Protocol for a pilot study to assess the feasibility of interrupting prolonged sitting in the evening with activity breaks in a group of free-living adults

Abstract

Background

Greater time spent sedentary, particularly when accumulated in long, uninterrupted bouts, is associated with poorer cardiometabolic health and an increased risk of disease incidence and mortality. Experimental studies have indicated that regularly interrupting sedentary time during the day, and more recently, in the evening, with acute (2–5 min) bouts of activity improves postprandial metabolism in a range of adult populations. The effects of interrupting evening sitting time have yet to be explored in a free-living setting. Drawing on the Behaviour Change Wheel and participant-identified barriers and facilitators, the regular activity breaks (RAB) intervention was designed to support participants in interrupting evening prolonged sitting. This pilot and feasibility study will explore the feasibility of this intervention and its effects on 24-h movement patterns, glycemic control, and blood pressure. Results from this study will inform the development of a future effectiveness trial.

Methods

This 4-week, single-group intervention trial consists of a baseline, a 2-week intervention, and a 2-week follow-up period. A total of 20 adults, ≥ 18 years who self-report habitually sitting for at least 3 h in the evening, have a smartphone, and can ambulate unaided will be recruited to participate. The RAB intervention aims to support participants to regularly (~ every 30 min) perform short bouts (2–3 min) of activity during periods of prolonged sitting in the evening. The intervention components include (1) a structured consultation with the study coach where behaviour change techniques will be used to create an individualised plan for performing activity breaks in the evening; (2) provision of a mobile application to provide scheduled reminders and activity break videos; and (3) follow-up support in the form of phone calls performed on days 3 and 7. Feasibility will be assessed by meeting recruitment and retention targets; the acceptability of the intervention will be assessed via semi-structured interviews. Pilot outcomes include the number of activity breaks performed, impact on 24-h movement patterns (sleep duration and quality, sedentary time, and physical activity), blood pressure, interstitial glycemic response, mobile application engagement and capability, and opportunity and motivation to change evening sitting behaviour.

Discussion

Should the RAB intervention meet the criteria to be deemed feasible and acceptable, this will provide justification and information for its use in a large-scale effectiveness trial.

Trial registration

This study is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR 12624000371594). Registered March 28, 2024.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40814-025-01719-0.

Background

Sedentary behaviours have become prevalent in modern life as a result of changes in how we interact with our environments for work, transport, and leisure, encouraging us to sit more and move less [1, 2]. Sedentary behaviours are conceptually distinct from physical inactivity (defined as not meeting the physical activity guidelines) and are defined as “any waking behaviour characterised by an energy expenditure of < 1.5 metabolic equivalents (METs), while in a sitting, reclining or lying posture” [3]. Higher levels of sedentary time are associated with a higher incidence of a myriad of cardiometabolic diseases, including type two diabetes and cardiovascular disease, independent of physical activity [4].

Observational studies with objective measures of sedentary time highlight that the pattern in which sedentary time is accumulated is also a risk factor for cardiometabolic disease [5–7]. Indeed, a recent study highlighted that compared to adults with the shortest mean sedentary bout duration, those with the longest bouts had an 18% (95% CI 1.01 to 1.38, p < 0.001) and 30% (95% CI 1.21 to 2.09, p = 0.002) increased risk of mortality from all-causes and cardiovascular disease, respectively, independent of physical activity, total sedentary time, and CVD biomarkers [8].

Experimental studies have confirmed these findings by showing that frequently interrupting prolonged sitting (every 20 to 30 min), with short bouts of activity (2 to 5 min), during the day, acutely lowers postprandial glucose and insulin responses in healthy adults [9–14], adults with type 2 diabetes [15–19], and those with overweight and obesity [20–22]. Additionally, several studies also found similar results using continuous glucose monitors (CGM) to measure interstitial glucose responses rather than blood glucose responses from venous blood samples [11, 15, 23].

