Maximal rate of blood lactate accumulation during exercise at
altitude in humans.
Grassi, Bruno, Guido Ferretti, Bengt Kayser, Mauro Marzorati, Angelo
Colombini, Claudio Marconi, and Paolo Cerretelli.
Section of Physiology, Istituto di Tecnologie Biomediche Avanzate,
Consiglio Nazionale delle Ricerche, 20131 Milano, Italy;
D[acute]epartement de Physiologie, Centre M[acute]edical
Universitaire, 1211 Gen[grave]eve 4, Switzerland.
APStracts 2:0073A, 1995.
The lower peak lactate accumulation in blood ([Lab]p) at altitude may
be associated with a reduced maximal glycolytic flux. Upon certain
assumptions the latter can be indirectly evaluated in vivo, during
short supramaximal exercises, by measuring the maximal rate of
lactate accumulation in blood ([Lab]max). D[Lab]max was determined on
6 Caucasians at sea level (SL1), after about 1 (ALT1) and 4 weeks
(ALT2) of a 35-day sojourn at 5050 m, and 1 week after return to sea
level (SL2). The subjects performed exercises of increasing duration
(5, 15, 25, 35, 45 s or until exhaustion) on a bicycle ergometer at
loads = 200% of the individual wmax. The latter was previously
determined in each condition as the greatest work rate that could be
sustained for 2-4 min during an incremental exercise. Net [Lab]
accumulation (D[Lab]) was measured after each exercise bout. D[Lab]
resulted linearly related to exercise duration (t). The slopes of the
individual D[Lab] vs. t lines were taken as D[Lab]max. Exhaustion
times were about 30-45 s in all conditions. Peak [Lab] during
recovery after the exhaustive load, i.e. [Lab]p (in mM), was higher
at SL1 (10.22 +/- 1.09; x +/- SD) than at ALT1 (5.08 +/- 0.82), ALT2
(8.13 +/- 2.67) and SL2 (8.18 +/- 1.43). D[Lab]max was lower at ALT1
(0.09 +/- 0.02) and at ALT2 (0.17 +/- 0.05) than at SL1 (0.25 +/-
0.05) and SL2 (0.23 +/- 0.06). Both [Lab]p and D[Lab]max increased
during acclimatization. It is concluded that the lower [Lab]p at
altitude was associated with a reduced D[Lab]max. In the presence of
a presumably normal maximal potential activity of glycolytic enzymes,
as described by several authors, the reduced D[Lab]max is indicative
of an $QUOTupstream$QUOT inhibition of glycolysis at altitude.
Received 18 May 1994; accepted in final form 21 February 1995.
APS Manuscript Number A484-2.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 7 March 1995.