How it works
RunCadence reads data from Apple Health in the background. You grant permission once, per data type, and you can revoke any of it at any time in iPhone Settings → Privacy → Health → RunCadence.
The data stays in our EU databases. We never sell, share, or use it for advertising. We don't use it to train AI models. See our Privacy Policy for the legal details.
Below is every metric we read, what it tells your coach, and why it matters for running.
Cardiac signals
Resting heart rate
The lowest heart rate you reach during the day. A downward trend over weeks means your aerobic fitness is improving. A sudden spike of 5 to 7 bpm above your baseline often signals stress, illness, or under-recovery, and your coach uses this as an early warning to dial back.
Heart rate variability (HRV)
The variation between consecutive heartbeats, measured during sleep. Suppressed HRV versus your personal baseline means your nervous system is taxed, a signal to choose recovery over intensity.
Heart rate recovery
How fast your heart slows down in the first minute after a hard effort. Faster recovery means better aerobic fitness. Trending downward after similar workouts suggests accumulated fatigue.
Respiratory rate
How many breaths per minute you take during sleep. A persistent 1 to 2 bpm rise above baseline can precede illness by 24 to 48 hours. Paired with rising temperature, it's a strong "take it easy" signal.
Blood oxygen (SpO2)
Useful for runners at altitude or in trail and ultra training. Below normal at rest can indicate altitude stress or sleep-disordered breathing.
Recovery signals
Sleep duration and stages
Total time asleep is the single biggest recovery lever. We also read sleep stages (REM, deep, core, awake) when available. Sleep debt over a 7-day window flags days when your coach should prescribe rest, not threshold.
Sleeping wrist temperature
Your overnight body temperature trend. A positive deviation of 0.5°C or more over several nights, combined with elevated HR and lowered HRV, is one of the strongest early-illness signals available outside a clinic.
Fitness and energy
VO2max
Apple's estimate of your maximum oxygen uptake, updated weekly when you run outdoors. We treat it as a long-term fitness trend. Our coach pairs it with your own field-test results to give a more accurate picture than the wrist-derived number alone.
Active energy
Calories burned through movement. We use this with distance and duration to estimate training load.
Body mass
You can enter your weight at onboarding, and we'll also read it from any smart scale that writes to Apple Health. Weight matters for metrics expressed per kilogram (like running power per kg). We won't comment on it, that's not our job.
Running biomechanics
Running power
How hard you're working in watts, adjusted for hills and wind. A pace-equivalent intensity that doesn't lie when terrain changes.
Ground contact time
How long each foot stays on the ground per stride. Shorter usually means better running economy. Sharp asymmetry after an injury is worth flagging.
Vertical oscillation
How much your torso bounces with each step. Lower is generally more efficient. Track personal trend over time, not absolute numbers.
Stride length
How far each step takes you. We track changes over time as a fatigue signal. Your stride often shortens when you're tired.
Activity and workouts
Workouts
Your runs (and any other workouts your Apple Watch records). We read distance, duration, average and max heart rate, pace splits, cadence, elevation, and the raw heart rate time-series. That's what powers the detailed workout analysis after each run.
Distance, running speed, step count
Daily movement totals. Step count is also a proxy for non-running activity (your overall NEAT, non-exercise activity thermogenesis) which affects recovery.
What we don't read
We deliberately don't request:
- Reproductive health (menstrual cycle, sexual activity)
- Mental health (mindfulness sessions, state of mind)
- Nutrition logs
- Blood diagnostics (glucose, alcohol, etc.)
- ECG and atrial fibrillation data
- Audiogram data
If we ever expand into nutrition coaching, we'll ask for additional permissions explicitly and explain why.
Your control
Open iPhone Settings → Privacy → Health → RunCadence to see every permission we hold and revoke individual types whenever you want. Disconnecting our HealthKit access entirely is one tap away.
Our full data handling rules are in the Privacy Policy.
Still need help?
Write to support@runcadence.app. A real person reads every message.