Research participant receives the Core Intervention + E-Coach + General Mindfulness Training

Research participant receives the Core Intervention + E-Coach + MVPA Specific Mindfulness Training + Buddy

Research participant receives the Core Intervention + E-Coach + MVPA Specific Mindfulness Training

Research participant receives the Core Intervention + General Mindfulness Training + Buddy

Research participant receives the Core Intervention + General Mindfulness Training

Research participant receives the Core Intervention + MVPA Specific Mindfulness Training + Buddy

Research participant receives the Core Intervention + MVPA Specific Mindfulness Training

Research participant receives the Core Intervention + General Mindfulness Training + MVPA Specific Mindfulness Training + Buddy

Research participant receives the Core Intervention + General Mindfulness Training + MVPA Specific Mindfulness Training

Research participant receives the Core Intervention + Buddy

Research participant receives the Core Intervention

Participants assigned to this condition will receive a weekly scheduled text message from their coach. Text messages will focus on building self-efficacy and self-regulation skills, setting realistic outcome expectations, overcoming barriers, and problem-solving and will directly support the participant's engagement in the intervention. The coach will provide a brief overview of the participant's recent progress and goals, ask if they are having any barriers and help them troubleshoot and set specific goals for the next week. Text message protocols will be informed by the investigators' previous experience using telephone coaching to promote MVPA in cancer survivors. In addition to the scheduled messaging, participants will also be instructed to reach out to their coach with any questions or for additional assistance.

Participants assigned to this condition will select a buddy of their choice (i.e. friend, co-worker, caregiver or family member) that is ≥ 18 years of age and willing to share their Fitbit data with the study team. The buddy will be mailed a Fitbit, share their Fitbit data with the study team, and be provided with access to, and instructions for, all of the study app modules the participant has access to for their assigned condition.

The study app include a buddy module where the buddy and participant can view each other's progress. The buddy will be expected to attend a 15-30 minute group orientation call and listen to four 10-15 minute podcast (one every 3 weeks) during the first 24 weeks of the intervention. Each webinar will provide social support training and peer discussion of challenges and successes in providing BCS with MVPA support.

Participants assigned to this condition will be instructed to watch 1 (1-2 mins), mindfulness education videos each week which lay the foundation for what mindfulness is and how it can be an important health behavior. Each week participants will also be asked to listen to general guided mindfulness audio files ≥5 days/ week. The length of recordings will gradually increase each week from 3-5 to 25-30 minutes. All videos and recording will be available via the study app.

Participants assigned to the MVPA-specific mindfulness training component will be instructed to watch 1-2 brief (1-2 minute), mindfulness education videos each week which lay the foundation for what mindfulness is and the importance of linking mindful awareness with MVPA. Each week participants will be provided access to MVPA-specific guided mindfulness audio files (e.g., 10-minute treadmill walking meditation, 20-minute bicycling meditation) that they will be asked to listen to during ≥3 MVPA sessions/week. The length and intensity of these audio files will correspond to their progression in the program. All videos and recordings will be accessed via the study app.

Symptom burden of fatigue will be measured at baseline, 24 and 48 weeks using the PROMIS Item Bank v1.0 - Fatigue - Short Form 8a.

Physical function will be measured at baseline, 24 and 48 weeks using the PROMIS Item Bank v. 1.0 - Physical Function - Short Form 20a.

Symptom burden of sleep disturbance will be measured at baseline, 24 and 48 weeks using the PROMIS Item Bank v1.0 - Sleep Disturbance - Short Form 8a.

Symptom burden of sleep disturbance will be measured at baseline, 24 and 48 weeks using the PROMIS Item Bank v. 1.0 - Sleep-Related Impairment - Short Form 8a.

Symptom burden on applied cognitive abilities will be measured at baseline, 24 and 48 weeks using the PROMIS v1.0-Applied Cognition-Abilities-Short Form 8a.

Symptom burden on emotional support will be measured at baseline, 24 and 48 weeks using the PROMIS Item Bank v2.0 - Emotional Support.

Symptom burden on self-esteem will be measured at baseline, 24 and 48 weeks using the Rosenberg Self-Esteem Scale.

This scale assesses global self-esteem and consists of 10-items asking participants to indicate their level of agreement/disagreement with each statement. Sample items include: "I feel that I'm a person of worth, at least on an equal basis with others;" and "I am able to things as well as most people." Participants respond on a 5-point Likert scale ranging from 1 (strongly agree) to 5 (strongly disagree). The minimum value one can score is 10, and the maximum is 50. Higher scores indicate a better outcome.

Social support for exercise will be measured at baseline, 24 and 48 weeks using the Social Support for Exercise Scale.

This scale assesses support for physical activity received from the following categories: family, friends, and other cancer survivors. Statements are scored on a Likert scale of 1 (never) to 5 (very often) for each of the three categories, with higher scores representing better outcome. The minimum value one can score for each category is 10, and the maximum is 50. The minimum value of the total measure is 30, and the maximum is 150. An additional "does not apply" response option is provided on the measure.

Physical Self-Perception will be measured at baseline, 24 and 48 weeks using the Physical Self-Perception Profile-Physical Self-worth Subscale.

This instrument used to assess self-esteem relative to several domains of physical functioning in a hierarchical, multidimensional fashion. The instrument contains a general physical self-worth scale (PSW) which subsumes four more specific scales of perceived sport competence (SPORT), physical condition (COND), attractive body (BODY), and strength (STRENGTH), with six items per scale. Participants indicated on a four-point scale the degree to which each item is characteristic or true of them. Responses range from 1 (not at all true) to 4 (completely true), with higher scores representing better outcome. The minimum value one can score is 6, and the maximum is 24.

Enjoyment of Physical Activity will be measured at baseline, 24 and 48 weeks using the Physical Activity Enjoyment Scale.

This 18-item scale assesses enjoyment for physical activity by asking participants to rate "how you feel at the moment about the physical activity you have been doing" using a 7 point bipolar Likert scale, from 1 (I enjoy it) to 7 (I hate it). Eleven items are negatively worded and seven items are positively worded. After reverse scoring the 11 negatively worded items, an overall enjoyment for physical activity score is determined by summing the items, with a value range of 18-126 being possible. Higher scores indicate higher enjoyment, better outcome.

Leisure time physical activity will be measured at baseline, 24 and 48 weeks using the Godin Leisure Time Exercise Questionnaire Physical Activity.

This is a measure of self-reported physical activity participation. Participants report "times per week" they participate in strenuous (e.g., jogging), moderate (e.g., fast walking), and mild (e.g., easy walking) exercise over the past 7 days and the "average duration each time you exercised (in minutes)" for each of the three activity categories. Weekly minutes of total, light, moderate, and vigorous activity are calculated by multiplying the frequency and time of each activity. This value is divided by 7 to obtain daily averages. The minimum value one can score is 0, and the maximum depends on the number of self-reported minutes of physical activity. Higher scores indicate better outcome.

Confidence in ability to be regularly active will be measured at baseline, 24 and 48 weeks using the Exercise Self-Efficacy (EXSE).

This short form assesses the participants' beliefs in their ability to be regularly active "for the next 12 weeks" on a scale from 0% (not at all confident) to 100% (completely confident), with higher scores representing better outcome.

Confidence in ability to be regularly active despite common barriers will be measured at baseline, 24 and 48 weeks using the Barries Self-Efficacy (BARSE).

This scale assesses the beliefs in ability to be regularly active despite common barriers "for the next 12 weeks" on a scale from 0% (not at all confident) to 100% (completely confident), with higher scores representing better outcome.

Exercise goal setting in breast cancer survivors will be measured at baseline, 24 and 48 weeks using the Exercise Goal Setting Scale.

This scale assesses exercise goal setting behaviors on a scale from 1 (does not describe) to 5 (describes completely), with higher scores representing better outcome.

