This study was granted ethical approval by the Stellenbosch University Health Research Ethics Committee (reference number S17/08/130) and institutional permission by the Western Cape Education Department (reference number 20170525-1279). It was also registered with the Pan African Trials Registry (PACTR201811799476016; International Registered Report Identifier [IRRID] RR1-10.2196/18522).

Prospective participants who expressed interest in participating in the project were provided with study information documents and consent forms. Learners were provided with child assent and parent/guardian consent forms, as well as study information for parents and guardians, which were then collected by the research team upon completion. Before the study began, learners were informed about the intervention and measurement methods. Study data were anonymized by assigning a unique participant identifier to data obtained from participants. As compensation, participants were offered retention of the intervention materials at the conclusion of the project.

A school-based, stratified, closed-cohort, randomized, 2-cluster, stepped-wedge design with a pragmatic approach was used for this study. Participant clusters (school classrooms) were the unit of randomization to determine the order of implementing the intervention. This study report followed the CONSORT (Consolidated Standards of Reporting Trials) extension statement for pilot and feasibility trials (Multimedia Appendix 1) [13]. The protocol for this feasibility trial has been published elsewhere [14]. The CONSORT stepped-wedge flow diagram (Table 1) for cluster randomized trials [15] shows the timing of crossover from control to intervention conditions.

The stepped-wedge design was used to allow the intervention to be evaluated within the bounds of the logistical constraints and context of each cluster [16]. Given the limited availability of measurement equipment, the stepped-wedge design allowed sequential baseline and follow-up measurements. Furthermore, given the evidence of the effectiveness of the mode of intervention in other contexts [4], and other classroom-based interventions, the stepped-wedged design allowed both clusters to receive the potential benefit of the intervention.

The study was conducted in the Western Cape province of South Africa, a region of broad language, cultural, and socioeconomic diversity. In South Africa, publicly funded (state schools) are categorized into quintiles according to socioeconomic factors, including income, literacy, and employment rates of the surrounding community [17]. Lower-quintile schools are more resource limited than upper-quintile schools and thus receive greater state funding per registered learner. In the metro central district, there are fewer lower-quintile schools, and most schools fall under the quintile 5 (Q5) category.

To ensure a diverse range of contextual factors, primary schools from quintile 3 (Q3) and Q5 were selected exclusively from the central metro district of the Western Cape Education Department. The rationale was that if it were deemed feasible to conduct a future trial in the more challenging, resource-strained context, it would be feasible in less challenging, adequately resourced contexts. A downloaded list of publicly funded schools in the central metro district from the Western Cape Education Department website was delimited to school categories Q3 and Q5. School principals, stratified according to Q3 and Q5 schools, were randomly contacted by the principal investigator via telephone or email for recruitment. Afterward, the principals nominated grade 5 or 6 teachers to attend an information session.

A sample size calculation was not performed as per the CONSORT extension statement for feasibility studies [18]. The sample target was to include a wide range of contextual factors relevant to the feasibility outcomes. The diversity between the clusters (namely classrooms from Q3 and Q5 schools) was considered sufficient to provide a range of considerations to assess the feasibility of the intervention and the pragmatics of data collection. The individual participants selected for measuring physiological outcomes (SB and postural dynamism) were randomly chosen from the class list provided by the class teacher. An equal number of male and female learners were sampled.

The aim of the intervention is to improve the long-term cardiometabolic and spinal health of the public by reducing the accumulation of prolonged SB that has been shown to be pervasive in schools. Providing learners with an opportunity to transition between sitting and standing during class time helps arrest sedentary physiology and provides respite from prolonged axial spinal loading. The study intervention comprised a novel height-adjustable sit-stand desk and a playlist of 9 health education and movement videos (HEMVs). The study authors (DF and QL) contributed to the development of the intervention. The design concept was informed in part by a systematic review of the efficacy of classroom-based interventions to improve spinal health and reduce the SB of schoolchildren [4], as well as a qualitative study of educators’ perceptions of learners’ movement during class time conducted in the Western Cape province, South Africa [7]. The systematic review provided compelling evidence for the efficacy of classroom-based interventions that include alternative, sit-stand classroom furniture and health education to improve spinal health and SB outcomes.

The feasibility outcomes include retention of the study, fidelity to the intervention (acceptance, and usage of the KUZE sit-stand desks, delivery of the HEMVs), and integrity of the physiological data collected (compliance with wearing the activPAL and IMU sensors). The success indicators (set a priori) and methods of measuring the 5 feasibility outcomes are outlined in Table 2.

