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Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth
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Journal of Science and Medicine in Sport journal homepage: www.elsevier.com/locate/jsams
Original research
Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth夽 Danilo R. Silva a,b , Cláudia S. Minderico b , Fernando Pinto c , Paul J. Collings d,e , Edilson S. Cyrino a , Luís B. Sardinha b,∗ a
Study and Research Group in Metabolism, Nutrition, and Exercise — GEPEMENE, Londrina State University, Brazil Exercise and Health Laboratory, CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Portugal c Departament of Social Sciences, Ec¸a de Queiros High School, Portugal d Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, United Kingdom e University of York, Department of Health Sciences, United Kingdom b
a r t i c l e
i n f o
Article history: Received 30 June 2017 Received in revised form 28 November 2017 Accepted 17 January 2018 Available online xxx Keywords: Sitting Standing desk Childhood obesity School-based intervention
a b s t r a c t Objectives: We investigated the impact of a standing desk intervention on daily objectively monitored sedentary behavior and physical activity in 6th grade school students. Design: Cluster non-randomised controlled trial. Method: Two classes (intervention students: n = 22 [aged 11.8 ± 0.4 years]; control students: n = 27 [11.6 ± 0.5 years]) from a public school in Lisbon were selected. The intervention involved replacing traditional seated classroom desks for standing desks, for a total duration of 16 weeks, in addition to performing teacher training and holding education/motivation sessions with students and parents. Sedentary behavior (ActivPAL inclinometer) and physical activity (Actigraph GT3X+ accelerometer) were measured for seven days immediately before and after the intervention. Results: There were no differences in baseline behaviors between intervention and control groups (p > 0.05). At follow-up (16 weeks), it was observed that the intervention group had decreased time spent sitting (total week: −6.8% and at school: −13.0% relative to baseline) and increased standing (total week: 16.5% and at school: 31.0%) based on inclinometer values (p-value for interaction group*time <0.05). No significant differences in activity outcomes were observed outside school time (week or weekend) between groups. Conclusion: We conclude that a 16 week classroom standing desk intervention successfully reduced sitting time and increase standing time at school, with no observed compensatory effects outside of school time. © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
1. Introduction Defined as any waking behavior characterized by an energy expenditure ≤1.5 METs while in a sitting or reclining posture,1 sedentary behavior constitutes a growing public health problem.2,3 It is estimated that sitting time is responsible for 433,000 deaths/year worldwide (almost 4% of the total).4 Although the strongest evidence for harmful effects associated with prolonged sitting is observed in adulthood, sedentary children and adolescents tend to have poorer physical and mental health.5 Sedentary
夽 ClinicalTrials.gov identifier: NCT03137836. ∗ Corresponding author. E-mail address: [email protected] (L.B. Sardinha).
lifestyles also seem to exhibit strong tracking from childhood to adulthood.6 Objective measures indicate that school-aged children spend almost 70% of their waking hours in sedentary behavior,7 with much of this sedentary time taking place in schools. Uninterrupted sitting time at school has been related to musculoskeletal pain (e.g. neck, lower back, hip, and knee discomfort).8 Nevertheless, despite many interventions that have targeted reduced recreational screen time9 and encouraging active rather than passive travel10 in youth, less attention has been paid to the school setting. Recently, some single and multi-component interventions have been performed to reduce sitting time at school. Changes to the general school environment, curriculum or orientation/education sessions have been trialed to improve activity and dietary habits.11 Considering that more than 90% of classroom time is spent sitting,12 a promising strategy may be replacement of traditional seated
https://doi.org/10.1016/j.jsams.2018.01.007 1440-2440/© 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007
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desks for standing desks. Few trials of this description have been conducted, but findings to date suggest that standing desks of different types (e.g. height adjusted/stand-biased, individual/in group use) may be an effective method to reduce classroom sitting time by around 40–60 min/day,13 with no reported adverse effects on cognitive function or academic achievement.14,15 However, most of current evidence is based on pilot studies16 with some focusing exclusively on postural and feasibility issues.17,18 Furthermore, studies have thus far only been conducted in Australia, New Zealand, the UK and USA. To broaden the evidence base investigation in different cultural, economic and educational systems is needed. These future studies should further consider possible variability of children’s physical activity dimensions19 in line with the concept of the “activitystat” hypothesis.20 This biological centered hypothesis has been proposed to explain physical activity compensatory behaviors, and implies that changes in a specific domain, for example decreased sitting in school, could be compensated or offset by increased sedentary time on the same day after school, or on subsequent days.21,22 Hence, in order to comprehensively understand the effects of domain-specific health behavior interventions, an integrative approach that considers 24 h movement behaviors is warranted.23 It remains unclear if reduced sitting time achieved in school time by introduction of classroom standing desks may impact on physical activity or sedentary behavior performed outside of school time during the week or at the weekend. Therefore, our primary aim was to investigate the impact of a 16 week standing desk intervention on classroom sitting time; secondly, we verified the effects of the intervention on whole-day objectively measured sedentary behavior and physical activity both during the week and at the weekend.
2. Methods The ERGUER/Portugal project is a school-based cluster controlled trial. The clusters were two sixth grade classes recruited from a large public school located in Lisbon. Students were aged between 11 and 13 years-old, had no limitations to perform postural changes and provided parent/guardian consent to participate in the study. Classes were labeled as either the intervention (IG) or control group (CG). Fifty-one students were eligible (IG = 22 and CG = 29) for the study, however two CG students did not return consent. Thus, the final sample was composed of 49 students (IG = 22 and CG = 27). Adjustable sit-stand desks were introduced to the intervention classroom for a period of 16 weeks, separated by two measurement (pre- and post-intervention) time-points. The study was approved by the local ethics committee. The intervention took place over a period of 16 weeks (February–May) and involved environmental (physical and social) changes and school teacher training. The physical environment was ® modified by exchanging traditional seated desks for the LearnFit Adjustable Standing Desk (Ergotron, USA). In addition to allowing postural changes, these desks can be moved and thus expand possibilities for classroom based activities. Also, in order to promote family support, three meetings with parents/guardians were conducted during the intervention. The first to explain the rationale and components of the study, invite students to participate and collect the written informed consent. The second meeting served to update the parents/guardians about the classroom work, and to collect prior perceptions and suggestions in order to improve pedagogical strategies and maintain motivation related to the intervention. In the final meeting the main results of the intervention were presented, individualized reports discussed, and further perceptions of parents/guardians about the intervention were collected. Throughout the intervention, six teacher training
