About this site
- Site name
- Muscle Diary
- URL
- https://muscle-diary.nacn.app/en/
- Operator
- nacn
- Launched
- October 2026
- Price
- Free (no account or install needed)
Why I made this site
Everyone knows that sticking with strength training makes you stronger, but it's hard to get a feel for how much muscle you can actually build in a few months, or how far your lifts will go up. Real training also runs into real-life obstacles: you skip rest and get stalled by fatigue or injury, or you do the same routine for so long that you stop making progress.
Muscle Diary turns that whole journey into a casual game where you raise a pixel-art character. It works the same way as Diet Diary, from the same operator: you can see how your choice of training, food, and sleep changes your body, based on research and widely used rules of thumb.
About the calculations
One-rep max estimates, protein targets, resting metabolism, and calories burned are based on formulas used in research and widely used guidelines. The formulas and sources are listed on How the Math Works.
That said, the numbers in the game are only estimates. This site is not medical advice and is not a personal training program. Talk to a doctor, certified trainer, or other professional about real training, nutrition, and injury prevention.
Contact
Please send feedback, comments, or bug reports about Muscle Diary through the contact form below.
The form's questions are in Japanese, but messages in English are welcome.
I'll review messages and reply as time allows. I may not be able to reply to every message. Any personal information you include will be used only to reply to you.
Related pages
- How to Play
- How the Math Works
- Privacy Policy (ads, analytics, and disclaimer)