Using Real-Time Data Capture to Examine Affective Mechanisms as Mediators of Physical Activity Adherence in Interventions: Formative Study
Phase: NA
Conditions: Physical Inactivity, Overweight or Obesity, Cancer
Sponsor: University of Southern California

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Official Title: Using Real-Time Data Capture to Examine Affective Mechanisms as Mediators of Physical Activity 
Adherence in Interventions: Formative Study 
 
NCT #: NCT06125964 
 
Document: Study Protocol  
 
Date: 04.02.25 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Study Procedures 
  
1. Background/Rationale 
  
Cancer is responsible for 600,000 deaths per year in the United States. Of these cases, 15% are potentially 
avoidable through adequate physical activity and weight maintenance.1 Despite public health guidelines outlining 
the frequency, duration, and intensity of exercise needed for these protective benefits, however, large-scale 
accelerometry research reveals that more than 95% of American adults remain physically inactive.2 To increase 
the probability of physical activity engagement, researchers have previously manipulated individual cognitions,3,4 
targeting constructs such as self-efficacy, outcome expectancies, and intentions.5–10 These interventions have 
had limited success. Research is desperately needed to elucidate novel mechanisms—beyond cognitive 
processes—that might change physical activity behaviors. 
  
The type, context, and affective responses surrounding physical activity engagement represent valuable 
mechanisms that might be contributing to the exercise intention-behavior gap.11 Recent evidence suggests that 
affect, independently of cognitive processes, is a powerful predictor of physical activity engagement and 
enjoyment.12–16 Exercise itself elicits robust changes to emotional states, triggering affectively-charged 
motivations that—per incentive salience theory—lead to pursuit or avoidance of future associated behaviors.17 
While many individuals react positively to light intensity exercise and negatively to vigorous intensity exercise,18 
great inter-individual variability exists in the affective response to moderate intensity physical activity.19–22 For 
example, individuals with overweight/obesity or who are typically inactive are more likely to experience 
unpleasant feelings when exercising.23 This can harm their intentions to maintain healthy levels of activity over 
time.24 Research shows that part of the heterogeneity in affective response is due to the activity type (e.g., dance, 
yoga, brisk walking)25,26 and context (e.g., being with others or outdoors).27–34 Interventions that leverage activity 
types and contexts to strategically increase favorable affective responses might therefore improve physical 
activity maintenance in groups vulnerable to avoidable cancers. 
  
The exploration of how and why certain treatment components bring about desired changes is a crucial step that 
has previously been overlooked. While later-stage interventions are well-positioned to address efficacy, they 
leave many unanswered questions about underlying behavior change mechanisms—resulting in limited 
generalizability and a field-wide replication crisis.11 Early-stage intervention development studies are needed to 
elucidate theoretical components that determine why certain interventions are successful—and why others fail.  
  
2. Purpose/Objectives/Aims/Research Questions 
 
In response to these research gaps, the present study will examine whether affective mechanisms (1) can be 
experimentally manipulated in real-world settings; and (2) mediate the relationship between interventions and 
physical activity behavior. As an ORBIT model phase 1 trial, the research will begin with a 3-week Formative 
study to assess acceptability and feasibility of a novel physical activity intervention in adults with increased risk 
for cancer. A 19-week Comparison study will then test the intervention to achieve the following aims.  
 
AIM 1: Refine and optimize treatments to experimentally manipulate affective mechanisms in real-world settings.  
H1: Within-subjects, positive affective responses and affectively charged motivations, and physical activity will 
be higher in the affect-based (vs. intensity-based) condition. 
H2: Between-subjects, positive affective responses and affectively charged motivations, and physical activity 
will be higher in the affect-based condition with TYPE/CONTEXT (vs. without TYPE/CONTEXT). 
H3: Between-subjects, the association between affective responses and affectively charged motivations will 
be stronger, and physical activity will be higher in the affect-based condition with SAVOR (vs. without SAVOR). 
 
AIM 2: Determine whether affective mechanisms mediate effects of treatments on physical activity. 
H4: Within-subjects, affective response and affectively charged motivations will mediate associations between 
intervention engagement and physical activity at the day-/week-level in all conditions of the Comparison study. 
 
AIM 3: Explore cross-person and cross-situation moderating effects. 

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H5: The above Comparison study effects will be larger among individuals with lower self-regulatory capacity 
(e.g., self-control, self-efficacy) and on days with more situational constraints (e.g., incidental stress, pain). 
 
