The pandemic shuttered many businesses, big and small. And one of the most badly-hit is a place we use to go to let off steam, push our body to the limit, and connect with people who share our passion for fitness. To this day, indoor public gyms, yoga classes, and pilates studios remain canceled.

Because of this, some people have revamped their exercise routines, either spending more time outside or buying one of those really expensive indoor exercise bikes. The topic of staying fit these days is so important that the CDC even created a list of outdoor activities that can be done without wearing a mask, but still following the golden rule of staying 6-feet apart and limiting contact with others. Also, we recently wrote about indoor activities and exercises that don't require extra equipment or take too much time out of your day.

Even though there are viable options to remain physically active during quarantine, it's become harder to avoid a sedentary lifestyle. A recent review published in the European Journal of Clinical Investigation noted "an elevation in the time watching TV (72.3%), logging to social media (81.9%), and using electronic gadgets (82.7%)". Not surprising given the requirements to work, school, and entertain ourselves at home. But being inactive isn't only affecting waistlines. It can also weaken the immune system and potentially increase the risk of getting COVID-19.

The review mentioned above investigated the impact of exercise on the immune system and how it may affect infection with COVID-19. Acute or chronic exercise gives the immune system a boost by improving the flow of leukocytes - the cells that help fight infection and disease - to the lungs, muscles, and spleen. It also reduces inflammation, a big contributor to the severe respiratory symptoms of COVID-19.

More or less exercise?

So how much should we be exercising to maintain a strong, active immune system? Is there an optimal time or intensity that gives the best results? An article published in Neuroimmunomodulation looked into this very question.

Shockingly, either intense or extended exercise (more than 2 hours) may inhibit the immune system from working to its full capacity. It's even been shown to increase rates of respiratory infections, such as the flu.

The sweet spot is with short (about 45 to 60 minutes) moderate-intensity exercise that's done regularly (at least three times per week). Remember leukocytes, the cells that keep infections and diseases at bay? Well, this type of exercise routine encourages the body to make more of them. Animal studies also indicate that short duration exercises done regularly can enhance these infection-fighting superpowers: