Effects of an Active Choice Intervention on Physical Activity Intentions and Behaviour Among Physically Inactive Adults: A Four-Arm Web-Based Experiment
Phase: NA
Conditions: Physical Activity
Sponsor: Amsterdam UMC, location VUmc

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Study Protocol 
 
Version: 29-06-2021 
 
Effects of an Active Choice Intervention on Physical Activity Intentions and Behaviour among Physically 
Inactive Adults: A Four-Arm Web-Based Experiment 
 
Lorraine L. Landaisa, Olga C. Dammana, Judith G.M. Jelsmaa, Evert A.L.M. Verhagena,b,  
Danielle R.M. Timmermansa 
 
a Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Public and Occupational Health, 
Amsterdam Public Health research institute, Amsterdam, The Netherlands 
b Amsterdam Collaboration on Health & Safety in Sports, Department of Public and Occupational Health, 
Amsterdam Movement Sciences, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The 
Netherlands 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 

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Title 
Effects of an Active Choice Intervention on Physical Activity Intentions and Behaviour among Physically 
Inactive Adults: A Four-Arm Web-Based Experiment 
 
Names protocol contributors 
Lorraine L. Landais 
Olga C. Damman 
Judith G.M. Jelsma 
Evert A.L.M. Verhagen  
Danielle R.M. Timmermans 
 
Abstract 
• 
Background: This web-based experimental study aims to ascertain whether promoting an active (i.e. 
conscious, autonomous and explicit) choice process about physical activity results in better behavioural 
outcomes (e.g. physical activity) and psychological outcomes (e.g. physical activity intention) compared 
to promoting a passive choice process in physically inactive adults. 
 
• 
Methods: Participants will be randomized to one of four groups. The active choice groups (GA and GA+) 
will read the national physical activity guideline, and complete exercises in which they will weigh 
advantages and disadvantages of physical activity, consider personal values, and identify barriers. The 
GA+ group will be supplemented with action and coping planning exercises. The passive choice groups 
(G and GI) will receive the guideline; group GI will additionally receive information about possible 
advantages and disadvantages and barriers to physical activity. Behavioural and psychological 
outcomes will be assessed at the first measurement (T1) and follow-up (T2). Intergroup differences will 
be examined by regression analyses. In addition, we will conduct sensitivity analyses and a process 
evaluation.  
• 
 
• 
 
• 
Discussion: N/A 
• 
 
• 
Trial registration:  retrospectively registered 
 
 
Keywords 
Inactive Adults, Active choice, Decision making, Web-based intervention, Intention, Physical activity 
 
Administrative information 

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Note: the numbers in curly brackets in this protocol refer to SPIRIT checklist item numbers. The order of the 
items has been modified to group similar items (see http://www.equator-network.org/reporting-
guidelines/spirit-2013-statement-defining-standard-protocol-items-for-clinical-trials/). 
 
Title {1} 
Effects of an Active Choice Intervention on Physical Activity Intentions 
and Behaviour among Physically Inactive Adults: A Four-Arm Web-
Based Experiment 
Trial registration {2a and 2b}. 
https://clinicaltrials.gov/. 
Retrospectively registered. 
Protocol version {3} 
Version 2, 29-06-2021 
Funding {4} 
No external funding was received. 
Author details {5a} 
Lorraine L. Landaisa, Olga C. Dammana, Judith G.M. Jelsmaa, Evert 
A.L.M. Verhagena,b, Danielle R.M. Timmermansa 
a Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Public 
and Occupational Health, Amsterdam Public Health research institute, 
Amsterdam, The Netherlands 
b Amsterdam Collaboration on Health & Safety in Sports, Department 
of Public and Occupational Health, Amsterdam Movement Sciences, 
Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The 
Netherlands 
Name and contact information for 
the trial sponsor {5b} 
N/A 
Role of sponsor {5c} 
N/A 
 
