THE EFFECTS OF INDUCED ALKALOSIS ON THE METABOLIC RESPONSE TO PROLONGED EXERCISE IN HUMANS

Citation
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
Citations number
30
Categorie Soggetti
Physiology
ISSN journal
03015548
Volume
74
Issue
4
Year of publication
1996
Pages
384 - 389
Database
ISI
SICI code
0301-5548(1996)74:4<384:TEOIAO>2.0.ZU;2-0
Abstract
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.