It’s no secret that exercise has positive health benefits. Regular physical activity improves body composition, builds strength and endurance and lowers the risk for health problems including heart disease, type 2 diabetes, obesity and some forms of cancer. Research shows people who work out most days of the week have a lower risk of dying prematurely. Who wouldn’t want those health benefits?

With exercise offering so many advantages, you might wonder what effect it has on your immune system. That’s an important question since a healthy immune system is key to protecting your body against foreign invaders including bacteria, viruses, fungi and cancer. Your immune system is like a dedicated police force that’s always on duty, shielding your body against unwanted attacks.

How Exercise Affects Immune Function

Does exercise improve immune function? It depends on the amount of exercise you do and how intensely you work out. Most studies show moderate-intensity exercise, like brisk walking, slow jogging or cycling at a leisurely pace, enhances immune activity and makes it less likely you’ll catch the latest upper respiratory virus going around. Research shows people who do recreational exercise for 30 minutes a day enjoy a lower incidence of colds.

But what happens when you ramp up the intensity of your workouts? More people are doing high-intensity workouts, like Cross Fit style, these days. Working out at a high-intensity, especially if you exercise for long periods of time may increase your risk for getting sick by suppressing immune function, especially if you don’t give your body time to recover.

Research shows high-intensity and prolonged workouts suppresses activity of several components of the immune system including white blood cells called neutrophils for periods of time ranging from several hours up to 72 hours. This is sometimes referred to as the “window period,” a period of time when you’re at higher risk for infection after a workout.

What better example of prolonged exercise than a marathon? Long distance runners and cyclists, especially marathon runners, are at higher risk for upper respiratory infections, especially after a race. One study found that 13% of the runners who took part in a marathon in Los Angeles came down with a cold the week after the event.

Intense Exercise Stresses the Immune System

How does intense or prolonged exercise suppress immune function? High-intensity exercise and prolonged endurance exercise like running where you work out for an hour or more stimulates production of a hormone called cortisol. This hormone, often called the “stress hormone,” is produced by the adrenal cortex, a gland that lies just above your kidneys. Cortisol is released in response to other types of stress too including extreme dieting or calorie restriction, lack of sleep and physical and mental stress. One of the negative effects of cortisol is it suppresses immune function. Any form of stress can reduce immune function for variable periods of time and cortisol plays a role.

Athletes and recreational fitness buffs that over train are also at higher risk for colds and other illnesses. Overtraining becomes a problem when you train hard without giving your body time to recover between workouts. Some studies have linked overtraining and intense exercise training with changes in neutrophils, natural killer cells and other components of the immune system.

What Does This Mean?

High-intensity and prolonged exercise seems to increase the risk for upper respiratory infections, including colds – but don’t stop exercising. Exercise has too many health benefits. If you work out frequently or do intense workouts, give your body time to rest between sessions. Don’t skimp on sleep. Lack of sleep and recovery time can suppress your immune system. Finally, give your body the immune support it needs through good nutrition and supplements.

Professional athletes are especially at risk because of the schedule they frequently find themselves trying to keep up with.  For example, playing a double header or extra innings game late into the night then immediately get on an airplane to travel across the country, with different time zones, to play a game the following day, with very little sleep, will play havoc with their immune system.  This will create immune suppression and put them at great risk to catch colds or flu, with muscle soreness, and place them in great jeopardy of missing the next important game or two, because of sickness and malaise.

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-By Alternative Health Concepts


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