Reframing Retirement: An Examination of Identity Change and Self-Regulation Approaches to Promote Physical Activity

Primary Outcome - MVPA will be measured with wGT3X-BT ActiGraph accelerometers, the gold standard for PA measurement in field settings. Participants will wear the devices during waking hours on a belt around the waist (with the device positioned above the right iliac crest) for seven consecutive days. Valid cut-points (counts per minute) for adults will be used to classify MVPA. For a day to be considered valid, there will need to be a minimum of 300 minutes (6 hours) within a 24-hour period of valid wear time.Missing data will be modelled from available data.

Secondary Outcome Measure 1 Title: Body Mass Index (BMI) Description: Body mass (kg) and height (cm) will be measured using standard procedures and combined to calculate BMI (kg/m²).

Unit of Measure: kg/m² Time Frame: Baseline and 6 months

Secondary Outcome Measure 2 Title: Waist Circumference Description: Waist circumference (cm) will be measured using standardized anthropometric procedures.

Unit of Measure: cm Time Frame: Baseline and 6 months

Secondary Outcome Measure 3 Title: Cardiovascular Fitness Description: Cardiovascular fitness will be assessed using the YMCA submaximal cycle ergometer test, with estimated cardiorespiratory fitness derived according to standard protocols.

Unit of Measure: Estimated VO₂ (mL/kg/min) or workload-based estimate (choose whichever you will report) Time Frame: Baseline and 6 months

Secondary Outcome Measure 4 Title: Upper-Body Strength - 30 second bicep curl strength test Description: Upper-body strength will be assessed using the 30-second bicep curl test. The test involves performing as many arm curls as possible in 30 seconds, while sitting in a chair holding a dumbbell in the dominant arm.

Test purpose: This test measures upper body strength and endurance.

Unit of Measure: repetitions Time Frame: Baseline and 6 months

Secondary Outcome Measure 5 Title: Lower-Body Strength Description: Lower-body strength and power will be assessed using the 30-second chair stand test.

Unit of Measure: repetitions Time Frame: Baseline and 6 months

Secondary Outcome Measure 6 Title: Flexibility Description: Flexibility will be assessed using the sit-and-reach test. Unit of Measure: cm Time Frame: Baseline and 6 months

Reflective Processes Description: Attitudes and perceived capability and opportunity will be assessed using M-PAC self-report items rated on 7-point bipolar Likert scales, with higher scores indicating stronger reflective processes.

Unit of Measure: score on 7-point scale Time Frame: Baseline, 6 weeks, 3 months, 6 months, 12 months

Regulatory Processes Description: Regulatory processes will be assessed using the Physical Activity Regulation Scale (PARS). Items are rated on a 7-point Likert scale, with higher scores indicating greater use of self-regulatory strategies.

Unit of Measure: score on 7-point scale Time Frame: Baseline, 6 weeks, 3 months, 6 months, 12 months

Habit automaticity will be assessed using the Automaticity Subscale of the Self-Report Habit Index (SRHI), a validated self-report questionnaire measuring the extent to which a behavior is performed automatically. Participants rate each item on a 5-point Likert scale (1 = strongly disagree to 5 = strongly agree). Higher scores indicate stronger habit automaticity.

Unit of Measure:

Score on the Automaticity Subscale (range: mean item score on 1-5 scale)

Reflexive Processes - Identity Description: Exercise identity will be assessed using the Exercise Identity Scale. Items are rated on a 7-point Likert scale, with higher scores indicating stronger exercise identity.

Unit of Measure: score on 7-point scale Time Frame: Baseline, 6 weeks, 3 months, 6 months, 12 months

Social Identity Social identity will be assessed using the Multidimensional Inventory of Physical Activity Identity (25-item version). Items are rated on 7-point Likert scales (1-7), with higher scores indicating stronger social physical activity identity.

Prior Identity Prior physical activity identity will be assessed using retrospective self-report items assessing identity "when younger" (e.g., when describing oneself to others in earlier life). Items are rated on 7-point Likert scales (1-7), with higher scores indicating stronger prior physical activity identity.