problem-solving sessions (four hours each) were conducted by physical education and psychology professionals. The first session involved dissemination of study information including the project rationale; teachers were then required to present perceived barriers/difficulties and good practices in order for group discussions to take place (next four sessions). In each session teacher perceptions about the effectiveness of the intervention were collected. The sixth and final session were used to present the results and collect concluding perceptions from teachers. Teachers that attended sessions received professional credits for carrier progression. The information gathered from both parents and teachers was used to continually modify the intervention. For example, some parents reported that their child felt tired when standing, and thus teachers were advised to allow tired children to sit briefly for recuperation. Furthermore, peer-to-peer teacher recommendations, such as adopting a U-shaped arrangement of classroom desks, were promoted as examples of best practice that teachers were encouraged to replicate. Subjects taught in school (seven classes timetabled daily with each class lasting 50 min) included Mathematics, Portuguese, History, English, Technology, Visual Arts, Music, and Physical Education. All Physical Education, Visual Arts and Music classes were conducted in different rooms to that which housed the standing desks. Thus, of the 35 weekly classes, 29 in total were held in the intervention classroom. Body mass index (BMI, kg/m2 ) was calculated from measured weight (nearest 0.1 kg) and height (nearest 0.1 cm). Waist circumference was measured to the nearest 0.1 cm, 1 cm above the iliac ® crest (Sanny metal tape). Somatic maturation was estimated by the peak of height velocity from trunk-encephalic height (50 cm bench). The ActivPALTM micro inclinometer (PAL Technologies Limited, Glasgow, UK) was used to assess time spent lying/sitting (main outcome), standing, stepping, sit-to-stand transitions, and total number of steps. The device was attached to students at the anterior mid-line of the right thigh by adhesive waterproof film (3 MTM TegadermTM ). Participants were asked to wear the inclinometer continuously for seven days, including when showering and sleeping, but were requested to remove the device for swimming. These data were reduced by ActivPALTM software v.7.2.32 with 15 s epochs (at 20 Hz). In addition, the Actigraph GT3X+ accelerometer was used to capture habitual physical activity. High correlations between ActivPALTM monitor with direct observation for the time spent sitting/lying, standing, and walking in children have been found.24 However, ActivPALTM seems to be less accurate when measuring fast walking and running in children.23 In contrast, Actigraph accelerometers are more valid for assessing moderate-to-vigorous physical activity (MVPA) in children,25 and less accurate in identifying the transition between sitting and standing. In other words, Actigraph poorly distinguishes light physical activity from sedentary time,26 and thus in the present investigation ActivPAL was used for the lower spectrum of physical activity (i.e. sitting and standing time), while the Actigraph was incorporated for assessment of MVPA. Participants were instructed to wear the Actigraph on the right rip (near the iliac crest) during waking hours for seven days. The device, initialized to collect data in 15 s epochs (at 30 Hz), was attached via an elasticated belt and was removed only for waterbased activities. The Choi et al.27 criteria were used to identify periods of monitor non-wear and Evenson et al.28 cutoff were used to derive MVPA using Actilife v.6.10.4 software. For both devices, activity records that had four or more days (including one weekend day) each with ≥600 min of wear were considered valid. Participants manually recorded if the device was removed at all, the time and reason. Using the same diary record, information regarding sleep timings was collected. In addition, data from the accelerom-
Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007
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eter and inclinometer were cross-checked in order to provide a more reliable estimate of the sleep period. For example, if consecutive zeros were observed from accelerometer data (which could indicate that the device was removed for sleep), yet the inclinometer registered standing or stepping activities, that moment was not considered sleep. Baseline assessments were performed prior to the beginning of the intervention. Descriptive statistics are expressed as frequencies, means with standard deviations or 95% confidence intervals. Shapiro–Wilk and Levene tests were used to check the normality and homoscedasticity of data. A comparison of baseline characteristics between intervention and control groups was performed by Chi-square, t-tests and Mann–Whitney tests, respectively. Generalized estimating equation models (Gamma distribution) were used for comparisons within and between groups for activity outcomes before and after the intervention. Data analyses were adjusted for wear time of the devices. Hegdes’ g was calculated as an effect size measure. Cohen’s29 convention was considered for effect size interpretation (small [0.2], medium [0.5], and large [0.8]). For analyzes, activity data were divided into four time and day specific categories considering the sleep time reported: week (Monday–Friday; 15 h: 08:00–23:00), school time (9 h: 08:00–17:00), outside school (6 h: 17:00–23:00) and weekend (14 h: 09:00–23:00). Statistical significance of p < 0.05 was adopted and data were analyzed by SPSS software version 21.0.
3. Results Baseline study characteristics are shown in Table 1. There were no differences between intervention and control groups, including with regards to accelerometer and inclinometer data which were available for all 49 participants. Table 2 displays the mean changes in activity behaviors from baseline to immediately post-intervention, in total during the whole week, then separated by school time and time outside of school during the week, and at the weekend. Group differences in mean change were found for sitting and standing time during the week (indicated by significant time*group interactions), which were clearly achieved in school time. Throughout the week and specifically during school time, the intervention group decreased sitting time (−6.8% and −13.0%) and increased standing time (16.5% and 31.0%), respectively. Over follow-up it was observed that the control group experienced a decline in MVPA performed during school time (−30.4%), but no change was observed in the intervention group. A time effect (reduction) was observed in standing time outside school at follow-up (intervention group = −3.6 min [95% CI: −17.9 to 10.8] and control group = −14.2 min [95% CI: −25.4 to −3.0], with no difference between groups. From baseline to followup both groups reduced (with no difference between them) light physical activity during the week, both during school hours and during the whole-day. Baseline and follow-up time distributions of activity behaviors for week and weekend days as well as during school and outside school time are shown in Fig. 1. Opposite changes were observed between groups with regard to sitting and standing during the week, with no changes in stepping, sleeping and no changes in behaviors on weekends. It was observed that the proportion of time spent sitting and standing during school time changed divergently between groups. Briefly, from a feasibility perspective, only one teacher (out of 9) reported that they did not want to continue post-intervention to use the standing desk in their classes. More than half of parents (58.6%) reported that they would like their children to continue using the new height adjustable desks.
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Table 1 Baseline characteristics of study groups. Intervention group (n = 22)
Control group (n = 27)
Chronological age (years) Female Caucasian Peak height velocity (years) Body mass index (kg/m2 ) Waist circumference (cm)
11.8 ± 0.4 10 (45.5%) 21 (95.5%) −1.05 ± 1.15 19.7 ± 3.0 68.8 ± 8.3
11.6 ± 0.5 16 (59.3%) 26 (96.3%) −0.93 ± 1.05 18.9 ± 3.4 70.2 ± 11.5
0.144 0.336 0.856 0.704 0.154 0.976
Week Sleep time (h) Sitting (min/15 h) Standing (min/15 h) Stepping (min/15 h) Step counts (n/15 h) STS transitions (n/15 h) LIPA (min/15 h) MVPA (min/15 h)
8.8 ± 0.8 509.8 ± 85.3 230.9 ± 62.8 171.4 ± 40.8 13,753 ± 3610 80.9 ± 27.5 246.7 ± 58.4 51.2 ± 20.0
8.9 ± 0.7 498.6 ± 71.4 231.1 ± 62.0 179.0 ± 51.5 14,272 ± 4318 82.2 ± 18.8 247.0 ± 51.5 61.8 ± 27.5
0.799 0.630 0.952 0.673 0.748 0.673 0.825 0.191
School time Sitting (min/9 h) Standing (min/9 h) Stepping (min/9 h) Step counts (n/9 h) STS transitions (n/9 h) LIPA (min/9 h) MVPA (min/9 h)
289.8 ± 40.1 134.7 ± 36.5 115.5 ± 27.5 9554 ± 2643 44.1 ± 19.7 157.6 ± 35.4 36.5 ± 14.8
285.7 ± 43.8 128.5 ± 27.6 125.9 ± 40.3 10,266 ± 3409 43.9 ± 12.5 162.9 ± 36.1 46.7 ± 23.1
0.630 0.688 0.433 0.587 0.763 0.315 0.127
Outside school Sitting (min/6 h) Standing (min/6 h) Stepping (min/6 h) Step counts (n/6 h) STS transitions (n/6 h) LIPA (min/6 h) MVPA (min/6 h)
220.0 ± 68.8 96.1 ± 39.4 55.9 ± 20.4 4199 ± 1666 36.8 ± 12.2 89.1 ± 28.3 14.7 ± 7.6
212.9 ± 49.0 102.6 ± 43.4 53.2 ± 22.2 4006 ± 1822 38.3 ± 9.7 84.1 ± 25.0 15.1 ± 10.0
0.802 0.546 0.560 0.673 0.587 0.601 0.794
10.1 ± 1.2 537.2 ± 112.2 186.2 ± 54.8 108.4 ± 45.0 8137 ± 3684 73.7 ± 24.0 180.1 ± 51.1 25.7 ± 19.9
10.6 ± 0.9 508.8 ± 99.0 189.8 ± 78.5 106.1 ± 47.3 7888 ± 4107 74.6 ± 23.4 193.2 ± 57.7 26.1 ± 14.8
0.692 0.455 0.507 0.651 0.533 0.952 0.658 0.488
Weekend Sleep time (h) Sitting (min/14 h day) Standing (min/14 h day) Stepping (min/14 h day) Step counts, (n/14 h day) STS transitions (n/14 h day) LIPA (min/14 h) MVPA (min/14 h day)
p-Value
Note: STS = sit-to-stand. LIPA = light physical activity. MVPA = moderate to vigorous physical activity.