Feasibility outcomes were measured using both qualitative and quantitative methods. For the qualitative measurement of the feasibility outcomes, individual depth interviews (IDIs) with the class teachers and focus group discussions (FGDs) with a subgroup of learner participants from each cluster were conducted at the end of the intervention period. The success criteria of the feasibility outcomes were used as the framework for the IDIs and FGDs. The quantitative methods encompassed the physiological data obtained from the activPAL and IMU sensors, as well as estimates of retention and compliance, which were monitored by the researcher.

The CONSORT flow diagram of the study is illustrated in Figure 1. The baseline demographic characteristics of participants were similar across clusters. The cluster 1 (Q5) school comprised a grade 6 class, while cluster 2 (Q3) was a grade 5 class. Thus, the ages of the learners in this study were 10-11 years. An equal number of male and female learners made up the study sample.

The cluster 1 (Q5) teacher withdrew her consent to participate in the study after the 13-week intervention and before physiological follow-up measurements were taken. However, the teacher and learners participated in the IDI and FGDs, respectively. Cluster 2 (Q3) remained in the study throughout the study period. Table 3 demonstrates at which stage the cluster 1 teacher withdrew.

Both teachers reported having developed a routine for playing the HEMVs during class. The cluster 1 teacher played the HEMVs intermittently during the day, while the cluster 2 teacher used the videos as a classroom management tool to his advantage. He played the videos at the start of the periods to engage learners and prepare them for the lesson.

Teachers and learners in both clusters accepted the KUZE as the classroom furniture for the duration of the intervention period. The cluster 1 teacher allowed the learners to stand during groupwork activities for specific subjects and during times where independent work was required.

Learners in cluster 2 were allowed to use their discretion in whether to sit or stand while completing their work and to break up periods of sitting. At the end of the intervention period, the KUZE desks were removed from cluster 1 and the usual classroom furniture was returned. The cluster 2 teacher requested that the KUZE remain as the standard classroom furniture in his class beyond the completion of the study. When asked about whether they wanted to return to using their usual classroom furniture, learners from cluster 2 chose to keep the KUZE furniture.

The teacher in cluster 2 reported that the KUZE desks provided a valuable advantage of more space to access all the areas of the classroom.

There was 100% compliance with wearing activPAL sensors and IMUs. No learners reported any adverse skin reactions to wearing the activPAL sensors at any stage of the study. During the 13-week follow-up measurement, 10 participants reported mild head discomfort from the elasticated Velcro strap used to secure the head IMU. In all cases, discomfort was resolved by readjusting the strap. Thereafter, the learners were able to return to class and resume learning activities. The mild discomfort that learners reported from the head strap had resolved before they were allowed to return to the class to complete the period of data collection. All learners selected for physiological measurements complied with wearing the activPAL sensors and IMUs throughout the study.

A low rate of data loss was recorded for physical activity and postural dynamism (Table 4). An average of 94.64% of recorded SB and spinal movement data had sound integrity and was considered eligible for inclusion in the analysis for the secondary objectives. The rate of data integrity met the a priori target of 80%. Data loss from wearable sensors was attributable to technical problems during downloading to the project computer or due to batteries running out of charge.

Three of the feasibility outcomes were achieved in 3 criteria in both clusters. As cluster 1 was not retained in the study, the acceptance and usage of the KUZE could only be assessed partially through qualitative feedback and was thus categorized as “partially met.” All 5 feasibility outcomes were achieved in cluster 2 (Table 5).

This study effectively assessed the feasibility of implementing a classroom-based intervention to reduce classroom SB and promote spinal health in primary school learners in the Western Cape province of South Africa. Our findings showed that the a priori success criteria to decide to continue with a large trial were met. Having met 3 feasibility outcome success criteria (delivery of HEMVs, compliance with wearing physical activity and postural dynamism sensors, and integrity of the data gathered) in both clusters indicates that with minor modifications to the study methodology, it is feasible to progress to a larger trial. Despite this positive finding, reduced cluster retention may be a risk of a larger trial. Therefore, strategies to enhance retention are an important consideration for a larger trial.

Individual teacher-related aspects should be considered in retention strategies. The last-minute substitution of the teacher meant that the research team was unable to establish a satisfactory level of engagement, rapport, and support before the study started. This may have led to a negative attitude toward the study, which was compounded by her perceived loss of autonomy due to the study-related change to the classroom furniture and configuration. Holistic support of teachers is important in classroom-based movement integration interventions [24] to maintain adequate levels of engagement and support throughout the process of the study. Such a holistic whole-school approach that includes senior school management and other school stakeholders has gathered traction in interventions to increase physical activity in UK primary schools [25]. However, such a whole-school approach will need to be contextualized for the South African school system, considering the scarce track record of implementation of similar interventions. Given the importance of teachers in implementing the study and the dynamic nature of school settings, the design of a future trial should incorporate pragmatism to ensure that timely and appropriate adaptation is possible throughout the study [26].

