Understanding Your Heart Rate
What your Apple Watch heart rate data tells you about your fitness and recovery.
By Just5K
Your heart, in plain language
Your heart rate is the most honest read on how hard your body is working in the moment. Pace can lie — terrain, weather, fatigue all skew it. Heart rate just tells you the truth.
Just5K reads your heart rate from Apple Watch and turns it into something useful: a personalised set of effort gears, and a long-term picture of how your fitness is changing.
Your pulse at rest
How fast does your heart beat when you're doing absolutely nothing? That's your resting pulse — usually measured first thing in the morning, while you're still in bed. For most adults, it sits between 60 and 100 beats a minute.
The interesting number isn't today's. It's the trend over weeks. As you get fitter, your resting pulse usually drops — sometimes by 3–5 beats. Your heart is pumping more blood per beat, so it doesn't need to beat as often. That's the most literal definition of "getting fitter" you'll find.
Tip: Check the trend in Apple Health, not the daily number. After a few weeks of training, you'll likely see it drift down. That's your heart getting stronger.
Your "ceiling"
Just5K estimates the highest your heart can go using a simple rule of thumb: 220 minus your age. So at 35, the ceiling is around 185.
This isn't perfect for everyone — some people run higher, some lower — but it's a reliable starting point that gets more personal as the app watches you train.
During your runs
Don't stare at the number mid-run. Glance at the gear — Easy, Moderate, or Hard — and adjust if needed. The gears do the math for you.
What you'll notice over time: the same pace produces a lower heart rate. Same effort on your side, less work for your heart. That's fitness happening — your body is becoming more efficient at moving oxygen to your muscles.