JST Fitness — Terms of Service

Last updated: 18 August 2026

These are the terms you agree to when you use JST Fitness. They are written to be read, not to be skipped — there is no fine print here and nothing is hidden in a defined term.

The short version: JST Fitness is a personal fitness tracker, free to use while it is in beta. It is not a doctor, it comes with no guarantees, and the numbers it shows you are estimates. Use it to keep track of your own training. A paid tier is coming — its terms are in section 1 — but nothing is charged today. If something in the app matters to your health, ask a professional, not an app.

If you do not agree with these terms, don't use the app — and if you've already got an account, you can stop using it and delete it at any time.

1. What JST Fitness is

JST Fitness is an app for tracking your own workouts, body weight, measurements, meals and daily steps. It runs on Android and in a web browser.

• It is free today. Nothing is charged and no payment details are collected yet. A paid tier — JST Fitness Pro — is coming, and because you should never be surprised by a price, its terms are written down here now, before any of it is switched on:

• Every new account starts with a 10-day free trial of the full app. Today the trial begins when the account is created, because nothing can be bought yet. When the paid tier goes live, starting the trial will mean picking a plan and setting the subscription up through Google Play, so a payment method goes on file at that point. Nothing is charged during the ten days — but at the end of them, the plan you picked starts and is charged automatically, unless you cancel first. Cancel any time before the trial ends and you are charged nothing. Cancelling is done in Google Play's Subscriptions screen, as described under "Cancel anytime" below. The app will say all of this next to the button that starts the trial, before it asks for any payment details.
• One free trial per person. A new account created with an email address that has already had its trial starts without one — deleting an account and signing up again does not reset the clock. (How we check this, and the little we keep to do it, is described in the Privacy Policy.)
• After the trial, continuing requires JST Fitness Pro: $4.99 / month or $29.99 / year (US dollars; local prices on Google Play may vary with currency and tax). The subscription renews automatically at the end of each period until you cancel.
• Cancel anytime. On Android, subscriptions are bought and cancelled through Google Play — open Play's Subscriptions screen and cancel there; cancelling takes effect at the end of the period already paid for, and you keep access until then. On the web, cancellation will be available from Profile → Subscription, and will be as easy as subscribing was — no phone calls, no retention maze.
• Refunds. Purchases made through Google Play follow Google Play's refund policy. For purchases made directly on the web, if something is genuinely wrong write to the address at the bottom of this page and it will be sorted out like adults.
• Price changes. If the price ever changes, existing subscribers are told in advance and asked to agree before the new price applies — a price change never just happens to a stored payment method.
• Your data is never hostage. If your trial or subscription ends, you can still export everything you recorded (section 6). Ending a subscription never deletes your data.
• A higher tier with AI features may come later. It will get its own terms here before it ships, the same way this one did.

None of the above is billed until the payment system goes live in a future update; when it does, these are the terms it will go live under, and the app will ask you to agree to any material change first (see section 11).

• Founding testers. If you took part in the JST Fitness private beta before the paid tier launched, your account receives the paid tier free of charge for as long as JST Fitness offers a paid tier ("lifetime access"). As of 5 August 2026 this is no longer a list kept on paper: founder status is recorded against each qualifying account on the server, granted to every account created during the closed beta, and it cannot be self-assigned — the app can read it but nothing a user does on a device can write it. It is attached to the account you tested with; it is personal and non-transferable, it ends if you delete the account, and it covers the paid tier's features as offered from time to time. It is not a promise that the app or any particular feature will exist forever, and it has no cash value.

• It is single-user. There are no friends, no feeds, no comments and no leaderboards, and nothing you record is published to other users of JST Fitness — no other user can see your workouts, your weight, your meals or anything else you log. One thing can reach other users, and only because you chose it: a food you added to the food list yourself and switched sharing on for. What is shared is the product — its name, brand, serving, barcode and label figures — shown in every user's food list marked "Community", with nothing about you attached: not your name, not your account, not what you ate or when. Sharing is off unless you switch it on, food by food, and section 9 says what you agree to when you do. You can also build a weekly summary image and send it yourself through your phone's own share sheet; that goes only where you send it. None of it is sold, and nothing is advertised against it. Three things reach the developer even if you never make an account, because they have to work that way: feedback you choose to send, automatic crash reports, and — because the demonstration clips are streamed rather than bundled into the app — a request to our hosting each time one plays. If you do make an account, what you sync is stored in the developer's own database too, because he is the one running the server. The Privacy Policy sets out exactly what each of those contains, and lists everything that syncs.
• It is a personal project, built and run by one person. It is not a company, a medical service or a certified device.

