The effects of hypercapnia on the metabolic response to steady-state exercise

Publisher Website
Google Scholar
Abstract
Studies on isolated muscle and resting man have demonstrated that altering CO2 stores influences intracellular lactate production and/or tissue lactate release. In the present project, subjects (N = 6) performed steady-state exercise for 30 min while inspiring 0, 2, 4, or 6% CO2 and 21% O2. They were tested on eight occasions, four at 50% and four at 65% V̇o2max. Arterialized venous blood Pco2 increased in proportion to F1CO2 (P < 0.05). Blood pH had a similar but inverse relationship, decreasing from 7.371 to 7.233 (P < 0.05). The V1 increased directly with PCO2(P < 0.05), but no differences were found for V̇o2 or V̇co2 The R decreased in proportion to Pco2 (P < 0.05) at both exercise intensities. Blood lactate was reduced (P < 0.05) with CO2. At 65% V̇o2max lactate had an inverse linear relationship with blood Pco2 (P < 0.05). The mean lactate decreased 43% from 3.88 mM·1−1 with 0% CO2 to 2.22 mM·1−1 with 6% CO2. The R shift suggests that carbohydrate metabolism may have been inhibited and lipid metabolism enhanced.