To date, most of the research targeting reductions in sedentary behaviour has focused on sedentary time accumulated during the day. However, focusing on the performance of activity breaks in the evening, at home, could be a prime time and location to target behaviours that influence cardiometabolic health for multiple reasons. Firstly, many of us accrue our longest periods of uninterrupted sitting during the evening [24–26]. Secondly, compared to the morning, insulin sensitivity is diminished in the evening [27], and finally, there is evidence that the average adult consumes almost half of their daily energy intake during this time [28]. Taken together, these factors promote an elevated postprandial glycemic response, which, when repeated day after day, can be detrimental to cardiometabolic health. Two recent lab-based intervention studies, which interrupted evening prolonged sitting with resistance exercises, resulted in reductions in glucose responses of 31% to 33% and insulin of 26 to 41% [29, 30]. A particularly novel finding from Gale et al. [31] was that participants slept almost 30 min longer after performing the activity breaks when compared to prolonged sitting over the same period [32]. Better sleep is associated with better cardiometabolic health, independent of the health effects associated with a reduction in sedentary time and increases in physical activity [33]. The beneficial effects of performing regular activity breaks in the evening on both postprandial metabolism and sleep quality suggest that this intervention has the potential to target multiple components of cardiometabolic health. Therefore, further investigation of the effectiveness of this intervention outside the laboratory in a free-living setting, over a longer time period, is urgently warranted.

Most free-living interventions that aimed to reduce sedentary time have targeted the occupational setting through the use of ‘sit less, move more’ messaging, and the provision of standing desks, rather than regular activity breaks interventions. Whilst many of these have proven effective [34–36] at replacing sitting with standing, there has been minimal focus on improving sedentary time outside of work hours, particularly in the evening. Targeting the performance of activity breaks at home allows those not in paid employment to benefit from the intervention and may also overcome barriers for those who do not want to, or are unable to, leave the house to perform physical activity or do not have access to other facilities [37, 38], and those who cite lack of time as a barrier [39, 40].

In the design process of this regular activity breaks intervention, we drew on qualitative data obtained following our laboratory-based regular activity breaks intervention, knowledge gained from successful real-world interventions using regular activity breaks in the occupational context [41], the Behaviour Change Wheel [42], and its associated COM-B model (capability, opportunity, motivation, and behaviour) [43] and theoretical domains framework [44]. The Medical Research Foundation recommends taking a theory-based approach when designing behaviour change interventions [45]. Indeed, utilisation of both the COM-B model and theoretical domains framework has been used in health settings to support context-specific behaviour change interventions that target reducing occupational sitting time [46], increasing physical activity [47], enhancing midwifery practice [48], and smoking cessation [49]. By using the COM-B and theoretical domains framework in the intervention design process, we were able to obtain an in-depth analysis of the key behaviour change constructs and specific behaviour change techniques in the context of performing regular activity breaks as a means of interrupting prolonged sitting time. The COM-B model identifies that in order for individuals to perform regular activity breaks in their habitual routines, they need the capability (psychological and physical ability to perform behaviour), opportunity (social and physical factors beyond the individual that influence one’s ability to perform a behaviour), and motivation (reflective and automatic processes that direct and energise behaviour) to do so. The integrative theoretical domains framework synthesises relevant constructs from existing behaviour change theories [44, 50] that can be used to identify important components required to enhance capability, opportunity, and motivation during intervention implementation, such as social support, knowledge, and goals.

Objectives

The objective of this pilot and feasibility study is to assess the potential of the regular activity breaks intervention to positively impact health outcomes by

1. Evaluating recruitment success and retention rates of participants throughout the study period.

2. Examining the acceptability of the intervention including barriers and facilitators to performing the intervention, experienced benefits and identified improvements using qualitative methods.

3. Evaluating the extent to which the intervention changes the number of activity breaks taken in the evening and adherence to the intervention protocol.

4. Examining the potential of the intervention to impact cardiometabolic disease risk factors including 24-h movement patterns (sleep quality and quantity, physical activity and sedentary behaviour), glycemic control and variability, and blood pressure

5. Explore participants capability, opportunity and motivation to perform the intervention.

The findings from this study will be used to further inform the development of the regular activity breaks intervention for a future effectiveness trial.

Methods

Study design and setting

This single group intervention study will be conducted at the University of Otago, Dunedin, New Zealand. Data will be collected between May and October 2024. This protocol has been prepared in accordance with the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) 2013 statement [51] as recommended [52]. The SPIRIT checklist can be found in Additional file 1. This trial has been approved by the University of Otago Human Ethics Committee (H23/105; October 2023) and is registered prospectively with the Australian New Zealand Clinical Trials Registry (ANZCTR 12624000371594). Protocol version 3 dated March 2024.

