Sdr. Galloway et Rj. Maughan, THE EFFECTS OF INDUCED ALKALOSIS ON THE METABOLIC RESPONSE TO PROLONGED EXERCISE IN HUMANS, European journal of applied physiology and occupational physiology, 74(4), 1996, pp. 384-389
To examine the effects of alkalosis on the metabolic response to prolo
nged exercise, seven healthy males cycled for 1 h at approximately 70%
of maximum oxygen uptake on two occasions, 1-week apart. Starting 3 i
t prior to exercise, subjects consumed either CaCO3 (placebo) or NaHCO
3 (0.3 g . kg(-1) body mass) over a 2-h period. Arterialised-venous bl
ood samples were drawn before and during exercise for the determinatio
n of acid-base status and blood metabolites (lactate, glucose, glycero
l and plasma free fatty acids). Expired gas was collected during exerc
ise for determination of oxygen uptake (VO2) and respiratory exchange
ratio to estimate fuel oxidation rates. Ratings of perceived exertion
(RPE) and heart rates were also recorded. A significant (P < 0.01) alk
alosis was observed at all limes following bicarbonate ingestion. Bloo
d lactate was significantly (P < 0.05) higher at all sample times thro
ughout exercise following bicarbonate ingestion. Blood lactate concent
ration [mean (SEM)] reached peak values of 2.90 (0.16) and 4.24 (0.45)
mmol . l(-1) following 20 min of exercise following placebo and bicar
bonate, respectively. No differences between treatments were noted at
ally time for the other metabolites. VO2 and RPE were significantly hi
gher (P < 0.01) with the bicarbonate trial. At a constant power output
increases in VO2 are generally associated with increases in fat oxida
tion, however, no evidence for an altered fuel oxidation was obtained
in the present study. The differences in blood lactate indicate that i
nduced alkalosis increased lactate efflux from muscle, but it cannot b
e confirmed whether this represents an increased rate of glycolysis wi
thin the muscle.