Creating an account is optional. Without one the app works entirely offline on your device. With one, most of your data is synced so it follows you between devices — exactly what is synced is listed in the Privacy Policy, which is part of these terms.

2. This is not medical advice

Read this section even if you skip the rest.

JST Fitness shows figures like BMI, BMR, TDEE, estimated calories burned, estimated walking distance, macro targets and body measurement trends. It also shows figures about your training: an estimated one-rep max and other estimated strength numbers, personal records and progress charts built from them, a difficulty rating on each exercise, the plate calculator's suggested loading, and which muscles an exercise is listed as working. Every one of those is a general-purpose estimate calculated from numbers you typed in, using standard public formulas. They do not account for your medical history, your body composition, your medications, your injuries, pregnancy, an eating disorder, or anything else about you as a person.

The estimated one-rep max deserves its own sentence, because it is the one figure here you might act on by loading a barbell. It is worked backwards from the reps and weight you logged, using formulas built from other people’s data in a narrow rep range. It is not a weight you have lifted, and not a weight you should assume you can lift. The app dims it and says so on screen when your rep count leaves the range those formulas can speak to.

Specifically:

• JST Fitness is not a medical device and has not been reviewed, cleared or approved by any medical or regulatory body.
• Nothing in the app is medical, nutritional, or professional advice, a diagnosis, or a treatment plan — not the numbers, not the goals, not the exercise descriptions or demonstration videos, and not the daily quotes.

• The yoga and meditation features time a practice and write down that you did it. They do not lead one: nothing is spoken, no audio plays over a sit, nothing watches you, and the app never paces your breathing or asks you to hold your breath. Some yoga sessions are presets, and where you tap one the app has chosen the sequences, their order and their minutes — but what it shows you is a general written description of a shape, the same for everybody. It is not a class taught to you and it is not supervision of what you are doing. Yoga and meditation are not treatment for anxiety, depression, insomnia, pain, or any other condition, and nothing in this app is offered as such. If you are looking for help with your mental health, please speak to a qualified professional.
• The app is not a substitute for professional medical advice. Talk to a doctor, dietitian or qualified trainer before starting a new exercise programme, changing your diet, or acting on anything the app shows you — and especially if you have a health condition, are pregnant, are recovering from injury, or are unsure.
• Never ignore or delay professional medical advice because of something you read in this app. If you think you are having a medical emergency, stop and call your local emergency number.

Exercise carries real physical risk — strains, injuries, and for some conditions worse. Everything in this app about training — the exercise descriptions and demonstration clips, the routine templates and preset circuits, the estimates and the targets — is general fitness content. It is not medical advice, it is not a programme designed for your body, and the app cannot tell you that any exercise, weight or pace is safe for you. Whether you are fit to do a particular exercise is for you to decide, with a doctor's help if you have any doubt. If you feel pain, dizziness, faintness or shortness of breath while exercising, stop at once and get medical help if it does not pass. By using JST Fitness you expressly, knowingly and voluntarily assume the risks of the exercise you choose to do, including the risk of injury. You confirm that you are able to do the exercise you choose, and you agree that what you attempt — and whether you attempt it at all — is your decision and your responsibility.

Some parts of the app run a timer over a sequence you started. A follow-along circuit counts work and rest intervals, names the next exercise, and sounds a cue at each change. It does not watch you, it does not know your form, and it does not adapt to how you feel. It does flag some things before you start: a movement that suits a countdown badly, a hold that a heart or blood-pressure condition makes harder, an effort level that is not for your first week. Those flags only catch what the app can recognise. They are general, they are partial, they are not a judgement that anything else is safe for you, and their absence is never a clearance. The work and rest lengths are general fitness content, not a plan built for your body. You can pause it, lengthen a rest, skip a station or stop it at any time, and it records honestly what you actually did.

That assumption of risk covers a follow-along circuit, or a routine template the app laid out, just as much as a lift you chose yourself. The app may count an interval and name the next station; whether you do that station, whether you keep going, and when you stop are yours and never the app's.

3. Who can use it

You need to be 18 or older to use JST Fitness.

This app sets calorie and macro targets and can be pointed at losing weight. Those are not things it can do safely for someone who is still growing, and there is no dietitian or clinician behind it. So it is for adults, in line with the other apps that do this — MyFitnessPal and Noom both require 18 or older for the same reason.