Participants inclusion and exclusion criteria

To be eligible for inclusion, participants must (1) be at least 18 years of age; (2) self-report habitually accumulating more than 3 h of sitting time in the evening; (3) have a smartphone that is compatible with the Stretch Minder application; and (4) be able to ambulate unaided (i.e., not using a wheelchair, crutches, or other assisted devices). Participants will be asked to gain clearance from their General Practitioner (GP) to participate in this study if their responses to the Physical Activity Readiness Questionnaire (PAR-Q), completed at screening, indicate that participating in physical activity may not be medically appropriate.

Recruitment

Recruitment of participants will be carried out through the distribution of print and electronic flyers in local primary health care and community settings as well as advertisements on social media. Interested participants will confirm their interest by registering online.

Sample

From a feasibility standpoint, a formal sample size calculation is not required, as the objective is to assess the practicality of study procedures. We chose a target sample size of 20 participants. A larger sample size would provide a more reliable estimate of standard deviation [53, 54]. However, we chose to balance the need for information about the feasibility of the intervention, budget and time restraints, and the reliability of the estimates of variance when deciding on the sample size of n = 20.

Study procedures

Participant registration

Upon online registration, participants will be sent a link to an online survey (REDCap software Research Electronic Data Capture, production server version 13.10.0, Vanderbilt University, Nashville, TN, USA), where they will be able to view an electronic copy of the participant information sheet, provide online consent, and complete a questionnaire to screen for eligibility. Once the participants have completed the consent and screening questionnaire, the responses to the PAR-Q will be checked. Participants who do not meet the eligibility criteria will be notified via email and thanked for their interest. If medical clearance is required, the participant will be emailed and asked to contact their GP to gain clearance to participate in the study. If this screening is required, participants will be provided with a grocery voucher to cover the cost of any GP consultation fees. Once medical clearance is obtained, or if it is not required, and participants are deemed eligible, participants will be scheduled to attend an introductory session. The flow of participants through the study is outlined in Fig. 1, while the summary of the study schedule is outlined in Fig. 2.

Fig. 1.

Flow diagram of the regular activity breaks pilot and feasibility study

Fig. 2.

Study schedule of enrolment, intervention, and assessments for the RAB intervention

Baseline assessment period

The aim of the baseline assessment period is to describe the participants’ usual 24-h movement patterns, interstitial glucose responses, and variability prior to the introduction of the intervention. At the beginning of the baseline assessment period, participants will attend the Mellor Laboratories (University of Otago, Dunedin, New Zealand), where the research assistant will

1. Measure standing height and weight in duplicate, using standardised procedures.

2. Measure blood pressure in triplicate 1 min apart; after 15-min seated rest using an automated sphygmomanometer (OMRON HEM-907; Omron Healthcare, Kyoto, Japan). If blood pressure is greater than 140/90 mmHg and participants have not already obtained medical clearance, then they will be asked to contact their GP to gain clearance to participate in the study.

3. Discuss the participant’s typical evening to identify the 3-h period in which the participant is mostly sedentary (e.g., 1700 to 2100 h), and the time the participant usually consumes their evening meal.

4. Fit participants with three activity monitors: two ActiGraph GT3 + accelerometers (ActiGraph, Pensacola, FL, USA), which they will be asked to wear on their non-dominant wrist and right hip, and an ActivPal3 accelerometer (PAL Technologies Limited, Glasgow, Scotland) which is attached to the midpoint of the front of the right thigh with adhesive dressing. Participants will be instructed to wear both activity monitors continuously (24-h a day) for a 3-day period to assess usual sleep and physical activity patterns.

5. Explain the wear time diary to the participant, in which they will record times accelerometer(s) was removed (such as when showering or playing contact sport), time participating in physical activities that are not accurately captured by the accelerometers (as some static activities such as cycling on a stationary bike) and sleep information (time attempted sleep, time woke up).

6. Fit participants with a Freestyle Libre Pro iQ continuous glucose monitor (CGM) (Abbott Diabetes Care, CA, USA), which will allow for a non-invasive measurement of glycemic response every 15 min. In the wear time diary participants will also be asked to keep an estimated diet record of all food and drink consumed during the defined evening sedentary period, as well as a record of their large evening meal if it was outside of this time.

7. Instruct participants to complete the Pittsburgh Sleep Quality Index questionnaire to assess baseline self-perceived sleep quality.

