There is nothing like a warm sunny day to motivate you to get outside and be active, but as the dark cold days of winter set in, the thought of getting out can quickly lose its appeal and the old wives’ tale of “catching a cold” might begin to feel more valid. Rest assured, the only way to catch a cold or other viral infection is to come in contact with virus particles that have been shed by someone who is sick – hence the distancing, masks and sanitizing measures we have become all too familiar with since the pandemic started. Beyond basic exposure prevention, one of the best ways to ensure your immune defenses against viruses remain strong is to maintain a regular exercise routine. Exercise doesn't just train your muscles, it trains your immune system too, making the body more resilient to pathogens that threaten our wellness.
The body’s immune system is very responsive to exercise. According to the American College of Sports Medicine (ACSM), “every bout of exercise instantaneously mobilizes literally billions of immune cells, especially those cell types that are capable of carrying out effector functions such as the recognition and killing of virus-infected cells.” These immune cells immediately go to work, moving throughout the body to areas where increased immune defense may be needed, such as the lungs and gut. Exercise can also benefit the immune system by supporting a healthy gut microbiome. Over 70% of the immune system resides in the gut. When we exercise, there is an increase in the number and diversity of microbial species which in turn, helps the body defend against infectious organisms.
Activating these immune defense mechanisms on a regular basis ultimately reduces our risk of getting sick as evidenced by epidemiologic studies and randomized human clinical trials which consistently report a 18-67% reduction in the incidence or risk of upper respiratory tract infection in adults who engage in regular moderate exercise compared to those who are sedentary. Moreover, when physically active adults do come down with upper respiratory tract infections, they are more likely to recover faster and experience less severe symptoms. A study published in the British Journal of Sports Medicine found that men and women who exercised five or more days a week had about a 30-40% reduction in severity of symptoms when they got sick compared to those who were less active.
While some scientists believe that exercise temporarily weakens the immune system, creating an “open window” that makes the body more vulnerable to infection, others in the field assert that there is limited reliable evidence to support this position. They explain that the decreased number of immune cells measured in the bloodstream immediately following exercise is not a sign of immune suppression but rather a signal that these cells, primed by exercise, are simply working in other parts of the body – a desirable effect! It is true that upper respiratory infections in competitive athletes are second only to injury for the number of lost training days, however, the increased risk of infection is more likely due to an inadequate diet, psychological stress, insufficient sleep, travel and importantly, pathogen exposure at social gathering events like marathons that put extra strain on the immune system -- rather than the act of exercising itself.
Exercise is indeed a potent means of boosting your immune system, especially in combination with a plant-based foods and botanicals that support your body’s ability to modulate stress and achieve a restful night of sleep. Next time it feels like winter is starting to derail your fitness routine, let the knowledge of the powerful effects of exercise on your immunity and overall wellness serve as motivation to get out there and dose up on movement so you can stay strong and resilient year round and lifelong.
By Hayley Helms & Taryn Forrelli