When you're trying to get bigger, you want the highest possible levels of anabolic hormones and lower levels of catabolic hormones such as glucagon. (bodybuilding-wizard.com)
Cortisol is a powerful catabolic hormone which is released after about 45 minutes of intense exercise. (howmuchprotein.com)
Another aspect of intense exercise is muscle damage that results from mechanical stress to your muscle fibers and catabolic hormones released in response to exercise. (strengthtrainingendeavors.com)