Study subjects:
* Patients aged 20 or older who were first diagnosed with breast cancer
* Patients scheduled to undergo neoadjuvant chemotherapy before surgery Study design: Prospective randomized controlled comparative clinical study
* Intervention is performed for at least 3 months during the neoadjuvant chemotherapy period before surgery.
* Treatment group: Individually tailored exercise consisting of aerobic, strength, and flexibility exercises is prescribed, self-exercise compliance monitoring through an application, and diet management education through nutritional counseling.
* Control group: One session of flexibility exercise training, diet management education through nutritional counseling
Result variable:
* Primary outcome variable:
1\) Incidence and severity of postoperative lymphedema: bilateral upper limb volume, ICG lymphography
* Secondary outcome variables:
1. Clinical information: Demographic, disease and treatment-related data
2. Physical-related: height/weight/waist circumference measurement, body composition test, physical examination (axillary membrane evaluation)
3. Upper extremity function (shortening of the pectoralis major muscle, adhesive capsulitis): evaluation of shoulder range of motion, upper extremity muscle strength/grip strength
4. Quality of life assessment: European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30(EORTC QLQ-C30), European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Breast cancer module 23(EORTC QLQ-BR23)
Assessment Schedule:
* Initial treatment and evaluation: Immediately after breast cancer diagnosis
* Follow-up evaluation: Immediately after completion of exercise intervention (preoperatively), and at 1, 3, and 6 months postoperatively.
Number of study subjects:
* This study will be conducted as a preliminary study for future research, and will be conducted on a total of 60 patients (30 in the experimental group and 30 in the control group) with an allocation ratio between groups of 1:1.
