How Exercise Keeps You Healthy

Apr 6th, 2020

I’m writing this article two weeks after the World Health Organization (WHO) declared COVID-19 a pandemic. People around the globe are practicing social distancing or going into quarantine. There is a sudden, intense focus on the movement of bodies. Everyone wants to know what to do with themselves and how to keep healthy.

Practices and policies from WHO and local governments that affect cyclists will continue to change with the situation, and people should follow the recommendations for their area. While cycling might be out of the question for many of us, now is not the time to stop moving but rather a time to get creative about how we move.

Over the last 15 years, I’ve cycled thousands of miles on long adventures around the world. But in the last three years, I’ve also spent months at a time confined to bed, rehabilitating from repeated knee surgeries. During this period, I’ve had to learn to shift my perspective toward what works instead of what doesn’t. If I can’t do the things I used to do, what can I do now?

Since none of us will be riding off on a bike tour in the next few weeks, we’ll have to adapt and approach our daily lives with a renewed spirit of adventure and resilience. As hard as it is right now to find the motivation to do anything other than drink all the vodka and binge-watch Tiger King, here’s why it’s so important for us to challenge ourselves to keep moving: it’s for the health of our immune systems.

Exercise and Health Outcomes

Physical activity is a cornerstone of human health. According to the WHO, “Regular physical activity of moderate intensity — such as walking, cycling, or doing sports — has significant benefits for health.” The WHO recommends that adults of all ages do at least 150 minutes of moderately intense physical activity throughout the week. 

If you are able to continue cycling outdoors, these recommendations can help you ride safely during the pandemic. If you are restricted from outdoor cycling, use a stationary bike at home. If you don’t have that, home exercises like core workouts, jumping rope, and burpees will keep you moving and grooving until your next epic bike ride. Household objects like gallon jugs, a backpack full of books, and sacks of dry beans make great weights.  

According to the Centers for Disease Control, physical activity is “one of the best things people can do to improve their health,” and can reduce chronic diseases and prevent early death. Exercise is often cited as a primary way to prevent noncommunicable diseases like cardiovascular disease, cancer, and diabetes. Some of these same diseases are now shown to be risk factors for more serious health complications from COVID-19. It is important for people of all ages to engage in physical activity on a regular basis to maximize health outcomes.

Exercise and Immunity

In addition to preventing or reducing noncommunicable diseases, exercise also has an effect on the immune system. Literature reviews of scientific articles about exercise immunology reveal a general consensus that moderate exercise is beneficial to the immune system.

In “Moderate Exercise Improves Immunity and Decreases Illness Rates,” published in 2011 in the American Journal of Lifestyle Medicine, the author explains how moderate exercise causes a temporary “surge” in immune cells, which reduce the incidence of upper respiratory illness (URI). These transient responses contribute to larger cumulative health gains. “As moderate exercise continues on a near-daily basis for 12 to 15 weeks, the number of symptom days with URI is decreased 25% to 50% compared with randomized sedentary controls.” In other words, exercise may actually trigger the body’s immune system to function at a higher level and protect the respiratory tract.

In layman’s terms: exercise keeps your immune system young and spry!

In “Exercise and the Aging Immune Systems,” published in 2012 in Aging Research reviews, the authors write that regular exercise has been associated with a variety of positive physiological responses, including enhanced vaccination responses, lower circulatory levels of inflammatory cytokines, lowered inflammatory response to bacterial challenge, and lower numbers of exhausted/senescent T-cells, all of which “indicate that habitual exercise is capable of regulating the immune system and delaying the onset of immunosenescence.” (Immunosenescence is the deterioration of the immune system with age.) In layman’s terms: exercise keeps your immune system young and spry!

And in “Immune Function in Sport and Exercise,” published in the Journal of Applied Physiology in 2007, the author states very clearly, “Regular moderate exercise is associated with a reduced incidence of infection compared with a completely sedentary state.” But in this same article the author goes on to say the opposite about strenuous exercise: “However, prolonged bouts of strenuous exercise cause a temporary depression of various aspects of immune function.” 

Numerous studies on exercise and immunology repeat this distinction: moderate exercise creates both transient and cumulative benefits to the immune system, while strenuous exercise may make the body temporarily more susceptible to illness. This temporary susceptibility is called the “open window” hypothesis of exercise immunology. According to this hypothesis, even though moderate exercise improves immune function, strenuous exercise can temporarily decrease immune function by creating an “open window” of susceptibility that can last several hours or days post-exercise.

However, in recent years this theory has become controversial. In the article “Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan,” published in Frontiers of Immunology in 2018, the authors highlight the limitations of past research and provide a new understanding of how we measure and interpret data in the field of exercise immunology. They posit that instead of suppressing immune function, changes in lymphocyte numbers and function after strenuous exercise “reflects a transient and time-dependent redistribution of immune cells to peripheral tissues, resulting in a heightened state of immune surveillance and immune regulation, as opposed to immune suppression.” In other words, what researchers thought to be immune suppression may actually just be a different form of immune function. The authors go on to explain, “Epidemiological evidence indicates that regular physical activity and/or frequent structured exercise reduces the incidence of many chronic diseases in older age, including communicable diseases such as viral and bacterial infections, as well as non-communicable diseases such as cancer and chronic inflammatory disorders […] We emphasize that it is a misconception to label any form of acute exercise as immunosuppressive, and, instead, exercise most likely improves immune competency across the lifespan.”

A recent article in the New York Times, “How Exercise May Affect Your Immunity,” reiterates these changing viewpoints and encourages people to continue exercise during the pandemic. “The latest science suggests that being fit boosts our immune systems, and that even a single workout can amplify and improve our ability to fight off germs.” The author also includes some basic caveats: if you don’t have a history of working out, you should start with moderation and always use good hygiene. Starting slow and using common sense is always good advice for anyone beginning a new exercise routine.

Before my last surgery in July, I had to do a lot of “prehab” exercises to strengthen my muscles in preparation for long weeks of bed rest. I hated these exercises, and I had a really hard time motivating myself. Then one day I decided to turn it into a game. I pretended that I was training to set a world record in sit-ups. I made a big training chart and taped it on the wall at work. Some of my co-workers joined in, and we tracked our progress. On the very first day, I did 30 sit-ups and then lay there thinking, oh no — this is my worst idea ever. But the next day I did 50. And a couple of days after that, I did 70. Every couple of days, I increased the repetitions by a small amount and always stopped if anything felt off. Six weeks later, I had worked up to over 1,000 consecutive sit-ups, and I walked into my surgery with the strongest core of my life.

We all have to make changes right now. Our normal lives and routines are disrupted. We face increased uncertainty about the future. This is simply the moment in time that we find ourselves in. But in this moment there is still room for creativity, adventure, connection, and resilience. We can still move and keep moving in ways that keep us strong and healthy.

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