Neuroendocrine responses of type A individuals to exercise.

Ten Type A and 10 Type B individuals exercised for 20 minutes on a bicycle ergometer at 40%, 60%, and 80% of maximal capacity to determine if differences in neuroendocrine reactivity exist. Pre-exercise plasma concentrations of beta-endorphin and epinephrine were similar for Type As and Type Bs. Pre-exercise plasma levels of norepinephrine tended to be higher for the Type As (p less than 0.07). Post-exercise plasma epinephrine concentrations were similar for As and Bs for all trials. The 40% and 60% trials resulted in no differences in post-exercise norepinephrine and beta-endorphin levels for the Type As and Bs. Conversely, the 80% trials resulted in significantly greater norepinephrine and beta-endorphin concentrations for the Type As (p less than 0.05). Plasma serotonin levels at rest and during exercise were always lower for the Type As (p less than 0.05). These results suggest that our Type As had a greater neuroendocrine response to high-intensity exercise than our Type Bs. The greater reactivity and analgesia may allow the Type A person to suppress feelings of fatigue, thus enduring higher levels of exertion for longer periods of time.