We get this question a lot. "Why can't I score competitions on HRV or VO2 Max?" Both are reasonable, popular metrics. Lots of wearables track them. Lots of athletes care about them. Why not use them?
Because they're great personal metrics and bad competitive metrics. The two requirements are different, and a metric that's useful for tracking your own progress can be actively unfair when you turn it into a scoring axis between two people.
The bar a scoring metric has to clear
For MoveTogether, a scoring metric has to do three things:
- Reward effort, not biology. The person who worked harder this week should win, not the person whose body happens to be more genetically gifted.
- Be hard to game. No metric is fully un-gameable, but the good ones at least require you to do the activity to score.
- Mean roughly the same thing across wearables. MoveTogether's whole pitch is cross-platform competition. If Garmin's "VO2 Max" and Apple Watch's "VO2 Max" use different estimation models, you're competing across incompatible numbers.
| Requirement | VO₂ Max | HRV | MoveTogether scoring metrics |
|---|---|---|---|
| Rewards effort, not biology | Fails, 40–70% heritable | Fails, genetics + lifestyle noise | Passes, measures activity this week |
| Hard to game | N/A, too stable to compete on | Fails, sleep, alcohol, stress move it | Passes, requires actual movement |
| Cross-wearable consistency | Different vendor models | Different measurement windows | Passes, normalized Percentage of Goals |
Why VO2 Max fails
VO2 Max is the maximum volume of oxygen your body can use during exercise, measured in milliliters per kilogram of body weight per minute. It's an excellent indicator of cardiovascular fitness. It's also one of the most strongly genetic fitness metrics there is, studies put heritability somewhere between 40% and 70%.
Day to day, your VO2 Max barely moves. Even during a focused training block, gains in measured VO2 Max happen over weeks and months, not days. So if we used VO2 Max as a scoring axis, two problems would show up immediately:
- The genetically gifted person wins by default.
- The metric is too stable to reward this week's effort. Going for a hard run on Saturday doesn't visibly move VO2 Max, so there's nothing to compete over.
Why HRV fails
Heart Rate Variability measures the variation in time between consecutive heartbeats. Higher HRV is generally better, it correlates with parasympathetic recovery, lower stress, and overall cardiovascular health. WHOOP, Oura, and Garmin all surface HRV trends prominently.
HRV has the opposite problem from VO2 Max. It's extremely noisy:
- Genetics drive a large baseline component.
- Sleep quality, alcohol, caffeine, hydration, and stress all move it significantly.
- Different wearables compute it from different windows (overnight averages vs. last-five-minutes vs. morning readings) so cross-platform comparison is impossible without a normalization layer that wouldn't be honest.
If we used HRV as a scoring metric, you'd win or lose based on whether you slept well, whether you had a glass of wine, and whether your wearable's algorithm happens to be optimistic. That's not a competition.
What we use instead
MoveTogether scores competitions on metrics that pass the three bars above:
| Scoring metric | What it measures |
|---|---|
| Percentage of Goals | Normalized percentage-of-goal across wearables |
| Active Calories | Raw effort, same wearable family for fairness |
| Ring Close Count | Daily show-up axis for Apple Watch users |
| Steps | Low-friction, broadly compatible step totals |
| Workout Minutes | Time-based consistency in logged workouts |
All five measure things you can change this week by doing more activity. None of them are determined by your baseline biology.
"But I want to track HRV in MoveTogether"
Fair. The app shows your HRV trend (when your wearable provides it) on your profile. We just don't score on it. Track it as a recovery and stress signal, which is what it's good at, and let the competition layer measure effort instead.
The principle
A good competition metric rewards what you did. HRV and VO2 Max reward, mostly, what you are. We picked the first.
