title: Plasma ammonia concentrations and the slow component of oxygen uptake kinetics during cycle ergometry.
abstract: The purposes of this study were to 1) compare the patterns of responses for plasma ammonia concentration ([NH3]) during moderate- vs. heavy-intensity cycle ergometry, and 2) examine the relationship between the V O2 slow component (V O 2SC) and plasma [NH3]. Thirteen healthy, untrained men (mean +/- SEM age = 24.8 +/- 0.6 years) performed a total of eight constant power output exercises (7 minutes in duration) at two different intensities (moderate, 60% gas exchange threshold [GET] = 60% of the gas exchange threshold; and heavy, Delta 50% = 50% of the difference between GET and V O2 max). Blood was collected from an antecubital vein before the exercise, during the last 3 minutes of the 6-minute warm-up, and during each minute of the 7-minute constant power output workbout. The time course of changes in plasma [NH3] and V O2 during the two constant power output exercise intensities were assessed separately using 2 (intensity) x 7 (time) repeated-measures analyses of variance. For 60% GET, there were no significant differences in the mean normalized plasma [NH3] during the 7-minute workbout. For Delta 50%, there was a significant increase in the mean normalized plasma [NH3] during the 7-minute workbout. These findings suggest a potential relationship between exercise-induced hyperammonemia and the V O 2SC during heavy-intensity exercise.
authors.affiliation: Division of Physiology, University of California-San Diego School of Medicine, La Jolla, California, USA. mhmalek@ucsd.edu
authors.forename: Moh H
authors.initials: MH
authors.lastname: Malek
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Housh
authors.forename: Larry D
authors.initials: LD
authors.lastname: Crouch
authors.forename: Glen O
authors.initials: GO
authors.lastname: Johnson
authors.forename: C Russell
authors.initials: CR
authors.lastname: Hendrix
authors.forename: Travis W
authors.initials: TW
authors.lastname: Beck
authors.forename: Michelle
authors.initials: M
authors.lastname: Mielke
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Schmidt
authors.forename: Dona J
authors.initials: DJ
authors.lastname: Housh
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D007700:Kinetics; D008297:Male; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology
chemical_list: D000641:Ammonia