About Zyra
Zyra is a small independent project that builds two focused fitness apps and publishes the math behind them. The people who write the apps write these pages.
What we build
- Zyra Workouts
- An offline-first workout logger, live as a web app at workout.zyra.fit. In active development — not yet submitted to the App Store. What it does →
- Zyra Nutrition
- A local-first macro and calorie tracker, live as a web app at nutrition.zyra.fit and under active development. What it does →
- This site
- Free calculators, an exercise library, muscle-group and program pages, a glossary, and guides — all built from the same formulas and catalog data the apps use.
Why the math is public
A tracking app asks you to trust its numbers. We would rather you could check them. Every calculator on this site runs the formula the app runs, the methodology page writes each one out with its constants and a worked example, and the exercise library is generated from the app's own catalog rather than written separately. When the app changes, the page changes with it.
The calculators run entirely in your browser. Nothing you type into them is sent anywhere.
The rules these pages follow
- No medical claims. Zyra copy makes no medical or health-outcome claims of any kind — nothing about injuries, conditions, or what training does for your health. Training effects are stated as training outcomes — reps, load, estimated 1RM, sets per week — and nothing more. Training guidance, never medical advice.
- Every number is derived or cited. A figure comes from a formula you can reproduce on the page, or from a named source we opened and checked. Where no citable source exists, the text says it is arithmetic, not a trial result.
- No hype about ourselves. No user counts, no ratings, no quoted praise — none exist to cite. Status is stated plainly wherever it matters.
- No ads, nothing sold. What the site measures, and with what, is on the privacy page.
- Corrections are welcome. If a number, a source, or a sentence is wrong, email privacy@zyra.fit. Corrections are made on the page and the page's updated date changes.
Who reviews the research
Every article's research is reviewed by Plamen Yankov, Data Scientist (BSc Computer Science (Machine Learning and Artificial Intelligence), First Class Honours, Goldsmiths, University of London). The review checks that each study says what the article says, that the numbers and statistics are read correctly, and that the limits are stated. His page lists what a review covers, what it does not, and every article reviewed.
One backend, one account
Both apps are clients of the same Zyra backend and account system. An account is optional in Zyra Workouts; when you do sign in, sync exists to back your data up and restore it, not to mine it. Your data is never sold and never used for advertising.
Reach us
Email is the channel: privacy@zyra.fit. See contact for what we can and cannot help with, and support for the apps.