Physical Fitness and a Healthy Immune System

Our immune system is what protects our bodies from bacteria and viruses that can make us sick. Our body is a vast network of cells and tissues constantly fighting against pathogens, an activity essential for our survival. Factors such as age, gender, dietary habits, as well as our medical condition influence our immune system. 

Even with the stay-at-home orders due to the novel Coronavirus, top institutions such as the CDC and WHO still encourage getting some exercise on a regular basis. Exercise has been found to improve health in some cases as it improves the body’s immune response, lowers the risk of illnesses, and reduces inflammation. Usually our bodies have a small number of immune cells. These cells are stored in lymphoid tissues and organs such as the spleen, thymus, bone marrow, and lymph nodes, where our bodies kill viruses and bacteria that cause diseases. Exercise increases blood and lymph flow as the muscles contract and this leads to an increased circulation of immune cells in our body. 

Your immune system's immediate reaction to increased physical activity will slowly fade out. That’s why regular exercise is emphasized as opposed to irregular exercising. One study found that those who engaged in aerobic exercise for five days a week or more over a 12 week period, lowered their risk of acquiring upper respiratory tract infection or URTI (common cold) by more than 40%. Inflammation is vital to the immune system as it responds to injury and infection to heal wounds. But it can also play a role in developing chronic diseases.  Increase your activity level to lower inflammation, as exercise has been found to decrease inflammation in the body. 


Moderate to high intensity exercise stimulates the immune system. Due to this immune- enhancing effect it's quite rare to see a physically active person with an upper respiratory tract infection (URTI) such as a sore throat, sinus infection or common cold. Strenuous activities on the other hand seems to temporarily alter the body’s immune defenses. Intense training, such as athletes preparing for a marathon, releases stress hormones (cortisol, endorphins, etc.) in the body. Repeated stress leads to, what the scientists call, an “open window” which is referred to a period of one to three days where the immune system is vulnerable to URTIs. There’s less research available regarding high-intensity interval training (HIIT) workouts and its effect on immunity. 

While practicing social distancing, good personal hygiene is of paramount importance during this time of novel Coronavirus. Regular moderate exercises (walking, cycling, and running) will improve a person’s overall well-being, besides giving the body its best chance to fight off infections.

Physical Activity Guide



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