Ambient means the surrounding air, which is what you inhale. Its temperature, pressure, and composition are among the inputs Calibre uses in calculating your respiratory and metabolic data.

There is a limit to the rate at which your body can utilize oxygen (aerobic metabolism), but when needed your body can supplement its energy supply through partial breakdown of certain fuels anaerobically, namely, without oxygen. Read more about this in our FAQ section.

The volume per breath, in liters, averaged over the entire session.

The average rate of energy use (calories per minute) over the entire session.

The concentration of CO2 in exhaled breath, averaged over the entire session. 4 - 5% is typical, but wider variations are not unusual. High CO2 concentration is typical of efficient, calm breathing, whereas consistently low CO2 can be a sign of "excessive" breathing or hyperventilation - namely, more than is required for metabolism.

The concentration of oxygen in exhaled breath. Whereas ambient air is typically between 20 - 21% (depending in part on humidity), exhaled air oxygen concentration is significantly lower. 14 - 17% is typical, but even lower values are not unusual. Generally speaking, low exhaled O2 concentration is a sign of efficient breathing.

This is the frequency of your breathing cycle, in terms of breaths per minute (BPM), averaged over the entire session.

The average rate of CO2 production (VCO2) over this recorded session, expressed in SLPM.

The average rate of oxygen use over this recorded session, expressed in SLPM.

Calibre contains a built-in barometer that measures the ambient pressure, in millibars (1000 mbar = 750 mmHg). Calibre is designed to take into account the ambient pressure so that your results are accurate at any elevation and weather. For example, at higher elevations the pressure is lower and you might need a larger volume of air to get the same metabolic amount of air.

The total number of breaths taken during a time period.

The average volume per breath, in liters.

Calibration means re-adjusting a sensor to maximize its accuracy. This is usually done by applying the sensor to a known quantity and adjusting its settings so that it provides the right value.

The Calibre Anaerobic Gauge™ is an indicator of the relative significance of anaerobic energy supply. There is a limit to the rate at which your body can utilize oxygen (aerobic metabolism), so when needed your body can supplement its energy supply through partial breakdown of certain fuels anaerobically, namely, "without oxygen". Read more about this in our FAQ section.

Your body's energy is produced by metabolizing nutrient fuels with oxygen while producing CO2. Measuring the oxygen uptake and CO2 production allows Calibre to determine the exact amount of calories you metabolize during a specific period of time.

This is your energy consumption in calories per minute (CPM). It is determined accurately and in real time from your breath, specifically from your oxygen use (VO2) and CO2 production (VCO2) per minute.

The total amount of calories "burned" during the session, which is determined from the total oxygen consumed and CO2 produced. The calculation is independent of the activities you engaged in.

Calories are a measure of energy - the energy is stored chemically in nutrients, or the energy is released by metabolizing these nutrients and utilized by the body.

Your energy is produced using oxygen to metabolize nutrient fuels - mostly carbohydrates and fats - while producing CO2. The cumulative CO2 production and oxygen use during the recorded session can be used to figure out the percent of energy derived from fat burn vs carb burn.

Short for carbohydrates. One of the three main nutrients found in foods and drinks, along with proteins and fats.

The cumulative CO2 production. It is related to VCO2 but summed up over the entire session (rather than per minute).

The concentration of CO2 in exhaled breath. 4 - 5% is typical, but wider variations are not unusual. High CO2 concentration is typical of efficient, calm breathing, whereas consistently low CO2 can be a sign of excessive breathing or "hyperventilation" - namely, more than is required by metabolism.

One of the three main nutrients found in foods and drinks, along with carbohydrates and protein.

Your energy is produced using oxygen to metabolize nutrient fuels - mostly carbohydrates and fats - while producing CO2. The cumulative CO2 production and oxygen use during the recorded session can be used to figure out the percent of energy derived from fat burn vs carb burn.

Shorthand for Ketosis or Ketotic, which describes a metabolic state or process where energy is delivered to the muscles using molecules called ketones (instead of sugars), which the body produces by breaking down stored fat. Typically this is triggered fasting but can also be induced by a ketogenic diet.

This is the volume of your breath over multiple breaths, expressed in liters per minute (LPM). Typical values at rest are well below 10 LPM, but can be substantially higher during exercise.

An approximate measure of your total anaerobic load during the session, where your workout time is weighted with the value of the Anaerobic Gauge (AG). As a simple example, 10 minutes with AG at 50% would be counted as 5 minutes of Net Anaerobic Time. It is not meant to imply that 5 minutes at AG = 100% are somehow equivalent to 10 minutes with AG = 50%, but it can be a handy metric to track and compare your workouts.

The cumulative oxygen used by your body over a measurement period, and is the difference between the inhaled amount and exhaled amount over that period, expressed in Standard Liters. It is related to VO2 but summed up over the entire session (rather than a rate per minute).

The highest rate of momentary energy burn (calories per minute) attained during the entire session.

This is the highest rate of carb burn (calories from carbs, per minute) attained during this session. It may not coincide in time with the peak of total calorie burn rate because your metabolic fuel mix can change during the course of an extended physical effort.

The highest rate of fat burn (calories from fat, per minute) attained during this session. It may not coincide in time with the peak of total calorie burn rate because your metabolic fuel mix can change during the course of an extended physical effort.

The highest rate of CO2 production (VCO2) attained during this recorded session.

The highest rate of oxygen use (VO2) attained during this recorded session.

Relative Humidity of the ambient air, expressed as a % of "saturation" humidity, which is where water from the air begins to condense spontaneously into small but visible liquid droplets. Two things worth noting: (1) even at RH = 100% (saturation humidity) airborne water molecules are still just a few % of the air. (2) RH depends also on temperature, because warm air can hold a lot more water vapor than cold air before onset of condensation.

The Respiratory Exchange Ratio or RER is the ratio of CO2 production to oxygen uptake. It is a key metabolic indicator which can be used, along with other respiratory data, to quantify calorie burn, fat/carb ratio, anaerobic metabolism and much more.

This is the net water loss associated with the excess humidity content in your exhaled breath relative to the inhaled breath. Keep in mind that your body loses water in several ways, so this is just your respiratory water loss, not your total water loss.

This is the frequency of your breathing cycle, in terms of breaths per minute (BPM). Slow breathing at rest is usually good, but it is natural for the rate to increase under exercise or stress.

Standard Liters Per Minute. Read more under FAQ.

Your energy is produced using oxygen to metabolize nutrient fuels - mostly carbohydrates and fats - while producing CO2. Your cumulative oxygen uptake and CO2 production during the recorded session tells the story of your energy metabolism: not only the total energy (calories) used but also the breakdown between the amount of fats and carbs used.

Your energy is produced using oxygen to metabolize nutrient fuels - usually a combination of carbs and fats - while producing CO2. Fat metabolism - in comparison with carbs - needs more oxygen and releases less CO2. This allows Calibre to determine in real time the percent of each nutrient fuel, simply from analyzing your breath.

VCO2 is the amount of CO2 production per minute, expressed in Standard Liters per Minute (SLPM).

VO2 is your net oxygen uptake per minute - the difference between inhaled & exhaled amounts, expressed in Standard Liters per Minute (SLPM). Read more about this in our FAQs (insert hyperlink) section.