Activity breaks intervention

The aim of the intervention is to support participants to perform regular activity breaks to interrupt prolonged sitting during their habitual evening routines at home. The regular activity break protocol used in this study is 3 min of low-intensity activity performed every 30 min. The intervention includes a one-on-one session with the study coach at the beginning of the intervention and two follow-up sessions completed over the phone on days 3 and 7 of the first week of the intervention. The intervention also includes the use of a mobile application to remind participants to perform regular activity breaks via pre-scheduled alerts, provides a series of regular activity break videos for participants to use for ideas of activity breaks, and has a self-monitoring function whereby participants can check their progress each day. Table 1 outlines the intervention components and their mapping to the COM-B model and TDF.

Table 1.

Links between the COM-B Model, Theoretical Domains Framework (TDF), intervention functions and Behaviour Change Techniques used in the Regular Activity Breaks (RAB) Intervention

COM-B component and barriers and facilitators influencing change	Theoretical Domains Framework	Intervention functions	Behaviour Change Technique	Description of intervention strategy
Capability
Psychological Lack of knowledge about why interrupting sedentary time with RABs is beneficial for physical health	Knowledge Increase knowledge that regularly interrupting prolonged sitting time improves postprandial metabolism, blood flow and sleep	Education persuasion	• Information about health consequences • Credible sources	• Information of the positive health consequences of interrupting evening prolonged sitting with regular activity breaks will be discussed by the Study Coach and reiterated in the participant booklet
Psychological Lack of knowledge about how and when to interrupt prolonged sedentary time	Knowledge Increase knowledge about how and when to interrupt prolonged sitting	Education	• Instruction on how and when to perform a behaviour	• Provision of a mobile application which provides a range of suitable activity break videos for participants to use each break
Psychological Lack of knowledge about habitual sedentary behaviour patterns	Knowledge Increase awareness of habitual sedentary behaviour patterns	Education persuasion	• Feedback on behaviour • Discrepancy between current behaviour and goal	• Discussion with study coach outlines current behaviour and how this will change by taking RAB
Psychological Lack of confidence to remember to interrupt sitting with regular activity breaks	Memory, attention, and decision processes Enable decisions to interrupt sitting time by performing regular activity breaks	Environmental restructuring, enablement	• Prompt/cues • Self-monitoring of behaviour	• Provision of a mobile application which will be set up to remind individuals to perform an activity break evening 30 min, during a personalised evening period
	Behavioural regulation Determining a method to self-monitor success of interrupting sitting with activity breaks
Opportunity
Social Perception that others would not be accepting of performing regular activity breaks	Social influences Create a culture within the home to promote incorporation of regular activity breaks in habitual routines	Environmental restructuring, modelling	• Information about others approval • Restructuring the social environment • Social support	• The study coach will prompt participants to discuss social influences in order to encourage social support to perform regular activity breaks
Physical Activities during typical evening (e.g., streaming) would not support interrupting to sitting time	Environmental context and resources Set up external reminders or cues in habitual evening routines to interrupt prolonged sitting behaviour	Environmental restructuring enablement	• Prompts/cues	• Provision of a mobile application which will be set up to remind individuals to perform an activity break evening 30 min, during a personalised evening period
Activity breaks require additional equipment to be performed	Environmental context and resources Provide activity breaks that require minimal space and equipment	Environmental restructuring enablement	• Prompts/cues	• Provision of a mobile application which provides a range of suitable activity break videos that do not require equipment of a large space
Motivation
Reflective Lack of motivation to want to interrupt sitting time with regular activity breaks	Beliefs about consequences Encourage reflection of experienced benefits of behaviour change	Enablement incentivisation	• Self-monitoring of outcomes	• Participants will be asked to reflect on experienced benefits at the end of weeks 1 and 2 of the intervention in the participant booklet which will be discussed during the phone call follow up • Information on positive health benefits available in participant booklet
	Reinforcement Recognising experienced benefits will reinforce benefits of behaviour change
	Intentions Develop conscious decisions to interrupt evening prolonged sitting time with regular activity breaks Goals Create an action plan to support decisions to perform activity breaks	Persuasion incentivisation	• Action planning • Barrier coping plans • Discrepancy between behaviour and goal • Goal setting	• Development of an action plan which will specify when and where activity breaks will be performed. Plans revisited during the follow up phone calls • Development of goals to be used within the action plan, which will be provided in the participant booklet • Contingency plans created in first coach session and revisited in follow up phone calls
Automatic Support to develop a new evening habit	Reinforcement Develop a routine of interrupting prolonged sitting in the evenings	Enablement	• Habit formation • Prompts/cues	• A regular activity break is taken after each alert during the personalised evening prompt/cue period

Activity breaks coach consultation

The consultation session with the Activity Breaks Coach includes several components (outlined below), the development of which was informed by behaviour change theory (see Table 1):

1. The evidence for the benefits of interrupting prolonged sitting will be discussed. This educational component of the intervention was included based on findings from our prior qualitative work, which identified ‘Knowledge of the benefits’ as a key facilitator to performing regular activity breaks at home.

