The need for effective interventions in the UK targeting the primary prevention of chronic diseases by encouraging healthy lifestyles in children has been highlighted in a number of recent reports. For example, the Chief Medical Officer for England’s 2012 annual report, Our Children Deserve Better: Prevention Pays198 and the UK’s Childhood Obesity: A Plan for Action199 highlight the importance of the school environment in promoting healthy behaviours. Sedentary behaviour is highly prevalent in children28 and is adversely associated with adiposity and weight gain, and clustered metabolic risk.13,200 As sedentary behaviours track from childhood into adulthood,15,40 reducing children’s sitting time could reduce the risk of numerous chronic conditions associated with prolonged sitting in adulthood.163 In the present study, at baseline our combined sample (intervention and control participants) spent, on average, 8.75 hours per day sitting, accounting for 63% of their waking hours. Over two-thirds (67%) of class time was spent sitting, confirming this environment as a suitable setting for behaviour change.
The purpose of this study was to undertake a pilot cluster RCT to test the feasibility of conducting and evaluating a school-based sit–stand desk intervention to reduce children’s sedentary behaviour. As a consequence, the implications of this study do not, at this stage, relate to practice, but to the feasibility and design of a follow-on full-scale cluster RCT. Study findings are discussed below in relation to the research objectives. When appropriate, the findings are compared with other studies and the lessons learnt from this study inform suggestions for a future trial.
Trial feasibility-related outcomes (objectives 1–4)
Objective 1: establish and refine a recruitment strategy for schools and pupils
A total of 24 eligible schools were approached for recruitment into this pilot study and the target number of eight schools consented to take part (recruitment rate = 33%). This recruitment rate is similar to recruitment rates seen in other primary school-based interventions located in this region201 and elsewhere in England.202 The eight recruited schools were located predominantly in urban areas throughout the Bradford metropolitan district. Across the eight schools, an average of 17.1% of pupils were eligible for free school meals; this figure matches the 17.2% of children across all schools in Bradford eligible for free school meals, suggesting that the recruited schools were largely representative of schools within this area. Similarly, the proportion of children eligible for free school meals from the 12 schools that declined to participate was 17.4%. In England, in 2017 (the time of the intervention), 14.8% of children were eligible for free school meals,113 demonstrating the slightly higher levels of deprivation within this study setting.
The recruited schools tended to have a higher proportion of children whose first language was not English (51.4%) than schools that declined to participate (38.4%), and schools in Bradford overall (42.3%).113 In England, in 2017, 20.6% of primary school children were registered as having English not as their first language, highlighting a greater ethnic diversity in the study sample and Bradford population than in national-level data.113 Of interest, the schools opting into the study were more likely to contain a higher proportion of South Asian children, with schools declining to participate being more likely to contain white British children (8 out of the 12 declined schools). This finding highlights that the present study was effective in recruiting a diverse range of schools into the study, in terms of the ethnic distribution of their pupils; however, additional strategies to recruit schools containing a higher proportion of white British children may need to be incorporated into a full trial.
Within the participating schools, 75% (n = 176) of eligible pupils provided parental consent and written assent to participate in the evaluation measures, which exceeded our target minimum sample size of 120 participants. This recruitment rate is higher than that seen in a recent RCT (59%) examining the effectiveness of a healthy lifestyle programme [the West Midlands ActiVe lifestyle and healthy Eating in School (WAVES) children study] conducted in primary schools from the West Midlands,202 and similar to that reported (79%) in a primary school-based sit–stand desk intervention in the USA.203 Overall, this pilot RCT has demonstrated the feasibility of our recruitment strategy for both schools and children into the Stand Out in Class study.
Objective 2: determine attrition in the trial (schools and children)
All eight participating schools completed the trial, leading to a 100% school retention rate. At 7 months’ follow-up, the overall retention rate of participating children was 97% (96% from the control group and 98% from the intervention group). Fifty per cent of children not returning for the follow-up measures had moved away from the area during the study and, hence, changed schools.