 
Introduction 

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Background and rationale {6a} 
Interventions that promote physical activity among inactive adults (i.e. adults not engaging in at least 150 
minutes of moderate-intensity aerobic physical activity per week [1]) generally show small effects, and 
effects usually diminish over time [2]. Intervention outcomes may be improved if interventions would support 
individuals in making a more active choice about their physical activity behaviour. Previous studies in the 
field of choice architecture and behavioural economics have shown that the way a choices are presented 
influences individuals’ decisions [3, 4]. In this field, the term ‘active choice’ is usually used to refer to explicit 
compulsory choices without a default option [5-7]. We use a broader conceptualisation; by ‘active choice’ we 
mean a conscious, autonomous and explicit choice in which an individual actively weighs the advantages 
and disadvantages of choice options, considers his/her values, and thinks about specific personal goals, 
possible barriers to achieve those goals, and possible ways to cope with those barriers. This 
operationalisation shows similarities with components from different approaches, including Acceptance and 
Commitment Therapy (ACT) [8], the Disconnected Values Model (DVM) [9], and Mental Contrasting with 
Implementation Intentions (MCII) [10]. Health-promoting interventions based on these approaches appear to 
be effective in increasing physical activity [11-13] and physical fitness [14, 15]. 
Promoting active choices may improve intervention outcomes for multiple reasons. Firstly, it has 
been demonstrated that providing individuals with a choice – instead of telling them more directly what to do 
– increases perceived autonomy, which is associated with higher intrinsic motivation and greater behavioural 
persistence [16, 17]. Secondly, choices that align with people’s individual values increase satisfaction about 
the choice and commitment toward the chosen option, which may induce greater behavioural persistence as 
well [6, 18, 19]. People regularly prioritize social and work-related values, leaving little time for physical 
activity [20]. Decision aids and motivational interviewing are examples of tools that may support individuals in 
clarifying their values and in resolving ambivalence between the value of ‘health’ and conflicting values, such 
as social and work-related values [21, 22]. 
Thirdly, promoting active choices likely empowers people to make more informed choices, as an 
active choice process encourages people to weigh advantages and disadvantages associated with choice 
options and to make a value-congruent choice [23, 24]. Whether individuals can actually make informed 
choices depends on multiple factors, including the quality of educational information/ decision support and 
individuals’ own information-processing motivation and skills [25].  
A fourth advantage of an active decision-making process is that spelling out personal goals – by 
planning when, where and how goal-directed behaviour will be performed (i.e. ‘action planning’) –increases 
the likelihood of goal-attainment and sustained behaviour change [26]. Such action plans, or ‘implementation 
intentions’, are formulated as ‘if-then plans’ in which a specific situational context (i.e. the ‘if’ component) is 
linked with a goal-directed cognition or behaviour (i.e. the ‘then’ component) [27]. A meta-analytic review 
showed that action planning is more effective in changing physical activity behaviour if individuals also plan 
how they will cope with potential barriers (i.e. ‘coping planning’) [28]. 
 
In the current web-based experimental study, we will compare the effect of promoting an active 
choice process versus a passive choice process about physical activity on behavioural outcomes (e.g. 
physical activity behaviour, perceived increase in physical activity) and psychological outcomes (e.g. 
physical activity intention, commitment) among physically inactive adults. 

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Objectives {7} 
To ascertain whether promoting an active (i.e. conscious and autonomous) choice process about physical 
activity results in better behavioural outcomes (e.g. physical activity) and psychological outcomes (e.g. 
physical activity intention) compared to promoting a passive choice process in physically inactive adults. 
Moreover, our aim is to gain a better understanding of the active choice process, including the importance 
that inactive adults attach to different values and to advantages and disadvantages of physical activity. 
 
Trial design {8} 
Pre-test post-test four-arm (1:1:1:1) parallel design 
 
Methods: Participants, interventions and outcomes 
Study setting {9} 
Web-based study conducted in the Netherlands among members of an online panel of research agency 
Flycatcher Internet Research. 
 
Eligibility criteria {10} 
Inclusion criteria: Adults who engage in low levels of physical activity (i.e. are physically active for at least 30 
minutes on <5 days a week and engage in <150 minutes of physical activity in total throughout an average 
week) 
Exclusion criteria: Pregnant women, wheelchair users and individuals who could not walk a minimum of 100 
meters. 
 
Who will take informed consent? {26a} 
Participants eligible for inclusion will be informed about the study and data storage. Participants will 
subsequently be asked to provide (online) informed consent; if they provide consent (by clicking a button), 
they continue to the study. 
 
Additional consent provisions for collection and use of participant data and 
biological specimens {26b} 
N/A 
 
Interventions 
Explanation for the choice of comparators {6b} 
The comparison group (group G) will only receive information about the national physical activity guideline, 
because this was expected to result in a passive choice process about physical activity. 

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Intervention description {11a} 
Group GA+: Participants will receive a web-based intervention consisting of the national physical activity 
guideline and several assignments to promote a very active choice process. Assignments include: 
completing a decision balance sheet; indicating the importance of personal values and the time, effort and 
energy spent on these personal values; action planning; identifying barriers to physical activity; coping 
planning. 
 
Group GA: Participants will receive a web-based intervention consisting of the national physical activity 
guideline and several assignments to promote an active choice process. Assignments include: completing a 
decision balance sheet; indicating the importance of personal values and the time, effort and energy spent 
on these personal values; identifying barriers to physical activity. 
 