3. Participants (sample) 
 
The sample (N=416) will be comprised of adults who are at an elevated cancer risk due to physical inactivity and 
overweight or obesity. Inclusion criteria are: (a) adults aged ≥18 years; (b) residing in the United States; (c) self-
reported BMI ≥ 25; (d) currently engaging in < 60 minutes per week of structured physical activity; (e) owning a 
personal smartphone device; (f) residing in an area with Internet or Wi-Fi connectivity during the study period; 
(g) able to speak and read in English; (h) interested and willing to start a physical activity program; (i) willing to 
wear a Fitbit Versa smartwatch provided by the study team everyday continuously (including at work and during 
physical activity), in place of any Fitbits or smartwatches they previously wore, for the duration of the study 
period; and (j) able to read the small font on a smartwatch screen without glasses, or willing to carry reading 
glasses during physical activity for the purpose of reading the smartwatch screen. In addition to those who do 
not meet the inclusion criteria, we will exclude individuals who (a) are unable to provide informed consent due to 
cognitive disability; (b) are unable to engage in one or more key treatment or assessment components, including 
those with medical conditions that preclude physical activity engagement or who cannot wear an accelerometer 
on the wrist for any reason; (c) are currently pregnant, given the extreme change to physical activity levels 
commonly observed within this population; or (d) are referred to the study by either another participant or through 
Reddit. Children are excluded given their unique physical activity needs.  
 
4. Recruitment & Screening 
 
Participants will be recruited online through ResearchMatch, a national health volunteer registry created by 
academic institutions and supported by the NIH as part of the Clinical Translational Science Award (CTSA) 
program. They can also be recruited through a link to our screener on our study website. All recruitment and 
screening procedures will be conducted remotely and on a rolling basis, with an expected 8 to 20 participants 
enrolled per month. Interested individuals will be directed to an online screening survey with medical history-
related questions based on the Physical Activity Readiness Questionnaire for Everyone (PAR-Q+).35 Individuals 
with contraindications to beginning a physical activity program as identified on the PAR-Q+ and clarified with a 
follow-up phone call (e.g., recent myocardial infarction or electrocardiography changes, complete heart block, 
acute congestive heart failure, unstable angina, and uncontrolled hypertension) will be asked to provide 
physician’s clearance before being eligible to join the study. Those determined to be eligible will be contacted by 
a study team member and scheduled for a private video conference consent session. During this session, 
participants will be provided with more information about the study’s purpose, procedures, and data 
confidentiality. The voluntary nature of participation will be emphasized. Participants will be informed that there 
is no guarantee of direct benefits from participation; risks related to participation will also be explained. Research 
staff will inform participants that they can withdraw from the study at any time without fear of consequences, and 
any concerns or questions about participation will be addressed at this time. Those who wish to participate will 
then be asked to sign a HIPAA-compliant informed consent document via REDCap. Study staff will screen, 
recruit, consent, and collect data in English. Study staff will clearly communicate to participants that they might 
be proactively removed from participation by investigators at any point in time and for any reason. For the 
Formative Study, recruitment will be stratified to achieve approximately equal representation of age, sex, and 
BMI groups in the sample. For the Comparison Study, recruitment will be stratified to ensure no greater that a 
70% female/30% male difference in sex distribution. Participants recruited to the Comparison Study starting 
March 2025  (n=120) will complete two additional types of assessments (i.e., “smartphone word match activity” 
and exit interview) that participants recruited befor and after those dates will not complete. . 
  
5. Methods 
 
Procedures 
Both the Formative and Comparison Studies will follow the general procedures outlined in Table 1.  
 
Consent. Participants provide informed consent during a scheduled private video conference with a trained study 
team member.  

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Baseline Questionnaire. Following informed consent, participants receive an email with a link to a 45-minute 
HIPAA-compliant REDCap baseline questionnaire. This survey measures self-regulatory capacity (self-control, 
intentions, self-efficacy) and importance of psychological needs; sociodemographic, anthropometric (self-
reported height and weight), personality, mental health, physical activity information, and participants’ addresses 
will also be collected. If participants indicate that they complete more than 800 minutes of MVPA or greater than 
60 minutes of vigorous physical activity on the baseline questionnaire, they can be found ineligible and be 
removed the study.  
 
Morning/Evening Goal Sessions (“text messages”). Following the baseline questionnaire, participants are asked 
to complete ≤3 days of morning and evening goal sessions (“text messages”). These sessions include seven 
affect items and include a question at the end asking, “Do you think you could answer a survey like this most 
morning and evenings for 19 weeks?”. The study team will use this as a brief check before sending participants 
a Fitbit Versa smartwatch.  
 
Mail Fitbit and Instructions. The study staff then mail a Fitbit Versa smartwatch with instructions to each 
participant.  
 
Orientation. Once study materials are received, the participant attends a remote orientation session where they 
will be introduced to the study and watch a summary presentation with instructions on how to participate. During 
this session, participants are led through setting up their smartphone and Fitbit Versa smartwatch to our study 
platform through Fitabase, to allow for tracking of physical activity and delivery of EMA (“check-ins”); study staff 
then teach them how to complete smartphone based morning and evening goal sessions and how to respond to 
EMA (“check-ins”) on their Fitbit smartwatch.  
 
