Three metrics, three different questions
Garmin now gives you VO2 max, Endurance Score, and Stamina, three metrics that all seem to measure "how fit you are for long efforts." Open your Garmin Connect app and you will find them scattered across different screens, with minimal explanation of how they differ or which one you should actually pay attention to.
Here is the short version: these three metrics answer fundamentally different questions about your fitness. VO2 max tells you how big your engine is. Endurance Score tells you how large your fuel tank is. Stamina tells you how much fuel you have left right now, mid-activity.
Understanding the distinction changes how you train.
VO2 max: your engine size
What it measures
VO2 max is the maximum amount of oxygen your body can consume during intense exercise, expressed in milliliters per kilogram of body weight per minute (ml/kg/min). It is the gold standard metric for aerobic capacity and has been studied for decades.
Garmin estimates your VO2 max by analyzing the relationship between your running pace (or cycling power) and your heart rate during aerobic efforts. If you can run faster at the same heart rate, or run the same pace at a lower heart rate, your estimated VO2 max goes up.
As a very rough orientation for adult runners, values below 35 read as untrained, 35 to 45 as recreational, 45 to 55 as competitive amateur, 55 to 65 as highly trained, and 65 and above as elite or near-elite. Treat that as a sanity check and nothing more. Garmin does not classify VO2 max on a single scale: it uses age- and sex-banded tables reprinted from The Cooper Institute, where the same number can be "superior" for one athlete and "good" for another. A 52 puts a 25-year-old man near the 80th percentile and a 65-year-old man well above the 95th. Read your own row, not the generic list.
What it does not tell you
VO2 max is a measure of your peak aerobic capacity. It tells you how fast your engine can rev. But it says nothing about how long you can sustain a high percentage of that capacity.
Two runners can have identical VO2 max values of 55 and have wildly different marathon times. The one who can sustain 80% of their VO2 max for three hours will crush the one who fades to 65% after 90 minutes. VO2 max does not capture that difference.
This is exactly the gap that Endurance Score was designed to fill.
How to improve it
VO2 max responds best to high-intensity training: intervals, tempo runs, and threshold work. The classic VO2 max workout is 4-5 repeats of 3-5 minutes at 95-100% of max heart rate with equal recovery. These sessions push your cardiovascular system to its limit and force adaptation.
But there is a ceiling. VO2 max is partly genetic, and it flattens out long before your race times do. Garmin's own endurance score page puts it plainly: "You may have personally experienced a plateau in aerobic fitness development but continued to see and feel improvements in your endurance." How long that takes varies enough between athletes that any single figure would be made up. Once you are there, further improvements come from running economy and endurance capacity, not from a higher VO2 max. You can estimate your VO2 max from a Cooper 12-min or 1.5-mile field test to get a benchmark outside of Garmin's algorithm. For a detailed guide on pushing your number higher, check out our complete guide to improving Garmin VO2 max.
Endurance Score: your fuel tank
What it measures
Endurance Score arrived in June 2023, on the fēnix 7 Pro and epix Pro, and reached other watches later that year. It quantifies your ability to sustain prolonged aerobic effort, something VO2 max explicitly does not capture. The classifications come from Firstbeat Analytics.
Correction, 1 August 2026. This article previously said the score "ranges from 0 to 100" and was introduced in 2024. Both were wrong, and the scale was wrong by two orders of magnitude. Endurance Score runs into the thousands. Garmin's Endurance Score Ratings table sorts it into seven named tiers, banded by age and sex. For males aged 21 to 39:
| Tier | Score |
|---|---|
| Recreational | Less than 5100 |
| Intermediate | 5100–5799 |
| Trained | 5800–6599 |
| Well Trained | 6600–7299 |
| Expert | 7300–8099 |
| Superior | 8100–8799 |
| Elite | 8800 and greater |
Those numbers apply to that band and no other. Females aged 21 to 39 hit Elite at 7300. Males aged 80 and older hit Elite at 5000. The tier name is the comparable thing across athletes; the raw number is not. On the watch, Garmin colours the tiers rather than showing you the table: red for Recreational through to pink for Elite.
Garmin builds the score from your VO2 max first, not from your training volume. Its technology page calls aerobic fitness "the most significant contributor," and falls back to estimating it from age, gender, BMI and recent activity if it has no recent VO2 max reading. On top of that it analyses your activity history for evidence of fatigue resistance, with your longest activities carrying "special consideration." Every activity you record with heart rate counts, across every sport, which is why a big week of cycling can move a runner's number.
An athlete who runs 30 miles per week with a weekly long run of 15 miles will tend toward a higher Endurance Score than someone who runs 30 miles per week in short daily 5-milers, even at the same VO2 max.
Why it matters
Endurance Score is the metric that best predicts how you will perform in events lasting longer than 60-90 minutes. A high VO2 max gets you a fast 5K. A high Endurance Score gets you through a marathon without falling apart.
Think of it this way: VO2 max is the horsepower of your engine. Endurance Score is the size of your gas tank and how efficiently your engine burns fuel at cruising speed.
For athletes focused on half marathons, marathons, ultramarathons, long-distance cycling, or triathlon, Endurance Score is arguably more important than VO2 max once you have reached a decent baseline aerobic capacity.
How to improve it
Endurance Score responds to exactly the kind of training that does not move VO2 max:
- Long slow distance. The weekly long run or ride is the single best driver of Endurance Score. Keep the effort in zone 2, keep the duration building gradually.
- Volume accumulation. More total training hours per week, as long as you can recover from them. Consistency matters more than peak weeks.