Group GI: Participants will receive web-based information about the national physical activity guideline, pros 
and cons of physical activity, and possible barriers to physical activity, to promote a somewhat passive 
choice process. 
 
Each group will receive the intervention at the first measurement (T1), after completing the IPAQ 
questionnaire. 
 
Criteria for discontinuing or modifying allocated interventions {11b} 
N/A 
 
Strategies to improve adherence to interventions {11c} 
N/A 
 
Relevant concomitant care permitted or prohibited during the trial {11d} 
N/A 
 
Provisions for post-trial care {30} 
N/A 
 
Outcomes {12} 
Primary outcomes: 
Outcome 
Measurement 
Time of 
measurement: First 
measurement (T1) or 

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follow-up (T2) 
Intention 
Intention to become more physically active (yes/no), 
assessed by a questionnaire item 
T1 
Physical activity 
Physical activity levels (MET minutes per week), assessed 
by the short form of the International Physical Activity 
Questionnaire (IPAQ) 
T1 and T2 (change 
from baseline) 
 
Secondary outcomes: 
Outcome 
Measurement 
Time of 
measurement: First 
measurement (T1) or 
follow-up (T2) 
Sitting time 
Sitting time (minutes per day), assessed by the short form 
of the International Physical Activity Questionnaire (IPAQ) 
T1 and T2 (change 
from baseline) 
Perceived increase 
in physical activity 
Participants' perception of an increase in physical 
between baseline and follow-up (assessed by a 
questionnaire item) 
T2 
Intention strength 
Participants’ intention strength toward becoming more 
physical active (assessed by a questionnaire item) 
T1 and T2 
Active choice 
Degree to which an active choice is made; a composite 
score of 9 items on a scale of 1 - 5 
T1 
Autonomous choice 
Degree to which an autonomous choice is made; 2 items 
on a scale of 1 - 10 
T1 
Commitment 
Commitment to become more physically active; 1 item on 
a scale of 0 - 10 
T1 and T2 
Self-efficacy 
Self-efficacy to become more physically active; 2 items on 
a scale of 1 - 10 
T1 and T2 
Satisfaction 
Degree of satisfaction with one's plan to become/ not 
become more physically active; 1 item on a scale of 1 - 10 
T1 
Alignment of choice 
with personal 
values 
Extent to which one's plan to become/ not become more 
physically active corresponds with what one considers 
important; 1 item on a scale of 1 - 10 
T1 
Perceived 
advantages and 
disadvantages of 
physical activity 
Open-ended questions about the perceived advantages 
and disadvantages of one’s current physical activity 
behavior, and of increasing physical activity 
T1 
Value of health 
Importance of the value ‘health’, and the time, effort and 
energy spent on health; both on a scale of 1 to 10 
T1 
Values influencing 
The extent to which the following values impact one’s 
T1 

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physical activity 
physical activity levels on a scale of 1 to 10: responsibility, 
achievement, pleasure, family, friendships, balance. 
Plans to change 
physical activity 
Open-ended questions about the preferred kind of 
physical activity, frequency, location, days and start date.  
 
Perceived barriers 
to physical activity 
Open-ended question asking about perceived barriers to 
physical activity 
T1 
Plans to cope with 
perceived barriers 
Open-ended questions about the ways one could cope 
with each perceived barriers 
T1 
Factors supporting 
physical activity 
Question about the factors that supported or would 
support physical activity. Multiple choice question.  
T2 
Barriers to physical 
activity 
Question about the barriers that hindered physical activity 
in the past two weeks. Multiple choice question. 
T2 
 
 
Participant timeline {13} 
First measurement (T1): Eligible participants will first complete the short form of the IPAQ; subsequently, 
each group will receive the intervention (either GA+, GA, GI, or G). Post-intervention, participants will be 
asked to complete a questionnaire that assesses most outcomes (see Outcomes {12}).  
 
Second measurement (T2): Approximately two weeks after the first measurement, participants will be invited 
to the follow-up measurement: a short questionnaire (see Outcomes {12}). 
 
