Most fitness tracking shows effort: how hard you pushed today. Fitness shows the opposite and more encouraging side: how much easier the same walk has become. It's one of the clearest signs that walking is working.
What does Fitness measure?
Fitness compares how fast you walk with how hard your heart works to do it, using the speed and heart rate your Apple Watch records during walks. If you walk at the same speed with a lower heart rate than before, or faster at the same heart rate, you've become fitter.
Why does the same walk get easier?
As you walk regularly, your heart pumps more blood with each beat and your muscles get better at using oxygen. The result is that a pace which once pushed your heart rate up now barely moves it. This is aerobic, or cardiorespiratory, fitness, and it's one of the most important measures of health there is.
Why does aerobic fitness matter?
- Kodama et al., 2009. A review of 33 studies covering more than 100,000 adults found that each 1-MET higher level of aerobic fitness was linked to a 13% lower risk of death from any cause and a 15% lower risk of heart disease and stroke.
A MET is a unit of energy use: sitting quietly is about 1 MET. Later reviews have confirmed aerobic fitness as one of the strongest predictors of long-term health.
How long does it take to see a change?
For people starting from little exercise, a few weeks of regular brisk walking is often enough to see the same walk take a slightly lower heart rate. The change is gradual, which is why Fitness looks at weeks, not days.
What can make Fitness look worse?
Heart rate is affected by more than fitness. Heat, hills, poor sleep, stress, caffeine, dehydration and illness can all make a walk look harder than it really was. Some medicines, such as beta blockers, lower heart rate overall. Look at the direction over several weeks rather than any single walk.
How can you improve your Fitness?
- Walk briskly, often. Most of the gain comes from regular moderate walking, at about 100 steps a minute or faster.
- Add some harder minutes. Short brisk stretches or hills once or twice a week push fitness up faster.
- Keep the route the same. Repeating a familiar walk makes the change easiest to see.
- Be patient. Fitness builds over weeks and months, and it fades if you stop.
Fitness in StepUp
StepUp reads walking workouts and heart rate from Apple Health and compares your walking speed with your heart rate over time, so you can watch the same walk get easier. It comes with a short note explaining what it measures. Fitness needs an Apple Watch and is part of StepUp Pro. Like every StepUp metric, it's calculated and stored on your iPhone.
The short version
- Fitness compares your walking speed with your heart rate.
- The same pace at a lower heart rate means you've got fitter.
- Higher aerobic fitness is strongly linked to longer life: about 13% lower risk of death per 1 MET.
- Brisk, regular walking is enough to move it. Watch the trend over weeks.
Questions
Can walking improve cardio fitness?
Yes. For people who don't exercise much, regular brisk walking is enough to raise aerobic fitness. You'll see it as a lower heart rate for the same walk over a few weeks.
Why is my heart rate lower on the same walk?
Usually because you're getting fitter: your heart pumps more blood with each beat, so it needs fewer beats for the same pace. Cool weather and a good night's sleep also help.
Is this the same as Apple's Cardio Fitness (VO2 max)?
They're related but not the same. Apple Watch estimates VO2 max, a single fitness score. StepUp's Fitness shows how your walking speed and heart rate change together on your own walks over time.
Does Fitness need an Apple Watch?
Yes. It needs heart rate during walks, which only an Apple Watch records.
Sources
Written by Dheeraj Kumar Sharma, who makes StepUp. How the guides are written.
