I know that there are several things which result in an increase of cortisol release, such as:
One influence is that cortisol will increase your insulin level which on the other hand will store sugar to fat (easy spoken). What I also heard is that cortisol will reduce your muscle gains, is that true and how does that happen?
Cortisol is actually released in a diurnal rhythm with a spike when you wake up, and tapering off during the day until the time you go to sleep where it is at its lowest. Cortisol levels are also proportional to the intensity of the training as well as length.
Elevated cortisol levels is linked to protein synthesis. A widely cited report is this one, which states that protein synthesis was impaired by 5-20% with higher (the highest is really high) cortisol levels. Elevated cortisol levels is also linked to gluconeogenesis (the conversion of protein to glucose). So by that rational an elevated level cortisol can not only reduce tissue growth but also break down tissue, as in cushing's syndrome.