Objective 3: determine completion rates for outcome measures (and whether or not these are sufficiently high to provide accurate data in a full trial)
Completion rates for the outcome measures ranged from 63% to 97%. The highest completion rates were seen for the anthropometric (94%) and questionnaire-based measures (97%), with the completion rates for these measures being comparable to those reported in the Active for Life Year 5 cluster RCT, a school-based intervention targeting physical activity, sedentary behaviour and fruit and vegetable consumption in children.119 The lowest completion rate (63%) was observed for the activPAL, with a number of children not providing valid data from this device across the two measurement periods. The proportion of children providing valid activPAL data in the present study is higher than that observed previously in a similar group of children29 and identical to that observed in a recent sit–stand desk RCT in Belgian children.204 These numbers are lower, however, than those observed (> 90% compliance) in other (non-RCT) classroom-based sit–stand desk interventions in which the activPAL was the primary outcome.68,205
In comparison with the activPAL, rates of compliance with the wear time criteria for the ActiGraph were higher (83%) when the same wear time criteria were applied (≥ 8 hours on at least 1 weekday). In the Active for Life Year 5 study, 60% of participants complied with their ActiGraph wear time criteria (≥ 8 hours of wear on at least 3 days206).119 Applying the same criteria to the ActiGraph data in the present study would have resulted in 68% of our sample providing valid data at baseline and follow-up, confirming the feasibility of this device. The acceptability of the activPAL as the proposed primary outcome measure for a definitive trial is discussed further in Objective 6: assess the acceptability of measurement instruments to teachers, children, parents and guardians, including the activPAL inclinometer as the tool for the measurement of the primary outcome. This pilot RCT has highlighted the need for further research to examine how wear protocols can be improved for the activPAL to increase compliance. Aside from this measure, however, completion rates for the remaining measures examined herein were sufficiently high to provide accurate data in a full trial.
Objective 4: assess whether or not there are any differences in trial recruitment, retention and acceptability between ethnic groups
There were no observed differences in trial recruitment, retention or compliance rates between South Asian and white British children. Ninety-eight per cent of white British and South Asian children provided parental consent and written assent to participate in the trial evaluation, and retention rates of 98% were observed in both ethnic groups. Sixty-five per cent of white British children and 68% of South Asian children provided valid activPAL data, whereas 87% and 84% of children within these ethnic groups provided valid ActiGraph data, respectively. No themes emerged during the process evaluation to indicate differences in the acceptability of the trial or intervention between different ethnic groups.
Lessons learnt from the process evaluation (addressing objectives 1 and 5–9)
Table 21 summarises the key lessons learnt regarding the acceptability of the procedures adopted, the measurement tools and the Stand Out in Class intervention, from our detailed process evaluation. Overall, the process evaluation offered a number of positive insights from teachers, children and parents about the recruitment strategy, the acceptability of randomisation, measurement tools and intervention, along with the fidelity of the intervention and its impact on day-to-day classroom management.
Objective 1: establish and refine a recruitment strategy for schools and pupils
Teachers, children and parents all considered the recruitment approach adopted to be appropriate and teachers liked how the study was explained to children by the research team during classroom visits. As highlighted in Trial feasibility-related outcomes (objectives 1–4), Objective 1: establish and refine a recruitment strategy for schools and pupils, 75% of eligible pupils from the participating schools provided parental consent to participate in the trial evaluation. Informal conversations with parents who did not provide informed consent for their child to participate revealed that the most common reason for this was that parents were unaware of the study, through not receiving or not reading the study information sheet sent home with their children. A future trial should explore with schools additional options to inform parents and guardians about the study, such as inclusion of a brief mention of an up and coming study in electronic school newsletters, for example, or via schools’ social media platforms.