4. Discussion Considering the high prevalence and harmful effects of sedentary behavior in youth, effective interventions to reduce sitting time in different contexts are warranted. Time spent in school represents a third of a child’s day and more than half of this time is spent sedentary.12 Following a 16 week multi-level classroom standing desk intervention, this study achieved significant reductions in sitting time, with increased standing during school hours. In addition, while the control group reduced MVPA performed in school, and reduced standing time outside of school hours at follow-up, no such compensatory changes were observed in other domains (i.e. outside school and at the weekend) among the intervention group. This highlights that school environmental changes supplemented with teacher training and parental involvement (social norms) can be an effective strategy to reduce youth sedentary behavior in school classrooms, in the absence of compensation effects outside of school time. Heterogeneity in the design of previous classroom standing desk interventions may explain the mixed study results reported to date. Many of the previous studies conducted a single-level intervention (environmental) with different types of standing desks (e.g. height adjusted/stand-biased, individually assigned vs. shared
Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007
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Table 2 Mean changes in activity behaviors during the week (in total, stratified by school time and outside school time) and at weekends after 16 weeks of follow-up. Intervention group (n = 22)
Control group (n = 27)
0.05 (−0.14 to 0.23) −34.9 (−82.2 to 12.4) 38.1 (7.8 to 68.4) −6.0 (−27.3 to 15.3) −553 (−2315 to 1210) 0.1 (−9.5 to 9.6) −20.1 (−42.3 to 2.2) 0.8 (−8.5 to 10.1)
−0.12 (−0.29 to 0.06) 31.6 (9.6 to 53.5) −19.0 (−34.9 to −3.0) −5.6 (−18.5 to 7.3) −270 (−1324 to 784) 2.5 (−3.3 to 8.3) −7.7 (−19.6 to 4.2) −9.0 (−15.7 to −2.3)
0.04 −0.14 0.18 −0.00 −0.02 −0.02 −0.05 0.11
School time Sitting (min/9 h* ) Standing (min/9 h* ) Stepping (min/9 h) Step counts (n/9 h) STS transitions (n/9 h) LIPA (min/9 h† ) MVPA (min/9 h* )
−37.6 (−69.7 to −5.5) 41.7 (18.9 to 64.5) −3.7 (−17.0 to 9.7) −431 (−1557 to 696) −3.7 (−11.2 to 3.7) −11.2 (−23.5 to 1.1) 0.3 (−6.4 to 6.5)
11.9 (−3.7 to 27.5) −4.8 (−14.2 to 4.6) −7.6 (−17.3 to 2.1) −451 (−1271 to 369) 2.8 (−1.6 to 7.1) −5.6 (−14.3 to 3.1) −8.6 (−14.6 to −2.5)
−0.15 0.20 0.03 0.00 −0.08 −0.05 0.13
Outside school Sitting (min/6 h) Standing (min/6 h† ) Stepping (min/6 h) Step counts (n/6 h) STS transitions (n/6 h) LIPA (min/6 h) MVPA (min/6 h)
2.7 (−25.2 to 30.7) −3.6 (−17.9 to 10.8) −2.3 (−15.6 to 11.0) −122 (−1198 to 954) 3.8 (−0.8 to 8.4) −8.9 (−23.7 to 5.9) 0.7 (−4.1 to 5.6)
19.7 (3.1 to 36.3) −14.2 (−25.4 to −3.0) 2.0 (−5.4 to 9.4) 181 (−413 to 775) −0.2 (−3.3 to 2.8) −2.1 (−10.5 to 6.3) −0.4 (−2.9 to 2.0)
−0.06 0.07 −0.03 −0.03 0.08 −0.04 0.02
−0.01 (−0.59 to 0.57) 1.4 (−61.7 to 64.4) −9.1 (−35.4 to 17.3) 8.3 (−22.3 to 38.9) 975 (−1709 to 3659) −2.0 (−11.4 to 7.4) 2.0 (−12.2 to 16.2) 2.1 (−10.0 to 14.2)
−0.32 (−0.71 to 0.06) 6.8 (−28.3 to 41.8) −3.8 (−20.8 to 13.2) 16.9 (−9.1 to 43.0) 1341 (−856 to 3539) 2.6 (−3.9 to 9.1) 13.6 (−7.7 to 35.0) 4.0 (−2.3 to 10.4)
0.14 −0.01 −0.02 −0.03 −0.01 −0.05 −0.09 −0.12
Week Sleep time (h) Sitting (min/15 h* ) Standing (min/15 h* ) Stepping (min/15 h) Step counts (n/15 h) STS transitions (n/15 h) LIPA (min/15 h† ) MVPA (min/15 h)
Weekend Sleep time (h) Sitting (min/14 h day) Standing (min/14 h day) Stepping (min/14 h day) Step counts (n/14 h day) STS transitions (n/14 h day) LIPA (min/14 h) MVPA (min/14 h day)
Hedges’ g
Note: STS = sit-to-stand. LIPA = light physical activity. MVPA = moderate to vigorous physical activity. Bold values signifies p < 0.05. * p < 0.05 for time vs group interaction. † p > 0.05 for time (whole group).
