Getting fitter? What your Apple Watch can tell you
By Stephan Seider, founder of V.Runner · Updated
Looking at your runs over the past week or so? Look at the data and think about how you felt. The number for your cardio fitness comes from Apple. It can help provide context for your runs and how they felt.
Maybe your usual loop has become easier. Maybe you’re able to run for a longer duration without wondering how you will get home. These are good things to notice, even when your runs don’t reflect a new personal best.
What does Apple Watch cardio fitness mean?
Apple Watch uses your heart and movement data from outdoor runs, walks, and hikes as well as other data in your Health profile to estimate your VO₂ max. This estimates how much oxygen your body can use during exercise, rather than measuring it directly in a lab.
On your iPhone, open Health and choose Heart → Cardio Fitness. Select a longer time frame, for example, one month or six months. Depending on your iOS version, categories are under Browse or Search. Apple has more information about how it makes this cardio fitness estimate and when it is available.
A missing reading is not a score of zero. Indoor workouts do not factor into this. An initial reading can take a few eligible workouts. Usually, a change in this graph means that you should take a closer look and analyse your data. A change does not mean that you should rewrite your goals for your next workout.
Find the runs behind the graph
Open Fitness on your iPhone, find Sessions and choose a run. Splits, heart rate, effort and route are shown in the summary when recorded. The Apple guide explains where the details are, but older versions may organise the history differently.
Choose a few runs meant to do similar jobs. An easy loop and a hard 5K race give different answers. Note the conditions and route. Pay attention to the stops. Add what you remember from the run: was it comfortable or a little harder than you expected?
A better question than “Was I faster?”
Try asking, “What was different, and does the comparison make sense?” Here is an illustrative note, not a runner’s result or a promised improvement:
Two runs show 5 km in 32 minutes. The first felt hard on a hilly route. The second felt comfortable on a flat route. The time is the same, but the routes differ, so these two records alone do not establish a fitness change.
Keep the detail instead of forcing a conclusion.
Keep a simple running note
Save these four bits of information after your next run and store them in the Notes app or a paper running diary. This system helps you keep your observations in one place.
- The run: route, distance and whether it was meant to be easy or harder.
- The context: hills, stops, weather or anything unusual.
- The feeling: how hard it felt, in your own words.
- The question: what would you like to compare with a similar run later?
Instead of analysing just the best or worst runs, look back on several runs and use them to organise your thoughts. This system is not intended to be a fitness test or a method to adjust your training.
How V.Runner uses your running
V.Runner keeps Apple’s cardio fitness reading separate from training paces, and a higher number on your Apple Watch alone doesn’t translate to an increase in training paces. Recent running performance is what provides the evidence for the plans made by V.Runner’s planner.
After a session, use V.Runner’s run feedback to explain how the effort and distance felt. This feedback can support a suggestion to make a coming run easier or shorter. You review proposed changes before accepting them. See how V.Runner plans your runs.
Missing a run from your history? Find where the recorded workout has stopped before comparing an incomplete set of runs.
Sources
Apple documentation checked on 24 October 2026. The running-note example is illustrative; it is not a measured V.Runner outcome.