Runners World: Why Trail Running is Good for You, http://www.runnersworld.com/trail-running-training/why-trail-running-is-good-for-you
Boston: Is Running the Boston Marathon Good for You, http://www.boston.com/lifestyle/health/mysteries/2013/04/is_running_the_boston_marathon_good_for_you.html
MensHealth: Are You Running Yourself to Death, http://www.boston.com/lifestyle/health/mysteries/2013/04/is_running_the_boston_marathon_good_for_you.html
NHS: Running and Walking Both Good for Your heart, http://www.nhs.uk/news/2013/04April/Pages/running-walking-good-for-heart.aspx
Harvard School of Public Health: The Benefits of Physical Activity, http://www.hsph.harvard.edu/nutritionsource/staying-active-full-story/