Random Assignment. Random assignment will be stratified by sex at birth and assigned using the randomization 
allocation table via REDCap. Participants will be assigned to one of eight groups (n=45 each), based on order 
and intervention components: Intensity > Affect (No Enhancements), Intensity > Affect (Tailored 
Recommendations), Intensity > Affect (Savoring), Intensity > Affect (Tailored Recommendations & Savoring), 
Affect (No Enhancements) > Intensity, Affect (Tailored Recommendations) > Intensity, Affect (Savoring) > 
Intensity, Affect (Tailored Recommendations & Savoring) > Intensity. 
 
Start-Up
Onboarding
Intervention
Exit
Informed Consent
Orientation
Morning/Evening Goal Sessions
Post-Study Questionnaire
Baseline Questionnaire
Random Assignment a
Wear Fitbit
Exit Interview b
Morning/Evening Goal Sessions ("Text Messages")
Run-In Period
EMA ("Check-Ins")
Mail Fitbit & Instructions
Mid-Study Questionnaire a
Implicit Associations Test (IAT)a
Table 1. Study Procedures
Note.  a Comparison Study only; b Formative Study only.
Start-Up
Onboarding
Intervention
Exit
Informed Consent
Orientation
Morning/Evening Goal Sessions
Post-Study Questionnaire
Baseline Questionnaire
Random Assignment a
Wear Fitbit
Exit Interview b
Morning/Evening Goal Sessions ("Text Messages")
Run-In Period
EMA ("Check-Ins")
Mail Fitbit & Instructions
Mid-Study Questionnaire a
Implicit Associations Test (IAT)a
Table 1. Study Procedures
Note.  a Comparison Study only; b Formative Study only.

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Run-in Period. The Comparison Study will begin with a week-long Fitbit smartwatch assessment-only run-in 
period to introduce participants to wearing and charging the Fitbit smartwatch and collect baseline physical 
activity data.  
 
Intervention Period. The 19 weeks of study participation for the Comparison Study and three weeks for the 
Formative Study officially “start” on the first day of the run-in period. While everyone receives physical activity 
prescriptions, treatment delivery varies by group assignment (affect- or intensity-based goal setting), which is 
randomized for the Comparison Study. Morning and evening goal sessions, Fitbit wearing, and EMA (“check-
in”) procedures are described in the Intervention and Instrumentation sections below. During the morning goal 
sessions, they also will complete a mobile Implicit Associoations Tests (IAT) (i.e., called a “smartphone word 
match activity”) (for the sub-sample recruited to the Comparison Study n=120). Participants in the Comparison 
Study will additionally respond to a Mid-Study Questionnaire halfway through the study. Upon study completion, 
participants are asked to fill out a 30-minute REDCap questionnaire, with Formative Study and participants in 
the Comparison Study subsample recruited starting March 2025  (n=120) additionally completing an open-ended 
qualitative exit interview. The consent, orientation, and exit interview remote sessions are all scheduled by the 
participant using a Calendly integration. Periodic emails and text messages will also be sent to encourage study 
participants’ progress every few weeks.  
 
The three-week Formative study (N=56) will iteratively test and refine the implementation of a novel treatment to 
manipulate affective mechanisms during physical activity. Acceptability and feasibility of content, delivery, device 
usage, engagement, and achieving clinically meaningful changes in affective mechanisms will be addressed.36 
Treatment components targeting intensity-based goals and affect-based goals will be tested separately in four 
groups of n=14 participants: [1] intensity-based goal setting alone; [2] affect-based goals + TYPE/CONTEXT; [3] 
affect-based goals + SAVOR; [4] affect-based goals + TYPE/CONTEXT + SAVOR. Testing occurs on a rolling 
basis with 1–2-week gaps to allow for iterative refinements. 
  
The 19-week Comparison study (N=360) will then use a Multiphase 
Optimization Strategy (MOST) design to determine the effects of 
each intervention component.37,38 Specifically, we will compare 
affect- and intensity-based goals within-persons and affect-based 
goal condition enhancements between-persons (Figure 1). 
Participants are randomly assigned to treatment groups. The study 
protocol begins with a run-in period (described above), followed by 
either affect- or intensity-based goals for the first 8-weeks, a two 
week  washout period, and a cross-over to receive the alternate 
condition for the remaining 8-weeks. During the affect-based goal 
condition, participants also randomly receive one of four possible 
combinations of TYPE/CONTEXT and SAVOR enhancements: [1] 
affect-based goal setting alone; [2] affect-based goals + 
TYPE/CONTEXT; [3] affect-based goals + SAVOR, [4] affect-
based goal setting + TYPE/CONTEXT + SAVOR. 
 
