Our bodies are beautiful well-tuned machines that house elegant and intricately interconnected systems. We are so much more than our numbers (age, height, weigh, heart rate, blood pressure, fasting glucose). We are made of trillions of tiny cells that come together to create a beautiful creature (YOU!). Your cells respond to what you think, how you feel, what you eat, what you surround yourself with, and how you move your body. 

Exercise is any physical activity that exerts the body through movement. A recent panel of experts of the American Society of Clinical Oncology (ASCO) reviewed clinical trials examining exercise during and after active cancer treatment and published their findings and recommendations. Historically, cancer patients were taught to rest and take it easy during treatment, but now oncologists recommend patients use exercise, if possible. The panel found that exercise improves symptoms and side effects during chemotherapy and radiation. Exercise helps patients recover from surgery faster with fewer complications and decreases fatigue, anxiety, and depression and improves quality of life. Other benefits of exercise include improved sleep, improved brain function, and a healthy weight. 

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The American Cancer Society recommends cancer patients exercise at least 150 minutes a week at moderate intensity (able to talk during the activity but not sing) or 75 to 100 minutes of vigorous exercise and including cardiovascular and resistance training. However, if you are younger/premenopausal, healthy weight and fitter, already into exercise, you may benefit from a higher dose (50-60 minutes a day). Cardiovascular activities can include walking, hiking, running, biking, tennis, dancing, or swimming and resistance training can include weight lifting or resistance bands. Try to take the time to stretch (at least 2 times per week), warm up, and cool down before and after workouts to prevent injury. Balancing exercises are also important to combat weakness, neuropathy and prevent falls. The most important thing is to enjoy what you’re doing! 

How does exercise fight cancer?

Exercises decreases the expression of cancer causing oncogenes, circulating sex hormones, inflammation, and insulin resistance. It can also increase antioxidant defenses and strengthens the immune system to attack cancer and prevent infection. Exercise also alters gut flow, motility, and digestive transit time which affects the gut microbiome. 

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When muscle cells contract, they release proteins or small chemicals called myokines which communicate between organs and mediate the effects exercise. One important myokine is interleukin-6 (IL-6). In a mouse model of melanoma, exercise decreased tumor size and growth via IL-6 and epinephrine mobilization of natural killer lymphocytes which migrated into tumors and destroyed tumor cells by apoptosis (cell death). Other myokines (oncostatin M, iris, and SPARC) may also play an important role in cancer cell death.

Alternatively, fat or adipose tissue are more than just excess calorie storage units. Fat cells release their own molecules call adipokines which negatively affect body metabolism and promote inflammation and obesity. Adipose cells also have the enzyme aromatase which converts the adrenal androgens into estrogen. The more fat tissue, the higher the aromatase level and circulating estrogen. Women with an estrogen positive tumor profile take aromatase inhibitor medications to block aromatase in fat, and this may be one way in which obesity increases risk of breast cancer and results in poorer outcomes. 

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Maintaining muscle mass during chemotherapy prevents chemotherapy toxicities, improves survival and prevents fatigue. Excess fat and low muscle mass in colorectal patients is associated with a 40% higher risk of mortality compared to those without excess excess and sufficient muscle mass.  Chemotherapy can cause malnutrition, loss of muscle mass and function (also known as cachexia). This can then cause weakness and delay or discontinuation of treatments or contribute to death.

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What is aerobic exercise and why is it important?

Aerobic exercise is cardiovascular training which increases your heart rate, breathing rate and blood flow in order to supply oxygen to working tissues. Cardio fitness is important for heart health because chemotherapy medicines (especially anthracyclines doxorubicin/ Adriamycin and HER2 blocker trastuzumab) can cause cardiotoxicity. Exercise before, during and after anthracycline treatment reduces the risk of developing cardiotoxicity. In one clinical intervention, breast cancer patients exercised on a treadmill for 30 minutes, 24 hours before the anthracycline infusion, and they had significantly lower blood levels of NT-pro-BNP, a marker of cardiotoxic effects than those that did not exercise. In mouse models of Ewings Sarcoma (a pediatric bone cancer) and pancreatic cancer, exercise increases the tumor blood vessel architecture which improves the ability of chemotherapy medicine delivery and penetration. This can translate into improved chemotherapy efficacy.

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What are the mood and mental benefits of exercise? 

