Cardiovascular Fitness and Selected Adrenal Hormone Responses to Cognitive Stress

Individuals manifesting high maximal oxygen consumption (VO2max) have augmented adrenal responsivity to physical stress. We subjected 17 males representing a wide range of VO2max to cognitive stress and measured their forearm venous plasma epinephrine, norepinephrine, and cortisol responses. Six repeated blood samples were collected at resting, stress, and recovery intervals. Significant increases were observed for epinephrine (x + SD; rest, 50 + 30; stress, 81 + 77 pg/ml; p + 0.05) and norepinephrine (rest, 404 + 235; stress, 481 + 314 pg/ml; p + 0.05). Cortisol changes were not significant. A positive association (r = 0.54; p + 0.05) was observed between epinephrine and VO2max during the first collection of the stress period. An inverse association (r = -0.49; p + 0.05) was present between VO2max and norepinephrine. No significant correlations occurred with cortisol. These results indicate that enhanced cardiovascular fitness is characterized by augmented epinephrine responsivity to cognitive stress. This association exists in the presence of an inverse relationship between plasma free norepinephrine response and VO2max.