The Endurance Science Podcast with Matt Carpenter

For as long as I can remember, I was told that lactate was the enemy, the toxic waste product that made my legs burn and forced me to slow down. It turns out almost everything I believed about it was wrong. In this episode, I trace the remarkable story of how lactate went from metabolic villain to one of the most important molecules in exercise physiology. I start with George Brooks, the UC Berkeley professor who spent four decades building the lactate shuttle theory, the idea that lactate isn't waste but a fuel, a gluconeogenic precursor, and a signalling molecule that shuttles between cells, tissues, and organs.

Then I dig into a stunning 2023 paper from Craig Thompson's lab at Memorial Sloan Kettering that takes the story even further: lactate doesn't just feed the mitochondria, it activates the electron transport chain without even being metabolised. It's a messenger that tells your mitochondria to produce more ATP, suppresses glycolysis, and shifts your energy system toward oxidative phosphorylation.

I explore what all of this means for how we think about the lactate threshold, pacing, interval training, recovery, and even immune function. If you've ever pushed into that burning zone on a hard run or ride, this episode will change how you think about what's happening inside your body.
References:
Cai, X. et al. (2023). Lactate activates the mitochondrial electron transport chain independently of its metabolism. Molecular Cell, 83, 3904–3920.
Brooks, G.A. (2018). The Science and Translation of Lactate Shuttle Theory. Cell Metabolism, 27, 757–785.
Brooks, G.A. et al. (2022). Tracing the lactate shuttle to the mitochondrial reticulum. Experimental & Molecular Medicine, 54, 1332–1347.
Hui, S. et al. (2017). Glucose feeds the TCA cycle via circulating lactate. Nature, 551, 115–118.
Leija, R.G. et al. (2024). Enteric and systemic postprandial lactate shuttle phases and dietary carbohydrate carbon flow in humans. Nature Metabolism, 6, 670–677.
Brooks, G.A. (2023). What the Lactate Shuttle Means for Sports Nutrition. Nutrients, 15(9), 2178.

Get equipped with essential tools to critically read and evaluate research claims, especially in the world of sports science and endurance performance. This episode unpacks the pitfalls of predatory publishing, how to spot misleading studies, and the importance of understanding the broader body of evidence to make informed decisions.In this episode:
The importance of not relying on single studies; why a body of research and systematic reviews are critical for true understanding
What predatory publishing is, how it misleads athletes and consumers, and how to use Jeffrey Beals’ list as a resource for evaluating journal credibility
Red flags in research papers: lack of transparency, superficial peer review, misleading impact factors, aggressive solicitation tactics
How social media and marketing exploit poor quality studies and cherry-pick data to promote supplements and gadgets
Practical steps to critically evaluate research: checking study design, conflicts of interest, replication, and alignment with meta-analyses
The hierarchy of evidence, from anecdotal reports to randomised controlled trials and systematic reviews, and why multiple replicated studies are necessary
The myth of “magic” supplements and why one promising study doesn’t prove effectiveness
How to distance yourself from misinformation and make evidence-based choices in endurance training and nutrition

In this episode I answer questions that you've sent in, covering nomio, beetroot juice, bicarb, collagen and training-based questions, as well as a big announcement towards the end!

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Q&A's will be monthly, let me know any questions you'd like covered.

See you next week.

In this episode I dive into a topic I've been studying for the past 10 years - the impact of ketogenic diets on endurance performance.

I talk about both the theory, research findings and social media commentary, as well as my own journey of 'belief' regarding keto.

Twitter thread mentioned: https://x.com/louisemburke/status/1289505145479294976?lang=en

Ever wondered why your muscles burn during a hard effort and whether you can do anything about it? In this episode, I break down the science of buffering agents: supplements designed to combat the acid build-up that contributes to fatigue during intense exercise.

Starting with the basics of why our muscles produce hydrogen ions and how our body's natural buffering systems work, I walk through the major players, including sodium bicarbonate, beta-alanine, sodium citrate, and lactate salts, explaining how each works, who they're best suited for, and what the research actually says.

I explore the intensity and duration sweet spot where these supplements have the strongest evidence, before diving into exciting emerging research suggesting buffering agents might also benefit longer endurance events. The episode wraps up with practical dosing protocols, timing strategies, and tips for managing the well known side effects. Whether you're a middle distance athlete, an endurance cyclist, or just someone who wants to understand the science behind the burn, this one's for you.