Objective 5: assess the acceptability of randomisation to schools
The process of randomisation was regarded as acceptable and fair by teachers, children and parents, and although participants from the control schools expressed disappointment at being randomised into the control arm, participants understood why a control condition was needed. Control arm teachers stated that participating in the study was still a positive experience for their class.
Objective 6: assess the acceptability of measurement instruments to teachers, children, parents and guardians, including the activPAL inclinometer as the tool for the measurement of the primary outcome
The majority of the measurement instruments used within this pilot trial were deemed to be acceptable by teachers, children and parents. Teachers reported that some children experienced irritation on their legs caused by the medical dressing used to attach the activPAL; however, they reported that this occurred in a small minority of children and did not feel that it was a big issue. However, some children also reported that the medical dressing was ‘problematic’ and this was echoed by some parents. Concerns regarding the attachment of the activPALs are reflected in the compliance data reported in Trial feasibility related outcomes (objectives 1–4), Objective 3: determine completion rates for outcome measures (and whether or not those are sufficiently high to provide accurate data in a full trial. Children reported generally preferring the ActiGraph and this was reflected by the higher compliance data seen for this device.
Further research should examine different attachment options for the activPAL in children. In the present study, we adopted a 24-hour wear protocol, with the anticipation that the hypoallergenic Hypafix dressing would stay on the skin for a number of days, and not require children to frequently take the device (and dressing) on and off. This approach has been used successfully in a recent sit–stand desk intervention with 11-year-olds.68 Other researchers, however, have enclosed the activPAL in a small pocket in an adjustable elasticised belt that is worn at the mid-anterior position of the thigh throughout waking hours only and removed for any water-based activities.38 This attachment option resulted in high compliance rates (> 90%) in a recent sit–stand desk intervention in 10- to 11-year-olds and has been used successfully in a cross-sectional study with > 200 8- to 11-year-olds.150,205
Other researchers have recently used the ActiGraph placed on the anterior aspect of the thigh attached using an elasticised belt as the primary outcome measure in recent sit–stand desk interventions in schools.66,207 When mounted on the thigh, the ActiGraph inclinometer algorithm has been found to be a valid and reliable method of measuring sitting and standing postures.208,209 The utility of the ActiGraph worn on the thigh and the activPAL placed within an elasticised belt should be explored in a sample of primary school children within the UK, to inform a definitive trial.
Children reported that the RVIP task was difficult and this is reflected by the relatively low levels of accuracy recorded on this test. This test has previously been used in slightly older samples of school children (12- to 13-year-olds),101 and may, therefore, not be appropriate for younger age groups. Some parents reported the health-related resource use questionnaire burdensome to complete and this is reflected in the low completion rate for this measure. Future studies should investigate more appropriate methods of obtaining this information from parents to inform economic evaluations.
Objective 7: assess the acceptability of the intervention to teachers, children, parents and guardians
Initial thoughts about sit–stand desks being installed within classrooms were generally very positive by teachers, children and parents. After a few weeks of the desks being installed, teachers’ views of the intervention remained positive and any initial apprehensions about the desks (including any potential negative impact on handwriting and general behaviour) were not experienced. Towards the end of the intervention, teachers commented on how the desks were now regarded as part of the norm within their classrooms. The overall design and features of the desks, including their wheels, which enabled them to be moved easily, were highlighted as positives by teachers. These comments about the desks fitting in within the classroom and their portability are in agreement with interview data collected from a high school teacher in the USA following installation of six LearnFit desks in their classroom over a 9-week period.210
Similar to the teachers, children were very positive about the desks throughout the intervention. A number highlighted that their comfort levels when working at the desks improved and some reported feeling healthier by standing up. A number of the children reported that they liked having their own space and they liked having the option to sit or stand when using the desks. These comments about space and having the option to sit or stand mirror those from a sample of 11- to 14-year-olds from a US middle school exposed to six LearnFit desks over 9 weeks.210 Some children in the present study reported that they felt that the desks improved behaviour within the classroom. This is something that has been reported previously by parents interviewed following a pilot sit–stand desk intervention in a primary school in Texas.58 In the Texas study, 61% of parents interviewed reported that they felt that the sit–stand desk had a positive impact on their child’s behaviour at school. In the present study, parents were also positive about the intervention, commenting that they liked how the desks promoted movement in class.
