Does Exercise Boost Your Immune System?

You can use fitness to your immune system’s advantage—here’s how.

In the pursuit of a robust immune system, we often turn to stress management and a balanced diet as our primary allies. However, exercise, too, emerges as a potent supporter of immune health, offering a multifaceted approach to enhancing overall well-being. While the mere thought of lacing up your sneakers for a workout may occasionally feel daunting, it’s essential to recognize that not all forms of exercise are created equal when it comes to immune benefits. In this comprehensive guide, we delve into the intricate relationship between exercise and immunity, shedding light on how physical activity can be harnessed to bolster your defense mechanisms against infections and illnesses.

The Immune-Boosting Power of Exercise

Beyond its well-documented mental health benefits, exercise plays a pivotal role in fortifying your immune system. A compelling 2019 scientific review published in the Journal of Sport and Health Science unearthed the profound impact of exercise on immune response, illness risk reduction, and inflammation mitigation.

Study author David Nieman, DrPH, a distinguished professor in the Department of Biology at Appalachian State University and the director of the university’s Human Performance Laboratory, asserts that this immune-boosting effect is particularly pronounced during bouts of “acute exercise.” This refers to moderate to vigorous intensity exercise sessions lasting under an hour, encompassing activities such as brisk walking, elliptical workouts, spin classes, or running.

Enhanced Circulation of Immune Cells

Dr. Nieman elucidates the mechanism behind exercise’s immune-enhancing prowess. Under normal circumstances, the human body harbors a limited number of immune cells circulating throughout. These immune warriors prefer to reside within lymphoid tissues and organs, such as the spleen, where they play a crucial role in combating viruses, bacteria, and other microorganisms responsible for causing diseases.

Exercise serves as a catalyst for this immune response by increasing blood and lymph flow as muscles contract. This surge in circulation results in a higher quantity of immune cells traversing the body at an accelerated rate. In particular, exercise aids in recruiting specialized immune cells like natural killer cells and T cells, which are adept at identifying and neutralizing pathogens such as viruses.

Dr. Nieman’s 2019 review revealed that individuals embarking on a 45-minute brisk walk experienced a notable increase in immune cell circulation, a phenomenon lasting up to three hours post-exercise.

Consistency Is Key

While the immediate immune response triggered by exercise is indeed remarkable, its effects are transient. To maintain and amplify these benefits, consistent exercise is essential. Dr. Nieman highlights that engaging in exercise for 45 minutes on one day and repeating the process the next day reinforces the immune response. In essence, the cumulative impact of regular exercise sessions contributes to a more resilient immune system.

Further substantiating the significance of exercise frequency, a study conducted by Dr. Nieman’s team demonstrated that individuals engaging in aerobic exercise at least five days a week over a 12-week period experienced a reduction of over 40% in upper respiratory tract infections, such as the common cold.

In 2022, a study published in the British Journal of Sports Medicine analyzed data from 16 studies involving individuals who remained physically active during the COVID-19 pandemic. The findings underscored the association between exercise and reduced infection risk, as well as a decreased likelihood of severe COVID-19 outcomes. Regular exercise enthusiasts worldwide exhibited a remarkable 36% lower risk of hospitalization and a 43% lower risk of COVID-19-related mortality compared to their less active counterparts.

Exercise as a Long-Term Investment in Immunity

Drawing an analogy, Dr. Nieman likens the enduring immune benefits of exercise to the effects of hiring a housekeeper. Suppose you invite a housekeeper to clean your home for 45 minutes several days a week. On the first day, the transformation in your home is evident. However, as the housekeeper continues to return regularly, the overall condition of your home continually improves.

Similarly, exercise serves as a form of “housekeeping” for the immune system. It enables immune cells to patrol the body vigilantly, detecting and combating bacteria and viruses. The key takeaway is that sporadic exercise yields limited immune benefits, whereas consistent physical activity empowers your immune system to effectively ward off illness-causing germs. Importantly, this principle remains relevant as individuals age, emphasizing the enduring relevance of exercise for immune health.

Inflammation Reduction

Another noteworthy facet of exercise is its capacity to reduce inflammation within the body, a factor closely intertwined with immune function. Existing research has highlighted exercise’s potential to enhance immune function while concurrently mitigating inflammation.

Dr. Nieman underscores the connection between decreased inflammation and enhanced immunity. Inflammation compromises the ability of immune cells to function optimally, perpetuating a chronically inflamed state within the immune system. This inflamed environment hinders the body’s capacity to combat infections effectively. Thus, elevating your activity level through exercise can serve as an effective strategy for reducing inflammation and, by extension, improving immunity.

