); MPA = moderate physical activity; VPA = vigorous physical activity; MVPA = moderate-to-vigorous physical activity. * p < .05. ** p < .01.
[()TD$FIG]
C.-Y. Pan et al. / Research in Autism Spectrum Disorders 5 (2011) 1042–1052
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Fig. 1. Percentage of time spent in MVPA for each time period according to daily total MVPA; asignificantly different from physical education (PE), recess, and lunch; bsignificantly different from recess and lunch; csignificantly different from recess and lunch; dsignificantly different from PE and lunch.
h2 = 0.15, observed power = 0.86). Further analysis according to grade by time revealed that for lower grade children, after school MVPA significantly contributed to daily MVPA as compared to PE (+29.99%), recess (+35.21%), and lunch break (+35.27%); PE MVPA was also significantly higher than recess (+5.23%) and lunch break (+5.29%). For middle grade children, after school MVPA significantly contributed higher daily MVPA as compared with PE (+22.07%), lunch break (+29.01%), and recess (+31.56%); PE MVPA was also significantly greater than recess (+9.49%) and lunch break (+6.95%). For upper grade children, MVPA during after school significantly contributed more daily MVPA than recess (+23.95%) and lunch break (+20.40%); recess was significantly lower than PE ( 7.95%) and lunch break ( 3.55%). No grade level differences were observed at any time periods (Fig. 1). 3.2. Comparisons of physical activity levels by weekday and weekend day The average registered time was 820.19 49.47 min on weekdays (F2,32 = 0.38, p = .69) and 733.04 77.19 min on weekend days (F2,32 = 0.27, p = .77). Proportions of children who accumulated at least 60 min of MVPA each day are: lower grade, weekdays = 100% (n = 13), weekend days = 84.62% (n = 11); middle grade, weekdays = 100% (n = 13), weekend days = 84.62% (n = 11); upper grade, weekdays = 100% (n = 9), weekend days = 33.33% (n = 3). None of children met 15,000 steps per day either during weekdays or weekend days, except one child in middle grade during weekend days. Table 3 displays the data stratified by weekdays versus weekend days. Results of the two-way ANOVAs with repeated measures on day of week indicate that there were significant differences between the three grade levels for all PA variables, regardless type of day (Table 4). Children in lower grade were more active overall than those in middle (+98.55) and upper (+112.50) grades and spent more percentage of time in MPA, VPA, and MVPA compared to middle (+2.58, +1.97, and +4.55, respectively) and upper (+5.20, +2.66, and +7.86, respectively) grade children. Middle grade children also engaged in significantly more percentage of time in MPA (+2.62) and MVPA (+3.30). In addition, results of the mixed two-way ANOVAs showed that there were no significant PA differences between weekdays versus weekend days, regardless of children’s grade levels. However, significant grade-by-day interactions were evident on all PA levels, indicating inconsistent directions of between-day differences within grade groups. Table 5 provides further analysis according to children’s grade level and day of week at each of significant PA levels. For weekday PA, total PA was significantly higher in the lower (+106.65) and upper grade children (+88.98) as compared to middle grade children. Percentage of time spent in various intensities of PA were significantly higher in lower grade children than middle (MPA%: +2.72; VPA%: +2.07; MVPA%: +4.79) and upper grade children (MPA%: +3.42; VPA%: +1.35; MVPA%: +4.76). For weekend PA, total PA was significantly higher (+207.32) in lower than upper grade children. Percentages of time spent in various intensities of PA were significantly higher in