Teachers found the training component of the intervention very helpful and found the examples of how they could rotate children around in their class to ensure equal exposure to the desks useful. The project manual provided to teachers after the training, and the use of the nudge cards, were not deemed necessary, however, by the majority of teachers, as they felt confident to deliver the intervention after the training session. Overall, findings from the process evaluation suggest that the Stand Out in Class intervention is acceptable to teachers, children and parents.
Objective 8: monitor any adverse effects, such as musculoskeletal discomfort and/or disruption to the classroom and learning, to inform the design of a full trial and minimise or eliminate any such effects
There were no reports of any adverse effects associated with the intervention in terms of musculoskeletal discomfort reported by children, or disruption to the classroom reported by teachers or children. These findings agree with others who have concluded that sit–stand desks can be introduced into the classroom environment without having a negative impact on student learning, behaviour or musculoskeletal comfort, and without causing classroom disruption.65,67,205,207,210 Indeed, some evidence suggests that sit–stand desks can have a positive impact on musculoskeletal comfort, with improvements in comfort ratings being observed in children following sit–stand desk use.63,207
Objective 9: assess intervention fidelity over the intervention period
Limited evidence currently exists on the fidelity of sit–stand desk interventions within the classroom environment.210 We undertook two classroom observations in each intervention school, one in the spring term and one in the summer term, to examine the fidelity of the Stand Out in Class intervention. It was clear from all observations that all sit–stand desks were being used across all intervention classes. However, the intervention differed slightly across intervention schools as the trial progressed. Two teachers decided to move the provided stools away from the desks to encourage children to stand at the desks, whereas in the remaining intervention schools, the stools were kept with the desks. Throughout the study the intervention teachers also modified how they rotated children around the class to be exposed to the desks. Only one teacher used the per-protocol rotation plan recommended during the training, which involved rotating groups of children at half-daily intervals; two teachers rotated children on a daily basis, so each group of children was exposed to the desks for 1 day per week; and one teacher rotated children on a weekly basis. Following contact with the research team about this rotation plan, this teacher modified it and agreed to rotate the children more frequently. Despite differences in how children were exposed to the desks, it was clear from the classroom observations and qualitative research with teachers and children that all children had access to the sit–stand desks throughout the trial, and all teachers tried to ensure that desk exposure was fair across their class. Although we observed some deviations from the intervention protocol, the observation that teachers started to utilise the desks in their own way suggests that the intervention may have real-world applicability and feasibility.
The addition of more sit–stand desks in classrooms, such as making up 50% of classroom furniture, as suggested elsewhere,210 could be a feasible solution for a future trial. This would probably make it easier for teachers to rotate children around for desk exposure and also, importantly, increase the dose of the intervention. Overall, in the present study, all intervention schools were fully committed to the trial, and participating teachers had the full support of head teachers and senior staff.
Preliminary estimates of intervention effectiveness and sample size calculation for a full trial
Although the main aim of this pilot RCT was to establish key information around recruitment, acceptability and feasibility of the Stand Out in Class intervention, along with the acceptability and feasibility of a range of outcome measures, preliminary estimates of the effectiveness of the intervention on the proposed primary outcome were examined to determine whether or not the intervention shows a positive direction of effect. As the study was not powered to determine effectiveness, these finding should be treated as preliminary.
