Myokines: How Exercise Fights Cancer

For decades, researchers have observed that physically active individuals experience lower rates of cancer and better outcomes when diagnosed with the disease. While many theories have tried to explain this relationship, emerging evidence suggests that muscles are not merely engines for movement but active endocrine organs that release potent anti-cancer molecules during exercise. These molecules, called myokines, represent a promising frontier in understanding how physical activity protects against cancer and supports those fighting the disease.

Muscles as Medicine-Producing Organs

The traditional view of muscles focused exclusively on their mechanical function, namely, contracting to produce movement. However, research conducted over the past two decades has fundamentally changed this understanding. Scientists now recognize that skeletal muscle is the largest endocrine organ in the human body, secreting hundreds of signaling molecules that influence virtually every organ system.

When muscle fibers contract during physical activity, they release myokines into the bloodstream. These hormone-like molecules travel throughout the body, communicate with distant tissues, and trigger a cascade of beneficial effects. Among the most studied myokines with documented anti-cancer properties are IL-6 (the exercise-induced, anti-inflammatory form), irisin, SPARC, and oncostatin M. Each plays a distinct role in the body’s defense against malignant disease.

How Myokines Combat Cancer

Exercise-induced myokines exert anticancer effects through multiple mechanisms. Laboratory studies show that these molecules can directly reduce cancer cell proliferation, slowing the rate at which malignant cells divide and multiply. Perhaps more significantly, certain myokines induce apoptosis (programmed cell death) in cancer cells while sparing healthy cells. This selective targeting represents a form of natural chemotherapy produced by the body itself.

Beyond their direct effects on cancer cells, myokines enhance immune surveillance. The immune system continuously monitors for abnormal cells, and myokines appear to improve the efficiency of this surveillance, helping immune cells identify and eliminate nascent tumors before they can establish themselves. Research has also shown that myokines alter the tumor microenvironment (the complex ecosystem surrounding cancer cells), making it less supportive of tumor growth and more hostile to metastatic spread.

The Immediate and Cumulative Benefits

One of the most encouraging findings from recent research is that the anti-cancer effects of exercise begin almost immediately. Studies have demonstrated that even brief bouts of vigorous physical activity alter the molecular composition of blood in ways that suppress genes implicated in cancer growth, activate DNA repair pathways, and improve metabolic signaling. When researchers exposed cancer cells to post-exercise blood in the laboratory, the cells showed reduced growth rates and improved DNA stability.

The benefits also accumulate over time. In a study of breast cancer survivors, twelve weeks of structured exercise training increased circulating myokine levels by up to fifteen percent. More importantly, when researchers applied blood serum from these exercising individuals to metastatic breast cancer cells in laboratory models, the cells showed twenty-two to twenty-five percent reductions in growth compared to controls. This finding suggests that regular exercise creates a sustained anti-cancer environment within the body.

Exercise and Cancer Prevention

For individuals seeking to reduce their cancer risk, the myokine pathway offers a compelling biological rationale for regular physical activity. Many cancers develop and thrive in metabolic environments characterized by elevated blood glucose, high insulin levels, chronic systemic inflammation, and compromised mitochondrial function. Exercise-induced myokines directly counteract each of these conditions.

Regular physical activity improves insulin sensitivity, reducing elevated insulin levels linked to increased cancer risk. Myokines enhance mitochondrial metabolism, improving the cellular energy production that supports healthy tissue function. They reduce systemic inflammation, which is increasingly recognized as a driver of cancer development and progression. They also support DNA repair mechanisms, helping the body correct genetic damage before it can lead to malignant transformation. Collectively, these effects create an internal metabolic landscape that is fundamentally hostile to cancer initiation and growth.

Supporting Cancer Treatment and Survivorship

For those already diagnosed with cancer, exercise-induced myokines offer additional benefits that complement conventional treatment. Research shows that physical activity during cancer treatment can improve treatment tolerance, helping patients complete prescribed regimens with fewer dose reductions or delays. The mechanisms underlying this benefit likely involve myokine-mediated improvements in immune function, tissue repair, and metabolic health.

Cancer survivors face an elevated risk of recurrence, and maintaining regular physical activity appears to reduce this risk substantially. Reviews on the role of myokines in cancer outcomes highlight their influence on immune cell infiltration into residual tumor sites, blood vessel formation, local inflammation, and cancer cell migration. By maintaining elevated myokine levels through regular exercise, survivors may suppress the growth of any remaining cancer cells and reduce the likelihood of metastatic spread.

