Physical activity is known not only to improve your overall health, but it also reduces your risk of breast cancer. While taking part in physical activity throughout your life is the best way to reduce risk, starting now will still positively impact your cancer risk, especially if you’re post-menopausal.

Exercise is linked to a reduced risk of breast cancer in two major ways: it reduces your bodyweight, and it lowers blood estrogen levels, which are important contributors to cancer risk. It is also postulated that exercise boosts the immune system, slowing or killing developing cancer cells and making your body more resilient.

Being active even after you receive your breast cancer diagnosis has been proven to lower your risk of mortality.

How to Increase Your Physical Activity

Taking part in a varied exercise program including strength training, mobility, and cardiovascular exercise is the most beneficial. For post-menopausal women, strength training also plays a critical role in ensuring longevity. After menopause, women generally tend to lose both muscle mass and bone density, making them more prone to injury, so strength training is a great way to slow or stop the loss of both muscle and bone.

The recommended amount of exercise recommended by the American Cancer Society is at least 2.5 hours of moderate activity like walking, doing yoga, or cleaning and at least 1.5 hours of vigorous activity, like jogging or swimming, per week.

But just increasing your overall activity can be effective as well. Add little bits of movement into your day, like taking the stairs, going on an extra long walk with a friend or pet, stretch during commercial breaks, setting step goals, using an under-desk bike pedal setup, etc. Just increasing your daily movement by even 20% can make a difference.

How Exercising Helps During Treatment

While the efficacy of working out during breast cancer treatment has always been supported, it was finally reinforced a few years ago when the American Society for Clinical Oncology released their evidence-based guidelines for exercise while undergoing treatment. To summarize, they recommend taking part in aerobic activity and strength training during treatment, and especially before surgery, for the best health outcomes. Here’s why:

1. Improved Lymphatic Drainage

Lymphedema is a common side effect experienced during breast cancer treatment or after lymph node removal. Historically, women were cautioned to stay away from heavy lifting or intense physical activity for fear of worsening swelling. New research suggests that this isn’t the case.

In a study of 100 women with breast cancer, the women underwent a 3 month period of supervised strength training designed for muscle gain. Researchers found that increasing muscle mass decreases the amount of extracellular fluid in the body compared to un-trained counterparts. Muscle contractions act as a natural “pump”that helps propel lymphatic fluid out of the extremities and back toward central circulation. As muscle mass increases, so does the body’s ability to move lymphatic fluid effectively.

This finding shows that building and maintaining muscle mass is one of the most effective ways to ameliorate treatment-induced lymphedema.

2. Reduces the Risk of Metastasis

One of the biggest dangers of cancer is metastasis, whereby cancer cells detach from the tumor site and travel around the body, allowing cancer to spread. Research shows that regular, moderate exercise can make the body more resistant to this process.

During treatment and recovery, movement helps normalize blood vessels and improve circulation. Healthier, more stable blood vessels are less “leaky” which makes it difficult for cancer cells to escape into the blood stream or lymphatic system. Since the integrity of the lining of blood vessels is improved, adhesion molecules are not expressed as strongly. This makes it more difficult for those tumor cells to find areas to stick to and invade.

These factors, combined with the fact that increased blood flow and vessel pressure (caused by exercise) can help destroy circulating tumor cells before they have the chance to attach to other tissues, poses exercise as a protective factor against metastasis.

3. Regulates Insulin Signalling

Insulin resistance typically occurs in people with a larger body size, and the result is the release of pro-growth signalling molecules, which tumor cells can exploit. These pathways ultimately support tumor cell survival, invasion, and progression. This is coupled with other side effects of insulin resistance, like chronic inflammation, dysfunctional cellular energy production, and negative shifts in gut microbiome diversity.

Exercise improves insulin sensitivity in skeletal muscle, essentially muting those growth signals that tumors like to exploit. This increases the amount of circulating glucose that muscles can absorb, improving the body’s control of blood sugar, even if you don’t lose any weight from your new exercise routine.

In a 16-week study of breast cancer patients, the combination of strength and aerobic training consistently improved insulin resistance markers. This shows a plausible pathway for reducing tumor-supportive signalling.

4. Increased Angiogenesis

Angiogenesis is the process of creating new blood vessels. Exercise causes angiogenesis, so that your blood can better reach your working muscle. These new blood vessels deliver more oxygen, blood, and nutrients to your bodily tissues, and they have better tissue architecture, making them less “leaky.” Tumors tend to thrive in an environment low in oxygen, which makes them harder to target with radiotherapy.

