The effect of graded epinephrine infusion on the blood lactate
response to exercise.
Turner, Michael J., Edward T. Howley, Hirofumi Tanaka, Muhammad
Ashraf, David R. Bassett, Jr, Daniel J. Keefer.
Exercise Science, The University of Tennessee, Knoxville,
Knoxville, TN 37996-2700
APStracts 2:0208A, 1995.
In an attempt to determine whether the lactate threshold is the result
of a sudden increase in plasma epinephrine (Epi), eight healthy,
college-aged males (22.4 +/- 0.4 yrs) were recruited to perform three
cycle ergometer exercise tests. Each subject performed a graded
exercise test (GXT) to determine the lactate (LT), epinephrine
(EpiT), and norepinephrine (NepiT) thresholds (64.6 +/- 2.4%, 62.5
+/- 2.4% and 60.8 +/- 4.3% o (.,V)O2peak, respectively). Each subject
also completed, in random order, two 30-minute submaximal (20% o
(.,V)O2peak below LT) exercise tests. During one test, graded Epi
infusions were carried out at rates of 0.02 [mu]g.kg-1.min-1 to 0.12
[mu]g.kg-1.min-1; the other served as a control test. Infusion
resulted in plasma Epi concentrations similar to those observed
during the GXT. The increase in blood lactate with Epi infusion was
significantly greater than during the control test (3.0 +/- 0.3 vs.
1.4 +/- 0.1 mmol/L at minute 30), but did not approach levels
exhibited during the GXT. We suggest an interaction of the increasing
plasma Epi with other factors may be responsible for the sudden
increase in blood lactate during graded exercise.
Received 14 November 1994; accepted in final form 17 May 1995.
APS Manuscript Number A1166-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.