The science

HRV measures the tiny variation in time between each heartbeat. It sounds like a small thing, but it's one of the most powerful markers of overall health and recovery that exists.

Higher HRV means your nervous system is in a balanced, recovered state — ready to handle stress, training, and daily life. Lower HRV means your body is under load: fighting off illness, recovering from a hard session, dealing with poor sleep, or carrying built-up stress.

HRV is sensitive to almost everything — training intensity, alcohol, sleep quality, emotional stress, illness. That sensitivity is what makes it so useful. It's your body's broadest recovery signal.

What matters most isn't a single reading, but the trend over time. A gradual rise in your average HRV over weeks means your body is adapting well. A sustained drop means something is off — even if you feel fine.

Your resting heart rate is how fast your heart beats when you're completely at rest. A lower resting heart rate means your heart is stronger — it can pump the same amount of blood with fewer beats.

Over time, as fitness improves, resting heart rate drops. A sudden spike — even by just a few beats per minute — can signal illness, dehydration, overtraining, or built-up stress.

The Signal tracks this daily and looks at the trend. A resting heart rate that's been slowly climbing for 2 weeks tells a different story than one that spiked for a single day after a bad night's sleep.

Sleep is where your body does most of its repair and adaptation. Without enough sleep, HRV drops, resting heart rate rises, and the benefits of training shrink.

Duration matters, but it's not the whole picture. Consistency — going to bed and waking up at roughly the same time every day — has a measurable effect on recovery. Someone sleeping 7 hours at the same time every night will typically show better HRV than someone sleeping 8 hours at random times.

The analysis tracks bedtime, wake time, total duration, and consistency. When your sleep timing drifts — say, bedtime moves from 22:30 to midnight over a few months — your Revelation will show you exactly what that drift is costing you in recovery.

Not all exercise is equal, and the difference often comes down to intensity — specifically, which heart rate zone you're training in.

Zone 2 (roughly 60–70% of your maximum heart rate) is where your body burns fat for fuel and builds endurance. It feels easy — conversational pace. The science recommends spending about 80% of your training time here.

Zone 4 and above (80–90%+ of max heart rate) is high-intensity work — intervals, sprints, hard efforts. Valuable in small doses, but it's taxing on your nervous system and needs serious recovery time.

The problem most people have — and this is one of the most common Revelations in the data — is spending too much time in Zone 3. Zone 3 is the dead zone: too hard to recover from easily, too easy to drive real improvement. It feels like a solid workout, but it's often the least productive zone to train in.

Every workout gets broken down by heart rate zone, so you can see exactly where your time is going. Often, the gap between what you think you're doing and what the data shows is the entire Revelation.

A single weigh-in tells you almost nothing. Weight fluctuates by a kilogram or more day to day based on hydration, food timing, and other factors.

What matters is the trend over weeks and months. The analysis tracks the direction — is weight gradually moving the way you want, stuck, or going the wrong way? — and looks at it alongside your training load, sleep patterns, and recovery.

A weight plateau despite heavy training and calorie restriction, for example, is a classic sign that your body is adapting to stress. It's holding on to everything it can because you're asking too much of it. That's exactly the kind of pattern that shows up in a Revelation.