Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Brands

Trail Tips

Should You Celebrate Your Watch’s V02 Max Numbers?

Are the watch estimates correct? And how much do they matter?

Lock Icon

Join O+ to unlock this story.

Already have an Outside Account? Sign in

Outside+ Logo

All-Access
Intro Offer
$3.99 / month*

  • World-class journalism from publications like Outside, Ski, Trail Runner, Climbing, and Backpacker.
  • Annual print subscription to Outside Magazine + 2 Gear Guides.
  • Outside Watch – Award-winning adventure films, documentaries, and series.
  • Gaia GPS – Premium backcountry navigation app.
  • Trailforks – Discover trails around the globe.
  • Outside Learn – Expert-led online classes on climbing, cooking, skiing, fitness, and beyond.
Join Outside+
Trail Runner Magazine

Digital + Print
Intro Offer
$2.99 / month*

  • Access to all member-exclusive content on TrailRunnerMag.com
  • Ad-free access to TrailRunnerMag.com
Join Trail Runner


*Outside memberships are billed annually. Print subscriptions available to U.S. residents only. You may cancel your membership at anytime, but no refunds will be issued for payments already made. Upon cancellation, you will have access to your membership through the end of your paid year. More Details

My watch just gave me an updated VO2 max number—should I celebrate?

—Gruia, San Jose, California

VO2 max for a runner is similar to the distance a golfer can hit on the driving range. It’s a component of success, but it’s not the whole story. No matter what, never put too much stock in a single metric related to your running fitness (or anything else). Life is always more complex than that.

Are the watch estimates correct? First, it’s helpful to think about what VO2 max is: maximum aerobic capacity, corresponding to the oxygen uptake peak during a period of intense exercise (usually an effort an athlete can sustain for 7 to 11 minutes, but with individual variance). Your watch is not directly measuring oxygen uptake, instead it’s approximating how much oxygen it thinks you use based on heart rate, pace, weight and other variables. It’s kind of like using a shadow of a tree to tell you how tall the tree is. That may work, but you need to have precise input variables like the angle of the sun and distance to the tree. Even then there may be some variance from actually measuring the tree.

RELATED: What You Need to Know About VO2 Max

Studies indicate that the shadow-drawings might not be that accurate. Three presentations summarized in the Medicine & Science in Sport and Exercise journal found statistically significant differences between watch VO2 max predictions and actual VO2 max. Some over-predicted, some under-predicted, some did both. Accuracy is further diminished if using optical wrist sensors rather than chest straps, which studies indicate are not fully reliable to measure heart rate across the population.

When thinking about what your watch is telling you, remember the old saying: “even a broken clock is right twice a day.” On top of that, even if the VO2 max number is correct, there’s no reason for it to inform your training approach. Training based on VO2 max changes is largely ineffective since VO2 max is primarily a genetic variable with most significant changes taking place when an athlete starts out. After that, further improvements are explained by other variables like running economy.

RELATED: The Body Doesn’t Know Miles, It Knows Stress

In conclusion, I fully support celebrating if your watch is telling you a fun story you want to hear. We can all use more celebration in our lives. But if the watch is being a jerk, assume that it’s a stupid, inaccurate jerk and pay attention to other performance metrics like changes in effort and increased joy while running uphill.

David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. With Megan Roche, M.D., he hosts the Some Work, All Play podcast on running (and other things), and they wrote a book called The Happy Runner.