Objective 10: derive preliminary estimates of the effect of the intervention on children’s total daily sitting time, physical activity, indicators of health (markers of adiposity and blood pressure), cognitive function, and academic performance, engagement and behaviour
A weighted linear regression model, after adjustment for mean baseline weekday sitting time and mean wear time across the measurement time points, revealed that children in the intervention group spent less time sitting than children in the control group did at follow-up. The mean difference (weighted by school size) in change in sitting time over the intervention period was –30.6 minutes per day (95% CI –56.42 to –4.84 minutes per day) between groups. This is a greater reduction in daily sitting time than that observed in a recent sit–stand desk RCT conducted in primary school children in Belgium, in which, relative to the control group, the intervention group experienced a reduction in daily sitting of –13.5 minutes per day at 8–12 weeks’ follow-up.204 In this study, however, only three sit–stand desks were placed in the classrooms of the intervention schools, which probably explains the reduced effect of the intervention on total daily sitting time. Based on the current findings, and those of Verloigne et al.,204 it would be logical to suggest that adding more sit–stand desks to the classroom environment, and thus increasing the exposure and ‘dose’ of the intervention, would probably result in even greater reductions in daily sitting time. If examined over a longer time period, with sufficient power, such a study would fill an important gap in the literature by investigating the impact of this intervention on markers of health in children, as discussed in further detail below.
To date, most sit–stand desk interventions in primary schools have reported within-group differences in sitting time over the intervention period, with reductions in mean weekday sitting times ranging from 12 minutes per day to 80 minutes per day in intervention groups.29,67,68,205,207 Of the few studies that have drawn comparisons between changes in weekday sitting times between intervention and control participants, changes between groups have ranged from +19 to –66 minutes per day.68,204,205 Although preliminary, this study adds to the very limited evidence base204 from a cluster RCT on the potential impact of a classroom sit–stand desk intervention on changes in weekday sitting time.
No data currently exist in children to inform the magnitude of a reduction in sitting time needed to bring about changes in health markers. Although such optimum reductions in sedentary time in children need to be established to inform public health messaging, data from adults have demonstrated that reallocating just 30 minutes of sedentary time per day to light movement is associated with a 2–4% improvement in cardiometabolic biomarkers.114 An earlier meta-analysis of RCTs and non-RCTs, examining sedentary behaviour interventions delivered in the school or home environment, reported an overall decrease in children’s sedentary behaviour of 18 minutes per day.211 The preliminary findings from this study hold promise, therefore, and support the need for further RCTs examining the impact of sit–stand desks in the classroom environment.
Preliminary findings from this study revealed that reductions in sitting and increases in physical activity occurred in both groups after school, suggesting no evidence of compensatory behaviours occurring within the intervention group outside school hours, as reported elsewhere.67,68 However, these findings should be treated with caution due to the confounding variable of measurement season (see Strengths and limitations).
There were no observed changes in measures of body composition or blood pressure within this study. However, significant reductions in BMI percentile have been observed in a sample of 7- to 9-year-olds exposed to sit–stand desks over a 2-year period in three US primary schools.203 In the same study, non-significant reductions in BMI percentile were also observed in children exposed to the sit–stand desks for 1 year. In this US study, all standard (seated) desks were replaced with sit–stand desks, suggesting that the intervention ‘dose’ was greater than that observed in the present study. However, as in the present study, stools were provided with the sit–stand desks and children could choose whether to sit or stand throughout their lessons. Sitting time was not directly measured in this study, therefore it is unclear by how much sitting time was reduced over the 1- and 2-year periods. This evidence, however, suggests that such a treatment effect of this simple intervention (i.e. providing children with more opportunities to stand while learning) may be seen over a longer exposure period, with a greater intervention dose, and this should be examined in a definitive trial.
Improvements in cognitive function were seen in both groups, suggestive of a potential learning effect of the cognitive test battery. To date, findings of the impact of sit–stand desks on cognitive function are inconclusive, with preliminary (non-RCT) evidence suggesting that sit–stand desks have a positive impact on some measures of cognitive function, whereas other evidence suggests no effect.66,212 No evidence currently exists, however, that suggests that sit–stand desks have a negative impact on cognitive function.