- Double days. Two moderate sessions in a day accumulate more endurance-building stimulus than one longer session, for some athletes.
- Back-to-back long days. Running long on Saturday and moderate-long on Sunday builds the fatigue resistance that Endurance Score captures.
The window is shorter than most people assume. Garmin runs two perspectives side by side: a long-term one covering "between 2 to 3 months of data," and a short-term one "limited to the most recent 2 weeks." That second number is why the score can drop faster than you built it. Garmin is explicit that "the peak benefits of endurance training can be lost in a relatively short period of inactivity," and the two-week window is how it notices.
Stamina: your real-time fuel gauge
What it measures
Stamina is different from the other two because it is a real-time, during-activity metric. Think of it as a battery indicator that depletes as you exercise and estimates how much effort you have left.
When you start an activity, your Stamina gauge shows two values:
- Potential Stamina: the total effort your body can sustain before complete exhaustion, expressed as a percentage from 100% down to 0%
- Current Stamina: your available effort right now, which drops as you push harder and partially recovers if you back off
The rate of depletion depends on your intensity relative to your thresholds. Running at zone 2 drains Stamina slowly. Running at threshold drains it much faster. Sprinting burns through it almost immediately.
How it differs from Body Battery
This is a common source of confusion. Body Battery measures your general energy level throughout the day. Sleep, stress, and activity all factor in. Stamina is purely an exercise metric. It only activates during a recorded activity and measures your remaining physiological capacity for that specific session.
Body Battery might say you have 85 points of energy when you start your run. Stamina tells you how that energy depletes and recovers during the run itself.
What it is good for
Stamina is most useful for pacing during races and long efforts. If you are running a marathon and your Stamina is at 30% at mile 15, you know you need to back off or you will hit the wall. If you are at 60% at mile 15, you have room to push.
Experienced athletes develop an intuitive sense of this, but Stamina gives beginners and intermediate athletes a real-time pacing tool that can prevent the most common racing mistake: going out too fast.
Can you train it?
Not directly. Stamina is a reflection of your underlying fitness: your VO2 max, your endurance capacity, and your metabolic efficiency. You do not train Stamina itself. You train the systems it measures, and Stamina improves as a consequence.
If your VO2 max goes up, your Stamina depletes more slowly at a given pace. If your Endurance Score goes up, your Stamina sustains better during long efforts. Stamina is the output. VO2 max and Endurance Score are the inputs.
Key differences at a glance
| VO2 Max | Endurance Score | Stamina | |
|---|---|---|---|
| What it measures | Peak aerobic capacity | Sustained effort ability | Real-time energy left |
| Score range | ~20-80 ml/kg/min | Thousands; 7 tiers whose thresholds run from ~3200 to ~8800 by age and sex | 0-100% |
| When it updates | After qualifying runs | Daily (based on history) | Live during activity |
| Time horizon | Last 4 weeks of data | 2-3 months long-term, plus the most recent 2 weeks | Current session only |
| Improves with | Intervals, tempo, threshold | Long slow distance, volume | Cannot train directly |
| Best predictor for | 5K-10K performance | Half marathon+ performance | Mid-race pacing |
| Available on | Most Garmin watches | Forerunner 265+, Fenix 7+ | Forerunner 255+, Fenix 7+ |
How the three metrics work together
The real power of these metrics is in combination, not isolation. Different combinations tell you different things about where you are and what you need:
High VO2 max + low Endurance Score
You are fast but cannot sustain it. Common in athletes who do a lot of intensity work but skip long runs. Your 5K is solid, but your marathon will be painful. Prescription: add more zone 2 volume and longer weekend sessions.
Low VO2 max + high Endurance Score
You can go forever but not very fast. Classic ultrarunner or high-volume jogger profile. You have a huge aerobic base but your top-end fitness is underdeveloped. Our trail running guide covers how to use these metrics off-road. Prescription: add one to two intensity sessions per week, such as intervals, hill repeats, or tempo runs.
High VO2 max + high Endurance Score
The sweet spot. You have a powerful engine and a large fuel tank. This is the profile of a strong marathoner or an Ironman athlete who can both go fast and go long. Maintaining this requires a balanced training approach with both intensity and volume.
Both low
You are early in your training journey, or you have been inconsistent. Focus on building an aerobic base with consistent, easy running before adding intensity. Three to four months of gradually increasing volume will move both numbers.
Which metric should you focus on?
It depends entirely on your goal:
- Racing 5K or 10K? VO2 max is your primary metric. Endurance Score matters less at these distances.
- Training for a half or full marathon? Endurance Score is arguably more important than VO2 max. Prioritize it.
- Racing an ultra or Ironman? Endurance Score is everything. Your ability to sustain effort for hours is the whole game.
- General fitness with no specific race? Watch the balance between VO2 max and Endurance Score. A rising trend in both means your training is well-rounded.
Stamina is useful during events and long training sessions regardless of your goal distance. Add it to your watch data screens for any effort over 60 minutes.
If you want to track how all three metrics trend alongside your training load and workout history, you need them plotted on one timeline rather than read off three separate screens a week apart. Understanding how changes in your training affect each metric is where the real insight lives.
The bottom line
VO2 max, Endurance Score, and Stamina are not redundant. They measure three distinct dimensions of aerobic fitness: peak capacity, sustained capacity, and real-time capacity. Confusing them leads to training that develops one quality at the expense of others.
Know which metric matters most for your goals. Train the systems that drive it. And use the others as a check on your overall fitness balance. The best endurance athletes do not just have one impressive number. They have all three working in concert.
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