desks rotated between students), accessories (e.g. stools, exercise balls or bean bags) and classroom structure (e.g. size and place for keeping school supplies).14 Generally, reductions in sitting time and increases in standing time of around 40–60 min/day have been described,15 which corroborate our current findings. However, previous studies have reported results for specific classes (min/h), according to the school day only (min/8 h) or all waking hours (min/15 h), which makes comparison across studies difficult. We observed that changes in sitting and standing time were achieved in school time. The absence of differences in physical activity outcomes indicates that sitting was predominately replaced by standing. Lanningham-Foster et al.30 found that an activity-permissive classroom was more effective to increase steps compared to a standing classroom only (similar to our approach). Clemes et al.31 (two trials: UK and Australia) observed that, even with similar sitting time reduction between trials, when few standing desks were provided for rotational use, more stepping time/movement counts were achieved compared to individual standing desks for all children. The size of the current intervention classroom (8 m × 7.5 m in dimensions) meant that there was limited space for 22 students + standing desks (50 cm × 50 cm each) + stools (30 cm × 40 cm each) to move, which might explain our observation of direct replacement of sitting with standing rather than higher-intensity movement. Few studies have investigated the effects of more standing time during school classes by utilizing a 24 h integrative approach,23 which is needed to investigate compensatory effects that may occur
outside of school or during weekends.19,20 Two previous studies (which constitute three trials) analyzed whole weekday effects of different classroom standing desks and consistently found that reduced sitting in school was accompanied by a trend of decreased sitting outside of school hours (synergistic effects).31,32 Here, we observed that a classroom based intervention affected sitting and standing accumulated throughout 24 h of a weekday, and that changes were achieved within school time (Fig. 1). Seemingly, there was no evidence of adverse or compensatory effects, as the intervention group maintained MVPA at school and standing time outside school compared to the control group. Also, no differences between groups were observed in behaviors outside school. This is the first study to show that classroom standing desks did not affect weekend behavior. With regards to student’s standing desk use, most previous studies have allowed students free choice to sit or stand. In our training sessions, teachers were encouraged to conduct the majority of their classes using standing activities. However, there was no specific target to meet and teachers and students were permitted flexibility in terms of how the desks were utilized. We have no statistical power to perform sub-group analyses, but we can presume that specific teachers and keener students may have been more likely to successfully incorporate or use standing desks, while other groups may demand more intensive and specific encouragement to change classroom behavior. For example, younger children who are more active during break-times could prefer to sit during classes for rest, whereas adolescents could have greater acceptance of standing
Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007
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Fig. 1. Distribution of week and weekend whole-day (24 h), school and outside school time-use, before and after 16 weeks of follow-up in both groups.
desks as they tend to be less active during intervals. The same can be hypothesized for adolescents with different fitness levels and body fat.19 The current findings provide important evidence for schoolbased health promotion; in addition to reduce school sitting time we found good acceptability of our intervention to teachers and parents. It seems clear that school environment can influence student’s activity behaviors.30 Although children are more active at school compared to outside school hours (week or weekend), more than half the school day is spent seated. It is encouraging that by combining multi-level actions (e.g. students orientation, teachers training), the current intervention strategy showed effectiveness to reduce sitting during classes. Additional research on how classroom standing desks may influence academic and cognitive outcomes would be informative. This is the first classroom standing desk intervention to be evaluated outside of Australia, New Zealand, the UK and USA. Our intervention content was designed to be considerate with respect to location, such as cultural norms, the education system and prevailing teaching styles. There may be no completely standardized way to conduct this kind of intervention and studies in additional contexts are warranted to broaden the evidence base. Because this was a non-randomized trial conducted with only two classes from the same school (intervention and control), the findings should
be viewed with caution. Also, although most cases of non-wear time from activPAL devide had been considered no valid assessment, we cannot exclude potential bias regarding the non-wear time detected as sitting or standing time. However, this is the first classroom standing desk intervention to incorporate multilevel actions (targeting both environmental and social domains) which were addressed to students, parents, and teachers. Also, we monitored sedentary behavior and physical activity using objective devices. Although these monitoring devices are not devoid of limitations, they are superior to subjective reports of movement behaviors which are prone to substantial error and bias
5. Conclusions We identified a strategy for reducing school sitting time that exhibited no adverse effects on other domains of activity. A multilevel classroom standing desk intervention therefore appears to be a feasible approach to help reduce daily sitting time in youth. Longer-term investigations should aim to understand links in the causal chain by process evaluation, performed as part of larger cluster randomized controlled trials.
Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007
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Practical implications • Multi-level classroom standing desk intervention was effective to replace sitting to standing time during school hours. • The reduced sitting time at school was not compensated with more sedentary behavior or less activity outside school or at the weekend. • In addition to the effects on sedentary time, intervention showed promising results regarding the mitigation of the tendency of reducing moderate to vigorous physical activity throughout adolescence. Acknowledgments The authors thank the school principal, teachers, children and their parents (Ec¸a de Queirós High School). The authors also thank the National Council of Scientific and Technological Development (CNPq/Brazil) for supporting ESC (productivity scholarship) and DRS (sandwich doctorate scholarship — Process 201022/20150). PJC is funded by a British HeartFoundation (BHF) Immediate Postdoctoral Basic Science Research Fellowship (grant FS/17/37/32937 ). References 1. Tremblay MS, Aubert S, Barnes JD et al. Sedentary Behavior Research Network (SBRN) — Terminology Consensus Project process and outcome. Int J Behav Nutr Phys Act 2017; 14(1):75. 2. Dempsey PC, Owen N, Biddle SJ et al. Managing sedentary behavior to reduce the risk of diabetes and cardiovascular disease. Curr Diab Rep 2014; 14(9):522. 3. Hadgraft N, Owen N. Sedentary behavior and health broadening the knowledge base and strengthening the science. Res Q Exerc Sport 2017; 88(2):123–129. 4. Rezende LF, Sa TH, Mielke GI et al. All cause mortality attributable to sitting time: analysis of 54 countries worldwide. Am J Prev Med 2016; 51(2):253–263. 5. Carson V, Hunter S, Kuzik N et al. Systematic review of sedentary behaviour and health indicators in school-aged children and youth: an update. Appl Physiol Nutr Metab 2016; 41(6 (Suppl. 3)):S240–S265. 6. Biddle SJ, Pearson N, Ross GM et al. Tracking of sedentary behaviours of young people: a systematic review. Prev Med 2010; 51(5):345–351. 7. Dowd KP, Harrington DM, Bourke AK et al. The measurement of sedentary patterns and behaviors using the activPAL Professional physical activity monitor. Physiol Meas 2012; 33(11):1887–1899. 8. Oyewole SA, Haight JM, Freivalds A. The ergonomic design of classroom furniture/computer work station for first graders in the elementary school. Int J Ind Ergon 2010; 40(4):437–447. 9. Wu L, Sun S, He Y et al. The effect of interventions targeting screen time reduction: a systematic review and meta-analysis. Medicine (Baltimore) 2016; 95(27):e4029. 10. Schoeppe S, Duncan MJ, Badland H et al. Associations of children’s independent mobility and active travel with physical activity, sedentary behaviour and weight status: a systematic review. J Sci Med Sport 2013; 16(4):312–319.