 
Intervention 

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This study will add affect-based physical activity goals to an existing mHealth intervention called MyDayPlan, 
which delivers morning and evening goal sessions. Every Sunday, participants receive a text message with a 
link to a brief REDCap questionnaire where they are asked about their tentative sleep and physical activity 
schedule for that upcoming week. On days participants have planned to do physical activity (according to the 
Sunday scheduling survey), they will engage in two goal sessions: one in the morning and one in the evening. 
Participants are alerted to complete a session with a text message that has a link to a REDCap form. Morning 
goal sessions provide an activity goal for the day (“goal module”); ask the participant to create a concrete plan 
for achieving this goal (“action plan module”); and prompt the participant to anticipate barriers and brainstorm 
solutions to accomplish the goal (“coping plan module”). Evening goal sessions have participants reflect on 
whether they were able to meet this goal (“self-monitoring module”). The focus of the goal module differs 
according to the participant’s assigned condition. For each condition, the Fitbit Versa smartwatch will feature a 
custom watch face with a clock (current local time), the date, current device battery levels, and a physical activity 
button. The physical activity button can be pressed whenever a subject wants to engage in physical activity, and 
provides real-time feedback on activity duration. If the subject’s moving average HR is too low following the 
physical activity button press, the Fitbit smartwatch will ask “Still exercising?” twice (options No; Yes) before 
auto-concluding the session. [Note: for the Comparison Study, the wording of this question will be “Still being 
physically active?”]. Participants will also have the option to view short explanatory 
videos throughout their participation that summarize aspects of what is expected of 
them in the study.  
 
The intensity-based goal condition asks participants to maintain a certain target heart 
rate range during physical activity (for example, “Today, your goal is to maintain a 
minimum heart rate of 130 bpm during physical activity.”). Starting heart rate reflects 
the approximate age-adjusted heart rate max, with goals progressively increasing from 
55% to 70% heart rate max across 8 weeks (i.e., the moderate intensity activity range) 
for the Comparison Study (see Table 3), and from 55% to 60% across 2 weeks for the 
Formative Study. Research staff will show participants how to monitor their heart rate 
using their Fitbit smartwatch. Specifically, when they press the physical activity button 
on the Fitbit smartwatch (described above), the watchface will display real-time heart 
rate in addition to activity duration.  
 
The affect-based goal condition asks participants to engage in either (1) a type (50% of daily goals) or (2) a 
context (50% of daily goals) of physical activity that allows them to experience positive affect. Goals focused on 
context are randomly generated to suggest that the participant performs activity (1) in a place; (2) in a social 
situation; or (3) while listening to something that makes them feel good.  
 
Two enhancements (TYPE/CONTEXT and SAVOR) will augment the treatment effects. TYPE/CONTEXT 
provides tailored recommendations for activity types and contexts that satisfy personally important psychological 
needs (i.e., relatedness, social esteem, individual esteem, creativity, mindfulness/reflection, learning, challenge, 
entertainment/escapism, aesthetic appreciation, morality) as rated by each participant at baseline. Ratings from 
a crowdsourced panel of adults on Amazon Mechanical Turk will be used to determine the potential for specific 
activity types39 and contexts to satisfy psychological needs; our tailoring algorithm will then recommend the 
corresponding activity type or context while accounting for reported constraints (e.g., ability, access). These 
details will be incorporated into a tailored recommendation provided to participants during the Sunday Scheduling 
survey. Specifically, the program will randomly select either type or context (i.e., location, audio, social) 
recommendations and will rotate every two weeks. For TYPE, participants’ top 3 activity types are displayed in 
the following message: “THIS WEEK, we recommend trying [top 3 activity types] because it will satisfy your 
unique needs and make the experience more enjoyable.” For CONTEXT, participants’ top 3 activity contexts are 
displayed in the following message: “THIS WEEK, we recommend trying a physical activity [top 3 activity 
contexts] because it will satisfy your unique needs and make the experience more enjoyable.” SAVOR 
implements a brief savoring exercise on the smartphone that takes place either after the planned physical activity 
session or during the evening goal session (after the self-monitoring module). Participants will respond to 
questions that are intended to enhance and prolong positive experiences during physical activity. To trigger 
attentional deployment, a common savoring strategy that involves intensifying experiences by focusing on 
them,40,41 participants will answer two open-ended prompts. These prompts are drawn from a prompt pool with 

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slightly varied wording to promote a sense of novelty. Examples of the three prompts are: “(1) Think about the 
most positive part of your physical activity session today. What about this part made it positive to you? (2) Next, 
think about the positive feelings you experienced during this session. Please describe them. (3) Take a moment 
to appreciate your physical activity session today. What about it are you grateful for?”. Savoring prompts will 
rotate daily and have a day lag built in every week (i.e., Week 1 Monday Savoring Prompts are Week 2 Tuesday 
Savoring Prompts). 
 