The app is not directed at children and does not knowingly collect information from anyone under 18. If we learn that an account belongs to someone under 18, it is closed. What happens to the data then depends on their age, because the two are governed by different rules:

• Under 13 — the account and its data are removed promptly and without notice, as required by the US Children's Online Privacy Protection Act (COPPA). The law does not give us the option of waiting, and it does not let us keep the data in the meantime.
• 13 to 17 — this is not COPPA. They are simply not eligible under these terms, so the account is wound down rather than deleted on the spot: they are told, and they get at least 30 days to export their data before it is removed, exactly as section 10 promises everyone else.

4. Your account

If you create an account:

• Give a real email address you control — it's the only way to reset a password or reach you about your account.
• Keep your password to yourself. You're responsible for what happens under your account.
• One person per account. Don't share a login.

If you think someone else has got into your account, change your password and email the address at the bottom of this page.

5. What you may and may not do

You may use JST Fitness for your own personal, non-commercial fitness tracking. That's what it's for, and normal use is all that's expected.

Please don't:

• Break the law with it, or use it to harm anyone.
• Try to access other people's accounts or data, or to get at parts of the service you weren't given access to.
• Attack, overload, probe or interfere with the service or the servers behind it — including automated scraping, mass account creation, or hammering the sync or barcode-lookup endpoints.
• Upload malware, or deliberately submit false data to the shared food or error-reporting systems.
• Resell, rebrand or redistribute the app as your own.

Reporting a security problem you found honestly is welcome, not a violation — email it to the address below.

6. Your data

The Privacy Policy explains in full what is stored, what leaves your device and what never does. The parts that matter here:

• Your training data is yours. Using the app doesn't give anyone the right to sell it, share it or advertise against it, and none of those things happen. The one thing of yours another user can ever see is a food entry you chose to share — section 9 says what that means.
• You can export it from inside the app at any time.
• You can delete it. Uninstalling clears everything held on the device; if you made an account, you can delete the account and its synced data too.
• Keep your own backups of anything you can't stand to lose. This is a free app run by one person — see the next section.

7. The app is provided "as is"

JST Fitness is provided as is and as available, with no warranties of any kind, express or implied. To the fullest extent the law allows, that includes any implied warranty of merchantability, fitness for a particular purpose, accuracy, or non-infringement.

In plain English, nobody is promising you that:

• the app will always be available, or will keep working in future
• it is free of bugs, or that every number it shows you is correct
• your data will never be lost — sync can fail, phones die, and a free service can go away
• Health Connect, the food database, or any other service the app talks to will keep working or keep giving accurate answers

Nutrition information looked up from Open Food Facts is contributed by the public and is often wrong, incomplete or out of date. Check the label.

Foods marked "Community" were typed in from a product's label by another user of JST Fitness. The app checks a shared entry only for figures that are plainly impossible — it does not, and cannot, check that the figures match the label — so a Community entry can be wrong in every way an Open Food Facts one can. Our own catalogue is rounded, typical figures from standard references, not lab-precise. None of the three is a promise that a number is right. Check the label.

Food and restaurant brand names appear in the app solely to identify products for nutrition logging. They are trademarks of their respective owners, and no affiliation, sponsorship or endorsement of or by JST Fitness is implied. Their published nutrition figures may change — check the label or menu.

The same goes for anything you type into the optional "Following" line on a session. That text is yours: a class, a channel, an instructor or a video title you chose to write down so your own log makes sense to you later. Any names in it belong to their owners, and JST Fitness neither suggests them, curates them, checks them, nor has any affiliation with, sponsorship from, or endorsement by anyone you happen to name. The app does not host, stream, embed or link-preview anybody's video — it stores your line of text and shows it back to you.

8. Limitation of liability

To the fullest extent permitted by law, the developer of JST Fitness is not liable for any indirect, incidental, special or consequential damages, or for lost data, lost profits, injury, or health outcomes, arising out of your use of (or inability to use) the app.

Where liability cannot legally be excluded, it is limited to the greater of (a) the amount you have paid for JST Fitness in the twelve months before the claim, and (b) US $100.

There is a time limit. Any claim arising out of your use of JST Fitness must be brought within one year of the events that gave rise to it. After that, it's too late to bring it.

Some places don't allow certain exclusions of liability. If you live in one of them, the exclusions above apply to you only as far as that law allows, and nothing here takes away rights you have that can't be waived — including consumer rights, and liability for death or personal injury caused by negligence.

