Why Is My VO2 Max Going Down?

Modern technology makes many special sports measurements available to anyone, making it easy to track physiological progress and abilities. One of the important performance indicators is the VO2 max, a great indicator of cardiovascular fitness. It can be very frustrating to see your VO2 max go down, especially if you've been training hard. In this article, we will explore the various factors that can cause a decrease in VO2 max even when training. Additionally, we will discuss the training methods that can improve VO2 max and how diet can influence this measure.
Jakub Gwiazdecki

Jakub Gwiazdecki

Fifth year medical student at the Medical Faculty of Comenius University in Bratislava.

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What is VO2 max?

Your VO2 max, or maximal oxygen uptake, is a measure of the maximum amount of oxygen your body can use during exercise. It's a key indicator of your cardiovascular fitness.

Aside from cardiovascular fitness, VO2 max is a great indicator of overall health. In fact, some studies show that increaseed VO2 max levels are correlated with an increased lifespan. Together with grip strength, VO2 max is a good indicator of longevity.

Why is my VO2 max going down?

Many people measure the effectiveness of their training by VO2 max, usually measured with a smartwatch. In the beginning of the training period, the progress is very motivational, because the maximal oxygen uptake ability of the body (VO2 max) increases relatively easily.

However, eventually the VO2 max levels stop increasing and athletes reach a plateau. The VO2 max levels may even decrease, which can be incredibly frustrating.

There are a few key reasons why VO2 max may decline even with training: Age-related decline: VO2 max naturally declines with age, regardless of activity level. The decline is estimated at around 10% per decade in both men and women. This decline is largely due to reductions in maximal heart rate and lean body mass 12. Insufficient training intensity: To significantly reduce the age-related VO2 max decline, high-intensity training must be maintained long-term. This becomes increasingly difficult with advancing age. Reduced training volume: Changes in VO2 max are closely related to changes in training volume. One study found that 54% of the VO2 max decline in male athletes and 39% in female athletes was explained by reductions in training volume. Genetic limitations: In some highly trained athletes, pulmonary gas exchange limitations may restrict VO2 max, as evidenced by exercise-induced reductions in arterial oxygen saturation 45.

In summary, while training is important for maintaining VO2 max, age-related declines still occur. Maintaining high-intensity and high-volume training can minimize this decline but becomes increasingly challenging with age.


Several factors can lead to a decrease in VO2 max. Some of them are internal factors that are not reversible, while others are very well under the control of the trainee.

Maximal VO2 max

The main reason behind the stopped progress in VO2 max levels is the achievement of the maximal VO2 max, the body’s physiological limit. In a healthy individual, the upper bound depends on the physiological sex, age, weight, and heart rate. Males have a generally better VO2 max than females.


Another limiting factor is age. With every year, the maximal oxygen uptake decreases by around 0.43 ml/kg/min in men and 0.3 ml/kg/min in women [1]. This slow degradation is caused by a constant decrease in the oxidative capacity of the muscles [2].

Hemoglobin concentration

Another factor is the hemoglobin (Hb) concentration. Lower values of Hb are found especially in women and in people on a not-well-planned vegetarian diet. Hemoglobin is responsible for the binding and transport of oxygen. A smaller concentration of this protein restricts the amount of oxygen that can be transported to the muscle, thus resulting in a lower VO2 max [2, 3].

The heart

The heart itself can also contribute to falling VO2 max results. It cannot beat faster than its physiology allows. The maximal heartbeat can be estimated by subtracting the age from 220. For example, a 30-year-old man will have a maximal heartbeat of 190 BPM.

The cardiac myocardium needs as much training as any other muscle. In cases of prolonged periods of inactivity or bed rest, the heart adapts to a lower blood demand. This is how longer breaks in training can lead to a decrease in maximal oxygen uptake [4].

Insufficient recovery and overtraining

An often overlooked aspect of training, which can also impact the VO2 max, is the recovery phase. During this phase, sleep, rest, and a proper diet allow the organism to rebuild and strengthen the muscles. When a person does not allow the body to rest, it can lead to overtraining and falling VO2 max values.

Health conditions

Lastly, certain health conditions, such as type 2 diabetes, can also lead to a decrease in VO2 max [5]. It is important to regularly review the health status. One- or two-time control of the blood and other parameters can allow for the identification of a disease before its onset and prevent its development.

Can diet influence VO2 max?

Diet can also impact VO2 max, but this also depends on the overall health and fitness of the individual.

Individuals with diseases where the normal physiological abilities of the body are limited, can benefit from a diet change.

Patients with diabetes type 2 can significantly increase their VO2 max following a low-oxidation diet, like a vegetarian diet [6]. However, this may not directly translate to performance. [7]

A high-carbohydrate diet in COPD (chronic obstructive pulmonary disease) after consumption showed a significant VO2 max increase when compared to a diet high in fats [8]. This indicates that a high-fat diet does not favor the aerobic capacity of the body and should therefore be omitted for a better increase in the VO2 max.

Of course, these examples are not for healthy individuals, and so they cannot be directly transferred into true statements about people not affected by the diseases. However, they show that there is an impact of the diet on the VO2 max. Certainly, there is more research needed on this topic. Nevertheless, the diets that help with the diseases could help a healthy individual to improve or preserve their VO2 max.

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Jakub Gwiazdecki

Jakub Gwiazdecki

Jakub is in his fifth year as a medical student at Comenius University in Bratislava, Slovakia. He has special interested in cardiology and in patient-centered medicine. His love for heart health isn't just book-smarts; he wants to know how it works, what it means for our feelings, and how key it is for health and happiness. Jakub thinks real good health care comes from always putting the patient at the centre, treating each person as a whole.