When you’re injured or exposed to a virus or bacteria, your immune system mounts an inflammatory response. Your immune system has an important function. Immune cells help protect you against viruses and bacteria that cause illness and allergens you’re exposed to. When it’s activated short term to protect you against a harmful invader, it’s beneficial. After all, you need something to chase away infection-causing viruses and bacteria. But when your immune system stays activated or is always turned on, even at a low level, it can damage tissues and lead to chronic health problems.
By now, you’re probably aware that chronic inflammation is unhealthy. Low-grade inflammation is linked to a number of chronic health problems including heart disease, autoimmune diseases and cancer. Inflammation is an example of how a good thing, your immune system, can turn against you when it rages out of control or stays turned on.
Exercise and Inflammation
Obviously, you want to reduce unnecessary inflammation that doesn’t serve a useful function like protecting you against bacteria and viruses. What role does lifestyle play, particularly exercise?
Exercise, especially high-intensity workouts, stresses your body. Bet you already knew that! In response to this stress, your body releases “stress” hormones, including epinephrine, norepinephrine and cortisol. Epinephrine and norepinephrine increase your heart rate and blood pressure to send more blood to your working muscles so they get more oxygen and nutrients while you’re working up a sweat.
Cortisol helps ensure your muscles have adequate fuel when you exercise. It does this by mobilizing fat stores, and when glucose and glycogen supplies are low, by breaking down muscle tissue so amino acids can be converted to glucose by the liver, a process called gluconeogenesis. Cortisol is most active when you haven’t fueled your body properly before a workout and when you exercise for long periods of time. Cortisol’s main function is to make sure your muscles have enough glucose during periods of stress and exertion
The release of this menagerie of hormones during exercise, often referred to as the stress response, is beneficial since your muscles need adequate fuel and blood flow during exercise. The stress response is usually followed by short-term inflammation as immune cells are activated to help repair damaged muscle tissue. Once repair is complete, the inflammation settles down. In fact, as you’ll see, moderate amounts of exercise helps your body keep inflammation in check longer term.
The Anti-Inflammatory Effects of Exercise
What evidence is there that regular exercise reduces inflammation? A large study involving almost 14,000 adults showed those who exercised regularly experienced a drop in inflammatory markers including C-reactive protein, a marker for inflammation. Other lifestyle factors linked with higher C-reactive protein and inflammation include exposure to toxins, diets rich in processed food, obesity and stress. People who have inflammatory disorders, including forms of arthritis, also have higher C-reactive protein levels due to the higher levels of inflammation in their body.
Inflammation and inflammatory markers like C-reactive protein go up with age. So, inflammation increases as you get older and may partially explain why diseases like cancer, heart disease and type 2 diabetes become more common as you get older. Fortunately, there’s evidence that regular exercise may help reduce the age-related increase in inflammation.
How Does Exercise Reduce Inflammation?
As discussed, exercise hypes up your immune system short term as your body goes into “repair” mode.” So, short term, exercise actually enhances your body’s inflammatory response. But when you train regularly, your body adapts by becoming better able to keep inflammation in check.
Some studies show inflammatory markers rise for a short period of time after an intense workout but decrease when you make exercise a regular habit. In fact, studies show people who work out on a frequent basis usually have lower C-reactive protein levels than those who don’t. If you were to measure your C-reactive protein after an intense bout of exercise, it would probably be elevated, but if you keep exercising on a regular basis your C-reactive protein will be lower after a workout and at baseline.
In one study, researchers followed over 4,000 healthy men and women for a decade.
Those who worked out at a moderate intensity between 2 and 3 hours a week saw a 12% decrease in blood markers for inflammation.
What Happens if You Overtrain?
When you train too frequently or train at a high intensity without giving your body a chance to recover, the inflammation response becomes more sustained. In response to the stress of overtraining your body releases pro-inflammatory chemicals called cytokines. Rather than being a short-term response to training that’s self-limited, the inflammatory response becomes chronic.
This type of sustained inflammatory response is more likely to occur if you’re also eating a pro-inflammatory diet, restricting calories excessively, experiencing mental stress or not getting enough sleep. The effect of cumulative stress – not enough recovery time between exercise sessions, a poor diet and lack of sleep can lead to chronic inflammation that takes months to correct. Although exercise helps reduce inflammation in moderate amounts, exercise without adequate recovery time and nutritional support can have the opposite effect. An increase in inflammatory markers has been seen in people who are long distance runners and spend many hours a week running.
The Bottom Line?
Regular exercise lowers your risk for diseases related to chronic inflammation like heart disease and some forms of cancer but it’s important to give your body a chance to recover between exercise sessions. Listen to your body. If you’re sore and fatigued from a tough workout, do a lower intensity workout like a yoga session the next day. Don’t forget adaptations to exercise occur not when you’re working out but during the recovery period. Also, make sure you’re eating a balanced diet and enough calories to fuel your workouts.
References:
Idea World Fitness Convention. “Exercise and the Inflammation Process”
R and D Systems. “Cytokines and Overtraining”
Epidemiology. 2002 Sep;13(5):561-8.
Science Daily. “Fitness Reduces Inflammation, Study Suggests”
Circulation. “Physical Activity and Inflammatory Markers Over 10 Years: Follow-Up in Men and Women from the Whitehall II Cohort Study” (2012)
Prevention Magazine. “The Habit That Can Save Your Life”
Med Sci Sports Exerc. 2007 Oct;39(10):1714-9.
Eur J Clin Invest. 2008 Apr;38(4):276-9. doi: 10.1111/j.1365-2362.2008.01935.x.
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