Hypothalamic-pituitary-adrenal responses to short-duration high-intensity cycle exercise.
beta-Endorphin (beta-EP), adrenocorticotropin (ACTH), and cortisol plasma concentrations were examined before and after maximal exercise at four intensities [36, 55, 73, and 100% of maximal leg power (MLP)] by means of a computerized cycle ergometer. All intensities were greater than those eliciting peak O2 uptake for the individual subjects. Blood samples were collected at rest, immediately after exercise, and at 5 and 15 min postexercise. Significant (P less than 0.05) increases were observed at 36% MLP for beta-EP and ACTH immediately after exercise and at 5 and 15 min postexercise. Plasma cortisol increased at 36% MLP at 15 min postexercise. Blood lactate significantly increased at all postexercise collection points for exercise intensities of 36, 55, and 73% MLP and at 5 min postexercise for 100% MLP. beta-EP concentrations at 36% MLP were significantly correlated (r = 0.75) with capillary density (mm-2), and cortisol concentrations at 36% MLP were significantly correlated (r = 0.89) with percentage of type II muscle fibers. No other significant relationships were observed. These data show that brief, high-intensity exercise up to maximal power production results in a nonlinear response pattern in peripheral blood hormone concentrations. Furthermore, blood lactate levels do not appear to be related to hypothalamic-pituitary-adrenal hormone plasma concentrations at high exercise intensities.
Kraemer
W J
WJ
Exercise Physiology Division, US Army Research Institute of Environmental Medicine, Natick 01760-5007.
Patton
J F
JF
Knuttgen
H G
HG
Marchitelli
L J
LJ
Cruthirds
C
C
Damokosh
A
A
Harman
E
E
Frykman
P
P
Dziados
J E
JE
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D001642:Bicycling; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D007773:Lactates / Q000097:blood; D008297:Male; D005082:Physical Exertion; D010913:Pituitary-Adrenal System / Q000502:physiology*; D010953:Plasma Volume; D013997:Time Factors; D001615:beta-Endorphin / Q000097:blood
D007773:Lactates; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone