Spark: The Revolutionary New Science of Exercise and the Brain

by John J. Ratey

In smokers, just five minutes of intense exercise can be beneficial. Nicotine is an oddball among addictive substances as it works as a stimulant and a relaxant at the same time. Exercise fights the urge to smoke because in addition to smoothly increasing dopamine it also lowers anxiety, tension, and stress levels—the physical irritability that makes people so grouchy when they’re trying to quit. Exercise can fend off cravings for fifty minutes and double or triple the interval to the next cigarette. And the fact that exercise sharpens thinking comes into play here, because one of the withdrawal symptoms of nicotine is impaired focus. As evidence of this, one study found that there are more workplace accidents during the Great American Smokeout than on any other day of the year. Many of my ADHD patients use cigarettes to help them focus when they have to write or push through a challenging task, and without the nicotine they feel lost.