lower grade children than upper grade children (MPA%: +6.98; VPA%: +3.97; MVPA%: +10.95). Middle grade children also spent significantly higher percentage of time in MPA (+4.54) and MVPA (+6.63) as compared to upper grade children. PA differences on day of week within each grade level showed that lower grade children did not differ on any of PA levels between weekdays and weekend days. For middle grade children, total PA (+69.74) as well as percentage of time spent in MPA (+1.88) and MVPA (+2.65) were significantly higher on weekend days than during weekdays. However, upper grade children were more active during weekdays than during weekend days (CPM [+136.10]; MVPA% [+3.54]; VPA% [+1.85]). 4. Discussion The aim of this study was to characterize age differences in the patterns of PA of various intensities in 7–12-year-olds children with ASD between and within days. Lower grade children were the most active both on weekdays and weekend days compared with the other two groups. In accordance with literature (Lopes, Vasques, Maia, & Ferreira, 2007; Pan & Frey, 2006) that there was an apparent PA differences with increasing age. Irrespective of total PA, the decline occurred in all three PA intensities evaluated (MPA, VPA, and MVPA) both on weekdays and weekend days. Furthermore, results on between-day
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Weekday
Length Counts Steps MPA VPA MVPA
Weekend day
Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
Lower grade (n = 13)
Middle grade (n = 13)
Upper grade (n = 9)
Minutes
%
Minutes
%
Minutes
%
Minutes
%
Minutes
%
Minutes
%
447.69 (102.96) 10.57 (2.04) 10.46 (1.42) 5.45 (1.37) 15.91 (2.44)
829.03 (49.66) 282,423.61 (47,994.86) 8096.94 (1575.91) 64.08 (13.94) 28.11 (8.78) 92.19 (18.30)
341.04 (55.66) 9.79 (1.94) 7.74 (1.60) 3.39 (1.00) 11.12 (2.07)
819.53 (59.37) 350,414.42 (54,181.30) 8937.90 (1079.19) 57.57 (10.51) 33.36 (7.99) 90.93 (15.75)
430.02 (76.02) 10.94 (1.36) 7.04 (1.26) 4.11 (1.13) 11.15 (2.11)
720.35 (77.08) 363,706.94 (136,486.03) 7585.85 (2820.28) 89.65 (32.04) 45.43 (21.02) 135.09 (49.90)
501.24 (186.81) 10.49 (3.76) 12.33 (4.27) 6.23 (2.91) 18.56 (6.70)
740.31 (78.85) 305,759.64 (100,659.98) 8111.46 (4162.18) 73.70 (27.76) 31.96 (15.15) 105.66 (39.39)
410.78 (111.79) 10.78 (4.72) 9.89 (3.22) 4.35 (2.19) 14.24 (4.89)
740.89 (81.64) 219,522.57 (96,228.05) 5510.56 (3108.49) 40.09 (16.81) 16.96 (10.65) 57.05 (26.29)
293.92 (114.34) 7.27 (3.58) 5.35 (1.96) 2.26 (1.25) 7.61 (3.03)
811.81 (44.23) 362,370.42 (78,181.66) 8569.43 (1588.26) 84.84 (11.95) 44.15 (10.73) 128.99 (19.63)
Note. Values reported as mean (SD).
C.-Y. Pan et al. / Research in Autism Spectrum Disorders 5 (2011) 1042–1052
Table 3 Physical activity, expressed in minutes and percentage of monitored length, between an average weekday and weekend day in children with autism spectrum disorders.
C.-Y. Pan et al. / Research in Autism Spectrum Disorders 5 (2011) 1042–1052
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Table 4 Two-way ANOVA with repeated measures on day of week. Variables
p
Partial h2
Observed power
5.12 0.03 6.53
.01 .86 .00
.24 .00 .29
0.79 0.05 0.88
15.95 2.20 4.93
.00 .15 .01
.50 .06 .24
0.99 0.30 0.77
9.83 0.01 5.39
.00 .92 .01
.38 .00 .25
0.97 0.05 0.81
15.95 0.81 6.01
.00 .38 .00
.50 .03 .27
0.99 0.14 0.85
F
CPM Grade level (G)* Day of week (D) G D** MPA% Grade level (G)** Day of week (D) G D* VPA% Grade level (G)** Day of week (D) G D* MVPA% Grade level (G)** Day of week (D) G D**
Note. CPM = counts per minute; MPA% = daily average percentage of time spent in moderate physical activity; VPA% = daily average percentage of time spent in vigorous physical activity; MVPA% = daily average percentage of time spent in moderate-to-vigorous physical activity. * p < .05. ** p < .01.
