All hormones are directly correlated with effort and inversely correlated with excess volume! Cortisol is directly correlated with volume, and GH and Testosterone are both inversely correlated with volume.Overtraining( excess volume) reduces the pituitary output of GH in addition to inversely affecting testosterone , insulin and cortisol.(Urhausen A, Gabriel H,Kinderman .Blood Hormones as Markers of Training Stress and Overtraining.Sports Med 1995;20:251) There are certainly other factors that would affect the production of these hormones but the principles here remain the same .It's simplicity is whats appealing, and as for generalization, science backs it up quite well! George Carvajal