People with an intense fear of the nausea, racing heart, dizziness, stomachaches and shortness of breath that accompany panic — known as "high anxiety sensitivity" — reacted with less anxiety to a panic-inducing stressor if they had been engaging in high levels of physical activity, said researchers at Southern Methodist University in Dallas and the University of Vermont in Burlington.
The research is worth looking at, but the methodology raises questions about the practicality of using this in treatment. Often, people with anxiety are encouraged to use physical activity as a way of reducing the anxiety; this research raises the question (but does not answer it) of whether or not the level of activity matters. In other words, do those who exercise more intensely suffer less from anxiety than those who exercise moderately? That is a question worth answering, I believe.
Here is the article.