differences in PA levels were inconsistent within grade levels. Upper grade children showed a higher PA levels on weekdays compared with weekend days, while both lower and middle grade children demonstrated a higher PA levels during weekend days than during weekdays. The within-day differences observed are unique in the current study as compared with previous accelerometer studies (Pan, 2008a, 2008b; Pan & Frey, 2006; Rosser-Sandt & Frey, 2005), highlighting particular time periods of the school day when grade level differences are most marked (e.g., recess and after school periods). In accordance with previous findings in youths with ASD (Pan & Frey, 2006) and those without a disability (Lopes et al., 2007), younger children were more active than older children. Part of the age differences in PA levels might be explained by more scheduled time spent at school with increasing age. It is possible that removal of the structured school environment at weekend days is detrimental to some children’s activity levels, with this effect being particularly noticeable in upper grade children. This is supported by assessment of activity levels during structured PE lessons demonstrating that upper grade children obtained the same amounts of MVPA in PE as middle and lower grade children. However, this is probably not the most important factor because our results also suggested a decline in PA by age during weekend days. It is possible that increased use of electronic recreation and increased sedentary behaviors with increasing age contribute. It is also possible that limited assess to PA facilities and programs, reduced outdoor spaces, and fierce academic competition reduce PA levels in this population. According to parent report, a higher proportion of lower grade children enrolled in after school organized PA than middle and upper grade children. Notably, in spite of spending more time on organized PA after school, lower grade children were still more active during recess than middle and upper grade children. These findings imply that increased opportunities for older children to be active in organized PA during free time are one avenue to increase their levels of PA. Altering weekend behavior or finding ways to be active while engaging in electronic recreation as well as reducing other time spent sedentary (e.g., increasing active transportation or staying busy with chores) may be another avenue to be effective in increasing PA of older children.
Table 5 Simple main effect of grade level by day of week at each of the various intensities of PA in children with autism spectrum disorders. CPM F Grade (G) At WD At WK Day At G1 At G2 At G3
6.26** 5.44** 1.14 6.30* 10.08*
MPA%
VPA%
MVPA%
Post hoc
F
Post hoc
F
Post hoc
F
Post hoc
G1, G3 > G2 G1 > G3
18.03** 11.16**
G1 > G2, G3 G1, G2 > G3
10.14** 7.84**
G1 > G2, G3 G1 > G3
18.79** 11.36**
G1 > G2, G3 G1, G2 > G3
WD < WK WD > WK
2.70 14.39** 4.46
WD < WK
1.13 3.09 14.23**
WD > WK
2.23 9.48* 10.31*
WD < WK WD > WK
Note. CPM = counts per minute; MPA% = daily average percentage of time spent in moderate physical activity; VPA% = daily average percentage of time spent in vigorous physical activity; MVPA% = daily average percentage of time spent in moderate-to-vigorous physical activity; WD = weekday; WK = weekend day; G1 = lower grade; G2 = middle grade; G3 = upper grade. * p < .05. ** p < .01.
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Previous studies examining differences in the amount of PA between weekdays and weekend days are not conclusive. For example, one study suggested that young children spend more time in MVPA during weekend days compared with weekdays, while the opposite was observed in adolescents (Trost, Pate, Freedson, Sallis, & Taylor, 2000). Others have shown that time spent in MVPA was greater during weekdays compared with weekend days in primary school children (Gavarry, Giacomoni, Bernard, Seymat, & Falgairette, 2003; Nyberg et al., 2009; Rowlands et al., 2008), while no clear difference was indicated in high school students (Gavarry et al., 2003). For youths with ASD, Pan and Frey (2006) have shown that no clear PA difference was observed during weekdays compared with weekend days in primary, middle, and high school students with ASD. Our results suggest that type of day may significantly influence PA behavior in ASD children with different age. Younger children were more active on weekend days than weekdays, while older children were more active on weekdays than weekend days. Consistent with some (Trost et al., 2000), but not all (Gavarry et al., 2003; Nyberg et al., 2009; Rowlands et al., 2008) previous research. Although weekend days likely offer more free time than school days, surprisingly small proportions of upper grade children in the current study were able to reach the current recommendation for healthenhancing PA in youths. Since weekend days had the greatest potential for increased PA and parents and significant others are primarily responsible for ensuring that children are sufficiently physically active, family involved interventions may be a prerequisite to increase PA in this age group. Our data suggest that within-day differences in PA levels exist and do not show a consistent pattern between different grade levels. Grade variation exists in children’s activity levels within school days, with this effect being most evident during children’s free time (e.g., recess and after school). Therefore, the free time of the data collection may contribute to the higher levels of activity seen on school days and weekend days in younger children. It is a concern that children in the current study did not achieve 50% of PE class time in MVPA, and the majority of middle and upper grade