Sample size {14} 
The study is powered to detect a 12% difference in ‘Intention to become more physically active’ (proportion 
‘yes’ versus ‘no’) post-intervention (T1) between group G and group GA+ (see Intervention) using an alpha 
level of .05 and a statistical power of 80%. This means that 182 participants are required per group. 
Consequently, at follow-up (T2) – assuming a dropout rate of 33% – we would be able to detect a difference 
of 598 MET minutes per week between group G and group GA+, as well as a 15% difference regarding the 
percentage of participants that would be ‘moderate/high active’ versus ‘low active’. 
Recruitment {15} 
The research agency will invite all panel members (n = 9395) by e-mail to participate. If needed, a few 
reminders will be sent by e-mail to panel members to achieve adequate enrolment. 
Assignment of interventions: allocation 
Sequence generation {16a} 
Participants will randomly be assigned to one of four experimental groups by the research agency, 
Concealment mechanism {16b} 

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Random allocation will be done by the computer. 
 
Implementation {16c} 
Research Agency Flycatcher will randomly assign panel member to one of the four groups. 
Assignment of interventions: Blinding 
Who will be blinded {17a} 
Trial participants will be blind to the group they are assigned to; they will not be informed about the other 
groups. 
 
Procedure for unblinding if needed {17b} 
N/A. 
 
Data collection and management 
Plans for assessment and collection of outcomes {18a} 
Self-reported physical activity and sitting time will be measured using the short form of the International 
Physical Activity Questionnaire (IPAQ) which has been shown to have reasonable reliability and validity. The 
questionnaire assesses time spent in vigorous intensity activities (e.g. heavy lifting or fast bicycling), 
moderate intensity activities (e.g. carrying light loads or doubles tennis) and walking for at least ten minutes 
over the last seven days, in addition to time spent sitting. Following IPAQ analysis guidelines, metabolic 
equivalents (METs) were used to calculate MET-minutes per week for each type of physical activity. All 
cases for which the sum of vigorous and moderate activity and walking is greater than 960 minutes (16 
hours) will be excluded from analysis. Moreover, responses of <10 minutes will be recoded ‘zero’. A 
combined total physical activity MET-minutes per week score will be computed by summing the vigorous, 
moderate and walking MET-minutes per week scores. A dichotomization will also be made: the ‘Low’ 
category from the analysis guidelines will be compared with a combination of the categories ‘Moderate’ and 
‘High’ (i.e. three or more days of vigorous-intensity activity of at least 20 minutes per day, or five or more 
days of moderate-intensity activity and/or walking of at least 30 minutes per day, or five or more days of any 
combination of walking, moderate-intensity or vigorous intensity activities achieving a minimum total physical 
activity of at least 600 MET-minutes/week). Although maximum values for sitting time are not specified in 
IPAQ guidelines, we will exclude cases with ≥1200 minutes (20 hours) of daily sitting time from analysis. 
We will assess perceived increase in physical activity by asking participants at T2 whether they have 
changed their physical activity behaviour in the past two weeks (yes/no) and, if so, what they have changed. 
Based on their answers, we will categorize participants as ‘more physically active’ or as ‘less physically 
active/no change’. The remaining outcomes will be assessed by questionnaire items. 
 

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Plans to promote participant retention and complete follow-up {18b} 
Participants will receive reminders to participate by e-mail. Participants who discontinue T1 and participate in 
T2 will be asked at the end of the follow-up questionnaire to provide a reason for not finishing T1. 
 
Data management {19} 
Anonymized SPSS-files with the collected data will be provided by the research agency. These files will be 
stored at Amsterdam UMC for 15 years (participants will be informed about this). 
 
Confidentiality {27} 
The SPSS files will be anonymized by research agency Flycatcher. Only the research team will be allowed 
access to participant’s data. 
 
Plans for collection, laboratory evaluation and storage of biological specimens for 
genetic or molecular analysis in this trial/future use {33} 
N/A 
 
Statistical methods 
Statistical methods for primary and secondary outcomes {20a} 
Statistical analyses will be performed in SPSS for Windows version 26. Differences in physical activity (MET-
mins per week), sitting time, intention strength, active choice, autonomous choice, commitment, self-efficacy, 
satisfaction and alignment of choice with personal values between group GA+, group GA, and group GI and 
group G (comparison group) will be assessed using linear regression analyses; logistic regression analyses 
will be used to analyse the effects on physical activity (moderate/high vs. low), perceived increase in physical 
activity and intention. The four groups will be dummy coded and used as independent variables in all 
analyses. For outcomes measured at both T1 and T2, we will use the T2 outcome as dependent variable 
and adjust for the T1 outcome (covariate). Participants who do not complete T1 will be excluded from 
analyses. Outliers (i.e. values exceeding 1.5 interquartile ranges below the 25th percentile or above the 75th 
percentile) in IPAQ data will be excluded from analysis. A significance level (alpha) of 0.05 was used. 
Outcome variables heavily skewed to the right will be log transformed for the regression analyses to meet 
the assumption of normal distribution. 
 
