Your Muscles Are Fighting Cancer And You Don't Even Know It

Muscle does more than move you around and hold your skeleton up.

Researchers now describe healthy skeletal muscle as functioning almost like an organ itself — one that actively works against tumor growth.

Exercise has long been recommended to help lower the risk of developing cancer. Now, there’s evidence it may also help reduce the risk of recurrence and improve survival after a diagnosis.

Muscle tissue releases tiny particles called extracellular vesicles which carry a molecule that helps restrain tumor growth. As we age and lose muscle mass we produce fewer of these particles, and the ones we do produce carry less of that protective molecule.

Aging muscle, in other words, gradually loses some of its built-in cancer-fighting ability.

Exercise appears to reverse part of that decline. Physical activity reactivates the biological pathway responsible for producing these protective particles, restoring some of muscle’s natural defense.

I’ve spent years telling clients that strength training matters for bone density, strength, metabolism, balance, and “just in case you fall.”

There’s a massive, clinical reason to add to the list!

This Trial Changed How Doctors Talk About Exercise

Doctors used to recommend exercise to help cancer patients manage treatment side effects and improve their quality of life. A 2025 trial published in theNew England Journal of Medicineindicates it might have an even more powerful effect--preventing cancer from recurring!

The CHALLENGE Trial​ was the first large randomized study to test whether a structured exercise program could change long-term outcomes for colon cancer patients after surgery and chemotherapy — not just how they felt, but whether they lived longer and stayed cancer-free.

After eight years of follow-up, patients who exercised had a 28% lower risk of their cancer returning, a new primary cancer, or death, compared to those who only received exercise education.

They also had a 37% lower risk of death from any cause.

Researchers say the magnitude of that benefit is comparable to what’s seen with many approved cancer drugs.

The exercise dose in the trial was about 150 minutes a week of moderate intensity aerobic activity — roughly the same recommendation you’ve heard for general health.

Researchers don’t know if smaller amounts offer similar protection, or how much resistance training adds on top of that, since most of the research so far has focused on aerobic exercise.

There’s also more to learn about whether these findings extend beyond colon, breast, and prostate​ cancers, which is where most of the research has concentrated.

Still, the evidence supports integrating exercise with standard cancer care.

How exercise affects cancer

Let’s be clear: exercise is not a cure for cancer. But it does:

• Activate immune cellsthat seek out and destroy abnormal cells. It may also interfere with the barriers that cancer cells use to prevent immune cells from destroying them.

• Reduce chronic Inflammation, which helps tumors thrive.

• Reduce estrogen levels and fat tissue, which affects cancers driven by hormonal and metabolic pathways, such as breast cancer. Diabetes, for instance, makes Triple Negative breast cancer more aggressive and increases the risk of brain metastasis.

• Improve insulin sensitivity, helping counter insulin resistance, which is associated with higher cancer risk and poorer outcomes. It helps regulate insulin-like growth factor 1 (IGF-1), a hormone linked to increased cancer risk when elevated.

Aerobic training increases cardiovascular fitness, improving metabolism. Resistance training increases muscle mass, improving metabolism.

Muscle “costs” calories to maintain, which increases metabolism. Fat slows metabolism, to conserve energy for a food shortage that, evolutionarily speaking, isn’t coming.

My Exhibit A

I have a personal stake in taking this research seriously. Six and a half years ago, my daughter, Katie, was diagnosed with stage 4 cancer only a couple of weeks after celebrating her 40th birthday...and then a few weeks after that, diagnosed with a rare lymphoma.

Today she told me her doctor thinks the lymphoma is in remission. She’s three and a half years beyond the prognosis she was given.

Who knows why.

Her treatment team deserves enormous credit, and so does she, for showing up to every hard day with more grace than I’d ever manage.

I’ve watched her build a life around habits that never waver, even on her worst weeks: she protects her sleep, is a whiz kid with her eating habits (puts me to shame!) and moves her body every single day — walking or runningearlyin the morning, Yoga With Adriene daily without exception, and strength training, which she mostly keeps up because I won’t stop bugging her about it.

I have no idea how much credit her yoga mat and her dumbbells deserve. Correlation isn’t causation, and I’m not a researcher. But we know she’s doing everything in her power to give herself a life that’s as close to normal as possible.

​The American Society of Clinical Oncology​ recommends that patients engage in regular aerobic and resistance exercise during treatment, shooting for just 150 minutes a week of brisk walking or any activity they enjoy.

Some experts envision a future where exercise oncology sessions are as routine for cancer patients as cardiac rehab is for heart patients.

As I was waxing enthusiastic about the power of exercise for fighting cancer, Katie reminded me that people who are dealing with cancer often feel too weary and ill to evenconsiderexercising.

That’s obviously a huge consideration.

If you or someone you care about is interested in exercising through cancer treatment or to prevent recurrence, check out this highly-rated book, Moving Through Cancer by Dr. Kathryn Schmitz.

None of us knows what’s ahead. Building strength today is one of the few things that we can control.

Don’t ever forget--each day is a gift!