For years, the link between exercise and cancer survival rested mostly on observational studies, which can show an association but cannot prove cause and effect. That changed in 2025, when the New England Journal of Medicine published the CHALLENGE trial, the first large randomized study to test whether exercise itself changes cancer outcomes. Researchers at 55 centers, mostly in Canada and Australia, enrolled 889 people who had finished surgery and chemotherapy for stage III or high-risk stage II colon cancer. Half received health-education materials alone. The other half received the same materials plus three years of coaching from a physical activity consultant, aiming to add roughly 45-60 minutes of brisk walking three or four times a week.

The results were remarkable. After a median follow-up of nearly eight years, the exercise group had a 28% lower risk of cancer returning, a new cancer developing, or death. At five years, 80.3% of the exercisers were alive and cancer-free, compared with 73.9% of those who received education alone. The findings also pointed to longer life: at eight years, 90.3% of the exercise group were living, compared with 83.2% of the education group. The researchers noted that this benefit is similar in size to that of many approved cancer drugs. Sore joints and other musculoskeletal complaints were somewhat more common among the exercisers (18.5% vs. 11.5%), a good reminder to build up gradually.

Two details from the trial speak directly to the biology described in this article. First, the benefit came mainly from fewer recurrences in the liver and fewer new cancers, including breast, prostate, and colorectal cancers. This suggests exercise changes the body’s internal environment in ways that make it harder for stray cancer cells to take hold anywhere. Second, the exercisers did not lose weight or inches from their waists, so weight loss cannot explain the benefit. The researchers pointed instead to stronger immune surveillance, lower inflammation, better insulin sensitivity, and changes in the tissues where cancer tends to spread, the very pathways myokines are known to influence. The trial did not measure myokines directly, and participants focused on walking rather than resistance training, but planned analyses of stored blood samples should help reveal which messengers from working muscle are responsible.

Exercise also helps counteract sarcopenia, the progressive loss of muscle mass that commonly accompanies cancer and its treatment. Because muscles produce myokines, preserving muscle mass maintains the body’s capacity to generate these protective molecules. This creates a positive feedback loop in which exercise preserves muscle, muscle produces myokines, and myokines support better outcomes.

The Role of Resistance Training

While all forms of physical activity stimulate myokine release, research suggests that resistance-type movements may be particularly effective. Studies have found that resistance training activates certain myokines more robustly than aerobic exercise alone. This finding has important implications for exercise prescription, particularly for older adults, who appear to respond especially well to resistance-type movements for myokine production.

Resistance training does not require specialized equipment or gym memberships. Any movement that challenges muscles against resistance, including the resistance provided by one’s own body weight, triggers the contraction-dependent release of myokines. This makes resistance-based exercise accessible to individuals across a wide range of fitness levels, health conditions, and resource constraints.

A Practical Strategy: Bodyweight Squats Throughout the Day

Understanding the science of myokines opens the door to practical strategies for maintaining elevated levels of these protective molecules. One of the most effective approaches is to distribute short bouts of resistance exercise throughout the day rather than concentrating all activity into a single session. This method, sometimes called exercise snacking, maintains elevated myokine signaling throughout the waking hours.

The bodyweight squat represents an ideal movement for this purpose. A single squat engages a substantial amount of muscle mass simultaneously, activating the quadriceps, hamstrings, gluteal muscles, adductors, calves, and core stabilizers. This large-scale muscle recruitment provides exactly the stimulus needed for robust myokine secretion. Because the movement requires no equipment and minimal space, you can do it virtually anywhere: at home, in an office, during breaks, or while traveling.

Research indicates that performing just five to ten bodyweight squats every hour throughout the day can meaningfully increase myokine signaling. This approach offers several advantages over traditional exercise prescriptions. It does not require dedicated workout time, making it easier to maintain consistently. It avoids the fatigue associated with longer sessions, which is particularly valuable for individuals undergoing cancer treatment. It provides repeated spikes in myokine release throughout the day, potentially maintaining a more consistently anti-cancer intracellular environment.

For individuals with mobility limitations or those new to exercise, modifications such as chair-assisted squats or partial-range movements can still elicit sufficient muscle activation to trigger myokine release. The key principle is muscle contraction against resistance, which remains present even in adapted versions of the movement. As strength and confidence improve, you can progressively increase the depth and intensity of squats.

Conclusion

The discovery that muscles function as endocrine organs that produce anticancer molecules has transformed our understanding of why exercise protects against malignant disease. Myokines represent a direct biological link between physical activity and cancer prevention, treatment support, and survivorship. They work immediately, accumulate with consistent training, and can be stimulated through accessible movements that require no special equipment or facilities.

Simple strategies, such as bodyweight squats throughout the day, offer a practical way to maintain elevated myokine levels. Whether the goal is to reduce cancer risk, support treatment, or prevent recurrence, regular muscle contraction provides one of the most powerful and accessible tools available. The evidence is clear: when muscles contract, they produce medicine. Making that contraction a regular part of daily life may be one of the most important health decisions a person can make.

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