2. Participants will be assisted to download the Stretch Minder application (Better Primates Lab Limited, Hong Kong) on to their mobile device and then guided though its use including showing links to the activity breaks exercise videos. Each activity breaks video is 3 min in duration and includes a series of exercises for the participant to complete during the break. The Stretch Minder app will be programmed to provide alerts to complete an activity break video every 30 min during the specified evening sedentary period, for the next 2 weeks. For example, if a participant identified 1700 to 2100 h as the periods when they are sedentary in the evening, this would be entered so that alerts would begin at 1700, and continue every 30-min until 2100 h, every night, for 2 weeks. Alerts/reminders were identified as a key facilitator in our previous qualitative work [41] and were therefore included as a behaviour change technique.

3. Participants will be shown how they can track their progress in the mobile application under the profile tab. This feature allows participants to track how many activity breaks they have completed in the application (i.e. how many times, per day, participants have completed an activity breaks video within the app), each day over the period of the intervention. This is a method of self-monitoring and utilises the perceived facilitator of ‘progress tracking’ as identified in our previous research.

4. Together the research assistant and participant will develop an individualised action and contingency plan [55]. For the action plan participants will specify when they perform the activity breaks, what particular activity they will do and where they will perform them (e.g., in the living room, outside, in the garage). The contingency plan involves participants identifying potential barriers they may face when implementing the activity break, and planning strategies or solutions to overcome these barriers.

5. During this discussion participants will explore how they could obtain support from those in their household, friends, or family to perform the regular activity breaks intervention. This discussion point is to encourage social support, which was identified as a key facilitator in our previous research.

6. At the end of week 1 and week 2, participants will be encouraged to reflect on experienced positive consequences, and factors that may have helped or hindered them from performing activity breaks during the past week. This will be prompted in the participant booklet (described below) and will provide a discussion point for the phone call follow ups to allow for adjustment to the contingency plan if required. This behaviour change technique of self-monitoring utilises the perceived facilitators of ‘progress tracking’ and ‘experienced benefits of the intervention’ as identified in our previous research.

Participants will be asked to complete the baseline adapted COM-B questionnaire [56] at the beginning of this session, rather than the baseline session, to reduce the chance that participants may change their behaviour as a result of completing the questionnaire. Additionally, participants will be provided with a booklet that will include summary information on the benefits of interrupting evening sitting time, the contingency and action plans, and space for participants to record (1) daily activity breaks, (2) sleep and wear time, and (3) evening meal, beverage, and snack consumption.

At the end of this session, participants are fitted with new activity monitors (ActiGraph GT3 + and ActivPal3) to be worn during the first 3 days and the last 3 days of the 2-week intervention period and a new CGM to be worn continuously over the 2-week intervention period. To minimise participant burden, the accelerometers are being worn for the first and last 3 days of the intervention period (a total of 6 days of wear) to identify acute changes and more sustained changes in activity patterns. Wear time and information about food and beverage consumption during the evening sedentary period will be monitored in the same manner as the baseline period.

Activity breaks mobile application

During the personalised evening period, the Stretch Minder application will deliver pre-scheduled alerts to the participant’s phone approximately every 30 min. Before beginning the activity break, participants will be able to select one 3-min exercise video to complete or initiate a walking activity break. Participants will be encouraged to initiate activity breaks (i.e. start the activity breaks video when alerted) using the mobile application as a form of self-monitoring of the behaviour. Available exercise videos built into the Stretch Minder app will be restricted to those that include simple body weight resistance exercises (e.g. squats, calf raises, and lunges). Static stretching or movements designed to be done while sitting at a desk, such as neck rotations, will be excluded. This is to ensure the exercise performed involves muscle contraction of the major muscle groups of the body, as contraction-mediated glucose uptake is one of the mechanisms believed to explain the effects of regular activity breaks on cardiometabolic health outcomes [57, 58]. The exercise videos depict the exercises participants should complete so they can follow along. Additionally, the videos contain a timer and the ability to mute the instructions so that breaks could be completed without the audio instruction interrupting television viewing. This overcomes one of the reported barriers to performing the activity breaks reported from our previous work.

