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Commitment at the gym: Can self-funded commitment contracts curb procrastination
Last registered on March 24, 2017

Pre-Trial

Trial Information
General Information
Title
Commitment at the gym: Can self-funded commitment contracts curb procrastination
RCT ID
AEARCTR-0001966
Initial registration date
March 24, 2017
Last updated
March 24, 2017 3:42 PM EDT
Location(s)
Region
Primary Investigator
Affiliation
Lund University
Other Primary Investigator(s)
PI Affiliation
Lund University
PI Affiliation
Lund University
Additional Trial Information
Status
In development
Start date
2017-04-01
End date
2019-12-31
Secondary IDs
Abstract
This study tests completely self-funded deposit commitment contracts for exercising. We also aim to explore the role of individuals' health-related behaviour on health inequality. In addition to exercise, we look at several outcomes, such as sleep and other stress-related variables. For this study, we have designed a Randomized Controlled Trial (RCT) to be carried out in the field in collaboration with Friskis & Svettis (F&S) Uppsala in Sweden. F&S is a not-for-profit sports club, with classes and gyms. F&S Uppsala has facilities at three locations in Uppsala, and approximately 28,000 members.
External Link(s)
Registration Citation
Citation
Gerdtham, Ulf, Erik Wengström and Linnea Wickström Östervall. 2017. "Commitment at the gym: Can self-funded commitment contracts curb procrastination." AEA RCT Registry. March 24. https://doi.org/10.1257/rct.1966-1.0.
Former Citation
Gerdtham, Ulf et al. 2017. "Commitment at the gym: Can self-funded commitment contracts curb procrastination." AEA RCT Registry. March 24. http://www.socialscienceregistry.org/trials/1966/history/15396.
Sponsors & Partners

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Experimental Details
Interventions
Intervention(s)
Interventions are hidden for now.
Intervention Start Date
2017-04-01
Intervention End Date
2018-02-28
Primary Outcomes
Primary Outcomes (end points)
Exercise (objective data, not self-reported)
Uptake of commitment contract, including type of contract and with/without economic incentives
Fulfilling commitment contract (objective data, not self-reported)
Difference between desired exercise (ex-ante, self-reported) and actual exercise (ex-post, objective data)
Sleep, general health, stress, BMI, smoking (self-reported)
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
Experimental design is hidden for now.
Experimental Design Details
For this study, we have designed a Randomized Controlled Trial (RCT) to be carried out in the field in collaboration with Friskis & Svettis (F&S) Uppsala in Sweden. F&S is a not-for-profit sports club, with classes and gyms. F&S Uppsala has facilities at three locations in Uppsala, and approximately 28,000 members. From a pre-study in September 2015, we have learnt that all respondents – current F&S Uppsala members as well as guests and other non-members – would like to exercise more frequently than they did the past month. (On average, the respondents would like to exercise 0.46 times more per week.) Hence, it is relevant to invite also current members, not only new members. Invitations to participate in the study will be included in a newsletter, which is emailed to all members, including those who are currently inactive. Additional promotion may be done with posters at the three F&S facilities in Uppsala and or an ad or banner at F&S Uppsala’s homepage. Those who agree to participate will first be asked to fill out a baseline questionnaire, including a set of questions on current exercise habits and desired/target exercise habits/goals. The baseline questionnaire also includes questions on age, gender, educational attainment, origin, household income, their purpose with exercise, reasons for not exercising as desired, trust in own knowledge about how one should exercise to take care of own health, how one should eat with the same purpose, length & weight, an index of self-control, and time preferences (impatience and consistency). The participants will be randomly divided into three groups: i) control, ii) goal iii) incentives. Those assigned to the control group will keep exercising as usual. The only further intervention for those will be a follow-up questionnaire administrated to all participants after two to four months. Those randomized to the goal and incentives treatments will be offered a tailored commitment contract. By tailored is meant that the frequencies of exercising covers their desired/target exercise habits/goals as expressed in the baseline questionnaire. The idea behind the tailored commitment contracts is the theoretical finding by Bhattacharya et al (2015), that increased exercise may not be welfare improving. The difference between the goal and the incentives treatments is that subjects will be able to attach economic incentives to the commitment contract in the incentives treatment. The economic incentives will be completely self-funded. Half of those offered to sign a contract with economic incentives will get a nudge about the effectiveness of stakes. Those randomized to an offer to sign a commitment contract with economic incentives, regardless of nudge or not, may choose any amount between SEK 10 and SEK 1,000. The amount is to be deposited via Swish. If the commitment contract is fulfilled, the money is repaid; else it is donated to a preselected charity or other organization. Each participant choosing to sign a deposit commitment contract also chooses an organization that will get the money in case they fail to comply with their contract. The sequence is that those in the incentives group first choose a contract, if any, and then are asked if they would like to attach economic incentives to it. Across all treatment arms, default frequency of exercise in the offered commitment contract will be randomized to either the respondent’s own target frequency or a higher frequency. Contract length is between 1 and 4 months. Across all treatment arms, those signing a contract will be randomized to no default, or a default contract length of four months (preselected, but possible to alter). The control group gets no offer to sign a commitment contract, and obviously no economic incentives. They only respond to the initial questions (after agreeing to participate), then we follow-up on their exercise habits at the end of the intervention, and ask them to fill out a follow-up questionnaire at the end of the study. After filling out the follow-up questionnaire, all participants are given the choice between a TRISS scratch card (retail price 30 SEK) or a donation of 30 SEK to a charity of their choice (same list of charities to choose from as in the incentives treatment) to thank them for participating. Both the baseline and the follow-up questionnaire include questions on weight (and length, so we can calculate BMI), sleep and other stress related variables, as well as questions on smoking.
Randomization Method
By computer (online)
Randomization Unit
Individual
Was the treatment clustered?
No
Experiment Characteristics
Sample size: planned number of clusters
600-2000 individuals
Sample size: planned number of observations
600-2000 individuals
Sample size (or number of clusters) by treatment arms
Main treatment arms:
About 330-660 individuals in each group: incentives treatment, goal treatment and control group.
Sub-treatment groups:
Incentives treatment group: About 160-330 individuals (50 % of those in incentives treatment group) are also treated with a nudge.
Incentives and goal treatment groups: About 660-1330 individuals (100 % of those in either of the treatment groups) are also treated with a high default for contract length.
Incentives and goal treatment groups: About 330-660 individuals (50 % of those in either of the treatment groups) are also treated with a higher default for frequency of exercise.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
If we assume the same standard deviation as for self-reported exercise from a questionnaire to members and guests at Friskis & Svettis Uppsala, we would be able to detect an increase in exercise frequency of 6 per cent if the sample is 600 individuals, and of about 2.3 per cent if the sample is 2000 individuals, with a power of at least 0.9 and alpha 0.05.
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
Lund Regional Ethics Review Board
IRB Approval Date
2016-12-07
IRB Approval Number
none
Analysis Plan

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Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
No
Is data collection complete?
Data Publication
Data Publication
Is public data available?
No
Program Files
Program Files
Reports, Papers & Other Materials
Relevant Paper(s)
REPORTS & OTHER MATERIALS