Fitness Metrics Glossary: VO2 Max, RPE, MHR, and More
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A plain-language reference to the most common fitness measurements — what each metric means and how it's typically used.
Why Fitness Metrics Matter for Every Level
Whether you're returning to exercise after years away or simply trying to understand what your fitness app is reporting, the numbers attached to your workouts can feel like a foreign language. Terms like VO2 max, RPE, and MHR appear on treadmill panels, wearable devices, and training plans — but rarely come with plain explanations.
This glossary cuts through the jargon. Each entry below defines a core fitness metric, explains what it actually measures, and describes how it's typically used in everyday training contexts. Think of it as a reference you can return to whenever a new term appears on your device or in your workout program.
If you're curious how metrics-style references work across other topics, our Computer Specs Glossary follows a similar plain-language approach for technology terms.
VO2 Max
Short for maximal oxygen uptake, VO2 max measures the maximum rate at which your body can consume oxygen during intense exercise. It's expressed in milliliters of oxygen per kilogram of body weight per minute (mL/kg/min) and is widely used as an indicator of aerobic fitness capacity. Higher values generally reflect a more efficient cardiovascular system.
RPE (Rate of Perceived Exertion)
RPE is a self-reported scale — commonly 1 to 10 or 6 to 20 (the Borg Scale) — that describes how hard an effort feels during exercise. A rating of 5 or 6 on a 10-point scale typically means moderate exertion, while 9 or 10 represents near-maximal effort. It's a practical tool when precise heart rate monitoring isn't available.
MHR (Maximum Heart Rate)
Maximum heart rate is the highest number of beats per minute your heart can sustain during maximal physical effort. It's often estimated using age-based formulas (a common general estimate is 220 minus age), though individual values can vary significantly. MHR serves as the baseline for defining heart rate training zones.
Heart Rate Zones
Training zones divide the intensity spectrum into ranges — typically five — expressed as percentages of maximum heart rate. Each zone targets a different physiological adaptation, from fat metabolism at lower intensities to lactate threshold improvement at higher ones. Zone-based training helps structure workouts for specific fitness goals.
Lactate Threshold
The lactate threshold is the exercise intensity at which lactic acid begins to accumulate in the bloodstream faster than it can be cleared. Training at or near this threshold is associated with improvements in endurance performance. It's often identified through lab testing or estimated via performance benchmarks.
RHR (Resting Heart Rate)
Resting heart rate is the number of times your heart beats per minute while you're at complete rest, ideally measured first thing in the morning before getting out of bed. A lower resting heart rate is often associated with better cardiovascular fitness, though normal ranges vary widely by individual.
METs (Metabolic Equivalents)
A MET is a unit representing the ratio of your working metabolic rate to your resting metabolic rate. Sitting quietly equals 1 MET; brisk walking is roughly 3–4 METs; vigorous running can exceed 8 METs. METs help researchers and clinicians compare the energy cost of different activities on a standardized scale.
Cadence
In running, cadence refers to the number of steps taken per minute (sometimes counted as total foot strikes, sometimes per foot). In cycling, it describes pedal revolutions per minute (RPM). Cadence is monitored to optimize movement efficiency and reduce injury risk.
Key Metrics at a Glance
The table below summarizes several of the most common fitness measurements alongside how they're typically expressed and what each one tracks.
| VO2 Max unit | mL of oxygen per kg of body weight per minute |
| RPE scale range | 1–10 (simple) or 6–20 (Borg Scale) |
| Common MHR estimate formula | 220 minus age (general approximation only) |
| Number of standard heart rate zones | 5 zones, from light to maximal effort |
| Resting MET value | 1 MET (equivalent to sitting at rest) |
| Running cadence target range | Roughly 160–180 steps per minute for many runners (General fitness guidance; individual variation applies) |
One metric that doesn't always appear on devices but has a meaningful impact on overall activity is NEAT — non-exercise activity thermogenesis. Our article on what NEAT actually means explains how everyday movement beyond structured workouts factors into your total energy expenditure.
~15%
VO2 max improvement possible with consistent aerobic training
Research published in sports medicine literature suggests aerobic training can meaningfully improve VO2 max, though gains vary by individual baseline and training volume.
60–100 bpm
Normal adult resting heart rate range
According to the American Heart Association, a normal resting heart rate for adults falls between 60 and 100 beats per minute.
This article is for informational purposes only and is not medical advice. Consult a qualified healthcare or fitness professional before beginning or modifying any exercise program, especially if you have an existing health condition.
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Health & Wellness Editorial Team
Health & Wellness Editorial Team is the collective byline for our editorial team and contributor network. Articles published under this byline or an editorial pen name are researched, written, and reviewed according to our editorial standards for clarity, consistency, and independence before publication.
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