Pupil behaviour conduct in the classroom and interactions with fellow pupils were examined using the teacher-reported Strengths and Difficulties Questionnaire. Preliminary observations from this measure indicated that the intervention group generally had reduced antisocial and hyperactive behaviours and increased self-control than the control group at follow-up. Interview data from teachers from US primary and high schools have highlighted observed improvements in behaviour when children use sit–stand desks,58,210 with teachers reporting that student attention and engagement increased during standing.
In this study, we demonstrated the feasibility of collecting academic progress data for maths, reading and writing from schools. However, as data relating to pupils’ progress across these key subject areas are not a requirement of the national curriculum for schools to collect, the lack of standardisation of this measure across participating schools made the interpretation of these data difficult, as we used routine data collected by each school to avoid placing additional burden on schools. When planning further research in this area, consideration in partnership with head teachers and teachers/assessment co-ordinators via PPI should be given to identify appropriate national curriculum-related/standard assessments routinely used by schools, which will enable direct comparisons between participating schools. In the absence of consensus over such measures, proxies of academic progress, such as attendance and/or in-class behaviour data, which can be measured consistently across schools, should be identified in collaboration with head teachers/teachers. Improvements in these measures would also be beneficial to inform an economic evaluation from an education perspective.
Objective 11: estimate the standard deviation of the primary outcome to inform a sample size calculation for a full randomised controlled trial
In this pilot study, a pooled SD of 95 minutes per day was observed in change in school day (weekday) sitting time, the proposed primary outcome in a definitive trial. Using this value, the sample size for a full trial was calculated to be 1276 participants from 58 clusters in total (638 participants and 29 clusters per arm). The sample size incorporates a 25% inflation to allow for losses to follow-up and missing data, along with the addition of one extra school in each arm to allow for whole-cluster dropout.
Lessons learnt from the preliminary economic evaluation
Objective 12: determine availability and completeness of economic data and conduct a preliminary assessment of potential cost-effectiveness
This study has demonstrated that it is feasible to conduct an economic evaluation alongside a cluster RCT of a sit–stand desk intervention within the classroom environment. Our preliminary analysis suggested little evidence of an effect in within-trial or extrapolated economic analyses. Based on current evidence using the most plausible scenarios, the intervention is unlikely to be cost-effective over a 30-year time horizon at a threshold of £30,000 per QALY. However, the Stand Out in Class intervention is typical of broader public health interventions, in that its comparatively small cost and QALY gain result in an ICER that is very sensitive to small changes in intervention cost and effectiveness.213
Comments on trial design and implementation: suggestions for improvements for a definitive trial
Cluster randomisation appears to have been ineffective in balancing ethnic characteristics between trial arms despite stratification of schools on ethnic characteristics with the intention to achieve ethnic balance. Methods to improve ethnic balance and, therefore, improve precision in estimation of any hypothesised variation in treatment effect across ethnic groups should be considered in any future trial. Incorporation of a range of schools with different deprivation profiles would also add to understanding of which groups benefit most from any such intervention and could be used to inform a distributional cost-effectiveness analysis. No attempt was made to control for ethnic imbalance in all analysis of treatment effect, with multiple imputation only rebalancing missing data within known ethnic categories.
The trial treatment ‘dose’ should also be considered in the light of comments regarding low compliance with the trial protocol rotation plan. If possible, more than six sit–stand desks should be incorporated into the classroom environment to ascertain whether or not the observed treatment effect follows a dose–response relationship.
