About SAYA

The story behind SAYA

It started with a simple observation: some nights give you an incredible amount of energy back, others hardly any — even after the same amount of sleep.

As an endurance athlete with a Garmin on my wrist, I had the data every morning: Sleep Score, HRV, Body Battery. But none of it answered the real question: why was this night so restorative — and that one not? And what could I have done differently the evening before?

Before that, I had spent some time in a research group working on heart rate variability, mostly on one question: how does one person's HRV change from day to day? It showed me how much these numbers reveal when you compare them not with other people, but with yourself.

Later, reading into longevity research, I kept coming back to the same topic: recovery during the night. It is one of the most powerful levers for performance and health — and one most of us barely use. In a fast-paced, screen-focused world, we take load to bed every evening and give away a large part of our recovery. And the evening, where that is decided, gets hardly any attention.

SAYA grew out of these questions: an app that connects what you do before bed with how your body recovers — using your own data instead of generic rules.

Deliberately little screen time

An app meant to support better sleep shouldn't keep you on a screen in the evening. That's why SAYA deliberately has no journaling tools: your evening is logged in a few taps, and SAYA reads the rest automatically from your Garmin. The goal isn't more time in the app — it's a real sense for an effective wind-down and good evening habits.

That's where the brand promise comes from: Optimize your Evening. Maximize your Recovery.

— Lukas Bröll, founder of SAYA

What SAYA is based on

• Your Garmin data: sleep, overnight HRV, heart rate, stress and activity — read with your permission. More on the Garmin page.
• Your evening log: a few taps about dinner, drinks, training and wind-down.
• Published research: the physiology behind each metric is explained, with sources, on the science page.
• Transparent methods: how scores and correlations are calculated — including their limits — is documented in the methodology.

Privacy

Your sleep and heart data are health data, and SAYA treats them that way: data is stored in Germany, there is no advertising, no data sale, no advertising or analytics SDKs and no cross-app tracking. You can export or delete your data in the app at any time. Details are in the App Privacy Policy.

Wellness, not medicine

SAYA is a wellness product. It helps you understand patterns in your own data; it is not a medical device and doesn't diagnose, treat or prevent any disease. If you suspect a sleep disorder or a heart condition, please talk to a doctor.

Contact

Questions, feedback or press enquiries: l.broell@freenet.de. Legal details are in the imprint.

Garmin™ is a trademark of Garmin Ltd. SAYA is not affiliated with or endorsed by Garmin.

Keep reading

• How SAYA analyzes your sleep & recovery data
• Garmin sleep & recovery analytics

SAYA is a wellness product, not a medical device. Nothing here is a diagnosis or medical advice — if you suspect a sleep or heart condition, please talk to a professional.