The influence of exercise on your immune system depends on the intensity of your workout. Exercise can protect and enhance your immune system by improving antibody and natural killer responses. Low to moderate intensity aerobic exercise, such as walking 20 to 30 minutes a day, supports a healthy immune system. Athletes that train at high intensities may have a greater risk of developing upper respiratory tract infections, such as a soar throat.
Short-Term Moderate Exercise
Moderate exercise may positively affect your immune system for a short period after your workout. Each moderate exercise session enhances your immune system's surveillance. Lymphocytes are the primary cells involved with immune response and interferons are proteins with antiviral properties. Moderate exercises may increase interleukin-1, an immune system stimulant that increases lymphocyte activity. Interferon production also goes up during moderate exercise and may remain elevated for two hours after your workout.
Long-Term Moderate Exercise
The long-term effects of moderate exercise may reduce your risk of infection. People that exercise regularly may experience fewer colds. Chronic stress repeatedly activates your autonomic nervous system and diminishes your immune system's protection. Ongoing psychological stress may reduce your immune system's reactions to hormonal secretions that normally help fight the inflammatory response. Regular moderate exercise may improve your immune system by reducing your stress levels over the long term.
During Intense Exercise
Your body relies on carbohydrates for energy during intense bouts of physical activity. Fatigue results from depleting carbohydrate energy stores in your body. Lower carbohydrate availability during intense exercise triggers the release of stress hormones. Stress hormones negatively influence the production of immune cells. Free-radicals are associated with oxidative damage to your muscles, liver, blood and other body tissues. Free radical production increases during intense exercise and the number of free radicals may exceed the capacity of your defense systems.
After Intense Exercise
Strenuous and prolonged exercise or heavy training may depress your immunity for a short period of time after exercise. Strenuous exercise can reduce the activity of anti-viral cells, antibodies and reduce lymphocyte proliferation in your body. Your upper respiratory tract may not be able to clear pathogens effectively during strenuous exercise. Heavy exertion can blunt your immune system's ability to respond to a challenge by viruses. The negative effects on your immune system may last between three and 72 hours after prolonged and intensive exercise. During this "open window" you have a greater risk of viral and bacterial infections.
References
- Fitness: Research Digest
- Cleveland Clinic: Diet, Exercise, Stress and the Immune System
- Pub Med: Exercise, nutrition and immune function.
- UNM: Exploring the Mysteries of Exercise
- Personality Research: Effects of Stress and Psychological Disorders on the Immune System
- Time to Run: Exercise and the Immune system
