Heart Rate

What Heart Rate Measures

Heart rate tracks how hard the heart is working to move blood, moment to moment. The sympathetic branch of the autonomic nervous system releases norepinephrine to push the rate up when the body needs more output, and the parasympathetic branch releases acetylcholine to pull it back down at rest, with hormones layered on top of both.^[1] Climbing stairs, a stressful email, caffeine, and a hot room all move the number, so daytime swings are the metric working, not noise. That makes heart rate different from resting heart rate, the single overnight baseline figure, and from HRV, which measures the timing variation between beats rather than the count.

How It's Measured

Wearables sample heart rate through the day with photoplethysmography (PPG), an optical sensor that reads the small blood-volume change under the skin with each beat. A study testing six wearables against a clinical ECG found them reasonably accurate at rest and at sustained elevated heart rates, with no statistically significant accuracy difference across skin tones. Absolute error ran about 30% higher during activity than at rest, so a reading taken mid-movement carries more noise than one taken while still.^[2]

Apple Watch also reports a walking heart rate average, a HealthKit metric built from the heart rate samples taken while you walk. The watch surfaces it as its own daily view alongside your heart rate range and resting rate.^[3] Because walking is light activity rather than rest or a workout, and heart rate rises with physical demand,^[1] the walking average captures the everyday load your heart carries between those two extremes.

Why People Track Heart Rate

Context is the point. A high number during a workout and the same number at your desk mean different things, so continuous heart rate is most useful read against what you were doing at the time. Watched over weeks, the daytime pattern shows how your heart responds to training, stress, and recovery. The overnight baseline story, including how resting heart rate shifts across the menstrual cycle, lives in the resting heart rate entry.

For how heart rate during workouts interacts with cycle phase and training load, see Exercise Heart Rate and Training Load Across Your Cycle.

How Go Go Gaia Tracks Heart Rate

Go Go Gaia syncs heart rate from Apple HealthKit, so the daytime samples and walking heart rate average your Apple Watch or connected wearable already records flow in without manual logging. The app charts them against your cycle phase alongside resting heart rate and HRV, so a daytime pattern shows up in the context of where you are in your cycle.

What the Research Shows

Wearable optical sensors hold up well when the body is still: the six-device ECG comparison found all devices reasonably accurate at rest and during prolonged elevated heart rate, with the devices differing mainly in how they handled changes in activity.^[2]

Overnight, the same optical approach feeds the resting heart rate calculation. A 2025 validation study comparing five consumer wearables against a chest-strap ECG reference overnight found accuracy varies by device, with the closest devices landing within a couple of beats per minute of the reference.^[4] How that overnight number shifts across the menstrual cycle is covered in the resting heart rate entry.

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

Is heart rate the same as resting heart rate?

No. Heart rate is the live beats-per-minute number sampled all day as you move, work, and rest. Resting heart rate is one daily figure your wearable calculates from sustained stillness, usually overnight during sleep. Resting heart rate is the baseline, and daytime heart rate is how your heart responds to everything on top of it.

What is walking heart rate average?

Walking heart rate average is a HealthKit metric built from the heart rate samples Apple Watch takes while you walk during ordinary activity. Because walking is light activity rather than rest or a workout, it captures the everyday load your heart carries, a different slice than resting heart rate or exercise heart rate.

How accurate is wrist-based heart rate tracking?

A study testing six wearables against a clinical ECG found the devices reasonably accurate at rest and at sustained elevated heart rates, with no significant accuracy difference across skin tones. Absolute error ran about 30% higher during activity than at rest, so readings mid-movement carry more noise than readings taken while still.