Inclusion Criteria:

          1. Age ≥ 18 years

          2. Diagnosis of DCIS or stage I, II, or III breast cancer 3 Planned to initiate an AI

               1. Post- menopausal defined as ≥ 60 years of age, prior bilateral oophorectomy, or
                  age over 50 and absence of any menstrual periods in the last 12 months, or FSH
                  and estradiol in the menopausal range

               2. Premenopausal patients receiving chemical ovarian suppression are allowed

               3. Prior aromatase inhibitor use (if this is a second primary, for example) is
                  allowed as long as it has been more than 12 months

               4. Prior tamoxifen is allowed if switching to an aromatase inhibitor, as long as it
                  has been 28 days between last tamoxifen dose and the baseline procedures (per the
                  half-life of tamoxifen)

        4. Completion of all primary therapy for breast cancer, including surgery, radiation, and
        chemotherapy. Patients must be ≥ 21 days from chemotherapy completion and ≥14 days from
        radiation completion. Ongoing HER2 targeted therapy with trastuzumab or pertuzumab, or TDM1
        is allowed. Neratinib, immunotherapy, or CDK4/6 inhibitor therapy is not allowed.

        5. Baseline T score > - 2.5 on DXA 6. Body weight less than 275 lbs., as dictated by the
        weight limit for the LIV platforms 7. ECOG performance status of 0-2 at the time of study
        enrollment 8. Informed consent and authorization of the release of health information must
        be obtained according to institutional guidelines 9. Physically able to stand unassisted
        for 10 minutes at a time 10. Currently not participating in regular exercise (defined as
        less than 90 minutes of moderate to vigorous exercise per week measured by the RPAQ
        questionnaire)

        Exclusion Criteria:

          1. Unwilling to co-enroll onto the companion FIT core study (IRB study #1707550885)

          2. Diagnosis of other disorder affecting bone function or turnover, such as Paget's
             disease, renal osteodystrophy, parathyroid disorders, vitamin D
             deficiency/osteomalacia, chronic renal disease (Cr > 1.4)

             a. Vitamin D will be checked during screening. Patients with Vit D < 20 can be
             enrolled if supplementation is initiated per the treating physician.

          3. Prior history of non-traumatic, fragility bone fracture

          4. Any muscle or neuromuscular disorder affecting muscle function, such as muscular
             dystrophy, myositis, or amyotrophic lateral sclerosis

          5. Use of bisphosphonates or denosumab within the prior 12 months

          6. History of retinal detachment

          7. Current or planned pacemaker

          8. Current or planned cochlear implant

          9. Any condition precluding power protocol participation (i.e. riding a stationary
             bicycle), including: NYHA class III or IV congestive heart failure, uncontrolled
             angina, myocardial infarction in the prior 12 months, orthopedic surgery in the
             previous 6 months or plans for orthopedic surgery during the study period, chronic
             uncontrolled pulmonary conditions such as uncontrolled asthma (symptoms > 2 days/week)
             or dyspnea requiring oxygen, symptomatic peripheral vascular disease, or any other
             comorbidity that would interfere with the ability to complete and comply with the
             protocol in the opinion of the investigator

         10. Metastatic breast cancer

             a. History of prior treated malignancies, other than breast cancer, that are now
             stable, are in remission, and do not require active therapy, are acceptable.

         11. Patients requiring chronic anticoagulation are excluded from participation in the
             optional muscle biopsy collection.