Welcome to the first post of the Endurance Performance Series! My goal for this series of posts is twofold. First, I would like to guide readers who know very little about endurance performance to a much deeper understanding of the mechanisms behind performance. For this reason, I will try to avoid straying too far into the weeds of exercise science. However, that is not to say that these posts won’t hold thought-provoking ideas for those of you with vast experience in endurance sports. I will do my best to strike the fine balance between accessibility and detail. I hope I can do so in a way that you enjoy!
Taking a look at the foundational paper by Joyner & Coyle (J&C) titled Physiological Determinants of Endurance Performance is a great place for this series to start. J&C succinctly outline the numerous subcomponents that contribute to the end-all-be-all metric of competition - Performance Velocity. They highlight the 3 most important subcomponents (VO2max, lactate threshold, economy) as well as several other components that influence these 3 metrics. Below, we will take a quick look at the three main pillars as well as briefly touch on the sub-levels.
1. VO2 Max
VO2 max, or maximal oxygen uptake, refers to the maximum amount of oxygen that an athlete can consume during exercise. It’s often viewed as the gold standard for measuring aerobic fitness. To achieve a high VO2max, an athlete must be able to take a large amount of oxygen from the air and deliver it quickly to the working muscles to be used in cellular respiration (which produces the energy for movement). When talking about VO2max, we usually refer to two components; the central component (the heart) and peripheral component (the muscles). The more blood that your heart can pump, the better. The more oxygen that your muscles can uptake, the better.
2. Lactate Threshold
The lactate threshold (LT) is often viewed as the most important metric in endurance sports. From the 5km to 70.3, athletes with a higher/faster lactate threshold will typically perform the best. The two primary mechanisms behind LT are lactate production, often called VLa max (performed by the anaerobic system) and lactate usage (performed by the aerobic system). In an ideal world, an athlete will be able to use a huge amount of lactate as a fuel while producing just the right amount of lactate.
3. Exercise Economy
Exercise economy refers to how efficiently an athlete uses the oxygen they breathe in. An athlete with better exercise economy will expend less energy at a given speed or power, allowing them to save “fuel”. This factor is often overlooked but is critical in determining endurance performance. Factors such as muscle fiber type, biomechanics, and technique all play roles in improving exercise economy.
Other Key Physiological Factors
Going one step further, there are several subcomponents to the three primary components. Three of the most important subcomponents have to deal with characteristics of the heart, blood and muscles.
Cardiac Output: High level endurance athletes typically have a high cardiac output, driven by a large stroke volume (the amount of blood pumped per heartbeat). This increases the amount of oxygen-rich blood delivered to muscles per time and can be improved with the right training.
Red Cell Mass: Higher levels of red blood cells/hemoglobin enable more oxygen to be carried to working muscles via the blood, increasing endurance capacity. This can be improved with training, altitude training and heat training.
Mitochondrial Density: Endurance training increases the number of mitochondria in muscle cells, which boosts the body’s ability to produce energy aerobically. This allows athletes to utilize fuel (fats and carbohydrates) at a faster rate. This can be improved with correct training.
Just like with anything complex, it can be helpful to break down your own performance into various subcomponents. By doing so, you can have a deeper understanding of what your own limiters are, allowing you to take a more precise training path. This seminal paper by J&C succinctly breaks down the primary and secondary factors affecting endurance performance, providing athletes and coaches with a clear picture of performance.
The following posts of this series will go into more detail on each of these components as well as several other important aspects of performance. The series will not only be informational - it will be actionable - giving you concrete ways to improve your own performance.
Train hard, train smart.
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