Instrumentation 
Study variables will be collected with online questionnaires via REDCap surveys, smartwatch-based EMA 
(“check-ins”), smartwatch-based accelerometry, and an exit interview (Formative Study only). 
 
Fitbit Versa smartwatch accelerometer: Participants will be loaned a Fitbit Versa smartwatch to be worn on the 
wrist for the duration of the study period, except while bathing. An internal accelerometer continuously measures 
physical activity intensity (sedentary, light, moderate, vigorous) and step count at the minute-level. Heart rate 
(covariate) is also recorded continuously and is used to determine smartwatch wear, as well as to calculate 
average heart rate during activity sessions >10 min. Only days with sufficient wear time (defined as ≥ 10 hours 
of valid data, where no more than 20 minutes per hour has a consecutive step count of zero) are used for 
analysis. Daily steps and minutes of light, moderate, and vigorous physical activity (outcome) are then 
calculated from minute-level data. Fitbit does not provide access to the raw acceleration data. However, activity 
intensities, steps, and heart rate measured by Fitbit devices have been shown to be reliable and valid as 
compared to other activity monitors including Actigraph.42–45 
 
EMA via Fitabase Engage: Real-time prompted EMA (“check-ins”) will be administered on the smartwatch using 
Fitabase Engage. If no interaction with the watch face is made, one reminder signal may be emitted before the 
prompt becomes inaccessible. EMA (“check-ins”) take approximately 30 seconds to complete. If a prompt occurs 
during an incompatible activity (e.g., driving), participants will be instructed to ignore it. To minimize participant 
burden, all questions are answered by tapping the smartwatch interface.46,47 Three types of EMA (“check-ins”)—
random, event-contingent, and evening—will be sent to participants. Random and event-contingent are used for 
the Formative Study, while the Comparison Study will use event-contingent and evening. Random EMA (“check-
ins”) will be randomly scheduled to be sent during normal waking hours, with a single prompt sent during each 
of four evenly spaced time windows: 0-4, 4-8, 8-12-, and 12-16-hours post-waking. Participants are asked to 
report their incidental affect via seven bipolar Likert Scale items. Five items (Energetic-Fatigued, Happy-
Discouraged, Relaxed-Tense, Excited-Bored, Satisfied-Frustrated) are drawn from Russell’s Circumplex Model 
of Affect;48 one (Good-Bad) represents core affective valence;49 and one (Proud-Embarrassed) represents self-
conscious emotion.50 One of these seven items is repeated as a validity check (i.e., for a total of eight items). 
Event-contingent EMA (“check-ins”) are triggered when Fitbit sensors detect physical activity via moving average 
heart rate max. At least a 10-minute buffer (Formative Study) or 30-minute buffer (Comparison Study) separates 
the first and second event-contingent EMA during a single exercise bout, such that the moving average heart 
rate is "reset” following completion of the first prompt and the earliest possible second prompt is sent at least 10-
minutes later (Formative Study) or 30-minutes later (Comparison Study) assuming the aforementioned threshold 
is met. A maximum of two event-contingent EMA will be sent within any given 60 min period. Participants are 
asked to safely pause their activity to answer questions about their affective response (mediator)49,51,52 with 
the same eight (i.e., 7 unique + 1 repeated) items as the random EMA above. Event-contingent EMA also include 
end a Rating of Perceived Exertion (RPE) item and end by asking whether the current physical activity is the 
participant’s planned session.53 Finally, evening EMA (“check-ins”) are sent to participants at 8 pm local time 
every day and ask participants to report their  feelings from that day using the same eight affective response 
items as the random and event-contingent EMA (only modified to ask about their overall affect from that day, 
rather than their current affect). A depiction of the daily intervention strategies and measures is shown in Figure 
2. 

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REDCap surveys during morning and evening goal sessions are scheduled to be sent at the same time every 
day: 5:00 AM with approximately 5 reminders sent once every hour (morning goal session), and 6:00 PM with 
approximately 5 reminders sent once every hour (evening goal session). Sessions are sent via text message 
and completed via REDCap. These sessions will deliver the intervention components, as discussed above. 
Morning goal sessions also assess affectively-charged motivations (mediator)54 with one item from the 
Attraction-Antipathy subscale of the AFFEXX,55 and anticipated affect (mediator) with another item.56 The 
morning goal session also measures incidental affective states using the same 7 items as the random and event-
contingent EMA, stress,57 pain,58 fatigue,59 illness, and sleepiness60 as key situational factors (moderator). 
Finally, the participant is asked whether they want to set a physical activity plan for that day, and whether their 
plan from the day before is the same or different from the plan they want to set for that day. Evening goal sessions 
measure physical activity type and context (covariates) by asking participants to report characteristics about 
the physical activity they performed that day (e.g., running, dance, hiking, home, park, alone, with spouse, 
perceived exertion58). They are also asked if they enjoyed the activity they did (if receiving affect-based goals) 
and whether they focused on their goal during physical activity. Three questions ask about the extent to which 
that day’s physical activity satisfied various psychological needs.  
 
