Behavioral correlates of sympathoadrenal reactivity: the toughness model.

Research with humans is reviewed showing that increased levels of urinary epinephrine (EPI) and norepinephrine (NE) from samples taken following mental challenge/stress situations are associated with better performance in those situations and with emotional stability. Another research tradition with humans and animals shows that various training protocols lead to increased peripheral and central catecholamine capacities. Those training protocols include continuous exposure to cold, periodic exposure to some intermittent stressors such as foot or tail shock (with intervening rest periods), or programs of aerobic exercise. While increasing catecholamine capacities, those procedures also result in lower base rates of the catecholamines and with the delay of pituitary-adrenal-cortical responses in challenge/stress contexts. That physiological pattern of "toughness" leads to improved performance in challenge/stress situations, increased tolerance of stressors (i.e., reduced behavioral suppression or depression), emotional stability, and immune system enhancement. The special conditions are discussed that are required for demonstrating increased catecholamine capacities rather than the attenuation of arousal associated with increased muscular and neuroendocrine efficiency. Finally, the role played by toughness in reducing anxiety while increasing energy in challenge/stress situations is discussed.