Why Exercise Makes You Less Anxious

“The stress-reducing changes wrought by exercise on the brain don’t happen overnight, however, as virtually every researcher agrees. In the University of Colorado experiments, for instance, rats that ran for only three weeks did not show much reduction in stress-induced anxiety, but those that ran for at least six weeks did. ‘Something happened between three and six weeks,’ says Benjamin Greenwood, Ph.D., a research associate in the Department of Integrative Physiology at the University of Colorado, who helped conduct the experiments. ‘It’s not clear how that translates’ into an exercise prescription for humans. We may require...

http://well.blogs.nytimes.com/2009/11/18/phys-ed-why-exercise-makes-you-less-anxious/