I was talking to a friend of mine last week and he mentioned to me that he had recently heard a podcast where the speaker argued that aerobic exercise increased the risk of neurodegenerative diseases due to the elevated cortisol levels. If I remember my friend’s comments correctly, he said that the podcast speaker noted that rowers and cross-country skiers have a high prevalence of Parkinson’s and related disorders, whereas power athletes and martial artists showed little or no decline brain function.

Since its been known for some time that regular aerobic exercise increases new brain cell formation, I was skeptical about the ‘aerobic exercise - neurodegenerative diseases’ theory.

Confirming my feedback to my friend about the podcast, a study was just published in a top tier journal, The Journal of Applied Physiology http://www.ncbi.nlm.nih.gov/pubmed/21817111 . There is a great summary of the paper here: http://well.blogs.nytimes.com/2011/09/28/how-exercise-can-strengthen-the-brain/

Here is an excerpt, with quotes from two of the leading scientific minds of our time, Professors Mark Tarnopolsky and Mark Davis, who discuss the findings of the study that showed aerobic exercise increased mitochondria in the brain.

 “There is evidence” from other studies “that mitochondrial deficits in the brain may play a role in the development of neurodegenerative diseases,” including Alzheimer’s and Parkinson’s diseases, Dr. Davis says. Having a larger reservoir of mitochondria in your brain cells could provide some buffer against those conditions, he says.

Dr. Tarnopolsky agrees. “Epidemiological studies show that long-term runners have a lower risk of neurological disease,” he points out.

So, I think I will assign the comment that aerobic exercise leads to neurodegenerative diseases due to elevated cortisol levels to the bottom drawer of theories that have no basis in science and fact. It can now sit along side the similar theory that aerobic exercise makes you fat due to elevated cortisol levels. Let's hope that the maladies frequently ascribed to aerobic training are once and for all exposed by modern research as the nonsense that they really are.