11. Hegarty LM, Mair JL, Kirby K et al. School-based interventions to reduce sedentary behaviour in children: a systematic review. AIMS Public Health 2016; 3(3):520–541. 12. Cardon G, De Clercq D, De Bourdeaudhuij I et al. Sitting habits in elementary schoolchildren: a traditional versus a moving school. Patient Educ Couns 2004; 54(2):133–142. 13. Benden ME, Blake JJ, Wendel ML et al. The impact of stand-biased desks in classrooms on calorie expenditure in children. Am J Public Health 2011; 101(8):1433–1436. 14. Minges KE, Chao AM, Irwin ML et al. Classroom standing desks and sedentary behavior: a systematic review. Pediatrics 2016; 137(2):1–18. 15. Hinckson E, Salmon J, Benden M et al. Standing classrooms: research and lessons learned from around the world. Sports Med 2015; 46(7):977–987. 16. Sherry AP, Pearson N, Clemes SA. The effects of standing desks within the school classroom: a systematic review. Prev Med Rep 2016; 3:338–347. 17. Blake JJ, Benden ME, Wendel ML. Using stand/sit workstations in classrooms: lessons learned from a pilot study in Texas. J Public Health Manag Pract 2012; 18(5):412–415. 18. Benden M, Pickens A, Shipp E et al. Evaluating a school based childhood obesity intervention for posture and comfort. Health 2013; 05(08):7. 19. Ridgers ND, Barnett LM, Lubans DR et al. Potential moderators of day-to-day variability in children’s physical activity patterns. J Sports Sci 2017:1–8. 20. Rowland TW. The biological basis of physical activity. Med Sci Sports Exerc 1998; 30(3):392–399. 21. Ridgers ND, Timperio A, Cerin E et al. Compensation of physical activity and sedentary time in primary school children. Med Sci Sports Exerc 2014; 46(8):1564–1569. 22. Long MW, Sobol AM, Cradock AL et al. School-day and overall physical activity among youth. Am J Prev Med 2013; 45(2):150–157. 23. Chaput JP, Carson V, Gray CE et al. Importance of all movement behaviors in a 24 hour period for overall health. Int J Environ Res Public Health 2014; 11(12):12575–12581. 24. Aminian S, Hinckson EA. Examining the validity of the ActivPAL monitor in measuring posture and ambulatory movement in children. Int J Behav Nutr Phys Act 2012; 9:119. 25. Rowlands AV, Rennie K, Kozarski R et al. Children’s physical activity assessed with wrist- and hip-worn accelerometers. Med Sci Sports Exerc 2014; 46(12):2308–2316. 26. Mitchell T, Borner K, Finch J et al. Using activity monitors to measure sitto-stand transitions in overweight/obese youth. Med Sci Sports Exerc 2017; 49(8):1592–1598. 27. Choi L, Liu Z, Matthews CE et al. Validation of accelerometer wear and nonwear time classification algorithm. Med Sci Sports Exerc 2011; 43(2):357–364. 28. Evenson KR, Catellier DJ, Gill K et al. Calibration of two objective measures of physical activity for children. J Sports Sci 2008; 26(14):1557–1565. 29. Cohen J. Statistical Power Analysis for the Behavioral Sciences, 2nd ed. Hillsdale, NJ, Lawrence Erlbaum Associates, 1988. 30. Lanningham-Foster L, Foster RC, McCrady SK et al. Changing the school environment to increase physical activity in children. Obesity (Silver Spring) 2008; 16(8):1849–1853. 31. Clemes SA, Barber SE, Bingham DD et al. Reducing children’s classroom sitting time using sit-to-stand desks: findings from pilot studies in UK and Australian primary schools. J Public Health (Oxf) 2015; 38(3):526–533. 32. Aminian S, Hinckson EA, Stewart T. Modifying the classroom environment to increase standing and reduce sitting. Build Res Inf 2015; 43(5):631–645.
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Contents lists available at ScienceDirect
Journal of Science and Medicine in Sport journal homepage: www.elsevier.com/locate/jsams
Original research
Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth夽 Danilo R. Silva a,b , Cláudia S. Minderico b , Fernando Pinto c , Paul J. Collings d,e , Edilson S. Cyrino a , Luís B. Sardinha b,∗ a
Study and Research Group in Metabolism, Nutrition, and Exercise — GEPEMENE, Londrina State University, Brazil Exercise and Health Laboratory, CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Portugal c Departament of Social Sciences, Ec¸a de Queiros High School, Portugal d Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, United Kingdom e University of York, Department of Health Sciences, United Kingdom b
a r t i c l e
i n f o
Article history: Received 30 June 2017 Received in revised form 28 November 2017 Accepted 17 January 2018 Available online xxx Keywords: Sitting Standing desk Childhood obesity School-based intervention
a b s t r a c t Objectives: We investigated the impact of a standing desk intervention on daily objectively monitored sedentary behavior and physical activity in 6th grade school students. Design: Cluster non-randomised controlled trial. Method: Two classes (intervention students: n = 22 [aged 11.8 ± 0.4 years]; control students: n = 27 [11.6 ± 0.5 years]) from a public school in Lisbon were selected. The intervention involved replacing traditional seated classroom desks for standing desks, for a total duration of 16 weeks, in addition to performing teacher training and holding education/motivation sessions with students and parents. Sedentary behavior (ActivPAL inclinometer) and physical activity (Actigraph GT3X+ accelerometer) were measured for seven days immediately before and after the intervention. Results: There were no differences in baseline behaviors between intervention and control groups (p > 0.05). At follow-up (16 weeks), it was observed that the intervention group had decreased time spent sitting (total week: −6.8% and at school: −13.0% relative to baseline) and increased standing (total week: 16.5% and at school: 31.0%) based on inclinometer values (p-value for interaction group*time <0.05). No significant differences in activity outcomes were observed outside school time (week or weekend) between groups. Conclusion: We conclude that a 16 week classroom standing desk intervention successfully reduced sitting time and increase standing time at school, with no observed compensatory effects outside of school time. © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
1. Introduction Defined as any waking behavior characterized by an energy expenditure ≤1.5 METs while in a sitting or reclining posture,1 sedentary behavior constitutes a growing public health problem.2,3 It is estimated that sitting time is responsible for 433,000 deaths/year worldwide (almost 4% of the total).4 Although the strongest evidence for harmful effects associated with prolonged sitting is observed in adulthood, sedentary children and adolescents tend to have poorer physical and mental health.5 Sedentary
夽 ClinicalTrials.gov identifier: NCT03137836. ∗ Corresponding author. E-mail address: [email protected] (L.B. Sardinha).
lifestyles also seem to exhibit strong tracking from childhood to adulthood.6 Objective measures indicate that school-aged children spend almost 70% of their waking hours in sedentary behavior,7 with much of this sedentary time taking place in schools. Uninterrupted sitting time at school has been related to musculoskeletal pain (e.g. neck, lower back, hip, and knee discomfort).8 Nevertheless, despite many interventions that have targeted reduced recreational screen time9 and encouraging active rather than passive travel10 in youth, less attention has been paid to the school setting. Recently, some single and multi-component interventions have been performed to reduce sitting time at school. Changes to the general school environment, curriculum or orientation/education sessions have been trialed to improve activity and dietary habits.11 Considering that more than 90% of classroom time is spent sitting,12 a promising strategy may be replacement of traditional seated
https://doi.org/10.1016/j.jsams.2018.01.007 1440-2440/© 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
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desks for standing desks. Few trials of this description have been conducted, but findings to date suggest that standing desks of different types (e.g. height adjusted/stand-biased, individual/in group use) may be an effective method to reduce classroom sitting time by around 40–60 min/day,13 with no reported adverse effects on cognitive function or academic achievement.14,15 However, most of current evidence is based on pilot studies16 with some focusing exclusively on postural and feasibility issues.17,18 Furthermore, studies have thus far only been conducted in Australia, New Zealand, the UK and USA. To broaden the evidence base investigation in different cultural, economic and educational systems is needed. These future studies should further consider possible variability of children’s physical activity dimensions19 in line with the concept of the “activitystat” hypothesis.20 This biological centered hypothesis has been proposed to explain physical activity compensatory behaviors, and implies that changes in a specific domain, for example decreased sitting in school, could be compensated or offset by increased sedentary time on the same day after school, or on subsequent days.21,22 Hence, in order to comprehensively understand the effects of domain-specific health behavior interventions, an integrative approach that considers 24 h movement behaviors is warranted.23 It remains unclear if reduced sitting time achieved in school time by introduction of classroom standing desks may impact on physical activity or sedentary behavior performed outside of school time during the week or at the weekend. Therefore, our primary aim was to investigate the impact of a 16 week standing desk intervention on classroom sitting time; secondly, we verified the effects of the intervention on whole-day objectively measured sedentary behavior and physical activity both during the week and at the weekend.
