A recent New York Times article by Gretchen Reynolds asked and answered the question: Does exercise boost immunity? The answer may surprise some, and its lessons extend well beyond the world of working out.

Reynolds reported on multiple studies, each showing the same thing. A little bit of exercise boosts immunity and can even help you recover from a cold or flu. But don't lace up your running shoes just yet-intense exercise does the opposite. Immediately after a strenuous workout-defined by many researchers as exercising with serious effort for over an hour-your immune system is suppressed. The effect can last for days and is intensified by training without adequate rest. In one animal study from the University of Illinois, intense exercise dramatically increased mortality rates from the flu–something that makes exercise addicts like myself a little nervous in flu season.

The NYT article does a great job discussing what's going on at the level of immunoglobulins and T-1 helper cells. What really caught my attention, though, was the simple bell-shaped curve: being sedentary is bad for your health, moderate exercise is good for your health, extreme exercise is....bad for your health.

Exercise is a form of stress that asks the body to adapt. That adaptation costs real energy and physical resources. These resources have to be borrowed from somewhere-say, the immune system. When the body recovers, it's stronger. But when you don't get enough rest and recovery, or when you are immediately exposed to another stressor (say, a flu virus or a fight with your spouse), you are too vulnerable to mount a protective response. 

Exercise is just one example of stress that we could apply this curve to. A little bit of challenge or change is good, but too much too soon (or without a break) weakens you.

At a time when people are paying $10K to suffer extreme stress to the body–and some dying–in the name of personal transformation, it's even more important to remember that extreme anything is more likely to harm than help. No matter how much you believe in the power of mind over body, pushing the body to its breaking point is a foolish strategy for staying sane and healthy.

We're so used to looking for the next level, the next mountain to climb, the way to make things harder. But sometimes less is more. Is there anything in your life that would be more rewarding or healthy if you lowered the intensity?

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