Areas for future work
We did not investigate the sensitivity of our conclusions to variation in the cost of sit–stand desks and whether or not this was viewed as an incremental cost over replacement of existing worn-out school furniture like for like. There is considerable variation in the cost of standing desks between different model designs and uncertainty in how best to incorporate any costs into economic modelling over their expected time horizon. A recent research briefing suggested that the unit price of a classroom standing desk varies from £25 for a basic model to > £600 for a sophisticated model.214 How accounting costs are considered is likely to have an impact on cost-effectiveness judgements. There is a valid query of the viability of individual schools being able to cover the high upfront cost of a standing desk intervention, without additional cost of financing over several years. The same research briefing indicates an approximate cost of £270,000 to equip a whole school with standing desks costing £300 each, equipping 30 classrooms, each capable of holding 30 students per class.214
As costing was conducted as a static classroom in this analysis, with no account of periods of non-use, costing assumptions at the school level would require change, given the current structure of UK primary school teaching, with asset usage being somewhat dynamic, unlike, for example, Italy, where teachers rather than children rotate between classrooms. If an intervention was extended to the whole school, incremental cost-effectiveness estimates may require consideration of children having access to standing desks in more than one classroom for lessons in different subjects. This would mean a higher cost per child, calculated as the total cost of desks in all classrooms divided by the expected population of the whole school over the expected lifespan of the desks.
At the increment, as in this study, the cost of setting up and maintaining these desks was not an important consideration; however, on a whole-school scale, consideration of these costs is likely to be relevant, with the benefit of an ‘active classroom’ environment needing to be compared with the opportunity cost of other potential investments forgone because of expenditure.
The main barrier to the current research agenda is an absence of evidence of an independent health effect of sedentary behaviours on generalised health measures, such as the QALY. Current evidence of health effects reported in intermediate health outcomes have inconclusive effect on measures that have meaningful impact on health-related quality of life. It is acknowledged that further research is needed to explore the impact of low-intensity activity on child and adolescent health, with interest in not only the volume of activity but also the distribution of activity throughout the day and school week.4,23
Within the existing modelling approach, future work to assess a range of plausible values for the decay parameter in health effect would be particularly valuable, given extreme modelled sensitivity to this parameter. The rate of decay in activity levels, or corresponding health effect, is likely to interact with other environmental factors, including the spread of active workstations and other active living interventions across regions and throughout the life course. Models linking non-health outcomes of physical activity changes to desirable general outcomes (such as improved attendance, classroom behaviour, progress/attainment) would similarly be a valuable addition to analysis, in helping understand the importance of the possible non-health benefits of the Stand Out in Class intervention and similar interventions. A lack of available evidence has prevented further examination of outcomes outside health at this time.
Strengths and limitations
The Stand Out in Class pilot cluster RCT adopted a mixed-methods approach, including quantitative, qualitative and health economic analyses, enabling a thorough evaluation of all trial procedures providing valuable information to inform the design, evaluation and value of conducting a definitive trial. The intervention was based on a theoretical framework and its development was informed by the literature,56,57,69 our early work29 and PPI (including focus groups with children and interviews with teachers and head teachers during the planning stages, along with ongoing consultations with teachers throughout the trial). The study setting is a further strength of this trial. Bradford was chosen as the study location given its ethnic composition (predominantly South Asian and white British) and high levels of deprivation, health inequalities and childhood morbidity.73 The characteristics of the participating schools suggest that they were largely representative of schools within the Bradford metropolitan district, enabling us to pilot this intervention under challenging circumstances. The acceptability and feasibility findings of this study therefore suggest that this trial would probably be feasible within other settings. Forty-eight per cent of the present sample of children were of South Asian ethnic origin. With the emergence of an increased cardiometabolic health risk profile observed in British South Asian children, in comparison with white British children,22 early health promotion interventions in such higher-risk groups could be an important strategy for reducing ethnicity-related health inequalities later in life. The classroom-based setting of the present intervention is important for addressing health inequalities, in that this environment is accessible to all children.
