title: Impact of acute exercise intensity on pulsatile growth hormone release in men.
abstract: To investigate the effects of exercise intensity on growth hormone (GH) release, 10 male subjects were tested on 6 randomly ordered occasions [1 control condition (C), 5 exercise conditions (Ex)]. Serum GH concentrations were measured in samples obtained at 10-min intervals between 0700 and 0900 (baseline) and 0900 and 1300 (exercise+ recovery). Integrated GH concentrations (IGHC) were calculated by trapezoidal reconstruction. During Ex subjects exercised for 30 min (0900-0930) at one of the following intensities [normalized to the lactate threshold (LT)]: 25 and 75% of the difference between LT and rest (0.25LT and 0.75LT, respectively), at LT, and at 25 and 75% of the difference between LT and peak (1.25LT and 1.75LT, respectively). No differences were observed among conditions for baseline IGHC. Exercise+recovery IGHC (mean +/- SE: C = 250 +/- 60; 0.25LT = 203 +/- 69; 0.75LT = 448 +/- 125; LT = 452 +/- 119; 1.25LT = 512 +/- 121; 1.75LT = 713 +/- 115 microg x l(-1) x min(-1)) increased linearly with increasing exercise intensity (P < 0.05). Deconvolution analysis revealed that increasing exercise intensity resulted in a linear increase in the mass of GH secreted per pulse and GH production rate [production rate increased from 16. 5 +/- 4.5 (C) to 32.1 +/- 5.2 microg x distribution volume(-1) x min(-1) (1.75LT), P < 0.05], with no changes in GH pulse frequency or half-life of elimination. We conclude that the GH secretory response to exercise is related to exercise intensity in a linear dose-response pattern in young men.
authors.affiliation: Department of Human Services, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Pritzlaff
authors.forename: L
authors.initials: L
authors.lastname: Wideman
authors.forename: J Y
authors.initials: JY
authors.lastname: Weltman
authors.forename: R D
authors.initials: RD
authors.lastname: Abbott
authors.forename: M E
authors.initials: ME
authors.lastname: Gutgesell
authors.forename: M L
authors.initials: ML
authors.lastname: Hartman
authors.forename: J D
authors.initials: JD
authors.lastname: Veldhuis
authors.forename: A
authors.initials: A
authors.lastname: Weltman
mesh_terms: D000328:Adult; D015992:Body Mass Index; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D012119:Respiration; D013147:Spirometry; D013997:Time Factors
chemical_list: D019382:Human Growth Hormone; D019344:Lactic Acid