Implicit Associations Test (IAT): For a sub-sample of particpants recruited starting March 2025 (n=120), they will 
receive a personalized ID code and an Internet link at the end of their morning goal session, prompting them 
click on the link, enter in the ID code, and complete a mobilelIAT on their personal smartphone device (i.e., 
smartphone word match activity). The mobile IAT asks participants to match to a conceptual target such as 
sedentary behavior (e.g., sitting, lying) or physical activity (e.g., walking, running) to affective attributes (e.g., 
good/bad).61–64 If the participant has a strong automatic association between the attribute and conceptual target, 
then the reaction time will be shorter.65 A D-score will be calculated by dividing the difference in the average 
reaction times between the positive and negative attributes by the pooled standard deviation of all the reaction 
times.65 A higher D-score indicated more favorable implicit attitudes toward the target. The mobile IAT will take 
2 min to complete. 
 
Baseline Questionnaire: Participants receive an email or text message to complete a 45-minute online 
questionnaire with the HIPAA-compliant REDCap system at baseline (Baseline Questionnaire).65 Self-
regulatory capacity (moderator) is measured with questions related to self-control,66 intentions,67 and self-
efficacy16 for physical activity. Participants answer a series of questions about various physical activity 
constraints (e.g., ability, access to equipment) and rate the importance of psychological needs (intervention 
enhancement tailoring variables) across 10 domains (e.g., relatedness, esteem, creativity, challenge, 
learning) using a 33-item instrument developed in our prior work as an adaptation of the Basic Psychological 
Need Satisfaction and Frustration Scale.68,69 The Baseline Questionnaire will also collect demographics and 
other traits/behaviors (covariates), including depression,70 anxiety,71 life satisfaction,72 perceived stress,73 
grit,74 personality,75 sensation seeking,76 stage of change for physical activity,77,78 self-reported physical activity 
(International 
Physical 
Activity 
Questionnaire 
[IPAQ]),79 
physical 
activity 
enjoyment,80 
exercise 
preference/tolerance,81 affective motivation for physical activity,82 intrinsic motivation for physical activity,83,84 
physical activity attitudes85 and identity,86 sleep,87 diet,88 health status,89 tobacco/alcohol/drug use, and 
demographics (e.g., race/ethnicity, income). Anthropometrics (covariates) in the form of height and weight, 

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self-reported physical activity habit90 and lifetime history of activity, implicit attitudes about activity,91 and mobility 
are also collected in the baseline questionnaire. Mailing address will also be collected during this time, to be 
able to send participants their Fitbit Versa smartwatch.  
 
Mid-Study Questionnaire: Comparison Study participants will be asked to respond to a 30-minute REDCap 
questionnaire halfway through their participation in the study. This questionnaire will contain many of the same 
measures in the Baseline Questionnaire: demographics, general health, sleep schedule, depression, anxiety, 
life satisfaction, perceived stress, satisfaction of psychological needs through physical activity, physical activity 
enjoyment, exercise preference/tolerance, affective motivation and intrinsic motivation for physical activity, self-
efficacy for physical activity, and physical activity intentions, attitudes, and identity. Participants also complete 
questions about their physical activity habits, as well as items about their sleep and mobility.    
 
Post-Study Questionnaire: Participants will be asked to respond to a 30-minute REDCap questionnaire upon 
Formative Study completion. This questionnaire will contain the same questions as the Mid-Study Questionnaire, 
with additional items to assess the accessibility/usability and sustainability/feasibility of the interactive 
technology.92 A similar questionnaire will also be administered after the Comparison Study. 
 
Exit Interview: Participants in the Formative Study, as well as a sub-sample recruited to the Comparison Study 
starting March 2025 (n=120), will engage in a 45-minute video conference exit interview to assess user 
experiences, accessibility/usability, burden, thoughts toward specific study components, and issues related to 
sustainability/feasibility. 
 
Compensation 
Participants will be compensated for their time and efforts based on measure completion. Participants in the 
Formative Study will receive up to $75/three weeks: $35 for wearing the Fitbit Versa smartwatch all day and 
night (≥23 h/day), $35 for answering all Fitbit Versa smartwatch EMA (“check-ins”; with no more than one missed 
per day), and $5 for completing the exit interview (Formative Study only).  
 
