How Exercise Lowers the Risk of Breast Cancer Development or Recurrence

The American Cancer Society reports that exercise has been shown to decrease the risk of breast cancer development and recurrence by reducing body fat and body mass index and helping regulate hormones.1

Exercise and Hormones

Regular, moderate exercise helps regulate hormone levels in the body by stabilizing menstrual cycles in premenopausal women, thereby preventing an excess of estrogen or progesterone, which has been linked to breast cancer development. If a patient has an estrogen or progesterone positive cancer, exercise is likely to benefit them more in the way of preventing recurrence. This is because their cancer has been shown to be influenced by estrogen and progesterone levels in the body and regulating these hormones will prevent any further effect on breast cancer.3 Exercise also enhances the function of the immune system and may encourage the body’s own ability to kill cancer cells and prevent tumor formation. Other benefits of a healthy immune system are fewer infections and rapid recovery if you do get sick.

In postmenopausal women, studies have shown that regular exercise or even a history of regular exercise can reduce the risk of developing breast cancer between 20-80%, depending on a variety of other factors.4 Even postmenopausal women who have never exercised before and begin exercising after menopause have been shown to have a lower risk of breast cancer development. These studies found that the likely explanation for this is the fact that in those who exercise, there are decreased levels of estradiol and sex hormone-binding globulin, which when elevated are linked to breast cancer development.5

Exercise During Chemotherapy

It is important to keep exercising during your chemotherapy treatment, as it will make you feel better overall and may offset some of the potential cardiovascular side-effects from certain chemotherapy drugs. Aerobic exercise increases your heart rate and respiratory rate, causing your heart to contract faster and harder to get oxygen-carrying blood to your organs. Putting strain on a muscle, just as you would any other muscle in your body, is how you strengthen it. Exercise will also help you control your weight. When you carry an excessive amount of weight around, your heart must work harder to allow you to function normally. This chronic strain can damage your heart and blood vessels. With the added stress of chemotherapy, the heart can be easily damaged.6

Exercise causes release of endorphins from the brain. Endorphins are a chemical that when released, cause you to feel pleasure and happiness. They can help with pain management, self-esteem and can minimize the feeling of depression. Exercising during chemotherapy will allow you to release endorphins into your system and potentially counteract depression and fatigue you may feel from treatment.

Exercise Type and Intensity

Most resources recommend that every person, regardless of age or gender, should exercise at a moderate intensity for at least twenty minutes a day, three to five times a week. Moderate exercise should increase your heart rate 60-80% above your resting heart rate to be effective. This may not be possible initially for some, but setting goals and striving toward them is a great place to start.


1 American Cancer Society. (2004). A Breast Cancer Journey: Your Personal Guidebook. Atlanta: American Cancer Society.

2 Bernstein, L., Henderson, B. E., Hanisch, R., et al. (1994). Physical Exercise and Reduced Risk of Breast Cancer in Young Women. Journal of the National Cancer Institute , 1403-1408.

3 Bernstein, L. (2009). Exercise And Cancer Prevention. Current Oncology Reports , 490-496.

4 Monninkhof, E. M., Elias, S. G., Vlems, F. A., et al. (2007). Physical Activity and Breast Cancer: A Systematic Review. Epidemiology , 137-157.

5 Friedenreich, C. M., Woolcott, C. G., McTiernan, A., et al. (2010). Alberta Physical Activity and Breast Cancer Prevention Trial: Sex Hormone Changes in a Year-Long Exercise Intervention Among Postmenopausal Women . Journal of Clinical Oncology , 1458-1466.

6 Scott, J. M., Khakoo, A., MacKey, J. R., et al. (2100). Modulation of Anthracycline-Induced Cardiotoxicity by Aerobic Exercise in Breast Cancer. Circulation , 642-650.

This article was originally published on July 27,2012 and last revision and update of it was 9/2/2015.