2. Methods The ERGUER/Portugal project is a school-based cluster controlled trial. The clusters were two sixth grade classes recruited from a large public school located in Lisbon. Students were aged between 11 and 13 years-old, had no limitations to perform postural changes and provided parent/guardian consent to participate in the study. Classes were labeled as either the intervention (IG) or control group (CG). Fifty-one students were eligible (IG = 22 and CG = 29) for the study, however two CG students did not return consent. Thus, the final sample was composed of 49 students (IG = 22 and CG = 27). Adjustable sit-stand desks were introduced to the intervention classroom for a period of 16 weeks, separated by two measurement (pre- and post-intervention) time-points. The study was approved by the local ethics committee. The intervention took place over a period of 16 weeks (February–May) and involved environmental (physical and social) changes and school teacher training. The physical environment was ® modified by exchanging traditional seated desks for the LearnFit Adjustable Standing Desk (Ergotron, USA). In addition to allowing postural changes, these desks can be moved and thus expand possibilities for classroom based activities. Also, in order to promote family support, three meetings with parents/guardians were conducted during the intervention. The first to explain the rationale and components of the study, invite students to participate and collect the written informed consent. The second meeting served to update the parents/guardians about the classroom work, and to collect prior perceptions and suggestions in order to improve pedagogical strategies and maintain motivation related to the intervention. In the final meeting the main results of the intervention were presented, individualized reports discussed, and further perceptions of parents/guardians about the intervention were collected. Throughout the intervention, six teacher training
problem-solving sessions (four hours each) were conducted by physical education and psychology professionals. The first session involved dissemination of study information including the project rationale; teachers were then required to present perceived barriers/difficulties and good practices in order for group discussions to take place (next four sessions). In each session teacher perceptions about the effectiveness of the intervention were collected. The sixth and final session were used to present the results and collect concluding perceptions from teachers. Teachers that attended sessions received professional credits for carrier progression. The information gathered from both parents and teachers was used to continually modify the intervention. For example, some parents reported that their child felt tired when standing, and thus teachers were advised to allow tired children to sit briefly for recuperation. Furthermore, peer-to-peer teacher recommendations, such as adopting a U-shaped arrangement of classroom desks, were promoted as examples of best practice that teachers were encouraged to replicate. Subjects taught in school (seven classes timetabled daily with each class lasting 50 min) included Mathematics, Portuguese, History, English, Technology, Visual Arts, Music, and Physical Education. All Physical Education, Visual Arts and Music classes were conducted in different rooms to that which housed the standing desks. Thus, of the 35 weekly classes, 29 in total were held in the intervention classroom. Body mass index (BMI, kg/m2 ) was calculated from measured weight (nearest 0.1 kg) and height (nearest 0.1 cm). Waist circumference was measured to the nearest 0.1 cm, 1 cm above the iliac ® crest (Sanny metal tape). Somatic maturation was estimated by the peak of height velocity from trunk-encephalic height (50 cm bench). The ActivPALTM micro inclinometer (PAL Technologies Limited, Glasgow, UK) was used to assess time spent lying/sitting (main outcome), standing, stepping, sit-to-stand transitions, and total number of steps. The device was attached to students at the anterior mid-line of the right thigh by adhesive waterproof film (3 MTM TegadermTM ). Participants were asked to wear the inclinometer continuously for seven days, including when showering and sleeping, but were requested to remove the device for swimming. These data were reduced by ActivPALTM software v.7.2.32 with 15 s epochs (at 20 Hz). In addition, the Actigraph GT3X+ accelerometer was used to capture habitual physical activity. High correlations between ActivPALTM monitor with direct observation for the time spent sitting/lying, standing, and walking in children have been found.24 However, ActivPALTM seems to be less accurate when measuring fast walking and running in children.23 In contrast, Actigraph accelerometers are more valid for assessing moderate-to-vigorous physical activity (MVPA) in children,25 and less accurate in identifying the transition between sitting and standing. In other words, Actigraph poorly distinguishes light physical activity from sedentary time,26 and thus in the present investigation ActivPAL was used for the lower spectrum of physical activity (i.e. sitting and standing time), while the Actigraph was incorporated for assessment of MVPA. Participants were instructed to wear the Actigraph on the right rip (near the iliac crest) during waking hours for seven days. The device, initialized to collect data in 15 s epochs (at 30 Hz), was attached via an elasticated belt and was removed only for waterbased activities. The Choi et al.27 criteria were used to identify periods of monitor non-wear and Evenson et al.28 cutoff were used to derive MVPA using Actilife v.6.10.4 software. For both devices, activity records that had four or more days (including one weekend day) each with ≥600 min of wear were considered valid. Participants manually recorded if the device was removed at all, the time and reason. Using the same diary record, information regarding sleep timings was collected. In addition, data from the accelerom-
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eter and inclinometer were cross-checked in order to provide a more reliable estimate of the sleep period. For example, if consecutive zeros were observed from accelerometer data (which could indicate that the device was removed for sleep), yet the inclinometer registered standing or stepping activities, that moment was not considered sleep. Baseline assessments were performed prior to the beginning of the intervention. Descriptive statistics are expressed as frequencies, means with standard deviations or 95% confidence intervals. Shapiro–Wilk and Levene tests were used to check the normality and homoscedasticity of data. A comparison of baseline characteristics between intervention and control groups was performed by Chi-square, t-tests and Mann–Whitney tests, respectively. Generalized estimating equation models (Gamma distribution) were used for comparisons within and between groups for activity outcomes before and after the intervention. Data analyses were adjusted for wear time of the devices. Hegdes’ g was calculated as an effect size measure. Cohen’s29 convention was considered for effect size interpretation (small [0.2], medium [0.5], and large [0.8]). For analyzes, activity data were divided into four time and day specific categories considering the sleep time reported: week (Monday–Friday; 15 h: 08:00–23:00), school time (9 h: 08:00–17:00), outside school (6 h: 17:00–23:00) and weekend (14 h: 09:00–23:00). Statistical significance of p < 0.05 was adopted and data were analyzed by SPSS software version 21.0.
3. Results Baseline study characteristics are shown in Table 1. There were no differences between intervention and control groups, including with regards to accelerometer and inclinometer data which were available for all 49 participants. Table 2 displays the mean changes in activity behaviors from baseline to immediately post-intervention, in total during the whole week, then separated by school time and time outside of school during the week, and at the weekend. Group differences in mean change were found for sitting and standing time during the week (indicated by significant time*group interactions), which were clearly achieved in school time. Throughout the week and specifically during school time, the intervention group decreased sitting time (−6.8% and −13.0%) and increased standing time (16.5% and 31.0%), respectively. Over follow-up it was observed that the control group experienced a decline in MVPA performed during school time (−30.4%), but no change was observed in the intervention group. A time effect (reduction) was observed in standing time outside school at follow-up (intervention group = −3.6 min [95% CI: −17.9 to 10.8] and control group = −14.2 min [95% CI: −25.4 to −3.0], with no difference between groups. From baseline to followup both groups reduced (with no difference between them) light physical activity during the week, both during school hours and during the whole-day. Baseline and follow-up time distributions of activity behaviors for week and weekend days as well as during school and outside school time are shown in Fig. 1. Opposite changes were observed between groups with regard to sitting and standing during the week, with no changes in stepping, sleeping and no changes in behaviors on weekends. It was observed that the proportion of time spent sitting and standing during school time changed divergently between groups. Briefly, from a feasibility perspective, only one teacher (out of 9) reported that they did not want to continue post-intervention to use the standing desk in their classes. More than half of parents (58.6%) reported that they would like their children to continue using the new height adjustable desks.