Phone call follow up

Participants will receive two follow-up phone calls during the 2-week intervention period (on day 3 and day 7). The purpose of these phone calls is to encourage the participants to continue following the regular activity breaks intervention, and to explore barriers and facilitators to performing this behaviour. Therefore, during these calls, the research assistant will discuss how the participant is finding the intervention. If new barriers or facilitators are identified during this session, the contingency and action plans will be discussed and adjusted where necessary.

Post-intervention period (weeks 3 and 4)

After the 2-week period, participants will attend a visit to Mellor Laboratories to return all equipment, including the accelerometer, sleep, wear time, and evening food diary and CGM, have the final blood pressure measurement taken, and complete the final Pittsburgh Sleep Quality and COM-B questionnaires. During this visit, participants will be reminded that the intention of the intervention is to facilitate long-term behaviour change. Therefore, participants are encouraged to continue to use the StretchMinder mobile application to support them with this behaviour change. Furthermore, participants will be assisted in revising their contingency plan to discuss the key factors that hindered them from performing the activity breaks during the 2-week intervention period and encouraged to use strategies that they identified as helpful over the previous 2 weeks. Use of the mobile application will be monitored over this time to give an indication of adherence to the regular activity breaks intervention in a free-living setting without strict monitoring (i.e. real life). At the end of the 2-week follow-up period (week 4), face-to-face semi-structured interviews will be held with participants, where they will be asked about their overall experience completing the intervention. At the end of the interview, participants will be provided with a supermarket voucher to the value of $100 New Zealand dollars in compensation for the costs associated with their participation in this trial.

Outcomes

Feasibility

The interview performed with participants at the end of the follow-up period will explore participants’ experiences of the intervention, including positive and/or negative outcomes experienced as a result of performing the activity breaks. They will be asked to identify what helped and hindered them in performing the activity breaks and what, if anything, could be changed or added to the intervention to support participants in performing regular activity breaks. If not spontaneously discussed, prompting questions will ask about their experiences of using the mobile application, the consultation with the coach, and the use of the participant booklet. This information will be used to understand if any design changes are required for any future delivery of the regular activity breaks intervention.

Feasibility will be assessed through the recruitment success and retention rates assessed at pre-intervention until the end of the intervention, in line with recommendations [52]. Successful recruitment and eligibility screening will be defined as recruiting 20 participants in 6 weeks. Successful retention will be defined as retaining at least 80% of participants from the baseline period through to the end of the follow-up period.

Pilot study outcomes

The primary outcome is the change in the average daily number of activity breaks performed during the evening, between the 7-day baseline period and the 2-week intervention period. This will be measured via self-reported activity break opportunities in the study participant booklet. An increase on average of at least four activity breaks per day (two thirds of the possible six activity breaks over the minimum 3 h evening period) in at least 50% of the sample will be used as the threshold by which we consider the intervention to be feasible. With a sample size of 20, we can estimate retention of 80% with a 95% confidence interval from 56 to 94% and intervention threshold achieved in 50% of participants with a 95% CI from 28 to 72%.

Pilot study secondary outcomes

The effect of the intervention (changes from baseline to the end of the 2-week intervention) on the following outcomes will also be explored:

• 24-h movement patterns including (1) sleep (sleep period time, efficiency, wake after sleep onset and latency), self-perceived sleep quality, (2) physical activity and (3) sedentary time.

• Interstitial glucose concentrations and variability.

• Blood pressure

• Participants’ capability, opportunity and motivation to perform activity breaks

Change in 24-h movement behaviour

Participants’ 24-h movement patterns (which include sleep, physical activity, and sedentary time) will be identified using data collected from three accelerometers. The ActiGraph Gt3x + (which provides information on the intensity of activity and also allows for measures of sleep duration and quality) will be worn on the non-dominant wrist using an elasticated strap. The ActiGraph will be initialised at a sampling rate of 30 Hz. The activPAL3 (which provides information about posture) will be adhered to the front midpoint of the right thigh with an adhesive dressing. Participants will wear all three devices during the baseline period (first 3 days) and during the first 3 days and last 3 days of the 2-week intervention period (i.e. for a total of 6 days). During these times, participants will be asked to complete a wear time diary in which they will record the time when either accelerometer was removed to identify non-wear time, as well as the time participants attempted to fall asleep each night and what time they woke in the morning. Participants will be asked to wear three different accelerometers to assess the external validity of an activity breaks detection algorithm developed by the research team. The agreement, sensitivity, and specificity between self-reported activity breaks and the algorithm-detected activity breaks (number of activity breaks) will be calculated over the 2-week intervention period.

