Exercise for Immunity

By Soren Ghorai

Exercise for Immunity

Constantly dealing with colds or coughs? Always feeling exhausted? You have likely heard you should take a daily vitamin to prevent you from getting sick, but what about your daily dose of activity? Forget the expensive, over-the-counter supplements — exercise has been linked to a healthy immune system.

How do we stay healthy?

We hear a lot about the immune system, but how does it actually work and protect us from disease? The immune system is a complex network of cells that defend our bodies from harmful intruders. These cells are called white blood cells or leukocytes. Leukocytes are referred to as “immune cells” because they are the critical defenders against infection. Leukocytes circulate throughout our bodies, looking to neutralize foreign bacteria, viruses, or other pathogens. Thus, a high number of white blood cells ensures our body can combat a wide range of threats to keep us safe and healthy.

Exercise linked to immunity

In a clinical study, researchers were curious about how exercise impacted our immune systems. Specifically, they examined the effects of exercise on blood leukocyte count, which indicates the activity of the immune system. The study consisted of 8 healthy male volunteers who were randomly subjected to four experimental conditions: high-intensity cycling for five minutes, moderate-intensity cycling for two hours, resistance training with 15 sets of 10 reps, and no exercise (control). Participants performed their assigned exercise over the course of 9 weeks with regular assessments of heart rate, oxygen consumption, and leukocyte count. After each session, researchers collected the participants’ blood samples in order to accurately measure their blood cell counts.

The results demonstrated a clear relationship between exercise and white blood cell count. Compared to the control, all three types of exercise provoked leukocytosis. The prolonged cycling group resulted in the highest leukocyte count, approximately 1.4x greater than the high-intensity cycling. Participants who did resistance training had cell counts slightly lower than the high-intensity group. Finally, the control group displayed the lowest leukocyte counts by far.

These findings underline the immune-stimulating effects of exercise. While all types of physical activity boosted the immune system, aerobic exercise generated the greatest response. This is because high-intensity exercise causes muscular damage, leading to a temporary increase in inflammation as the body undergoes repairs. As a result, leukocyte levels rise immediately after exercise to aid recovery and strengthen the body for future physical challenges​. This regular stimulation that comes with consistent exercise can keep the immune system in a state of readiness to reduce the likelihood of infection.

The above findings were supported in another clinical study, which monitored 1,002 adults (ages 18-85, both male and female) for upper respiratory tract infections (URTI), such as the common cold, sinus infections, or sore throats. After 12 weeks during the fall and winter seasons, researchers saw that daily aerobic activity reduced URTI frequency by 46% compared to those who did little to no exercise. Additionally, exercising reduced the severity of URTIs by 41%, meaning active individuals remained significantly healthier.

How much exercise do you need?

A key takeaway from both studies was that prolonged, high-intensity, or aerobic exercise yields the greatest immune effect. To keep exercise consistent, find an enjoyable routine that works for you. This could look like daily biking, playing golf, taking walks, or lifting weights at the gym. The CDC recommends at least 150 minutes of physical activity per week, with at least 2 days of muscle strengthening as well. See the CDC’s steps for getting started with exercise here.

Should you exercise when you’re sick?

Whether you should exercise when you’re sick largely depends on the severity of the illness and how you’re feeling. With mild symptoms like a runny nose or sore throat, light exercise such as walking or gentle yoga may be appropriate. However, it’s best to refrain from physical activity while suffering from moderate sickness like fever or fatigue. Make sure to prioritize rest and allow your body to recover smoothly. The bottom line? Listen to your body and don’t push yourself too hard while under the weather.

The TL;DR

Studies:

Natale VM, Brenner IK, Moldoveanu AI, Vasiliou P, Shek P, Shephard RJ. Effects of three different types of exercise on blood leukocyte count during and following exercise. Sao Paulo Med J. 2003 Jan 2;121(1):9-14. doi: 10.1590/s1516-31802003000100003. Epub 2003 Jul 4. PMID: 12751337.

Nieman DC, Henson DA, Austin MD, Sha W. Upper respiratory tract infection is reduced in physically fit and active adults. Br J Sports Med. 2011 Sep;45(12):987-92. doi: 10.1136/bjsm.2010.077875. Epub 2010 Nov 1. PMID: 21041243.

Strengths:

  • Examines different types/durations of exercise to find optimal conditions
  • Studies spanned over 9 and 12 weeks to capture reliable results
  • 2nd study included diverse demographics to make data generalizable to large populations

Weaknesses:

  • Not one “best” type of exercise. People should find what works for them
  • External factors like diet, sleep, and stress levels affect the immune system and could have influenced the results
  • Future research should examine how immunity is affected over years, not just months

Takeaway:

There is a positive correlation between exercise and increased immunity. Exercise induces inflammation to temporarily boost the immune system to assist in repairing working muscles, and consistent physical activity is proven to keep individuals healthier on a long-term basis. Focus on moderate movement throughout the day. Instead of prioritizing intensity, focus on consistency so your immune cells continually circulate and fight off infections. Finally, choose a physical activity that you enjoy, because exercise should be fun!