Cardio Fitness Below Average on Apple Watch

If your Apple Watch is showing “Below Average” or “Low” cardio fitness, do not panic. This is common and often partially explained by how Apple Watch measures VO2 Max rather than your actual fitness level. Use our Cardio Fitness Level Checker to see exactly where you rank. Here is what the classification means, why it might be inaccurate, and what you can do about it.

What Below Average Actually Means

Apple compares your estimated VO2 Max against population data for your age and sex, drawn from the Fitness Registry and the Importance of Exercise National Database (FRIEND). “Below Average” means you fall in the lower 20-40% range. “Low” means you are in the bottom 20%. These classifications are based on the same percentile data used by researchers and clinicians.

The classification itself is straightforward. But the estimate feeding into it may not be accurate, which is where the confusion starts.

Why Your Reading Might Be Wrong

This is the most important section. Several common scenarios produce artificially low VO2 Max readings on Apple Watch:

You mostly exercise indoors. Apple Watch only estimates VO2 Max during outdoor walk, run, or hike workouts. If you do CrossFit, spin classes, indoor running, swimming, or weight training, none of those sessions contribute to your VO2 Max estimate. Your reading may be based on limited or outdated data.

You walk or run right after intense exercise. This is one of the most common causes of inaccurate readings. If you finish a HIIT class and then walk to your car, your heart rate is still elevated from the workout. Apple Watch sees a high heart rate at a slow walking pace and calculates a low VO2 Max.

Your watch is loose or positioned incorrectly. Optical heart rate sensors need consistent skin contact. A loose band produces noisy heart rate data that can push the estimate in either direction.

You take heart rate medications. Beta blockers and similar medications limit how high your heart rate can go, which affects the submaximal prediction model Apple Watch uses.

You have not done enough qualifying workouts. If your most recent qualifying outdoor workout was weeks or months ago, the estimate may simply be stale.

What If It Is Accurate

If you genuinely have low cardio fitness, the good news is that the bottom quartile sees the largest absolute improvement from training. Research on VO2 Max and longevity shows that moving out of the bottom 25% provides the single largest reduction in mortality risk. Eight to twelve weeks of consistent aerobic exercise can move you from “Low” to “Average” or better.

The strategies for improving VO2 Max are straightforward. Start with 3-4 sessions per week of moderate aerobic exercise (brisk walking, cycling, swimming) for 30 minutes. Add one higher-intensity session per week as your fitness improves.

How to Get a More Accurate Reading

Do a dedicated 20+ minute outdoor walk or run at a steady, moderately brisk pace on flat ground. Do this when you are fresh, not after another workout. Wear your watch snugly. Repeat 3-5 times over 2 weeks. This gives Apple Watch the cleanest possible signal for its VO2 Max estimation.

Luen shows your VO2 Max trend alongside your daily habits, so you can see whether your reading is improving over time and what patterns correlate with the changes.