Effects of endurance training on lactate removal by oxidation and gluconeogenesis during exercise

Publisher Website
Google Scholar
Abstract
This report describes the effects of 9 weeks of endurance-training on the relative rates of lactate removal via oxidation and gluconeogenesis in humans. Before and after training, eight subjects performed incremental (60 W plus 40 W every 6 min) exercise tests, while14C-lactate was infused into one forearm vein and “arterialized” venous blood was sampled from the other forearm. During the trial, the volume of expired14CO2 and circulating14C-lactate and14C-glucose specific radioactivities were measured. Such measurements revealed that training increased the estimated oxidation of equivalent venous blood lactate concentrations [VLa] of greater than 1.6 mmol/l. These increases in lactate oxidation were more than would be predicted from the approximately 40% higher O2 uptake values at any [VLa] after training. At a [VLa] of 6 mmol/l, rates of lactate oxidation were increased by some 100% following training, from 105±12 to 208±33 μmol/min/kg (PP<0.01). Thus, unlike in rats, human endurance-training does not increase gluconeogenesis. In the final stages of progressive exercise after training, more than 80% of lactate was oxidised and accounted for approximately 45% of overall carbohydrate oxidation.