Glossary

Definitions of terms used on this site. References for sourced definitions are listed at the end of the page.

VO₂Max (maximal oxygen uptake)

The maximum amount of oxygen the body can take in per minute during exercise. Expressed per kilogram of body weight in mL/kg/min, it is a measure of cardiorespiratory fitness. See “What is VO₂Max?” for more. Related page

VO₂peak (peak oxygen uptake)

The highest oxygen uptake observed during the exercise test actually performed. Like the strict maximum (VO₂Max), it is considered a strong predictor of mortality and disease incidence (Japan’s MHLW, 2023).

Cardiorespiratory fitness

The ability to sustain exercise. MHLW uses peak oxygen uptake per kilogram of body weight (VO₂peak/kg) as an indicator.

METs (metabolic equivalents)

A unit of physical activity intensity. Fitness values or reference values expressed in METs can be multiplied by 3.5 to convert to oxygen uptake (mL/kg/min). Converting an activity’s MET value does not give an individual’s peak oxygen uptake. One study describes a 1-MET difference in fitness as equivalent to about 1 km/h in running speed (Kodama et al., 2009).

Reference values (Japan’s MHLW, 2023)

Cardiorespiratory fitness levels expected to reduce risks of lifestyle-related and other diseases and associated mortality, provided by sex and age. They do not determine an individual’s health or future disease. See the age-based reference tables. Related page

Maximum heart rate

The highest heart rate reached during exercise. Direct measurement is the most reliable way to determine it, but equations can estimate it from age. This site uses 208 − 0.7 × age (Tanaka et al., 2001).

Resting heart rate

Heart rate when resting calmly. An equation estimates VO₂Max using the ratio of maximum to resting heart rate (Uth et al., 2004). Related page

Moderate and vigorous intensity

MHLW recommends moderate-to-vigorous exercise to improve cardiorespiratory fitness. To balance safety and benefit, it gives guidance of about 50–75% of peak oxygen uptake, or a perceived effort of “somewhat hard.” This range is not a boundary separating moderate from vigorous intensity.

Perceived exertion

Exercise intensity described by how it feels to the person, such as “easy,” “somewhat hard” or “hard.” People taking medication that affects heart rate use this as a guide instead of heart rate (MHLW, 2023, INFORMATION 4).

HIIT (high-intensity interval training)

Repeated bouts of near-maximal exercise alternating with rest or light exercise. This is distinguished from sprint interval training (SIT), which uses brief all-out efforts above the exercise intensity that elicits VO₂Max (MacInnis & Gibala, 2017). Related page

Interval walking

Walking that alternates three minutes of brisk walking with three minutes of slow walking. In a five-month study of men and women averaging 63 years old, fitness improved more than with continuous moderate-intensity walking. Individual results are not guaranteed (Nemoto et al., 2007). Related page

Randomized controlled trial (RCT)

A study that randomly allocates participants to groups, like drawing lots, to compare the effects of different approaches. It is suited to investigating cause and effect.

Cohort study

A study that follows many people over years to investigate associations between a characteristic, such as VO₂Max, and subsequent disease or death. It finds associations rather than proving causation. Related page

Meta-analysis

A method that statistically combines results from multiple studies addressing the same question into a single estimate.

Estimate

A value calculated by an equation or device rather than measured directly. Smartwatch VO₂Max values and this site’s tool results are estimates, with errors for individual users. They are not diagnoses. Related page

No specialist review; sources provided|Content last checked: October 24, 2026|Editorial policy