Delays experienced with the start date of this study (see Chapter 2, Changes from the original protocol/grant application) meant that our intervention duration was shorter than that originally proposed. Originally, baseline measurements were due to take place when children were at the end of Year 4 (in June/July), with the desks being installed into their new Year 5 classroom at the start of term. This would have enabled us to pilot the intervention over 1 school year, with the follow-up measurements planned in the subsequent June/July when participants were at the end of Year 5. With the baseline measurements not taking place until November/December, the differences in the season of the measurements are probably a confounding factor in the present study. This should be mitigated in a further trial, if such a trial begins the baseline measurements earlier and examines the impact of this intervention over an entire academic year. Although not an aim of this present pilot study, based on evidence from a longer-term sit–stand desk intervention in the USA,203 which incorporated both a 1- and 2-year intervention period, a longer-term intervention (≥ 1 year) will be more likely to detect potential health impacts (e.g. favourable changes in markers of adiposity) of the intervention.
Conclusions and suggestions for further research
This pilot study has provided evidence of the acceptability and feasibility of the Stand Out in Class intervention and evaluation measures. Participant recruitment rates exceeded expectations and retention rates at follow-up were high (97%). The majority of evaluation measures were deemed acceptable and important lessons have been learnt on improvements that should be made in the planning of a definitive trial. All participating schools were committed to the trial, and we received widespread engagement and enthusiasm for the intervention from teachers, head teachers, children and parents.
Preliminary quantitative evidence suggests that the intervention may have a positive direction of effect on weekday sitting time, which warrants testing in a definitive cluster RCT. Importantly, quantitative and qualitative data from this study suggest that the introduction of sit–stand desks into the classroom environment did not negatively impact classroom behaviour and children’s learning. These outcomes are likely to be of key interest to schools considering participating in such interventions and/or adopting these desks in the future. Although the amount of change in sedentary time required in children to bring about positive changes in health markers is yet to be established, a longer-term US sit–stand desk intervention revealed favourable reductions in BMI percentile in primary school children.203 Furthermore, other evidence suggests that sit–stand desks can have a positive impact on musculoskeletal comfort in children, potentially reducing the risk of future musculoskeletal ill health.63,207 The feasibility findings of the present study, and emerging evidence on the potential health benefits of sit–stand desks, support the need for a definitive trial. Such a trial could provide novel and robust evidence of the longer-term (≥ 12 months) health and education impacts of this intervention and may have the potential to enhance the classroom environment. Based on the findings of the present study, the following recommendations for the planning of a definitive trial are made:
- As standing provides a potentially important but small increase in metabolism compared with sitting, this stimulus needs to be applied regularly and over a longer time period than the 4.5 months experienced by the children in the current pilot study. A definitive trial should be conducted over a minimum of 1 academic year, and more sit–stand desks should be incorporated into the classroom to (1) make it easier for teachers to rotate children around to be exposed to the desks and (2) increase the overall dose of the intervention. Such a trial could provide novel and robust evidence on the impact of this intervention on sitting time, markers of health and academic progress.
- Different methods to attach the activPAL accelerometer to children should be examined to improve comfort and compliance with this measure, or alternative measures of objectively classifying children’s posture should be examined (e.g. use of the ActiGraph on the thigh could be investigated).
- Efforts should be made to make parental surveys easier to complete; reporting of health-care resource use could be streamlined to minimise reporting and recall bias, for example allowing parents to record health-care incidents in real time using a trial-specific application or website.
- In consultation with head teachers and teachers or assessment co-ordinators via PPI, further consideration should be given to measuring academic progress to identify appropriate national curriculum-related and standard assessments used by schools, which will enable direct comparison between participating schools. In the absence of consensus over such measures, proxies of academic progress, such as attendance and/or in-class behaviour data, which can be measured consistently across schools, should be identified in collaboration with head teachers and teachers.
- Based on teachers’ feedback in the current study, an infographic detailing the benefits of reducing sitting time should be produced in collaboration with teachers for use in a full trial, instead of the teachers’ handbook, which was deemed to be too long. The nudge prompts should also not be included in a future intervention.
- The cognitive assessment test battery should not be included in a full trial, given the limited evidence surrounding the links between sedentary behaviour and cognitive function in children and due to the inappropriateness of some of the tests used (e.g. the RVIP) for this age group.