VO2 max is a number many people encounter through fitness trackers and health apps, and it represents a personal measure of cardiorespiratory fitness. This value, expressed as milliliters of oxygen consumed per kilogram of body weight per minute (mL/kg/min), indicates the maximum rate at which your body can use oxygen during intense exercise. Understanding whether a specific score like 42 is “good” requires looking beyond the number itself and considering the context of your age, biological sex, and training history.
Understanding VO2 Max
The physiological definition of VO2 max is the maximum capacity of your body’s systems—lungs, heart, blood vessels, and muscles—to take in, transport, and utilize oxygen during maximal exertion. It is an index of your body’s efficiency at producing energy through aerobic metabolism. The measurement is typically expressed relative to body weight (mL/kg/min) to allow for a fair comparison between individuals of different sizes. A higher score indicates a more efficient oxygen delivery and utilization system.
The gold standard for determining this value is a laboratory-based test called indirect calorimetry, where you exercise to exhaustion while wearing a mask that analyzes the oxygen and carbon dioxide in your breath. Many modern fitness devices estimate VO2 max using algorithms that combine heart rate data, movement speed, and demographic information. While convenient, these wearable estimates can be inaccurate, sometimes underestimating the value compared to the lab standard.
Contextualizing a Score of 42
A VO2 max score of 42 mL/kg/min is not inherently good or bad; its meaning is entirely dependent on the individual being measured. For a young, sedentary male, this score would likely fall into the “average” or “below average” range, as the average for untrained young men is typically around 40-45 mL/kg/min. However, for a 25-year-old female, a score of 42 would be considered “good” or even “excellent,” given that the average for untrained young women is lower, often in the 30-35 mL/kg/min range.
Biological sex creates a difference in average scores because men generally possess a higher percentage of lean muscle mass and greater hemoglobin concentration, which aids in oxygen transport. The score’s rating also shifts significantly with age, as VO2 max naturally declines by about 1% per year after age 30. For a man in the 56-65 age bracket, a score of 42 would be categorized as “good” or “excellent,” placing him well above the general population average for his age group.
A score of 42 generally represents a level of cardiorespiratory fitness that is above the general population average for most age and sex groups over 30. This number is a strong indicator of overall health, as a higher VO2 max is linked to a reduced risk of various chronic diseases.
Key Determinants of Your VO2 Max
The current value of your VO2 max is a product of several interacting biological and behavioral factors. Genetics sets a significant boundary on your maximum potential, contributing up to 50% of the variation seen between individuals. This inheritance influences oxygen transport mechanisms, such as heart size and mitochondrial density in muscle cells. Genetics dictates how high your score can ultimately climb, regardless of training intensity.
Age is another non-modifiable factor that dictates a decline curve for the score over time. Peak VO2 max is usually reached in the late teens or mid-twenties, and the subsequent annual decline occurs due to reduced maximum heart rate and changes in body composition. However, the rate of this decline is heavily influenced by training status; a physically active lifestyle can cut the age-related drop by as much as 50%.
Your training status represents the most modifiable determinant, as consistent endurance exercise can significantly raise your score from its untrained baseline. Regular physical activity improves both the heart’s ability to pump blood and the muscles’ capacity to extract oxygen from the blood. This means that while genetics establishes a ceiling, training determines how close you get to that limit.
Strategies for Improvement
Improving a VO2 max score involves challenging the body’s oxygen delivery and utilization systems with specific forms of exercise. High-Intensity Interval Training (HIIT) is one of the most effective methods, characterized by short, repeated bursts of near-maximal effort followed by periods of low-intensity recovery. This type of training pushes the heart and lungs to adapt to higher demands, which ultimately increases their efficiency and capacity. Studies suggest that HIIT can be more potent at raising VO2 max than continuous, moderate-intensity exercise alone.
Another strategy is sustained threshold training, which involves exercising at an intensity just below your maximum sustainable effort, often referred to as Zone 4. These efforts, which may last between 10 and 30 minutes, improve the body’s ability to clear metabolic byproducts like lactate, allowing you to sustain a higher intensity for longer periods. Combining these high-intensity efforts with long, slow distance (LSD) training, which builds a strong aerobic base, is considered a well-rounded approach.