Self-reported sleep and wake times from the participant wear time diary will be manually entered into ActiLife software (Version 6.13.4, ActiGraph LLC, Pensacola, FL) to constrain the Cole-Kripke algorithm for wrist-worn accelerometry. Time-stamped data from the ActiGraph accelerometers will be downloaded using ActiLife software, and data from the ActivPAL will be downloaded using activPAL3 software (Version 7.2.38, PAL Technologies Limited, Glasgow, Scotland) and imported into Stata (Version XX, StataCorp LLC, College Station, TX). For a day to be considered valid, total wear time must be at least 10 h per day. Time spent sedentary and in light and moderate-to-vigorous physical activity will be calculated using validated cut points for wrist-worn [59] and hip-worn [60] accelerometers. For activity performed during self-reported non-wear time (e.g. swimming), the duration and intensity reported will be identified and manually overwritten in Stata. The activPAL data will be used to identify time spent sitting, standing, and stepping.

Change in perceived sleep quality

The change in perceived sleep quality will be assessed using the validated Pittsburgh Sleep Index (PSQI), which will be adapted to assess the previous 2 weeks rather than 4 weeks [61]. Participants will be asked to complete the questionnaire at the beginning of the intervention period (before the intervention has been introduced) and at the end of the 2-week intervention period. The PSQI contains 19 self-rated questions, answers to which are combined to form seven ‘component scores,’ which range from 0 to 3 (components: (1) subjective sleep quality, (2) sleep latency, (3) sleep duration, (4) habitual sleep efficiency, (5) sleep disturbances, (6) using sleep medication, and (7) daytime dysfunction), where a score of ‘0’ indicates no difficulty and a score of ‘3’ indicates severe difficulty. A sum of the seven component scores is calculated to give the ‘global’ PSQI score (out of 21), which will be used to assess change in self-perceived sleep from the start of the intervention to the end of the 2-week intervention.

Difference in glycemic control and variability

Measures of glycemic control and variability will be measured using a Freestyle Libre Pro iQ CGM, which measures interstitial glucose concentrations every 15 min. The CGM will be adhered to the posterior upper arm so that a thin filament sits in the subcutaneous tissue. Participants will wear the CGM during the baseline period and during the 2-week intervention period (as one sensor can last for 2 weeks). Time-stamped interstitial glucose concentrations will be downloaded from the readers using the FreeStyle Libre Pro software (Version 1.0, Abbott Diabetes Care Limited, Oxcon, UK) and exported into Stata.

Glycemic control will be assessed using mean glucose concentration, total and incremental area under the curve for the baseline and intervention periods. To assess glycemic control during different times of the day, data will be categorised into four different time points: (1) total (means for the total 24-h period from midnight to midnight), (2) daytime (defined as time between self-reported wake and sleep times), (3) evening (defined by the individualised 4-h period typically spent sedentary between ~ 1700 h and participant bedtime), and (4) nocturnal (defined by self-reported participant sleep and wake times). Glycemic variability will be assessed using a range of commonly reported metrics, including standard deviation of glucose (SD_glucose), time in range (TIR), and continuous overall net glycemic action at 1 h (CONGA-1) for each time point, for the baseline and intervention periods.

intervention period.

Blood pressure

Systolic and diastolic blood pressure will be measured using an automated sphygmomanometer (OMRON-HEM907), using the right arm and an appropriately sized cuff. Measurements will be taken after the participant has been seated for at least 15 min in triplicate with 1 min intervals between each measure. Blood pressure will be measured at three time points, (1) baseline, (2) end of the 2-week intervention, and (3) end of the 2-week follow up.

Change in capability, opportunity and motivation to perform activity breaks

The change in participants’ capability, opportunity, and motivation to perform regular activity breaks between the start and end of the intervention will be measured using an adapted version of the questionnaire developed by Keyworth et al. [62] and adapted for the sedentary behaviour context by Niven et al. [56]. The questionnaire asks participants to “rate your ability and willingness to perform regular activity breaks in the evening at home” with regard to each of the six constructs of the COM-B model (physical and social opportunity, automatic and reflective motivation, and physical and psychological capability). The seventh item specifically asks about the impact of knowledge. Each item is scored on an eleven-point scale (0 = strongly disagree and 10 = strongly agree). Higher scores reflect greater capability, opportunity, and motivation, and the change in each component will be calculated between baseline and the end of the intervention.