children did not achieve 40% of recess time in MVPA. PE teachers might take into consideration the PE contents they offer to provide students with substantial amounts of PA. Playground environment at school and accessibility to game equipment during free time should be conducive for PA (e.g., larger space, more equipments, playground facilities, and adult supervision and support). It is also clear that the majority of children are unable to accumulate 60 min of MVPA during school time alone. After school PA seems to contribute, perhaps more than expected, to the total amount of time spent at MVPA, and subsequently, for achieving the daily 60-min MVPA recommendation. Given that school time offers less potential time for PA compared with after school, PA-promoting efforts including increased opportunities for being active after school seem warranted to support larger proportions of school-age youths to meet the current recommendations. Few studies have focused attention on the contribution of the various segmented school time periods within a weekday (e.g., PE, recess, lunch break, after school) to total daily MVPA. Inconsistent with pervious study (Rosser-Sandt & Frey, 2005), time engaged in MVPA at recess in the current study contributed the least to total daily MVPA, suggesting that elementary school playgrounds in Taiwan should provide an ideal setting for promoting PA of children with ASD. Strategies to enhance children’s PA at school recess time include: (a) reduced or eliminated recess time for the sake of academic time or behavior problems, (b) modified game strategies taught during PE that can be played at recess that focus on inclusion, low organization, and maximize activity, (c) appropriately designed school playgrounds and the availability of equipment, and (d) adult-assisted social context with varying levels of support in recess (e.g., verbal or physical prompts to engage in MVPA). Nevertheless, our results support the idea that appropriate engagement in MVPA after school can make a significant contribution to total daily PA levels (Tudor-Locke, Lee, Morgan, Beighile, & Pangrazi, 2006; Wickel & Eisenmann, 2007) and has the potential to impact future practice after schools and possibly increase the physical fitness components (Dencker et al., 2008) and movement skills (Houwen et al., 2009) of school children with ASD. Future studies examining the effect of the recess and after school environment on PA and the exact activities that children chose to participate at recess and after school are needed because they may provide educators with important strategies to employ during the segmented school day. Our findings are encouraging in light of the current recommendations for 60 min of MVPA in youths, consistent with other studies that have reported that the majority of elementary school-aged children exceed the current recommendations (Lopes et al., 2007; Pan & Frey, 2006; Rosser-Sandt & Frey, 2005). Considerably fewer achieved the target if only daily step counts are included. Therefore, a paradigm shift re-examining the current daily step recommendation for children perhaps should take into consideration of PA intensity. Although a national recommendation on children’s PA in Taiwan has not yet established, however, it has been suggested by the Taiwan’s Ministry of Education that elementary school-aged children should exercise three times for at least 30 min that raise the heart rate to 130 beats per minute each week. In addition, children should also be physically active for at least 30 min each day to accumulate at least 210 min of overall PA each week (Taiwan Ministry of Education, 2004). As compared with the US, this may be not comprehensive. For young children, PA can be carried out as part of active play, and not regular exercise. Emphasizing the accumulating of intermittent PA in short bouts (e.g., 5 or 10 min in one shot) and more occur over the day could be more practical approach in children (Lopes et al., 2007; Rowlands et al., 2008). The following limitations should be considered when interpreting our results. First, data from this study are from 35 children with ASD in a relatively small region in the Southern of Taiwan; therefore, the findings are not fully generalizable to the ASD population in Taiwan. Second, because the aim of the current study was to assess habitual PA levels, it is likely that the most physically active children with ASD chose to participate. Third, it might also be that all children with ASD were from middle income families and parents in this urban community were more aware of the health benefits of PA and therefore encourage their children to be physically active. Future studies should extend the assessment of the PA patterns in children
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with ASD to larger samples across more than one location. Longitudinal measurements of PA are also needed to provide reliable results about the daily variation in PA of children with ASD. More research is also needed to understand the reasons for decreasing levels of PA during free time and weekend days for older children with ASD. Further study and more precise descriptions of the PA environment and personal correlates may also help to explain PA behaviors of this population. In conclusion, differences in PA patterns between weekdays and weekend days seem inconsistent across different grade levels; that is, younger children were more active at weekend days, while older children were more active during weekdays. Furthermore, older children were less active than younger children both between and within days, with this effect being most evident during children’s free time. 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