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.

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.

Age

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.