Interim analyses {21b} 
N/A 
 

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Methods for additional analyses (e.g. subgroup analyses) {20b} 
We will conduct multiple sensitivity analyses. In the first set of sensitivity analyses, we will examined possible 
confounding by age and possible effect modification by gender, educational level and health condition on our 
primary outcome measures (physical activity and intention), as previous literature suggests an association 
between these sociodemographic variables and physical activity behaviour [36-39]. We will use a liberal 
significance level (alpha = 0.10) for interaction terms. In case of confounding or effect modification on the 
primary outcome measures, we will additionally analyse possible confounding or effect modification on the 
remaining outcome measures. In case of confounding, we will adjust for the confounder in the analyses. In 
case of effect modification, we will analyse the results for each subgroup of the effect modificator (again by 
regression analyses).  
In the second set of sensitivity analyses, we will combine group G with group GI and group GA with 
group GA+, and compared their effects on all outcome measures.  
In the third set of sensitivity analyses, we will conduct all main analyses without the participants in 
group GA+ who do not complete the action and coping planning assignments because they do not want to 
become more physically active. 
Fourthly, we will conduct a sensitivity analysis for physical activity (MET-minutes per week) in which 
we will exclude all participants who physical or mental health conditions that severely hinder physical activity, 
including illness, pain, and depression. 
Finally, we will conduct exploratory analyses on (a) perceived advantages and disadvantages of physical 
activity; (b) the value of ‘health’, as well as the experienced discrepancy between the ‘importance of health’ 
and the ‘time, effort and energy spent on health’; (c) other values influencing physical activity; (d) individual 
plans to increase physical activity; (e) perceived barriers to physical activity, and plans to cope with those 
barriers; (f) factors that supported or hindered physical activity between T1 and T2. 
 
Methods in analysis to handle protocol non-adherence and any statistical methods 
to handle missing data {20c} 
Pairwise deletion will be used for missing data. 
 
Plans to give access to the full protocol, participant level-data and statistical code 
{31c} 
We plan to make all data available during publication, e.g. via clinicaltrials.gov.  
Oversight and monitoring 
Composition of the coordinating centre and trial steering committee {5d} 
Research team CHOiCE of the AmsterdamUMC, Department of Public and Occupational Health, will 
coordinate and steer the trial. This team consists of five researchers who meet bimonthly. 
 

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Composition of the data monitoring committee, its role and reporting structure {21a} 
Research agency Flycatcher Internet Research (www.flycatcher.eu) will collect and monitor the data. After 
collecting the data, the research agency will send the data to the CHOiCE research team (Amsterdam UMC). 
Flycatcher Internet Research is an independent research agency with no competing interests. 
 
Adverse event reporting and harms {22} 
N/A 
 
Frequency and plans for auditing trial conduct {23} 
N/A 
 
Plans for communicating important protocol amendments to relevant parties (e.g. 
trial participants, ethical committees) {25} 
N/A; retrospectively registered trial. 
 
Dissemination plans {31a} 
Publication in a scientific journal. 
 
Discussion 
 
Trial status 
Protocol version 2 (retrospectively registered), 29-06-2021. Start recruitment: September 4, 2020. End of 
recruitment: October 9, 2020. Trial status: completed. 
 
Abbreviations 
N/A Not applicable; IPAQ International Physical Activity Questionnaire 
 
Declarations 
 
 

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Acknowledgements 
We would like to thank all participants for their participation in this study. We would also like to thank Dr. 
Judith Rijnhart (Amsterdam UMC) for her statistical advice. 
 
Authors’ contributions {31b} 
All authors contributed to the conceptualization of the study and to the development of the intervention and 
questionnaire. LL analysed the data and drafted the manuscript. All authors interpreted the data. JJ checked 
the quantitative analyses as well as the qualitative coding. JJ, OD, EV and DT critically reviewed and edited 
drafts of the manuscript. All authors approved the final manuscript. 
 
Funding {4} 
No external funding was received for this research. 
 
Availability of data and materials {29} 
We will provide public access to the anonymized final dataset, e.g. via clinicaltrials.gov. 
Ethics approval and consent to participate {24} 
In accordance with local regulatory guidelines and standards for human subjects’ protection in the 
Netherlands (Medical Research Involving Human Subjects Act), our study was exempted from review by the 
medical research ethics committee of Amsterdam UMC (2020.142). All participants provided informed 
consent. 
 
Consent for publication {32} 
Not applicable. 
 
Competing interests {28} 
The authors declare that they have no competing interests. 
 
Authors’ information (optional)  
 
 
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