Lactate production under fully aerobic conditions: the lactate shuttle during rest and exercise.
Level 5 - mechanism / opinion, no new human data
Narrative review and theoretical framework based on animal and human physiological data
What was done
The author synthesized evidence from human and animal metabolic models (including postabsorptive and postprandial humans, in situ canine gracilis muscle, in vivo myocardium, and human brain) to evaluate lactate production, oxidation, and turnover under fully oxygenated conditions.
What was found
In resting postabsorptive humans, 25% to 50% of the total carbohydrate combusted passes through the lactate pool. During sustained submaximal exercise, rates of lactate production and oxidation increase compared to rest, but increase relatively less than oxygen consumption, leading to a decreased lactate production index. Glycolysis and lactate production also occurred under aerobic conditions in contracting canine gracilis muscle, healthy myocardium, and human brain.
Why it matters
This review establishes the "lactate shuttle" hypothesis, redefining lactate from a waste product of oxygen-deprived tissue to a major metabolic intermediate that redistributes carbon across tissues for oxidation and gluconeogenesis.
Limits
The abstract describes a narrative review without systematic search methods, pooled statistics, sample sizes, or confidence intervals. The synthesis relies partly on animal tissues and does not provide quantified effect estimates for all cited tissue preparations.
Cited by
- supports Skeletal muscle produces lactate continuously under fully aerobic conditions.