When tumors are provided with more blood flow, that means not only that tumors are receiving more oxygen, but it also means that any chemotherapy drugs patients are on can more effectively reach the tumor site. In a study of women with breast cancer taking part in aerobic exercise, 12 weeks of training resulted in significant improvements in tumor vascularization without worsening any cancer-related aggressive markers.

5. Reduced Inflammation

One of the most consistent biological threads across cancer development is chronic inflammation. Elevated levels of inflammatory markers are seen across all types of cancers and are closely linked to cancer development, progression, and recurrence. These markers are associated with fatigue, insulin resistance, higher mortality risk, and they make the body more resistant to treatment.

Physical activity, specifically strength training reduces the presence of those inflammatory markers in favor of anti-inflammatory molecules. During and after muscle contractions, muscle fibers release myokines, which suppressed inflammatory markers and helps recalibrate the immune system away from chronic, tumor-promoting inflammation toward balanced immune surveillance.

In studies or women undergoing breast cancer treatment, a combined aerobic and strength training program reduced inflammatory markers, even without weight loss.

6. A Stronger Body = A Stronger Immune System

Your immune system is your defence against cancer. Regular, moderate exercise improves how immune cells are produced, circulate, and function. The key here is not working out at high intensity, because that can actually stress your immune system.

Every time you exercise, your heart pumps faster and your muscles contract rhythmically, helping immune cells move through the bloodstream and lymphatic system more efficiently. This mobilizes your natural killer cells, T cells, and macrophages, which are the main cells that your immune system uses to kill cancer cells. Even one bout of exercise can temporarily increase the number of natural killer cells in circulation.

Over time, this leads to better immune readiness, increased regeneration of immune cells in the bone marrow, increased filtration of the blood and lymph, and more balanced regulation of stress hormones like cortisol. Together, this creates a stronger and more adaptive immune system that is more equipped to keep cancer in remission and protect your health.

Improving Recovery From Surgery

Surgery is a big step in cancer care and the way you prepare for it can make a huge difference in your recovery, complication risk, and timing of next treatments. Supervised exercise acts as a “pre-hab,” allowing your body to recover more quickly after surgery. Here’s how:

• Stronger heart-lung capacity, which makes going under anesthesia safer, meaning fewer complications during surgery and shorter hospital stays for recovery.

• More muscle mass will allow you to get out of bed sooner, walk farther, and regain independence faster, all factors that prevent deconditioning and blood clots after surgery.

• Improved blood flow will allow surgical wounds to heal more quickly since they are receiving more oxygen. This also reduces the chance of infection.

• Surgery is usually followed by radiation, chemotherapy, or endocrine therapy to eradicate all remnants of cancer. Having fewer complications after surgery means that you can start your other therapies sooner, making it more likely that you achieve remission.

• Movement soon after surgery helps reduce postoperative fatigue, constipation, and sleep disruption, all factors that can slow the healing process.

Exercise after surgery is a great way to regain your strength and improve your health, but it must be approached with care. Everyone’s recovery timeline is different, so you should work with your surgeon and rehabilitation team to plan your exercise regime. Here are some general guidelines to keep in mind for activity after surgery:

1. Start slow, and listen to your body by honoring mobility restrictions and reduced energy levels.

2. Protect your incision and surgical area. You should not incorporate any movements that strain the healing site until cleared by your care team. Keep the area clean, dry, and be sure to monitor for any changes like redness, drainage, or swelling. Working on your posture and some gentle shoulder and chest mobility work will help prevent tightness in the healing tissue.

3. Notify your team right away if you’re experiencing lasting swelling in the arm or chest.

4. Don’t push through pain and fatigue.

5. Stay connected to your rehabilitation team to ensure your exercises are safe and you are recovering normally.

Movement as Medicine for Remission that Lasts

For all of the reasons listed above, movement is a long term investment in your remission, resilience, and quality of life. The same mechanisms that help you heal faster also play a role in keeping cancer from returning.

Research consistently shows that women who maintain regular physical activity after breast cancer treatment have lower risk of recurrence and longer overall survival compared to those who are inactive. Exercise helps regulate the hormones and metabolic pathways linked to tumor growth, keeps body fat and insulin levels in check, and strengthens immune surveillance, the body’s natural ability to detect and eliminate abnormal cells before they can take hold. The key is consistency.

At Reunion Rehabilitation Hospital, our therapists understand that recovery doesn’t end when treatment does. Through guided, individualized exercise programs, we help survivors restore their strength, prevent complications like lymphedema, and build habits that support lifelong wellness.