Exercise and Cortisol

"If you want to be thin and unhealthy, run lots and lots and lots of slow miles so that your body fills up with cortisol, eating away fat and muscle." – Karl King

Jenn demonstrates the athletic and physical benefits of low cortisol (and kick-ass hair!) Cortisol is a hormone that plays a critical role within the body.  It is released in response to stress, which is why it has been referred to as “the stress hormone”.  We need it and use it every day of our lives, but when we have elevated levels of cortisol for prolonged periods of time, things can go awry.

Effect of Exercise on Cortisol - More is NOT Better

Within the exercise setting, excessive cortisol can lead to immunosuppression and overtraining syndrome.  If you exercise for more than 60 minutes, even at a low intensity, the body's glycogen stores (fuel) will decrease significantly and the increased stress will cause more cortisol release.¹ The high levels of cortisol after prolonged exercise in the body has a catabolic (wasting) effect on lean body mass.

When concerned with prolonged aerobic exercise, cortisol clearly functions to preserve body carbohydrate stores.  Cortisol increases alternate fuels for muscle, such as fatty acids and amino acids (from muscle amino acid stores and protein catabolism), impairs glucose entry into skeletal muscle, and supplies the fuels (amino acids) for the liver to increase glucose production.²  

What this means is that as we continue to exercise, instead of our body using carbohydrate stores to fuel activity, cortisol retains them and forces the breakdown of muscle tissue to provide the energy that is in demand.

Other Negative Effects of Cortisol

Excessive cortisol release leads to a lowered testosterone:cortisol ratio, a prime marker of anabolic status and the ability to recover from exercise and build muscle. Further, as cortisol continues to increase, chances for muscle atrophy (muscle breakdown), impaired immunity, vitamin depletion and increased blood pressure increase as well.

Key Points to Take Away From This

- Putting in hours and hours of "cardio" each week is detrimental to your training, your health, and your recovery as an athlete.

- Those long exercise sessions (distance running, etc) lead to breakdown of muscle tissue due to high levels of cortisol.

- Less is more.

- Train hard, train smart, keep it under an hour.

1) http://www.livestrong.com/article/86687-exercise-cortisol-levels/#ixzz1HNF1lVUa

2) http://www.unm.edu/~lkravitz/Article%20folder/cortisol.html