Cancer and cardiovascular diseases are often understood as completely separate conditions. However, recent scientific evidence shows that they are deeply connected. Not only do they share risk factors such as sedentary lifestyle, aging, and habits, but they also affect the body in surprisingly similar ways, altering essential processes like metabolism, energy production, and cardiovascular function.

When we think about cancer, it is common to imagine a localized tumor. But in reality, the impact of the disease goes far beyond that. The entire body enters a state of biological stress in which multiple systems begin to progressively fail. The heart, muscles, blood vessels, and even the cells responsible for producing energy are affected. Added to this is the effect of treatments, which, although essential to fight the tumor, can generate cardiovascular toxicity, increasing the risk of heart failure, arrhythmias, or hypertension.

In this context, a key concept is gaining increasing attention: cardiorespiratory fitness. This term describes the body’s ability to transport and use oxygen efficiently, from the lungs to the cells. More than just a measure of physical performance, it is a direct indicator of overall health. In cancer patients, this capacity is often significantly reduced, leading to fatigue, lower tolerance to effort, and a worse clinical prognosis.

Much of this alteration originates at the microscopic level, in the mitochondria. These structures are responsible for producing the energy that cells need to function. In cancer, their function becomes impaired: they produce energy less efficiently, generate higher oxidative stress, and lose their ability to maintain cellular balance. This not only promotes tumor progression but also damages healthy tissues, especially those with high energy demands such as the heart and skeletal muscle.

This progressive deterioration explains why many patients experience a significant loss of physical capacity even before noticeable changes in the tumor appear. And this is where an element that was long underestimated in oncology comes into play: exercise. Far from being just a general health recommendation, it is now understood as a biological intervention capable of acting on multiple key mechanisms in cancer.

Exercise does not only improve physical condition. At the cellular level, it enhances mitochondrial function, improves energy efficiency, and regulates the production of reactive oxygen species. At the vascular level, it promotes blood circulation and tissue oxygenation. And at the immune level, it activates key components of the immune system, such as natural killer (NK) cells, which can recognize and eliminate tumor cells.

Moreover, something particularly interesting is that exercise can modify the tumor environment. By improving blood perfusion, it facilitates the delivery of oxygen and treatments directly to tumor tissue. This could make some therapies more effective. It has also been observed that exercise influences cellular signaling related to tumor growth and metastasis, helping reduce its aggressiveness in certain contexts.

However, this relationship is not entirely linear. Cancer is a complex disease, and some studies suggest that under certain conditions, improving oxygen or nutrient availability could also benefit tumor cells. This is why the current approach is not simply “to exercise,” but to design personalized strategies that consider the type of cancer, the patient’s condition, and the treatment being received.

Despite these complexities, the clinical benefits of exercise are clear. Patients who maintain adequate levels of physical activity have a lower risk of cardiovascular complications, better tolerance to treatments, and improved quality of life. Even small improvements in cardiorespiratory fitness have been associated with significant reductions in mortality risk.

 

Figure 1. Cancer disrupts oxygen delivery, muscle function, and cellular energy production, reducing overall physical capacity. Exercise counteracts these effects by improving energy production, lowering cellular stress, and enhancing immune function. These changes in cardiorespiratory fitness (CRF) play a key role in patient outcomes.

 

The problem is that, in practice, many patients do not reach recommended activity levels. This may be due to fatigue, fear, lack of guidance, or simply the absence of structured programs within the healthcare system. Unlike other treatments, exercise is not yet fully integrated as a standard part of cancer care, despite the growing evidence supporting its impact.

Another key point is that not all types of exercise have the same effect. Aerobic training improves cardiovascular function and oxygen transport capacity. Strength training helps preserve muscle mass and improve metabolism. More intense modalities, such as interval training, can generate faster adaptations at the mitochondrial and vascular levels. A combination of these approaches, tailored to each patient, appears to be the most effective strategy.

To achieve this, proper evaluation is essential. Tools such as cardiopulmonary exercise testing help understand how the body responds to physical activity and allow safe and effective training levels to be established. This personalized approach is especially important in cancer patients, where conditions can change rapidly due to treatments.

It becomes increasingly clear that exercise is not simply a complementary recommendation, but an essential component of comprehensive cancer care. It does not replace conventional treatments, but it can enhance their effects, reduce complications, and improve the body’s resilience against the disease.

 

Main reference:

Wernhart, S., & Rassaf, T. (2025). Exercise, cancer, and the cardiovascular system: clinical effects and mechanistic insights. Basic research in cardiology, 120(1), 35–55. https://doi.org/10.1007/s00395-024-01034-4 

 

Other references:

Wernhart, S., & Rassaf, T. (2024). Relevance of Cardiovascular Exercise in Cancer and Cancer Therapy-Related Cardiac Dysfunction. Current heart failure reports, 21(3), 238–251. https://doi.org/10.1007/s11897-024-00662-0 

Tong, C. K. W., Lau, B., & Davis, M. K. (2020). Exercise Training for Cancer Survivors. Current treatment options in oncology, 21(7), 53. https://doi.org/10.1007/s11864-020-00752-w 

Kaminsky, L. A., Arena, R., Ellingsen, Ø., Harber, M. P., Myers, J., Ozemek, C., & Ross, R. (2019). Cardiorespiratory fitness and cardiovascular disease – The past, present, and future. Progress in cardiovascular diseases, 62(2), 86–93. https://doi.org/10.1016/j.pcad.2019.01.002