When you exercise, blood flow increases to the brain and feel good chemicals are released. They’re called endorphins! Exercise positively impact stress, anxiety and depression, learning and memory. These brain boosting effects are from Brain-derived Neurotrophic Factor (BDNF). Exercise has been shown to decrease the rate of cognitive decline in healthy people and in those with neurodegenerative disorders. One study has found that physical activity before, during and after chemotherapy was associated with better cognitive function immediately and 6 months after chemotherapy completion. In other words, exercise may prevent the side effect of “chemo brain" so start exercising as soon as you get your diagnosis. There is also huge, empowering psychological benefit to being able to use movement as medicine to fight your cancer.

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How does exercise improve the immune system and lymphatics? 

Our immune system is made of immune cells, spleen, and lymphatic fluid. Exercise boosts the immune system (our crucial cancer, infectious disease and toxin fighting system) by increasing the heart rate and moving the muscles which pump lymph fluid. So exercise releases immune cells and moves the immune cells around through the body which helps with surveillance. Lymph nodes are removed and lymphatic vessels can be disrupted during breast cancer surgery and radiation. When the lymphatic system is disrupted, it can lead to tissue and limb swelling called lymphedema. Being overweight can increase the lymphedema risk, but exercise prevents and improves lymphedema (see below for specifics on the PAL protocol).

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What can exercise do for bone health? 

Cancer treatments often place breast cancer survivors into premature menopause because of tumor estrogen mutations and/or the effects of chemotherapy and this places survivors at a higher risk of osteoporosis. Weight-bearing exercises like lifting weights, running, walking, hiking, and tennis build bone density to prevent osteoporosis. Guidelines recommend resistance training twice a week and doing daily weight bearing exercise (like walking). While swimming can help with stretching, cardiovascular health, muscle building against some resistance and the hydrostatic pressure improves lymphedema, you are not working against gravity so it is not as good at building bone as running. Myokines released during exercise positively regulate bone formation by stimulating osteoblasts (cells that build bone) and inhibiting osteoclasts (cells that degrade bone). 

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How does movement effect cancer recurrence and survival? 

Physically active cancer survivors have lower rates of cancer recurrence and improved survival compared to inactive survivors. Exercise after diagnosis has been shown to have a 24% lower risk of breast cancer recurrence and 34% lower risk of breast cancer death. In another retrospective study, in which breast cancer patients were given questionnaires about their exercise habits before, during and after cancer treatment, breast cancer survivors who were more active before diagnosis and at a 2-year follow up had a 55% reduced chance of recurrence and 68% reduction in overall mortality. Take heart, those that did not exercise before cancer diagnosis but did after diagnosis, still had a 46% reduction in recurrence and 43% reduction in overall mortality. Highly active patients (those exceeding the minimum exercise guidelines of 150 minutes per week) had the greatest risk reduction of mortality (69%). 

It is not just one work out a day that impacts your recurrence and mortality rate, but the general activity level of your day. Researchers found the longer time spent in sedentary (seated, nonmoving) behavior was associated with increased risk of cancer death. Furthermore, replacing 30 minutes of sedentary (sitting) time with light intensity physical activity was associated with an 8% lower risk of cancer death and by replacing it with moderate to vigorous physical activity, mortality decreases by 31%.  

How to know if you are exercising too hard?

Yes, there is such a thing as too much exercise! If the body is unable to recover, it may have trouble building muscle, gaining weight appropriately, and might have increased infections. The immune response can decrease after prolonged moderate to vigorous physical activity (over 90 minutes). 

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What about diet and exercise lifestyle changes? 

When you combine a healthy, plant based diet with exercise, the cancer fighting effects are amplified. Blood from sedentary (non-exercisers) eating a normal diet, strenuous exercisers on a normal diet, and moderate exercisers eating a plant based diet was used in prostate cell culture. The strenuous exercisers had better cancer cell death (apoptosis) than the sedentary normal diet group but the moderate exercising plant based diet group had greatest cancer cell death overall. So don’t use exercise as an excuse to eat whatever you want. A healthy diet coupled with regular exercise will work the best to prevent cancer growth. Another lifestyle intervention study showed that after only 14 days of women with breast cancer eating a low-fat, high-fiber diet and daily moderate exercise, the women’s serum insulin and insulin-like growth factor decreased. When their blood was applied to cancer cells in cell culture, the cell growth decreased and cancer cell death (apoptosis) increased compared to before lifestyle intervention. Visualize moderate exercise and a healthy diet killing those cancer cells. Now go get moving! You can do it!

* As always, remember that you must speak with your medical team before starting any exercise regimen. Every body is different, especially in the setting of cancer treatment.