title: Effects of different heavy-resistance exercise protocols on plasma beta-endorphin concentrations.
abstract: To examine the changes of plasma beta-endorphin (beta-EP) concentrations in response to various heavy-resistance exercise protocols, eight healthy male subjects randomly performed each of six heavy-resistance exercise protocols, which consisted of identically ordered exercises carefully designed to control for the repetition maximum (RM) resistance (5 vs. 10 RM), rest period length (1 vs. 3 min), and total work (joules). Plasma beta-EP, ammonia, whole blood lactate and serum cortisol, creatine kinase, urea, and creatinine were determined preexercise, midexercise, immediately postexercise, and at various time points after the exercise session (5 min-48 h), depending on the specific blood variable examined. Only the high total work-exercise protocol [1 min rest, 10 RM load (H10/1)] demonstrated significant increases in plasma beta-EP and serum cortisol at midexercise and 0, 5, and 15 min postexercise. Increases in lactate were observed after all protocols, but the largest increases were observed after the H10/1 protocol. Within the H10/1 protocol, lactate concentrations were correlated (r = 0.82, P < 0.05) with plasma beta-EP concentrations. Cortisol increases were significantly correlated (r = 0.84) with 24-h peak creatine kinase values. The primary finding of this investigation was that beta-EP responds differently to various heavy-resistance exercise protocols. In heavy-resistance exercise, it appears that the duration of the force production and the length of the rest periods between sets are key exercise variables that influence increases in plasma beta-EP and serum cortisol concentrations. Furthermore the H10/1 protocol's significant challenge to the acid-base status of the blood, due to marked increases in whole blood lactate, may be associated with mechanisms modulating peripheral blood concentrations of beta-EP and cortisol.
authors.affiliation: US Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760-5007.
authors.forename: W J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: J E
authors.initials: JE
authors.lastname: Dziados
authors.forename: L J
authors.initials: LJ
authors.lastname: Marchitelli
authors.forename: S E
authors.initials: SE
authors.lastname: Gordon
authors.forename: E A
authors.initials: EA
authors.lastname: Harman
authors.forename: R
authors.initials: R
authors.lastname: Mello
authors.forename: S J
authors.initials: SJ
authors.lastname: Fleck
authors.forename: P N
authors.initials: PN
authors.lastname: Frykman
authors.forename: N T
authors.initials: NT
authors.lastname: Triplett
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood; D000693:Anaerobiosis / Q000502:physiology; D003402:Creatine Kinase / Q000097:blood; D003404:Creatinine / Q000097:blood; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007773:Lactates / Q000097:blood; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D014508:Urea / Q000097:blood; D014891:Weight Lifting; D001615:beta-Endorphin / Q000097:blood*
chemical_list: D007773:Lactates; D001615:beta-Endorphin; D000641:Ammonia; D014508:Urea; D003404:Creatinine; D003402:Creatine Kinase; D006854:Hydrocortisone