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Understanding Fat Oxidation II: Practical Insights and Recent Studies

  • Introduction


The last blog post (see here: https://www.thethreshold.coach/single-post/optimizing-fat-oxidation-for-peak-cycling-performance-a-comprehensive-guide) explained the basics to understand about fat oxidation. This blog will provide some studies and practical viewpoints that can be used and applied to the training and performance of an athlete for improved performance. At the very least, a better understanding of the latest research in this quite controversial space within exercise metabolism.


Questions that we will examine:


  1. What is the importance of preserving muscle glycogen?

  2. What is durability/fatigue resistance/stamina?

  3. What is the correlation between VO2 max, FTP, and Fatigue Resistance/Durability (Training Component)?

  4. What is the correlation between glycogen stores and Fatigue Resistance/Durability (Nutrition Component)?

  5. Summary






1. Importance of Preservation of Muscle Glycogen.


Maintaining muscle glycogen is important as depletion is linked to fatigue and performance decrement. Athletes need to enhance their fat oxidation, allowing more preservation of this limited fuel source where muscle stores approximately 2400kcal and the liver holds around 375kcal only. By preserving glycogen, athletes can ensure they have an ample supply of this vital fuel available for key race moments. Moreover, improving fat oxidation enables athletes to decrease the quantity of glucose they must carry, as well as potentially preventing gastrointestinal problems.

The Crossover point, as discussed in the previous blog post and illustrated in Fig 1 below, represents the concept of increased fat oxidation. This is the point at which carbohydrate utilization surpasses fat oxidation at higher exercise intensities. This phenomenon helps conserve muscle glycogen and improves fatigue resistance (referred to as durability in scientific literature), enabling athletes to exercise for longer durations or sustain high-intensity performance levels.



Crossover
Fig 1. Crossover Point in metabolism

Let's further explore the idea of fatigue Fatigue Resistance/Durability below:


2. The Idea of Fatigue Resistance/Durability.


Being able to sustain muscle glycogen and perform well in the final stages of an endurance event is referred to as durability, fatigue resistance, or stamina. It involves maintaining performance levels throughout a given period of time. In Figure 2, it can be observed that the mean maximal power at 5 minutes is 444w, remains at 443w after 500kj, and even after expending 2000kj, there is no decline in power output. This cyclist demonstrates exceptional durability up to 2000kj, but beyond 3000kj, there is an 80w decrease in performance that requires attention. This situation suggests the need to consider both physiological (VO2 max, FTP etc) and nutritional factors to address the decline in performance.