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This episode breaks down the origins of endurance performance and how cells control substrate oxidation. We review a paper looking at the difference in adaptive aerobic signals when participants used significantly different amounts of fat and carbs at the same intensity. We then look at the role of mitochondria in cellular energetics, the pivotal role they play in aerobic endurance adaptations, and finally what the training implications are. Plus we answer your listener questions submitted to Kolie's Instagram.
Show Notes Carbohydrate improves exercise capacity but does not affect subcellular lipid droplet morphology, AMPK and p53 signalling in human skeletal muscle Regulation of skeletal muscle mitochondrial fatty acid metabolism in lean and obese individuals Metabolic adaptations to short-term training are expressed early in submaximal exercise Biochemical adaptations in muscle
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Think your FTP is the power you can hold for 60 minutes? Think again! We dig into a classic Billat paper on time to exhaustion (TTE) and training threshold by adding time in zone. Then we discuss into the metabolic implications of these results, how they align with real world experience, and how this affects training and assessment of its effectiveness. Finally, we answer your questions as asked in Kolie's Instagram stories @empiricalcycling.
Show Notes Billat TTE paper on masters runners Introduction to TTE in WKO5 
While the phosphocreatine energy system is well known for sprinting, it also has another crucial role as part of the aerobic energy system. We delve into creatine's part in not only temporal energy buffering, but spatial too, and how cells are organized to support this and how badly organisms suffer without it. Then we look at more research showing that the aerobic recovery of phosphocreatine is highly correlated with repeated sprint power, and come to some practical conclusions we can make from the research.
Show Notes "Conveyor Belt" paper: Mitochondrial creatine kinase in human health and disease Impaired voluntary running capacity of creatine kinase-deficient mice Relationship between different measures of aerobic fitness and repeated-sprint ability in elite soccer players The Recovery of Repeated-Sprint Exercise Is Associated with PCr Resynthesis, while Muscle pH and EMG Amplitude Remain Depressed You're Training Too Hard For Criteriums -- Here's Why 
The "creatine conveyor belt" main pathway.
The mitochondrial structure of embedded creatine kinase enzymes to aid energy buffering.
Does your training zone determine the fiber type used? Does fiber type determine aerobic or anaerobic pathways, carbs or fats? We answer these questions by looking at evidence and concepts that show that fast twitch fibers can be just as aerobically capable as slow twitch fibers, nearly as good at burning fats, and why that might be. We dissect a paper on elite cross-country skiers, and another paper on whether or not fast twitch fibers had been recruited at relatively low intensity. In-depth discussion follows on fiber type distribution, muscle mass recruitment and force availability, why endurance athletes defy the expected metabolic properties of fast twitch fibers, and why these expectations may have started with cats.
Show Notes XC Skiers paper The Muscle Fiber Profiles, Mitochondrial Content, and Enzyme Activities of the Exceptionally Well-Trained Arm and Leg Muscles of Elite Cross-Country Skiers Ramp test muscle recruitment paper Progressive metabolite changes in individual human muscle fibers with increasing work rates 
Figure 2 from XC ski paper, showing HAD and CS activity of arm and leg muscle samples against MHC1 proportion in those samples.
Figure showing metabolite changes at rest and after ramp test stages to 2 below LT (t2), 3 above LT (t3), and to exhaustion (t4).
In this episode we look at what fatmax is, where the promise lies, and what validity there is. Do you get better at burning fat by burning more fat? Do you lose more weight by burning more fat? How does e=mc^2 relate to the energy stored in food? This episode answers all these questions and more.
Show Notes 2001 Jeukendreup and Achten fatmax paper Elevated calcium and mitochondrial biogenesis in rat muscle (full text) Papers not referenced in main podcast: Exercise: It's the real thing! Maximal fat oxidation during exercise in trained me 
Idealized fatmax curve, from original Jeukendrup and Achten paper
If you've ever thought about using the ketogenic diet for cycling, you may want to listen in. We look at a pair of modern classic studies that compare traditional high carbohydrate diets to periodized low carb and keto. This includes a study with, and a study without a carbohydrate re-adaptation period.
Show Notes Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5407976 Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272074
We look deeper into how the body chooses to use carbohydrates and fats, and specifically when and how carbohydrates inhibit fat oxidation. This serves as a jumping off point to take a critical look at VLamax and how it may, or may not, affect your FTP.
Show Notes Study on increased gene expression following endurance exercise https://pubmed.ncbi.nlm.nih.gov/19705999/ 
Acetyl buffering via carnitine frees CoA for continued pyruvate shuttling into the Krebs cycle.
Malonyl-CoA inhibition of CPT1.
What does it really mean to burn something aerobically? This episode concludes the first phase of this series by looking at both the Krebs cycle and the electron transport chain, and putting them in perspective. In what way is burning fats or carbs aerobic, and how aerobically different are they from each other?
Show Notes 
The Krebs cycle
The electron transport chain and abbreviated Krebs cycle together
This episode starts by looking at the chemical mechanisms of glycolysis, the stepwise dismantling of glucose for energy, and finishes with some big picture learnings about this deceptively simple pathway.
Show Notes 
Glycolysis with straight chain sugars in Fischer projection
Glycolysis with NADH/NAD+ cycle
Free energy change of glycolysis. Note reactions 6 and 7 are coupled. Via https://slideplayer.com/slide/8083993/
Energy levels of glycolytic intermediates, via http://www.columbia.edu/cu/biology/courses/c2005/lectures/lec9_10.html
This episode takes a wide angle view of the chain of events between starting exercise and successfully burning fat, and where the main bottlenecks are in that process. Nuances discussed are the differences between adipose tissue and intramuscular fats, energy demand rates, diet, and potential training strategies to improve fat utilization at most exercise intensities.
Show Notes https://www.proteinatlas.org/ https://www.brenda-enzymes.org/ Effect of physical training on the capacity to secrete epinephrine https://pubmed.ncbi.nlm.nih.gov/3281927/ Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration https://pubmed.ncbi.nlm.nih.gov/8214047/ Fat metabolism during low-intensity exercise in endurance-trained and untrained men https://pubmed.ncbi.nlm.nih.gov/7810637/ Beta-blockade and lipolysis during endurance exercise https://pubmed.ncbi.nlm.nih.gov/8223828/ The different relationship of VO2max to muscle mitochondria in humans and quadrupedal animals https://pubmed.ncbi.nlm.nih.gov/2218095/ 
Lipolysis reaction
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