Exercise is critically important for physical and mental health because it helps stave off diseases related to obesity and reduces the symptoms of anxiety and depression. However, there is reason to believe that exercise might also protect against infectious diseases. In fact, a 2010 study showed that near-daily aerobic activity and the perception of being physically fit significantly reduced the frequency and severity of respiratory infections in both men and women during a twelve-week study period. Although we don’t know whether physical activity can help protect us against SARS-CoV-2 specifically, studies in exercise immunology, a relatively new but increasingly important area of scientific research, show that exercise may give your immune system a significant boost.
Short bouts (under sixty minutes) of moderate and vigorous exercise, such as walking, running, or cycling, may enhance the activity of innate immune cells, such as macrophages and natural killer cells. Macrophages help the body fight infection by engulfing and destroying invading pathogens (e.g., viruses and bacteria). Macrophages also secrete molecules that promote the activation of natural killer cells which can detect and kill infected cells to stop the infection from spreading.
In addition, aerobic exercise can help orchestrate the adaptive immune response by mobilizing two main types of lymphocytes: T-cells and B-cells. T-cells kill infected cells and use messenger molecules, known as cytokines, to increase the overall activation of the immune system. T-cells can also directly activate B-cells, which help us fight off bacteria and viruses by producing antibodies that “tag” invaders and help other immune cells eliminate them. In the short run, exercise may enhance immunosurveillance by recirculating immune cells found within various tissues and organs in the body, such as the lymph nodes and spleen, back into the bloodstream. In the long run, regular exercise may help ward off infection by redistributing immune cells to the organs favored by viruses and bacteria, such as mucosal membranes and the lungs.
Early-stage research shows that exercise may also promote defense against infectious diseases by increasing the production of antioxidants. Our bodies produce an antioxidant molecule known as extracellular superoxide dismutase (EcSOD), which breaks down free radicals that damage cell membranes, proteins, and DNA. Elevated EcSOD in blood and vital organs, including the lungs, may protect against acute respiratory distress syndrome (ARDS), a common and often lethal complication of COVID-19.
Finally, exercise may boost your immune system indirectly, by reducing stress and improving sleep. In fact, aerobic exercise reduces the levels of stress hormones, such as adrenaline and cortisol, which can interfere with our immune system’s ability to fight infection. Regular exercise can also help normalize disrupted sleep, which is crucial for the proper function of immune cells.
If you reside in New York City, you might not be able to get back to your gym or your favorite fitness class for a while, but there are several excellent alternatives that can help you stay fit and boost your immune defenses while social distancing:
Walk, run, or cycle responsibly. If you are an avid runner, continue to enjoy this solitary form of exercise, but take precautions, such as wearing a face covering and staying at least six feet away from other people in parks and on sidewalks. If wearing a surgical mask or a thick cloth mask while running is uncomfortable, consider investing in moisture-wicking multifunctional headwear. If you are new to running, make sure to start easy (several apps, including Nike Run Club and 5K Runner: Couch to 5K might help) and choose the right pair of running shoes to avoid injuries. Finally, if running is too hard on your joints, a brisk walk or a bike ride will offer similar benefits as long as you practice social distancing.
Replace a stair stepping machine with actual stairs. If your building or street has a mostly-empty staircase, fire up your legs and glutes by walking or jogging up and down the stairs,giving yourself a thirty second break between circuits. Mix it up by doing additional exercises such as calf raises, squats, or seesaw lunges at the top of each flight.
Do bodyweight exercises at home. With a little bit of space and some imagination, you can reach your fitness goals even during a pandemic. Follow workout classes on YouTube or Instagram Live, take advantage of Nike’s promotion that allows you to access Nike Training Club Premium for free, or start a fun exercise challenge with your friends. Rockefeller’s own Tim Blanchard offers strength/cardio classes via Zoom (you can also access Tim’s classes on YouTube). If mountain climbers and burpees aren’t your thing, you can get your heart rate up by joining TikTok dance challenges. Who knows, you might even become the right kind of viral!