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Table 1 Baseline characteristics of study groups. Intervention group (n = 22)
Control group (n = 27)
Chronological age (years) Female Caucasian Peak height velocity (years) Body mass index (kg/m2 ) Waist circumference (cm)
11.8 ± 0.4 10 (45.5%) 21 (95.5%) −1.05 ± 1.15 19.7 ± 3.0 68.8 ± 8.3
11.6 ± 0.5 16 (59.3%) 26 (96.3%) −0.93 ± 1.05 18.9 ± 3.4 70.2 ± 11.5
0.144 0.336 0.856 0.704 0.154 0.976
Week Sleep time (h) Sitting (min/15 h) Standing (min/15 h) Stepping (min/15 h) Step counts (n/15 h) STS transitions (n/15 h) LIPA (min/15 h) MVPA (min/15 h)
8.8 ± 0.8 509.8 ± 85.3 230.9 ± 62.8 171.4 ± 40.8 13,753 ± 3610 80.9 ± 27.5 246.7 ± 58.4 51.2 ± 20.0
8.9 ± 0.7 498.6 ± 71.4 231.1 ± 62.0 179.0 ± 51.5 14,272 ± 4318 82.2 ± 18.8 247.0 ± 51.5 61.8 ± 27.5
0.799 0.630 0.952 0.673 0.748 0.673 0.825 0.191
School time Sitting (min/9 h) Standing (min/9 h) Stepping (min/9 h) Step counts (n/9 h) STS transitions (n/9 h) LIPA (min/9 h) MVPA (min/9 h)
289.8 ± 40.1 134.7 ± 36.5 115.5 ± 27.5 9554 ± 2643 44.1 ± 19.7 157.6 ± 35.4 36.5 ± 14.8
285.7 ± 43.8 128.5 ± 27.6 125.9 ± 40.3 10,266 ± 3409 43.9 ± 12.5 162.9 ± 36.1 46.7 ± 23.1
0.630 0.688 0.433 0.587 0.763 0.315 0.127
Outside school Sitting (min/6 h) Standing (min/6 h) Stepping (min/6 h) Step counts (n/6 h) STS transitions (n/6 h) LIPA (min/6 h) MVPA (min/6 h)
220.0 ± 68.8 96.1 ± 39.4 55.9 ± 20.4 4199 ± 1666 36.8 ± 12.2 89.1 ± 28.3 14.7 ± 7.6
212.9 ± 49.0 102.6 ± 43.4 53.2 ± 22.2 4006 ± 1822 38.3 ± 9.7 84.1 ± 25.0 15.1 ± 10.0
0.802 0.546 0.560 0.673 0.587 0.601 0.794
10.1 ± 1.2 537.2 ± 112.2 186.2 ± 54.8 108.4 ± 45.0 8137 ± 3684 73.7 ± 24.0 180.1 ± 51.1 25.7 ± 19.9
10.6 ± 0.9 508.8 ± 99.0 189.8 ± 78.5 106.1 ± 47.3 7888 ± 4107 74.6 ± 23.4 193.2 ± 57.7 26.1 ± 14.8
0.692 0.455 0.507 0.651 0.533 0.952 0.658 0.488
Weekend Sleep time (h) Sitting (min/14 h day) Standing (min/14 h day) Stepping (min/14 h day) Step counts, (n/14 h day) STS transitions (n/14 h day) LIPA (min/14 h) MVPA (min/14 h day)
p-Value
Note: STS = sit-to-stand. LIPA = light physical activity. MVPA = moderate to vigorous physical activity.
4. Discussion Considering the high prevalence and harmful effects of sedentary behavior in youth, effective interventions to reduce sitting time in different contexts are warranted. Time spent in school represents a third of a child’s day and more than half of this time is spent sedentary.12 Following a 16 week multi-level classroom standing desk intervention, this study achieved significant reductions in sitting time, with increased standing during school hours. In addition, while the control group reduced MVPA performed in school, and reduced standing time outside of school hours at follow-up, no such compensatory changes were observed in other domains (i.e. outside school and at the weekend) among the intervention group. This highlights that school environmental changes supplemented with teacher training and parental involvement (social norms) can be an effective strategy to reduce youth sedentary behavior in school classrooms, in the absence of compensation effects outside of school time. Heterogeneity in the design of previous classroom standing desk interventions may explain the mixed study results reported to date. Many of the previous studies conducted a single-level intervention (environmental) with different types of standing desks (e.g. height adjusted/stand-biased, individually assigned vs. shared
Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007
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Table 2 Mean changes in activity behaviors during the week (in total, stratified by school time and outside school time) and at weekends after 16 weeks of follow-up. Intervention group (n = 22)
Control group (n = 27)
0.05 (−0.14 to 0.23) −34.9 (−82.2 to 12.4) 38.1 (7.8 to 68.4) −6.0 (−27.3 to 15.3) −553 (−2315 to 1210) 0.1 (−9.5 to 9.6) −20.1 (−42.3 to 2.2) 0.8 (−8.5 to 10.1)
−0.12 (−0.29 to 0.06) 31.6 (9.6 to 53.5) −19.0 (−34.9 to −3.0) −5.6 (−18.5 to 7.3) −270 (−1324 to 784) 2.5 (−3.3 to 8.3) −7.7 (−19.6 to 4.2) −9.0 (−15.7 to −2.3)
0.04 −0.14 0.18 −0.00 −0.02 −0.02 −0.05 0.11
School time Sitting (min/9 h* ) Standing (min/9 h* ) Stepping (min/9 h) Step counts (n/9 h) STS transitions (n/9 h) LIPA (min/9 h† ) MVPA (min/9 h* )
−37.6 (−69.7 to −5.5) 41.7 (18.9 to 64.5) −3.7 (−17.0 to 9.7) −431 (−1557 to 696) −3.7 (−11.2 to 3.7) −11.2 (−23.5 to 1.1) 0.3 (−6.4 to 6.5)
11.9 (−3.7 to 27.5) −4.8 (−14.2 to 4.6) −7.6 (−17.3 to 2.1) −451 (−1271 to 369) 2.8 (−1.6 to 7.1) −5.6 (−14.3 to 3.1) −8.6 (−14.6 to −2.5)
−0.15 0.20 0.03 0.00 −0.08 −0.05 0.13
Outside school Sitting (min/6 h) Standing (min/6 h† ) Stepping (min/6 h) Step counts (n/6 h) STS transitions (n/6 h) LIPA (min/6 h) MVPA (min/6 h)
2.7 (−25.2 to 30.7) −3.6 (−17.9 to 10.8) −2.3 (−15.6 to 11.0) −122 (−1198 to 954) 3.8 (−0.8 to 8.4) −8.9 (−23.7 to 5.9) 0.7 (−4.1 to 5.6)
19.7 (3.1 to 36.3) −14.2 (−25.4 to −3.0) 2.0 (−5.4 to 9.4) 181 (−413 to 775) −0.2 (−3.3 to 2.8) −2.1 (−10.5 to 6.3) −0.4 (−2.9 to 2.0)
−0.06 0.07 −0.03 −0.03 0.08 −0.04 0.02
−0.01 (−0.59 to 0.57) 1.4 (−61.7 to 64.4) −9.1 (−35.4 to 17.3) 8.3 (−22.3 to 38.9) 975 (−1709 to 3659) −2.0 (−11.4 to 7.4) 2.0 (−12.2 to 16.2) 2.1 (−10.0 to 14.2)
−0.32 (−0.71 to 0.06) 6.8 (−28.3 to 41.8) −3.8 (−20.8 to 13.2) 16.9 (−9.1 to 43.0) 1341 (−856 to 3539) 2.6 (−3.9 to 9.1) 13.6 (−7.7 to 35.0) 4.0 (−2.3 to 10.4)
0.14 −0.01 −0.02 −0.03 −0.01 −0.05 −0.09 −0.12
Week Sleep time (h) Sitting (min/15 h* ) Standing (min/15 h* ) Stepping (min/15 h) Step counts (n/15 h) STS transitions (n/15 h) LIPA (min/15 h† ) MVPA (min/15 h)
Weekend Sleep time (h) Sitting (min/14 h day) Standing (min/14 h day) Stepping (min/14 h day) Step counts (n/14 h day) STS transitions (n/14 h day) LIPA (min/14 h) MVPA (min/14 h day)
Hedges’ g
Note: STS = sit-to-stand. LIPA = light physical activity. MVPA = moderate to vigorous physical activity. Bold values signifies p < 0.05. * p < 0.05 for time vs group interaction. † p > 0.05 for time (whole group).
