In this conversation, Dr. Robert A. Jacobs and I discuss his recently accepted paper on carbohydrate oxidation and performance in sub-2 hour marathons. We explore the role of fuel utilization, the impact of exogenous carbohydrate intake, and the limitations of respiratory exchange ratio (RER) as a measurement. We also discuss the importance of training the gut and the balance between carbohydrate intake and training. The conversation touches on the differences between elite athletes and the general population, as well as the definition of health and fitness.

The conversation explores the differences between running and cycling, the importance of watts per kilogram versus absolute power, the relationship between VO2 max and performance, the impact of weight on performance, the role of body fat percentage in performance, the significance of mitochondria in overall health and performance, the concept of critical power and critical oxygen, and the axis of oxidation as a key factor in performance.

TAKEAWAYS
1) Fuel utilization and carbohydrate oxidation play a crucial role in endurance performance, particularly in sub-2 hour marathons.

2) Exogenous carbohydrate intake can enhance performance, but there is a saturation point beyond which absorption is limited.

3) Training the gut is important for athletes to prevent gastrointestinal distress during exercise.

4) Running up a hill engages similar muscles as cycling, making it a valuable training exercise for cyclists.

5) Absolute power is more important for flat courses, while watts per kilogram becomes a stronger predictor for uphill courses.

6) VO2 max is a valuable measure, but other factors such as threshold and efficiency also play a role in performance.

7) The axis of oxidation, referring to the role of mitochondria in cellular energy production, is a key factor in performance.

Dr. Jacobs Paper -
https://journals.physiology.org/doi/full/10.1152/japplphysiol.00521.2023

Enjoying these podcasts? Don't forget to subscribe to get notified when new episodes are released.

If you have a question or topic you want us to address, leave a comment!

Follow Phil on Instagram - https://www.instagram.com/criticalo2

Interested in testing, courses, or other long form content check out the critical oxygen website - https://www.criticaloxygen.com

CHAPTERS
00:00 Introduction and Paper Acceptance
01:06 Interest in Fuel Utilization
03:56 Research Project on Carbohydrate Oxidation
08:39 Role of Carbohydrate and Fat Oxidation in Sub-2 Hour Marathon
09:22 Effect of Exogenous Carbohydrate Intake on Fat Oxidation
13:45 Limitations of RER as a Measurement
17:19 Higher Exogenous Carbohydrate Intake for Female Athletes
18:38 Carbohydrate Intake and Oxidation in the Study
19:38 Impact of Increased Carbohydrate Intake on Performance
21:24 Saturation Point of Carbohydrate Absorption
22:28 Factors Affecting Gastrointestinal Distress
25:21 Training the Gut
26:41 Balancing Carbohydrate Intake and Training
28:22 Elite Athletes and Peak Human Performance
30:08 Comparing Physical and Intellectual Abilities
32:46 Defining Health and Fitness
35:24 Acceptable Speed for Running a Mile
37:51 Measuring Mechanical Output in Running
38:38 Calories Burned While Running
40:02 Power Output in Running Uphill
41:09 Running vs Cycling
47:36 Watts per Kilogram vs Absolute Power
51:07 VO2 Max and Performance
53:16 Weight and Performance
56:09 Body Fat Percentage and Performance
59:26 Mitochondria and Performance
01:02:54 Critical Power and Critical Oxygen
01:05:13 The Axis of Oxidation