2. To compare the chronic effect of performing exercise (within 24 hours before every infusion) compared to no exercise (no exercise for 72 hours prior to every infusion) on markers of cardiotoxicity 7 to 14 days after the final anthracycline infusion 5) Research Method This study will be a two-arm randomized control trial. Twenty-four women aged 18 or older newly diagnosed with stage I-IIIA breast cancer, and scheduled to receive neoadjuvant or adjuvant doxorubicin chemotherapy in cycles of 2-3 weeks will be recruited by oncologist referral and posters. Participants will be randomized to one of two conditions: i) an acute bout of exercise performed ≤24 hours prior to each cycle of anthracyclines and no exercise for 24-48 hours post; or ii) no exercise for 72 hours prior or 24-48 hours post each cycle of anthracyclines.