As an endurance athlete or cyclist, you inevitably have heard from the VO2max. Most people know that a good endurance capacity is linked to a high VO2max. But what’s the added value of knowing your VO2max, when you already know your Lactate Threshold?
We’ve already established that the Lactate Threshold is the point at which the lactate production rate (and hydrogen-ion production) exceeds the removal rate. Ultimately this starts to affect the performance. This makes the LT the “single most important physiological determinant of performance in events ranging from as short as a 3km pursuit to as long as a 3-week stage race”, according to Dr. Coggan PhD, a well-respected exercise physiologist.
Nevertheless, a lot of endurance athletes want to know their VO2max as well. So, what is the VO2max? The VO2max is the maximal oxygen uptake of the body. The greater the maximal oxygen uptake of the body, the better it’s capable of using oxygen to produce energy aerobically.
In order to determine the VO2max accurately, a maximal exercise test is required. The VO2max can be determined using gas exchange measurements. During these measurements, the oxygen uptake and CO2-production will be measured. The maximal oxygen consumption (VO2max) will be measured as a volume per time unit (for example, millilitre per minute). Because some people are bigger and/ or heavier than others, and body composition heavily influences the VO2max, it will be divided by body weight. This way, the VO2max values can be compared between individuals of different sizes.
The VO2max is a really good measure for cardiovascular fitness and endurance performance and can be trained. However, up to 50% of the VO2max may be genetically predisposed.
The VO2max is roughly determined by two physiological processes:
- Cardiorespiratory system.
- Muscle Endurance
The cardiorespiratory system
As the name already suggests, the cardiorespiratory system is the combined system that consists of the cardiovascular system (heart, blood & blood vessels) and the respiratory system (respiratory tract). On the latter, the respiratory system, training only has a limited effect.
However, training may have significant effects on the cardiovascular system. Several adaptations may develop. One of them is the ability of the heart to increase the cardiac output, which means an increased volume of blood that is pumped around by the heart muscle each minute. The cardiac output is the result of an interaction between Heart Rate (beats per minute) and the Stroke Volume. The latter is the amount of blood that is pumped into the body with each contraction of the heart muscle or heartbeat.
Since the rest and submaximal heart rate both decrease with fitness (the body is capable to deliver the oxygen and nutrients more efficiently), the increase in cardiac output is the result of an increase in stroke volume. This increase in stroke volume therefore exceeds the decrease in heart rate.
Due to training, the heart’s (muscle) mass increases and the heart will be able to fill up with blood to a greater extend (amongst other adaptations). Both adaptations will result in the ability to pump more blood into the blood vessels if needed. At the same time, the oxygen uptake and transport processes may be improved. Therefore, less blood is needed to get the same amount of oxygen and nutrients to the muscles and other organs. This is one of the reasons that the blood pressure at rest decreases with increased fitness.
VO2max improvements are often specific to an activity. This means that a high VO2max in cycling doesn’t necessarily mean a high VO2max in running. Training will elicit central adaptations (heart), but also local adaptation (muscle endurance). Remember, one uses different muscles for different activities. Therefore, VO2max may differ between activities.
The muscle endurance
Local improvements that result in an improved VO2max may include changes in oxygen transport and usage in muscles. For example, the regional blood flow around and through muscles may improve. In addition, the mitochondrial density may increase. Mitochondria are the little energy-factories of the human body. It’s within these energy-factories that fats and carbohydrates are converted or oxidized (aerobically) to energy.
Training may induce an increase in the number of mitochondria, as well as an increase in the size of the mitochondria. Further local adaptations may include an increase in carbohydrate (glycogen) and fat stores within the muscle, increasing the fuel availability.
But why is the maximal oxygen uptake capacity important for cyclists? As a matter of fact, you will be able to plan your training just with your Lactate Threshold just fine. However, the Lactate Threshold represents the fraction of the VO2max that can be used by the body without fatiguing significantly. When you know your LT, but not your VO2max, you don’t know the relationship between both. In other words; you might have a big engine (VO2max), but you might not have optimized it (low LT compared to VO2max).
Also, the VO2max provides a good border value when determining your training zones and it is a nice reference value of your fitness compared to others.
Next: Setting your Training Zones
- Friel J. The Cyclist’s Training Bible. 5 ed: VeloPress; 2018.
- Allen H, Coggan A, McGRagor S. Training + Racing With a Power Meter. 3 ed. Boulder, Colorado: VeloPress; 2019.
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