desks rotated between students), accessories (e.g. stools, exercise balls or bean bags) and classroom structure (e.g. size and place for keeping school supplies).14 Generally, reductions in sitting time and increases in standing time of around 40–60 min/day have been described,15 which corroborate our current findings. However, previous studies have reported results for specific classes (min/h), according to the school day only (min/8 h) or all waking hours (min/15 h), which makes comparison across studies difficult. We observed that changes in sitting and standing time were achieved in school time. The absence of differences in physical activity outcomes indicates that sitting was predominately replaced by standing. Lanningham-Foster et al.30 found that an activity-permissive classroom was more effective to increase steps compared to a standing classroom only (similar to our approach). Clemes et al.31 (two trials: UK and Australia) observed that, even with similar sitting time reduction between trials, when few standing desks were provided for rotational use, more stepping time/movement counts were achieved compared to individual standing desks for all children. The size of the current intervention classroom (8 m × 7.5 m in dimensions) meant that there was limited space for 22 students + standing desks (50 cm × 50 cm each) + stools (30 cm × 40 cm each) to move, which might explain our observation of direct replacement of sitting with standing rather than higher-intensity movement. Few studies have investigated the effects of more standing time during school classes by utilizing a 24 h integrative approach,23 which is needed to investigate compensatory effects that may occur
outside of school or during weekends.19,20 Two previous studies (which constitute three trials) analyzed whole weekday effects of different classroom standing desks and consistently found that reduced sitting in school was accompanied by a trend of decreased sitting outside of school hours (synergistic effects).31,32 Here, we observed that a classroom based intervention affected sitting and standing accumulated throughout 24 h of a weekday, and that changes were achieved within school time (Fig. 1). Seemingly, there was no evidence of adverse or compensatory effects, as the intervention group maintained MVPA at school and standing time outside school compared to the control group. Also, no differences between groups were observed in behaviors outside school. This is the first study to show that classroom standing desks did not affect weekend behavior. With regards to student’s standing desk use, most previous studies have allowed students free choice to sit or stand. In our training sessions, teachers were encouraged to conduct the majority of their classes using standing activities. However, there was no specific target to meet and teachers and students were permitted flexibility in terms of how the desks were utilized. We have no statistical power to perform sub-group analyses, but we can presume that specific teachers and keener students may have been more likely to successfully incorporate or use standing desks, while other groups may demand more intensive and specific encouragement to change classroom behavior. For example, younger children who are more active during break-times could prefer to sit during classes for rest, whereas adolescents could have greater acceptance of standing
Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007
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Fig. 1. Distribution of week and weekend whole-day (24 h), school and outside school time-use, before and after 16 weeks of follow-up in both groups.
desks as they tend to be less active during intervals. The same can be hypothesized for adolescents with different fitness levels and body fat.19 The current findings provide important evidence for schoolbased health promotion; in addition to reduce school sitting time we found good acceptability of our intervention to teachers and parents. It seems clear that school environment can influence student’s activity behaviors.30 Although children are more active at school compared to outside school hours (week or weekend), more than half the school day is spent seated. It is encouraging that by combining multi-level actions (e.g. students orientation, teachers training), the current intervention strategy showed effectiveness to reduce sitting during classes. Additional research on how classroom standing desks may influence academic and cognitive outcomes would be informative. This is the first classroom standing desk intervention to be evaluated outside of Australia, New Zealand, the UK and USA. Our intervention content was designed to be considerate with respect to location, such as cultural norms, the education system and prevailing teaching styles. There may be no completely standardized way to conduct this kind of intervention and studies in additional contexts are warranted to broaden the evidence base. Because this was a non-randomized trial conducted with only two classes from the same school (intervention and control), the findings should
be viewed with caution. Also, although most cases of non-wear time from activPAL devide had been considered no valid assessment, we cannot exclude potential bias regarding the non-wear time detected as sitting or standing time. However, this is the first classroom standing desk intervention to incorporate multilevel actions (targeting both environmental and social domains) which were addressed to students, parents, and teachers. Also, we monitored sedentary behavior and physical activity using objective devices. Although these monitoring devices are not devoid of limitations, they are superior to subjective reports of movement behaviors which are prone to substantial error and bias
5. Conclusions We identified a strategy for reducing school sitting time that exhibited no adverse effects on other domains of activity. A multilevel classroom standing desk intervention therefore appears to be a feasible approach to help reduce daily sitting time in youth. Longer-term investigations should aim to understand links in the causal chain by process evaluation, performed as part of larger cluster randomized controlled trials.
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Practical implications • Multi-level classroom standing desk intervention was effective to replace sitting to standing time during school hours. • The reduced sitting time at school was not compensated with more sedentary behavior or less activity outside school or at the weekend. • In addition to the effects on sedentary time, intervention showed promising results regarding the mitigation of the tendency of reducing moderate to vigorous physical activity throughout adolescence. Acknowledgments The authors thank the school principal, teachers, children and their parents (Ec¸a de Queirós High School). The authors also thank the National Council of Scientific and Technological Development (CNPq/Brazil) for supporting ESC (productivity scholarship) and DRS (sandwich doctorate scholarship — Process 201022/20150). PJC is funded by a British Heart
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Please cite this article in press as: Silva DR, et al. Impact of a classroom standing desk intervention on daily objectively measured sedentary behavior and physical activity in youth. J Sci Med Sport (2018), https://doi.org/10.1016/j.jsams.2018.01.007