• Well-being (Psychological Flourishing)

Description:

Psychological well-being will be assessed using the Flourishing Scale. The scale includes 8 items assessing self-perceived success in areas such as relationships, self-esteem, purpose, and optimism. Items are rated on a 7-point Likert scale (range: 1-7) and summed to produce a total flourishing score, with higher scores indicating greater psychological flourishing.

Subjective Norm - Descriptive Description: Descriptive subjective norm will be assessed using M PAC self report items rated on a 7 point Likert scale, with higher scores indicating stronger perceived norms. Unit of Measure: score on 7 point scale Time Frame: Baseline, 6 weeks, 3 months, 6 months

• Subjective Norm - Injunctive Description: Injunctive Description: Injunctive subjective norm will be assessed using M PAC self report items rated on a 7 point Likert scale, with higher scores indicating stronger perceived social approval. Unit of Measure: score on 7 point scale Time Frame: Baseline, 6 weeks, 3 months, 6 months Time Frame: Time Frame: Baseline, 6 weeks, 3 months, 6 months

Relatedness Description: Relatedness will be assessed using the relatedness subscale of the Basic Psychological Need Satisfaction and Frustration Scale. Items are rated on a 5 point Likert scale, with higher scores indicating greater perceived relatedness. (8 items total, but only using 4 satisfaction items) Unit of Measure: score on 5 point scale Time Frame: Baseline, 6 weeks, 3 months, 6 months

Perceived Mental and Physical Health Description: Perceived mental and physical health will be assessed using the 12-Item Short Form Health Survey (SF-12). The survey yields a Physical Component Summary (PCS) score and a Mental Component Summary (MCS) score. Scores are standardized (range: 0-100), with higher scores indicating better perceived physical and mental health.

Sociodemographic variables will be collected at baseline including age, sex, gender, marital status, highest level of education, current employment status, income, ethnicity, PA history. We will disaggregate and analyze all primary and secondary outcomes by gender and sex. Other demographic (e.g., age, ethnicity) variables that intersect with gender will also be considered. The approach recommended by experts in gender related measures is the two-step approach (Centre of Excellence for Transgender Health), which involves asking participants about both their current gender identity and their sex assigned at birth. Specific M-PAC constructs (e.g., perceived capability, habit, identity) may vary by sex and gender, thus targeting these considerations may maximize the potential effectiveness of PA interventions

Personality Traits Description: Personality traits will be assessed using a study-developed self-report questionnaire based on the Five-Factor Model of personality (McCrae & Costa), assessing Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness. Each domain is assessed using 12 items rated on a 5-point Likert scale (range: 1-5), with higher scores indicating greater expression of the respective personality trait.

Time Frame: 3 months only

Experience with Computers - Years of Use Experience with computers will be assessed by self-report of the number of years the participant has been using computers (years), with higher values indicating greater experience.

Experience with Computers - Weekly Use Experience with computers will be assessed by self-report of the typical number of hours per week the participant uses a computer (hours/week), with higher values indicating greater use.

Home Environment for Physical Activity Description: The home environment for physical activity will be assessed using the Home Environment Survey (Gattshall et al.), which evaluates availability and accessibility of physical activity equipment. Items are rated on 4 point Likert-type scale, with higher scores indicating greater support for physical activity in the home.

Unit of Measure: score on scale Time Frame: 6 weeks only

Ecological Momentary Assessment (EMA):

EMA smartphone check-ins to capture within-day changes in motivation and feelings toward physical activity behaviors.

Time on Platform Description: Website usage will be assessed using automatically collected platform analytics, including average time spent on the platform per week and average time spent on module pages per week.

Unit of Measure: minutes per week Time Frame: Baseline, 6 weeks, 3 months, 6 months

Engagement Breadth Description: Engagement breadth will be assessed using automatically collected platform analytics, defined as the percentage of total available pages accessed.

Unit of Measure: percent of pages accessed (%) Time Frame: Baseline, 6 weeks, 3 months, 6 months

Engagement Duration Description: Engagement duration will be assessed using automatically collected platform analytics, defined as the total number of weeks participants engaged with the online platform.

Unit of Measure: weeks Time Frame: Baseline, 6 weeks, 3 months, 6 months

Process Evaluation will involve a brief quantitative questionnaire to assess use of the intervention material and overall satisfaction of the study similar to our prior trials. Semi-structured interviews will be used to examine each of the subcomponents described in the first step.