Selecting the Ideal Exercise Regimen for Immunity Enhancement

While the immune-boosting potential of exercise is indisputable, questions often arise regarding the type of exercise that delivers maximum benefits. While research in this area remains limited, most studies, including those conducted by Dr. Nieman, primarily emphasize aerobic activities such as walking, running, or cycling.

Walking

To derive immune benefits from walking, Dr. Nieman recommends striving for a slightly brisk pace. For most individuals, this translates to a 15-minute mile, which has been associated with promising results in his research. To determine the ideal intensity for other forms of exercise, Dr. Nieman suggests aiming to reach approximately 70% of your maximum heart rate.

High-Intensity Interval Training (HIIT)

High-Intensity Interval Training (HIIT), characterized by short bursts of intense exercise followed by brief rest periods, has gained popularity in recent years. While research on HIIT and immunity is relatively scarce, a 2018 study focused on arthritis patients suggested that HIIT could improve immune function. Additionally, a 2014 study in the Journal of Inflammation Research indicated that HIIT workouts do not compromise immunity.

Dr. Nieman advises that interval workouts, including HIIT, are generally considered acceptable for immune health. The body is accustomed to intermittent bouts of high-intensity exercise, even if sustained for several hours, as long as it does not entail unrelenting high-intensity exertion.

Strength Training

Strength training, involving resistance exercises such as weightlifting, is another avenue for potential immune system enhancement. Dr. Adam Jajtner, an assistant professor of exercise science and physiology at Kent State University, has conducted research on exercise and immune response and commends resistance training as a viable strategy for improving immunity.

Nevertheless, Dr. Jajtner cautions against engaging in muscle-damaging workouts, such as lifting extremely heavy weights or performing eccentric exercises that involve a slow, controlled lowering phase. These strenuous activities have the potential to disrupt the muscle repair process, potentially competing with immune function. Therefore, it is advisable to avoid embarking on an intense strength training routine, particularly if you are new to such workouts.

The Perils of Overexertion

While exercise undeniably offers a myriad of immune benefits, it is crucial to recognize that, like most good things in life, moderation is key. Overexertion through excessive or prolonged exercise can elevate the risk of infection. However, it’s important to note that reaching this level of exertion typically requires pushing well beyond the realm of “acute” exercise.

For instance, studies have previously highlighted an increased risk of illness among marathon runners engaged in extreme exercise. Dr. Nieman’s research, dating back to 1990, detailed adverse changes in immunity following marathon-type exertion. Nonetheless, these negative consequences typically manifest when individuals engage in high-intensity activities such as half-marathon running, extended cycling, or demanding swimming for approximately 90 minutes or more.

Dr. Nieman emphasizes that extended, intense activities can induce stress on the body, resulting in compromised immune function. This stress-induced dysfunction can persist for a few hours to several days following such exertion.

In a 2021 review published in Sports Medicine, researchers examined the health implications of ultra-endurance running (UER). Their findings indicated that following UER, individuals experienced a transient immunosuppression lasting several hours. This phenomenon elevated the risk of viral and bacterial infections.

Dr. Jajtner concurs with the notion that incorporating weeks of high-intensity workouts into one’s routine may prove counterproductive. The “J curve” phenomenon illustrates that as individuals maintain a moderate-intensity exercise regimen over weeks to months, their risk of infection diminishes. Conversely, excessive and intense exercise elevates the risk of infection.

The duration and intensity thresholds at which overexertion occurs may vary depending on an individual’s fitness level. Therefore, it is prudent to prioritize maintenance rather than unrelenting intensity. Dr. Jajtner underscores the significance of moderate-intensity exercise as the ideal route to bolstering immunity while avoiding the pitfalls of overexertion.

In Summary: Harnessing Exercise for Immune Health

In the quest for immune resilience, exercise emerges as a powerful ally. While other lifestyle factors, such as dietary choices, stress management, and sleep quality, undoubtedly contribute to immunity, exercise offers a dynamic and multifaceted approach to fortifying your defense mechanisms against infections and illnesses.

The key to unlocking exercise’s full potential for immune health lies in regularity and moderation. Aerobic activities like running, cycling, and brisk walking are exemplary immune boosters. For those new to exercise, walking offers an accessible entry point, provided it aligns with your healthcare professional’s recommendations.

Strength training can also serve as a viable strategy, but individuals should exercise caution, especially when it comes to muscle-damaging workouts. Avoiding overexertion is pivotal; high-intensity, prolonged exercise can compromise immune function.

Ultimately, moderation, consistency, and tailored exercise choices are the cornerstones of harnessing the immune-boosting potential of exercise. By adhering to these principles, you can empower your immune system to better defend against illness, all while enjoying the multifaceted benefits of an active and healthy lifestyle. Remember, exercise is not merely a tool for fitness; it is a pathway to robust immune health and overall well-being.