Although not retaining cluster 1 (Q5) was disappointing, it provides a valuable learning opportunity to inform a larger trial. It is, therefore, recommended that a customized school context–specific program of engagement, awareness, and involvement in the study precede a future trial to improve participants’ experience of participation [27] and to optimize its acceptability and efficacy [28]. Prior teacher involvement and program monitoring may also provide an opportunity to codevelop cluster retention strategies for implementation in a future trial; aid the development, implementation, and adaptation of the intervention; and track cluster progress against study goals [29]. Cocreation of school-based health interventions has been shown to improve the feasibility of interventions in the complex environment of the school context [30]. Including teachers in the development and implementation of an intervention can leverage their expertise of the classroom environment and enable them to find solutions to concerns about the potential classroom disruptions and reconfiguration of classroom furniture. Raising awareness about the study with a view to including teachers to codevelop the intervention may be important considerations for a future trial, given the sizeable investment requirement in this emerging area of research in South Africa.

Despite no previous classroom-based interventions including sit-stand desks in South Africa, the KUZE desk was well accepted by teachers and learners. Teachers recognized the positive impact of allowing learners to stand on their ability to work independently and on their concentration after prolonged periods of sitting. However, some concerns were raised about disruption to teaching and learning and loss of control of the classroom, which presents a potential threat to the rollout of a future trial. Similar concerns were voiced by teachers in a previous UK-based trial [11]. These concerns are reasonable, given the longstanding tradition and practice of enforcing learners to remain seated during class time. Interrupting periods of sitting with standing tasks challenges teachers’ practice and propensity to enforce sitting during teaching and learning activities. In a study of teachers’ perspectives of learners’ movement during class, participants reported that they believed that sitting enhances learners’ concentration [7] and were unaware of the evidence that interrupting prolonged sitting may enhance their concentration and engagement with cognitive tasks [31,32]. Teachers in the study by Fisher and Louw [7] associated enforcing that learners remain seated with teachers’ maintaining control of the classroom and their level of classroom management skill and teaching pedagogy. It may be prudent to emphasize the benefits of interrupting prolonged sitting for learners in future teacher training and support as part of a future trial of the intervention.

The activPAL sensor wear protocol used in this study did not appear to impact the logistics or integrity of the physical activity data collected. The decision to apply and remove the activPAL sensors daily was mainly motivated by not wanting to risk losing the expensive devises. The research team also considered the ethics of the potential safety risks study participants would bear by wearing expensive devices in their communities without any mitigating measures in place. Most studies of free-living physical activity using activPAL adopt a 24-hour, 7-day wear protocol [33]. However, this wear protocol has drawn some criticism, with evidence of dose–response noncompliance with wear protocols approaching the 7-day period [34]. Reports of skin irritation caused by perspiration, particularly in warm, humid conditions, have threatened study participants’ compliance with wearing the sensors [35]. The fact that no skin irritation was reported by study participants justifies the rationale for the wear protocol. If this activPAL wear protocol was adopted in a future study, it may be useful to determine the validity of the single wear protocol compared to the 24-hour, 7-day wear protocol.

The study was limited to schools in a specific geographical and socioeconomic context. Therefore, the findings may not be broadly generalizable. The interpretation of some findings was limited by the suboptimal retention of 1 cluster. The study was also limited to specific preset feasibility criteria and important implementation factors; for example, teacher and school dynamics were not considered. The feasibility study’s data are also arguably too limited for sample size considerations for a larger trial, and further research is required.

This study addressed the uncertainty of the acceptability of a classroom-based SB and spinal health intervention, its impact on teachers’ practice, and the logistical and pragmatic considerations of data collection in a previously unresearched setting. Having established the feasibility of some aspects of the intervention in the local context, the acceptance of sit-stand desks remains questionable and presents a potential risk to the success of a larger trial. Although teachers and learners from both clusters accepted and used the intervention classroom furniture for the duration of the intervention period, the feedback from the cluster 1 teacher raises some uncertainty. However, these concerns can be addressed, as described in the recommendations. The results of this study indicate that minor revisions to the current methodology are required to conduct a large cluster randomized controlled trial (RCT) of an intervention aimed at reducing SB and improving spinal health in primary schools in the Western Cape province.

Recommended changes to the methodology include: