Participants assigned to Affect-Rx will receive instructions to "select a pace of exercise that makes you feel as good as possible." The exercise intensity prescription section of their exercise plan will include the Feeling Scale as an attachment and participants will be given the instruction to "stay in the green zone" on the Feeling Scale.

Participants assigned to RPE-Rx will receive instructions to "select a pace that would make it challenging for you to carry on more than a short conversation." The exercise intensity prescription section of their exercise plan will include the Rating of Perceived Exertion (RPE) scale as an attachment and participants will be given the instruction to "stay in the green zone" on the RPE Scale.

Number of participants who complete the 2-week follow-up assessment out of the number of participants who enroll in the study.

Number of participants who complete the 6-week follow-up assessment out of the number of participants who enroll in the study.

Number of participants who complete the 12-week follow-up assessment out of the number of participants who enroll in the study.

A 4-item self-report questionnaire used to measure acceptability of the affect-regulated exercise prescription using a Likert scale ranging from 0 (not at all) to 4 (very much). Total scores range from 0 - 16. Higher scores indicate greater acceptability.

A 6-item self-report measure of exercise performed over the last month and week. Two items range from 1 (never) to 7 (often) and four items range from 0 (0 days per week) to 7 (7 days per week). Total scores range from 2-21. Higher scores reflect higher levels of voluntary exercise behavior.

A single item self-report measure that present six statements describing various levels of monthly physical activity. Response options range from 1 (I did not do much physical activity) to 6 (I did vigorous activities almost daily). Total scores range from 1-6. Higher scores reflect more vigorous, more frequent physical activities completed in the past month.

A 7-item self-report measure calculating the amount of health-related vigorous and moderate-intensity physical activity as well as sitting time performed by adult participants over a one-week period. The number of minutes per day participants report for 3 categories vigorous, moderate, and walking activities are multiplied by the average metabolic equivalent (METs) for each category (8.0 METs, 4.9 METs, and 3.3 METs, respectively). Scores for each category are summed to calculate a physical activity score for the past week quantified as total MET values. Higher METS demonstrate a higher total volume of physical activity completed in the prior week. MET values between 0-599 are considered "low active," MET values between 600-1499 are considered "moderately active," and MET values 1500 or higher are considered "High active." This measure also assesses participants' total sitting time in the past week. Total number of minutes reported for sitting time is not part of the physical activity

A 10-item self-report measure with response options ranging from 1 (poor/never/not at all) to 5 (excellent/completely/always) for items 1-9 and 0 (no pain) to 10 (worst pain imaginable) for the item 10. Total scores range from 9 - 45. Higher scores represent better health-related quality of life.

An 8-item self-report measure with response options ranging from 1 (unable to do) to 5 (without any difficulty) and the degree to which health limits specific activities on a scale from 1 (cannot do) to 5 (not at all). Total scores range from 8 - 40. Higher scores reflect better physical function.

An 8-item self-report measure with response options ranging from 1 (never) to 5 (always). Total scores range from 8 - 40. Higher scores reflect higher levels of anxiety.

An 8-item self-report measure with response options ranging from 1 (never) to 5 (always). Total scores range from 8 - 40. Higher scores reflect higher levels of depressive symptoms.

An 8-item self-report measure with response options indicating the level of sleep disturbance a participant may experience. The first question asks about sleep quality and ranges from 1 (very good) to 5 (very poor). Questions 2-8 further inquire about the specifics of the sleep experience, ranging from 1 (not at all) to 5 (very much). Total scores range from 8 - 40. Higher scores reflect a greater degree of sleep disturbance or poorer quality of sleep.

A 5-item self-report measure of intentions to exercise in the next week. Response options range from 1 (not at all likely) to 7 (very likely). Responses are summed and then averaged; total scores range from 1-7. Higher scores represent stronger intentions to exercise in the next week.

A 4-item self-report measure with response options ranging from 1 (Strongly disagree) to 5 (Strongly agree). Total scores range from 4 - 20. Higher scores reflect higher levels of pleasure when performing physical activity.