For the Comparison Study, participants will receive four payments of up to $100 each (paid every 4 weeks): $50 
for wearing the Fitbit Versa smartwatch all day and night (≥23 h/day) and $50 for answering all smartwatch EMA 
(“check-ins”; except for those that occur while driving, sleeping, or another activity that precludes responding). A 
$50 payment will also be given during the 2-week “washout” break for wearing the Fitbit Versa smartwatch all 
day and night (≥23 h/day), and another $50 payment will be given for completing the Baseline ($20), Mid-Study 
($15), and Post-Study Questionnaire ($15) s. The total possible compensation for the 19-week Comparison 
Study is $500, and participants also keep the Fitbit Versa smartwatch upon completion. For the 120 participants 
in the Comparison Study sub-sample (recruited starting March 2025), the compensation structure will be the 
same, except they will instead receive four payments of up to $120 each (paid every 4 weeks): $60 for wearing 
the Fitbit Versa smartwatch all day and night (≥23 h/day) and $60 for answering all smartwatch EMA (“check-
ins”; except for those that occur while driving, sleeping, or another activity that precludes responding), and $20 
for completing an exit interview, for a total of $600.  
 
Participant Privacy & Data Management 
Participants will be informed that all collected data is confidential. The study team will provide participant’s 
personal study data upon request. The participants’ names will be removed and replaced with an ID number on 
all records to preserve the participant’s anonymity. Coded data is then entered into a database that will be stored 
and backed up on a university secured server. All physical materials pertaining to this study will be stored in a 
locked cabinet in the Real-Time Eating and Activity Children’s Health (REACH) Lab that has key code access. 
Study staff undergo PI-guided specialized training for handling sensitive data in addition to the standard IRB-
required training. All lab computers and laptops are password locked. Data collected by the screener will be 
destroyed after it is used to determine eligibility. Coded EMA (“check-in”) and accelerometer data will be sent 
from the Fitbit to the linked smartphone; the data will then be securely transferred to Fitabase, a fully hosted, 
cloud-based software solution that implements robust industry standards to maintain secure databases and keep 
data private. Fitabase code and databases physically reside on the Microsoft Azure platform. Morning and 
evening goal session and online questionnaire data will be collected through REDCap. USC will store all data 
captured in REDCap on University servers. Results of the IAT (word match activity) are saved as individual de-

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identified files in a limited-access encrypted Google Developer file system. Files are downloaded to secure USC 
servers for storage, processing, and analysis before being deleted from the Google system. Data will be 
downloaded from Fitabase servers and stored in a de-identified format on secure servers at USC that operate 
behind a firewall. Participants are assigned study-specific Fitbit accounts to use for the duration of the study; 
these accounts are deactivated (i.e., deleted through Fitbit.com by the study team) upon participant completion 
of the study. All Fitbit smartwatches returned to the study team (i.e., for the Formative Study or participants not 
finishing the Comparison Study) will be factory reset prior to being reused. Comparison Study participants who 
keep their Fitbit smartwatches will be instructed to create a new (private) Fitbit account for further use with the 
device. Participants will be informed of this during the informed consent process. All researchers with access to 
the data will undergo data sensitivity training specific to this project, beyond standard training required by our 
IRBs. Publications and presentations of study data will not contain any personal information about the 
participants. Breach of confidentiality is highly unlikely, given the de-identification and encryption of all sensitive 
information and materials. A master key linking participant names and ID numbers will be stored in a separate 
electronic location accessible only by the PI and Project Manager. 
 
The majority of study staff will be blinded to participant assignment for most of the study period.  
 
Data Analysis 
 
Formative Study 
 
For the Formative Study, DTx RWE Framework benchmarks will be assessed with descriptive statistics (e.g., 
mean scores, frequencies tallied and expressed as percentages of the sample). Most benchmarks explicitly 
specify the percentage (e.g., <1% or ≥51% of participants) of the sample or the mean score of the scale/measure 
(e.g., System Usability Scale score ≥68, Delighted-Terrible Scale score of 2-4) that define "success" for that 
benchmark. The analytic plan for the few benchmarks that are not explicit about the exact statistics used is 
outlined below. See also the attached document for more details. 
 
For the equity benchmark (overall physical activity program), accessibility and efficacy of the intervention will be 
compared between the following groups of participants: sex (male; female), race (white; non-white), ethnicity 
(Hispanic; non-Hispanic), age (continuous/frequency distribution), BMI (continuous/frequency distribution), 
income (≤$44,999; $45,000 to $84,999; $85,000 to $124,999; ≥$125,000), able-bodied (continuous/frequency 
distribution of total constraints and total difficulties with mobility). It should be noted that the Formative Study is 
not statistically powered to compare groups of subjects, so these between-group comparisons will be a 
subjective examination of System Usability Scale scores (for accessibility) and reported change/lack of change 
in physical activity enjoyment (for efficacy) across all levels of each of the sub-groups. If these values are 
approximately equal between the groups, then the benchmark will be achieved. Even though statistical testing 
will not be performed for this benchmark due to a lack of power, we will report raw tallied data to promote 
transparency.  
 
