Why Heart Rate Matters
Your heart rate is the single best real-time indicator of how hard your body is working. Unlike pace — which varies with terrain, weather, and fatigue — heart rate tells you the true effort your body is making.
Just5K uses your heart rate data from Apple Watch to personalize your intensity zones and track your fitness improvements over time.
Resting Heart Rate
Your resting heart rate (RHR) is measured when you're completely at rest. For most adults, it's between 60–100 bpm. As you get fitter, your RHR will drop — sometimes significantly.
A lower RHR means your heart is pumping more blood per beat, so it doesn't need to beat as often. It's one of the most reliable signs of improving cardiovascular fitness.
Tip: Check your resting heart rate trend in Apple Health. After a few weeks of training, you'll likely see it decrease by 3–5 bpm. That's your heart getting stronger.
Max Heart Rate
Just5K estimates your max heart rate using the formula 220 minus your age. This isn't perfect for everyone, but it's a reliable starting point that improves as the app collects more data from your workouts.
During Your Runs
Don't obsess over the number mid-run. Glance at your zone — Easy, Moderate, or Hard — and adjust if needed. The zones do the math for you.
Over time, you'll notice that the same pace produces a lower heart rate. That's fitness happening. Your body is becoming more efficient at delivering oxygen to your muscles.
