Journal of Applied Physiology, Vol 77, Issue 1 223-230, Copyright © 1994 by American Physiological Society
Lactate and acid-base exchange during brief intense contractions of skeletal muscle in situ
W. F. Brechue and W. N. Stainsby
Department of Physiology, University of Florida Health Science Center, Gainesville 32610.
Our goal was to design a stimulation-contraction paradigm using an isolated
in situ dog gastrocnemius muscle preparation that would provide an
experimental model for brief intense intermittent (IC) exercise in humans.
Second, acid-base and ion exchanges across the muscle were investigated
using four 30-s bouts of isotonic tetanic contractions (2 s-1, 100-ms
train, 50 impulses/s) with 4 min of rest between bouts. During the bouts,
peak power output (W) was 18.2 mW/g in the first bout; it declined by 4.4%
by the fourth bout and by 12-16% in each bout. Compared with repetitive
continuous contractions (CC) at maximal O2 uptake (VO2), W was greater and
VO2 (approximately 3.5 mumol.g-1.min-1) and CO2 production (approximately
4.5 mumol.g-1.min-1) were less with IC. Venous-arterial (v-a) differences
and lactate output peaked immediately after each bout and were not
different from the values reported for CC at maximal VO2. Thus, with IC,
VO2/W was lower and the CO2 production/VO2 and lactate output/VO2 ratios
were greater than those seen with CC. These differences suggest that this
stimulation-contraction paradigm may be an appropriate model for brief
intense exercise. The v-a [H+] difference was a direct result of the v-a
PCO2 difference. The venous strong ion difference was always greater than
or equal to the arterial strong ion difference because the v-a [Cl-]
difference was opposite and greater than the v-a lactate concentration
difference, whereas the v-a [Na+] and [K+] differences were small.(ABSTRACT
TRUNCATED AT 250 WORDS)
