The purpose of this study is to demonstrate the feasibility of assigning breast cancer survivors currently receiving chemotherapy to exercise at a specific time of day, e.g., morning or afternoon/evening, for a 4-week exercise intervention. Information gathered from this study will help inform a future, larger trial.

Study Aims:

1. Assess the feasibility of engaging in exercise at an assigned time-of-day (e.g., morning or afternoon/evening) in breast cancer survivors on chemotherapy. Hypothesis: Assigning windows of time within the day to complete exercise (e.g. 5-10am exercise start time vs. 3-8pm exercise start time) will be feasible among this patient population.

1a. Determine the acceptability engaging in exercise at an assigned time-of-day (e.g., morning or afternoon/evening) in breast cancer survivors on chemotherapy. Hypothesis: Engaging in exercise at an assigned time-of-day will be acceptable in this patient population.

2. To generate evidence on the magnitude of the effect sizes and outcome variability of physical function and human performance variables. Tests to be conducted at baseline and end of study to measure physical function and human performance variables include: Timed up and go test, 30-second chair stand, handgrip strength, cardiorespiratory fitness.

Participants will be randomized 1:1 to an exercise timing group (AM or PM), of which they will be required to complete their exercise during a specific time of day. Participants randomized to the AM group will be required to start their exercise between 5am and 10am for the duration of the 4-week intervention. Participants randomized to the PM group will be required to start their exercise between 3pm and 8pm.

At baseline and end of study assessments, participants will complete the following physical tests to evaluate physical function, strength, and cardiorespiratory fitness: timed up and go test, 30-second chair stand test, handgrip strength test, cardiorespiratory fitness test. These tests and assessments will be carried out with the Huntsman Cancer Institute (HCI) Wellness Center's Personal Optimism With Exercise Recovery (POWER) program. These tests will occur at the HCI Wellness Center gym. At the end of study assessments participants will also be asked to complete an exit survey, and two short questionnaires related to sleeping and eating habits.

Participants will complete two personalized resistance exercise training sessions supervised by a Cancer Exercise Specialist via the telehealth platform in the electronic medical record. These resistance training sessions are part of the POWER program. Participants will also be required to engage in weekly, moderate-intensity aerobic exercise, with the goal of completing 90 minutes of aerobic exercise per week. The type of aerobic exercise engaged in (e.g., walking, biking, hiking, etc), and location to complete the aerobic exercise (e.g., at home, local park, local gym, HCI Wellness Center gym, etc.) is the participant's choice. Participant's will be required to submit weekly aerobic exercise training logs.

Inclusion Criteria:

• Stage I-III Breast Cancer patients with plans to start chemotherapy or just started chemotherapy. Just started chemotherapy is defined as already receiving one cycle of chemotherapy.
• ECOG 0, 1, 2

Exclusion Criteria:

• Stage IV Breast cancer patients
• ECOG >/= 3
• Stage I-III Breast Cancer patients who do not have plans to start chemotherapy or who have received more than one cycle of breast cancer chemotherapy.

There is no plan to make IPD available