For the Psychological Needs Component's accessibility/usability benchmark, the total number of self-reported 
physical activity type, location, and listening context constraints are tallied for each person. Cross-tabulation 
tables will then allow for the reported ability to follow activity recommendations (yes/no) to be qualitatively 
compared across the full range of total constraints (physical activity type, location, and listening context) reported 
by all participants. To achieve the benchmark, there must not be an observable trend between the number of 
constraints reported and a person's ability to follow the activity recommendations (e.g., when the cross-tabulation 
table is studied, participants in the upper half of the distribution for total constraints should be, at the very least, 
approximately equally as heterogenous as the lower half of the distribution for reported ability to engage [yes/no] 
in the activity recommendations). As above, the raw tallied data will be reported to promote transparency. 
 
Comparison Study 
 
Exploratory analysis will examine the distributions, identify needed data transformations, investigate 
multicollinearity, and identify extreme observations. Data will be analyzed with SAS and R. Missing data analyses 
will involve considerations of imputation methods,93,94 attrition propensity scores95 based on the 
compliance/dropout for each participant,96 and sensitivity analyses. We will consider age, sex, income, 

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race/ethnicity, BMI, and fitness as confounders. Other variables associated with outcomes (p<.10) will be 
included as covariates. Exploratory tests of moderation will also be conducted, as there may be sex and age 
differences in physical activity97,98 and affective mechanisms.99–101 Power estimates were evaluated using Monte 
Carlo simulations in Mplus.102–105 The estimated effect size of affect-based physical activity interventions range 
from a small effect on the primary outcome (affective response) (f2 =0.04, representing a 0.3 point increase on 
a 5-point affect scale)54 to a medium effect on the secondary outcome (physical activity) (f2 =0.17, representing 
a 30/min week increase in MVPA).106 A sample of N=200 participants (100 per condition) (after ~30% attrition) 
is needed to detect small between-subject effects on change in the outcomes (H2 and H3) with β =.80 and α=.05. 
To detect within-subject effects (H1 and H4), our level-1 sample sizes will be much larger (e.g., 200x4x4x7 level-
1 N for daily data). Thus, we should have sufficient power to detect very small effects for the remaining 
associations. H5 is exploratory and not statistically powered.    
AIM 1: Determine whether affective mechanisms can be experimentally manipulated. In the Formative study, 
descriptive statistics (means, frequencies) will assess acceptability and feasibility of content, delivery methods, 
device usage, engagement, and raw values for change in affective mechanisms. The Comparison study will use 
an “intent to treat” approach to test the (1) within-subject effects of affect- vs. intensity-based goals (H1), (2) 
between-subject effects of affect-based goals with vs. without TYPE/CONTEXT (H2), and (3) between-subject 
effects of affect-based goals with vs. without SAVOR (H3) on the primary outcome (affective responses and 
affectively-charged motivations) and secondary outcome (physical activity). We will use random-effect 
regression models (level 1-days, level 2-subjects), which adjust for clustering within subjects and incorporate 
random effects.107 Each treatment effect and each outcome will be tested in separate models. We will examine 
cross-level interactions between affect-based goals with vs. without savoring (level 2) and affective responses 
(level 1) to test H3.  
AIM 2: Determine whether affective mechanisms mediate effects of interventions on physical activity 
(Comparison Study). Multilevel mediation will be tested using a 1-1-1 strategy that fits a set of simultaneous 
equations using path analysis in R.108 Analyses will test the effects of intervention engagement on same-
day/same-week affectively-charged motivations and affective response; the effects of affectively-charged 
motivations on same-day/same-week physical activity and the effects of affective responses on next-day/next-
week physical activity; the indirect effects of intervention engagement on same- and next-day/same- and next-
week physical activity via affective mechanisms (H4); and the total effects (mediated plus unmediated) of 
intervention engagement on physical activity.  
AIM 3: Explore cross-person and cross-situation moderating effects (Comparison study). We will add interaction 
terms for time-varying and time-invariant effect moderators (H5).109 
 
Dissemination of Findings 
Team members are actively engaged in professional activities and routinely make presentations to the national 
and international conferences. We will share data and results generated by this study in several ways, including 
meetings with weight management clinics, physical and occupational therapists, physical activity practitioners, 
conference presentations, and publications. The results obtained in this study will be made available to the 
scientific community through publication in peer-reviewed journals (e.g., Annals of Behavioral Medicine, Health 
Psychology, Journal of Physical Activity and Health, American Journal of Preventive Medicine), presentations at 
national and international scientific meetings, and seminar presentations in academic departments. Efforts will 
be made to share findings with physical activity and public health practitioners by presenting results at 
conferences of obesity, public health, and physical activity organizations (e.g., Obesity Society, American Public 
Health Association) and by distributing the information through the Los Angeles County Health Department, 
which has a long and close collaboration with the University of Southern California. 
 
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