Sitting time in breast cancer survivors will be assessed at baseline, 24 and 48 weeks using the Sitting Time Questionnaire.

This questionnaire assesses the amount of hours and minutes spent sitting during weekdays and weekends, with lower scores representing better outcome.

Outcome expectations for exercise in breast cancer survivors will be assessed at baseline, 24 and 48 weeks using the Outcome Expectations for Exercise_MOEES.

This scale assesses the beliefs and expectations about the benefits of regular exercise and physical activity on a scale from 1 (strongly disagree) to 5 (strongly agree), with higher scores representing better outcome.

Mindful awareness of distressing thoughts and images will be measured at baseline, 24 and 48 weeks using the Southampton Mindfulness Questionnaire (SMQ).

This 16-item scale measures mindful awareness during distressing thoughts and images. Using a 7-point Likert scale (0=strongly disagree to 6=strongly agree), items reflect the following subscales: mindful observation (4 items), letting go (4 items), non- aversion (4 items), and non-judgment (4 items). The minimum value one can score on any of the subscales is 0, and the maximum is 24. The minimum value of the total measure is 0, and the maximum is 96. The higher scores represent better outcome.

Mindful self-compassion will be measured at baseline, 24 and 48 weeks using the Self-Compassion Short Form.

This short form is a 12-item scale measuring items related to self-kindness, self-judgment, and common humanity. Statements on the Self-Compassion Scale are scored on a Likert scale of 1 (almost never) to 5(almost always). To calculate an overall compassion score - Items representing uncompassionate responses to inadequacy or suffering (the self-judgment, isolation, and over-identification subscales) are reverse-coded only when calculating the overall compassion score. In this way, higher scores represent a lower frequency of these responses.

Post-traumatic growth will be measured at baseline, 24 and 48 weeks using the Post-traumatic Growth Inventory.

This 21-item self-report scale assesses growth or benefits after a specific traumatic life event. The Post Traumatic Growth Inventory (PTGI) is scored by adding all the responses, with higher scores representing better outcome.

This indicator of implementation feasibility for the interventions delivered is defined by the overall enrollment rate being >/= 70% (e.g., total number of individuals enrolled/total number approached). Enrollment rate will be tracked continuously during the 48 week study.

This indicator of implementation feasibility for the interventions delivered is defined by the retention rate being >/= 70% (e.g., total number of participants who drop out/ total number randomized). Retention rate will be tracked continuously during the 48 weeks of the study and significant differences between the study interventions in the number of participant withdrawals will be tracked.

Adherence to the study app + Fitbit will be monitored and usage tracked continuously during the 48 week study.

Objective data include Fitbit wear time, number of times app is opened each week, time spent in app each time it is opened, and for participants who receive each component, usage of general and moderate to vigorous intensity physical activity specific mindfulness videos (i.e. whether clicked, how many times and for how long), number of e-coaching exchanges, number of buddy training webinars attended, and number of buddy interactions in the app.

Acceptability will be measured using a brief, Likert-type survey assessing participant enjoyment, satisfaction, perceived benefit, and ease of use. Acceptability is defined as >/= 70% of survey responses in affirmation of this.

Change in body mass index in breast cancer survivors will be assessed at baseline, 24 and 48 weeks using the Health History Questionnaire, a local questionnaire developed by the study researchers.

Participants will report on the following: height and most recent weight. BMI will be calculated. Significant change will be indicated by p<.05 on reported health behaviors between baseline and follow up time points between study interventions.

Change in health behaviors in breast cancer survivors will be assessed at baseline, 24 and 48 weeks using the Health History Questionnaire, a local questionnaire developed by the study researchers.

Participants will report on the following: weekly leisure-time physical activities; weekly consumption of fruits, vegetables, fast food/snacks, caffeine, carbonated beverages; cigarette and alcohol use. Unhealthy behaviors will be reverse scored. Higher scores represent better outcome. Significant change will be indicated by p<.05 on reported health behaviors between baseline and follow up time points between study interventions.