Mobile application engagement

Engagement with the mobile Stretch Minder application used in the intervention will be measured using analytics from the application developers (Better Primates Lab Limited, Hong Kong). This will include the average number of times per week that participants (1) open the mobile application and (2) begin an activity break video or walking activity break. These analytics will be reported as averages for the 2-week intervention and 2-week follow-up.

Data analysis

To assess the feasibility outcomes, the length of time taken to recruit 20 participants and participant retention will be reported. The acceptability of the intervention will be assessed by thematic analysis of transcribed interviews. The number and consistency of activity breaks performed will be described using descriptive statistics. The change in health outcomes will be described using descriptive statistics, including standard deviations and within-person correlations for future sample size estimates.

Criteria to indicate future effectiveness trial

Drawing on suggested criteria [63], in order to determine whether or not an effectiveness trial is warranted, the following criteria will be assessed: (1) acceptability of the intervention, the usefulness of the intervention components, and the potential for any barriers participants experienced with the intervention to be overcome, and (2) an average increase from baseline of at least four activity breaks per day, achieved by at least 50% of the participants at the end of the intervention period.

Data management

No formal data monitoring will take place for this trial. Consent, eligibility, and demographic data will be directly entered into an online survey using the data capturing software REDCap. All data (e.g., weight, height, blood pressure) will be collected following Standard Operating Procedures and entered into REDCap. Upon enrolment, REDCap will assign a unique identifying code (ID number) to each participant. To preserve confidentiality during data collection, all data will be recorded using this ID number, and any information linking the participants’ identity to their ID number will be kept in a password-protected computer file.

Adverse outcomes

This intervention is not expected to produce significant adverse outcomes. There is a small risk of loss of balance when performing exercises. To reduce the possibility of loss of balance resulting in a fall, participants will be encouraged to perform exercises within reach of a stable surface (e.g., back of chair or wall) so they have something to grab on to should they lose their balance. Regarding the use of the CGM, a small amount of discomfort may be experienced during application. Additionally, just like wearing a plaster, it may leave a mark on the arm after it has been removed, which should disappear after a few hours. In the unlikely event that a participant experiences an injury during the trial, participants will be covered by the New Zealand Accident Compensation Corporation scheme.

Discussion

Prolonged uninterrupted sedentary time is associated with an increased incidence of a myriad of cardiometabolic diseases [4] and all-cause mortality [5, 6, 8]. Previous research has largely focused on occupational sitting time; however, even office workers have been found to accrue the longest uninterrupted sitting time in the evening [24]. Therefore, the evening period is a high-risk time for cardiometabolic disease development due to behavioral [28] and metabolic factors [27] that promote an elevated postprandial response. Experimental studies have shown beneficial improvements in postprandial metabolism and sleep duration when evening sitting time is regularly interrupted with short bouts of resistance exercises in a laboratory setting [30, 31]. Examining the feasibility and impact on health outcomes of the regular activity breaks intervention will determine if this intervention has the potential to be useful in a real-world setting.

The regular activity breaks intervention is grounded in theory, which is a recommended approach when designing behaviour change interventions [45]. By exploring the experiences of individuals who complete the intervention, we can provide evidence for real-world acceptability as well as build on our understanding of the barriers and facilitators to changing evening sedentary behaviors. If this trial meets the outlined criteria, it will provide evidence that a large-scale, real-world effectiveness trial is warranted.

Authors’ contributions

All authors contributed to the design of this study. MP is the grant holder. JG wrote the initial manuscript. All authors have read and approved the final manuscript.

Funding

This study was funded by an Otago Medical Research Foundation Grant. This funding played no role in the study design, nor will it have any role in running the trial, data analysis, or interpretation of results.

Data availability

Data described in this manuscript may be made available upon reasonable request to the corresponding author.

Declarations

Ethics approval and consent to participate

This study was approved by the University of Otago Human Ethics Committee in October 2023, reference number H23/105. Upon expression of interest in the study, participants will be asked to acknowledge that they have read and understood the participant information sheet and consent form, and thus provide informed consent prior to completion of the eligibility questionnaire. Any future amendments will be submitted to the University of Otago Human Ethics Committee through a formal protocol amendment.

Consent for publication

Not applicable.

Competing interests

The authors declare they have no competing interests.