We all want a healthy immune system, one that protects against nasty viruses and bacteria that cause stuffy noses, cough, and fever. However, we also need our immune system not to overreact and attack healthy tissues. How our immune system responds to threats depends on genetics and age, but lifestyle also plays a role. Factors such as the diet you eat, how much you sleep, stress level and how well you manage that stress are factors.
Another factor that affects the immune system function is how active you are. Some studies suggest that exercise improves immune system function and may help your body better fight viruses and other pathogens. But how often you exercise, how hard, how long, and the type of exercise you perform may impact your immune system. Also, the short-term effects of exercise on immune function may differ from the longer-term effects. Let’s look at what science reveals about exercise and its impact on immune health, short-term and long-term.
The Short-Term and Long-Term Effects of Exercise on Immune Function
What effect does exercise have on your immune system short term? You’ve just nailed a 30-minute workout. and you’re tired but pleased with your performance, but how is your immune system holding up? Aerobic exercise may be beneficial short term in at least one way. When you breathe harder during an aerobic workout, the forceful movement of air in and out of your lungs helps flush viruses and bacteria out of your airways so they don’t take up residence there and cause an infection.
However, lengthy exercise sessions may affect your immune system negatively. Studies show that prolonged, exhausting workouts can diminish the activity of white blood cells that shield against infection short term. Think of a marathon runner or someone training for a marathon and how long they exercise. It’s not unusual for a runner training for a marathon to run for several hours per session, more than a few times per week. Although the drop in white cell function after protracted exercise may be brief, the transient suppression in function could allow a virus or bacteria to gain a foothold in the nasal passages, airways, or lungs and cause an infection. Some studies suggest that marathon runners are at a higher risk of coming down with an upper respiratory infection after the big race. In fact, a study that looked at over 2,300 runners after the Los Angeles Marathon found that 13% of marathoners developed an illness, usually a cold, the week after the event relative to only 2.2% of control runners.
The short-term impact of exercise on the immune system varies with intensity and duration. Workouts, where you exercise at 60% of your aerobic capacity for longer than an hour at a moderate intensity, are more likely to cause a short-term disruption in the immune system. In fact, several studies reveal that competitive exercise events, such as marathons, and prolonged workouts cause oxidative stress, inflammation, and immune disruption.
Shorter Workouts Are Easier on Your Immune System
In contrast, moderate and high-intensity exercise of shorter duration, less than an hour, has the opposite effect. It puts your immune system on “high alert” and increases surveillance against pathogens. In fact, exercise that lasts less than an hour boosts the release of anti-inflammatory cytokines that protect against immune system disruption. It also increases infection-fighting immune cells that your body needs while viruses are around. Plus, exercise drives the transfer of immune cells from the lymphatic system to the bloodstream. Therefore, you have more immune cells in your bloodstream ready to react to and wipe out viruses. In addition, your immune system is also on higher alert for cancer cells too after a short exercise session. That’s because immune surveillance for all abnormal cells and pathogens is higher.
Why does the length of an exercise session matter? When an exercise session is short-lived, you don’t get a surge in cortisol, the stress hormone, as you do with long-duration exercise. Cortisol suppresses immune function, so when cortisol is elevated, you have a higher risk of catching a viral infection. Cortisol has some benefit, though. It mobilizes energy stores, including glucose and fat, so they’re available to your hardworking muscles. However, you want the cortisol surge to drop back to baseline quickly to minimize its impact on your immune system. Longer-term, too much cortisol contributes to bone loss and infertility too. Cortisol can be friend or foe depending upon the amount, timing, and how long it stays up.
The Bottom Line
Workouts less than an hour may give your immune system a short-term advantage in fighting off viruses, but prolonged or very intense workouts may have the opposite effect because of the immune-suppressive effect of cortisol. It’s hard to make firm conclusions since most studies look at only a few aspects of immune function and the immune system is complex. Plus, factors like age, other health problems, type of workout, and even medications impact the immune response to exercise. However, exercise in moderation is unlikely to enhance your risk of infection and may even lower it. Plus, when you consider the other benefits to your health, exercise is an easy decision. On the other hand, take it easy if you feel like you’re coming down with a cold and skip your workout if you’re running a fever or have muscle aches or a productive cough. And don’t forget that sleep is vital for healthy immune function. Even one night of inadequate sleep suppresses immune function and increases the risk of catching an upper respiratory virus. Most people need 7.5 to 8 hours per night for optimal mental and physical health.
- Front Immunol. 2018; 9: 648. Published online 2018 Apr 16. doi: 10.3389/fimmu.2018.00648./
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