Exercise and recovery responses of adrenal medullary neurohormones to heavy resistance exercise.Med. Sci. Sports Exerc.,Vol. 31, No. 4, pp. 554-559, 1999.Purpose:The purpose of this study was to examine the effect of dynamic resistance exercise on the response patterns of adrenal medullary neurohormones in strength-trained men.Methods:Ten strength-trained men (21.7 ± 0.58 yr) gave informed consent and performed two resistance exercise protocols, high force and high power, of equal total work in a randomized order separated by 1 wk. Blood samples were obtained pre-exercise (baseline), 0 (R-0), 15 (R-15), and 240 (R-240) min postexercise and under resting control conditions for each time point.Results:There were no significant differences in control concentrations for each time point and no difference in pre-exercise values between the two resistance exercise protocols for plasma lactate, epinephrine, plasma peptide F (P-F), or norepinephrine (NE). Plasma lactate significantly (P≤ 0.05) increased from baseline for both protocols; however, concentrations were higher in response to the high force protocol. Plasma epinephrine was significantly increased from baseline at R-0 and returned to baseline at R-15 for both protocols. In contrast, plasma P-F was significantly decreased at R-0 from baseline; however, at R-240 P-F had significantly increased to >80% baseline for both protocols.Conclusions:These results indicate that the adrenal medulla was activated in response to the acute stress of both types of heavy resistance exercise. Furthermore, during longer recovery periods, the adrenal medulla was also active above baseline conditions as increased concentrations of proenkephalin fragments (i.e., P-F) were detected in the circulation.