Know your numbers
Your iPhone and Apple Watch measure a lot. Here's what each number means, what tends to move it and how to read your own, in plain words. Every page lists the sources it was checked against.
Heart and breathing
Resting heart rate
How many times your heart beats a minute when you're properly at rest. Apple Watch estimates it each day from calm moments.
Heart rate variability (HRV)
The tiny changes in time between your heartbeats. Apple Watch records it as SDNN, in milliseconds, from short readings when you're still.
Heart rate
How many times your heart beats a minute, right now. Apple Watch measures it with light sensors on the back of the watch.
Walking heart rate average
Your average heart rate while walking during the day. Apple Watch works it out from readings taken as you walk, walking workouts included.
Heart rate recovery
How far your heart rate falls in the first minute after a workout ends, as estimated by Apple Watch.
Cardio fitness (VO2 max)
The most oxygen your body can use during hard exercise. Apple Watch estimates it during outdoor walks, runs and hikes.
Respiratory rate
How many breaths you take a minute while you sleep. Apple Watch estimates it overnight when you wear it to bed with sleep tracking on.
Blood oxygen
How much oxygen your red blood cells are carrying, as a percentage. Apple Watch estimates it on supported models, in supported regions.
Wrist temperature
How your skin temperature at the wrist during sleep differs from your own baseline. Apple Watch measures it overnight on supported models.
Sleep
Sleep duration
How long you were actually asleep, as estimated by your Apple Watch, naps included. Lying awake in bed doesn't count.
How much sleep you need
Most adults do best on 7 to 9 hours, but needs differ. Pajdo estimates yours from your own nights and keeps it within that range.
Sleep stages
Your Apple Watch's estimate of how many minutes you spent awake and in REM, core and deep sleep each night.
Sleep efficiency
The share of your recorded sleep time that you actually spent asleep. Higher means less time lying awake.
Night awakenings
How many times you woke during your main sleep, and for how many minutes in total, as estimated by Apple Watch.
Bedtime consistency
How much the time you fall asleep wobbles from night to night over the last week. A smaller spread means steadier timing.
Sleep debt
Pajdo's estimate of how far your sleep fell short of your personal sleep need over the last 7 nights, with long nights paying back short ones.
Moving through the day
Steps
How many steps your iPhone and Apple Watch counted today, from Apple Health.
Active energy
An estimate of the energy you burned by moving today, on top of what your body uses at rest. It fills your Move ring.
Exercise minutes
Minutes of movement at a brisk walk or harder, as counted by Apple Watch. They fill your Exercise ring.
Stand hours
How many hours today you stood up and moved for at least a minute, as counted by Apple Watch for your Stand ring.
Walking and running distance
How far you walked and ran today, estimated by your iPhone and Apple Watch and saved in Apple Health.
Flights climbed
How many flights of stairs you walked or ran up today, counted by your iPhone or Apple Watch.
Training
Training load
How much work your workouts add up to, from minutes in each heart rate zone, with a recent average and a longer one.
Acute:chronic load ratio
Your last week's training load compared with the weeks before it. A soft hint that you've ramped up fast, never a prediction.
Heart rate zones
Five heart rate bands from easy to all-out, set automatically from your Apple Health data like Apple's Workout app, or from values you enter.
Rest is part of training
Fitness grows while you recover, not only while you train. Rest days and good sleep let a hard session pay off.
Mind
Small experiments
Caffeine curfew
Stop caffeine at lunch for 10 days and see whether your sleep notices. Pajdo keeps an eye on how long and how soundly you sleep.
A wind-down half hour
Give yourself a calm 30 minutes before bed for 2 weeks: lights low, phone down, something relaxing. Then see what your sleep says.
Same wake-up time, every day
Get up at the same time every day for 2 weeks, weekends included. Your body likes knowing when the day starts, and Pajdo will show what changes.
Dinner a little earlier
Move your main evening meal a bit earlier for 2 weeks and see if your nights change. The research is still mixed, which makes it a fun one to test.
How to read your numbers
Your usual range
Pajdo compares your numbers with your own recent days, not with everyone else's. Your usual range is your typical value plus its everyday wobble.
Watch numbers are estimates
Apple Watch estimates most of what it records. Heart rate tends to be close, energy much less so, so a change over several days says more than one number.
Trends
A trend is a steady change over weeks, not one odd day. Pajdo only calls one when the change is clearly more than everyday noise.
Linked isn't caused
When two of your metrics move together, that's a link, not proof that one causes the other. Pajdo needs 30 paired days before he mentions one.
This is general wellness information, not medical advice. If a number worries you, or stays away from your usual for a while, talk to a doctor.