We’ve got another episode with Sergio going deep on the metabolism of lactate—and its underrate role as a signaling molecule and a preferential fuel source for many internal organs. In this episode of Science with Sergio, we review some of the highlights for performance-based athletes in George Brooks’s extensive 2018 review of lactate shuttle theory in Cell Metabolism: The Science and Translation of Lactate Shuttle Theory As we discussed in our previous Science with Sergio episode, lactate gets an unfair bad rap—being blamed for all kinds of things like muscle soreness and fatigue. Like most biological systems, it can be difficult to disentangle causation from correlation in the metabolism of lactate, and we attempt to do so in this episode. While this does get pretty deep, we try to offer explanations for some of the more technical concepts and jargon as we go. Check out the full conversation with Todd and Sergio for a technical perspective on what’s actually going on with lactate and lactic acid—as well as some wild speculation about how to apply these concepts to practical training for athletes. If you're not already subscribed to our newsletter, head over to www.legionsc.com to get a weekly selection of training tips and our favorite articles. You can follow us on Instagram as well for regular training tips and crunchy tactics: @legion.sc Learn More from Sergio Medium: @pecirnosergio Instagram: @sergiopecirno Links & Resources Mentioned The Science and Translation of Lactate Shuttle Theory Calcium ions Conjugate acid-base pairs Lactate dehydrogenase Todd Nief’s Show: Evan Peikon (Training Think Tank) Partial pressure Torr Maintained exercise-enhanced brain executive function related to cerebral lactate metabolism in men Show Notes: [00:13] Some common misconceptions about lactate: it causes soreness and fatigue. [06:45] How does pH work and what does it mean for something to be an acid-base pair? [13:10] How do metabolic byproducts actually cause fatigue? And, is there a separate role for lactate in fatigue other than through the production of hydrogen ions? [20:14] Does lactate have anything to do with soreness? Is there value in “flushing” after a training session? [33:14] Why do some tissues seem to prefer lactate as a fuel source? And, how can the correlation of elevated blood lactate levels with negative health outcomes confuse us? [41:14] What is lactate’s role as a “signaling molecule?” [44:30] What are actionable takeaways for athletes and coaches based upon a better understanding of lactate metabolism on interval training and recovery protocols?