9. Who owns what

• The app belongs to its developer. JST Fitness — the app itself, its code, its name and branding, its design, and the mascot artwork — is owned by the developer. Using the app gives you a personal, non-transferable, non-exclusive licence to use it for your own fitness tracking, and nothing more: no ownership of any part of the app, and no right to copy, sell, rebrand or redistribute it (section 5 already asks the same thing).
• Your data belongs to you. Nothing in this section touches your workouts, weights, meals or anything else you record — that stays yours, exactly as section 6 says. The one exception is a food entry you choose to share — see "Foods you share" below.

• Suggestions. If you send feedback, an idea or a suggestion, you agree it can be used to improve the app — freely, without payment, credit or any other obligation to you. This is the normal deal for suggestion boxes everywhere, stated out loud instead of buried: if your idea ships, the feature belongs to the app, and the thanks belong to you. It applies to ideas only, never to your data — sharing a food is a separate choice with its own bullet below.

• Foods you share. The food list has a switch on foods you add yourself. Leave it off and the food stays private to your account. Switch it on and the entry — the product's name, brand, serving, barcode and label figures — is shown to every user of JST Fitness, marked "Community". When you switch it on you agree to this:
• You dedicate the entry to the public. You give up all copyright, database and related rights in it, worldwide, under the Creative Commons CC0 1.0 Public Domain Dedication — and where that dedication is not effective, you grant everyone a perpetual, irrevocable, royalty-free licence to use it for any purpose, as CC0's own fallback licence provides. So anyone — us, other users, and public food databases such as Open Food Facts, which we may pass shared entries on to — may use, copy, correct and redistribute it, without payment or credit to you. Label figures are facts and were never anyone's property; this makes the rest of the entry match.
• It can outlive your account. Because other people's logs may already rely on it, a shared entry stays in the list when you delete your account or switch sharing off again. What we cut is the private link between the entry and you — a scrambled reference we keep so that reports can be acted on, never shown to anyone — so that nothing on our servers connects the entry to you. Sharing never puts your log, your name or your account on anyone's screen.
• You promise it is a real food, copied from its label. A shared entry may only be a packaged food with a barcode, with figures taken from that product's label or its maker's published nutrition information. It may not contain anything else: not a person's name, email address, phone number or other personal data, not a message, a link, an advertisement or a joke, and not figures you made up. A food you looked up from Open Food Facts is not yours to share here — it already lives there, under a different licence. Deliberately sharing false figures is the misuse section 5 names.
• We may edit, merge, hide or remove any shared entry, before or after it appears — for accuracy, because it was reported, or because it breaks these terms. There is no review before an entry appears; the app checks it only for figures that are plainly impossible, and earlier versions are kept as a record of what changed. If we hide or remove an entry for breaking these terms and can reach you, we say why; if you think we got it wrong, email the address at the bottom of this page and a person will look again.
• Anyone can report a shared entry from the food list. Reports are read by a person, not a program, and the entry may be hidden or corrected as a result. Repeatedly sharing bad entries is the misuse section 5 describes and can end an account under section 10.
• We claim nothing either. We treat shared entries as public-domain facts, and we may release the whole community list under a public-domain dedication or an open database licence at any time.

10. Ending it

You can stop at any time. Uninstall the app, or delete your account from inside it. You don't need to tell anyone why.

Accounts can also be terminated from this end. An account may be suspended or deleted if:

• it is being used in a way that breaks section 5;
• it is being used to attack or abuse the service;
• the account holder does not meet the minimum age in section 3; or
• the law requires it.

What happens then depends on why, because the two situations are not the same:

• If the law requires it — in practice, if we learn the account belongs to someone under 13 — the account and its data are removed promptly and without notice. The law does not give us the option of waiting, and it does not let us keep the data in the meantime.
• In every other case, including the minimum age, you get told first: a notice in the app, and at least 30 days to export your data from inside the app before anything is deleted. If there is a way to email the address on the account, an email goes out as well — but the notice in the app is the one you can rely on. If the account is one that cannot be allowed to keep running in the meantime, it may be signed out or made read-only during that window — but your data stays exportable until it ends.

The service itself may also be discontinued. If JST Fitness is ever shut down, reasonable notice will be given in the app — and by email to account holders where there is a way to send one — so you can export your data before it goes.

11. Changes to these terms

These terms will change occasionally — when a feature is added, or when something here turns out to be unclear.

When they do:

• material changes — anything that meaningfully affects your rights, what you're allowed to do, or what happens to your data — move the "Last updated" date at the top of this page, and the app shows you the updated documents and asks you to agree again before you keep using it
• small corrections (typos, clearer wording, a fixed link) do not move that date and do not ask you to agree again

So the date is the signal. If it has not changed, nothing that affects you has.

If you keep using JST Fitness after a change, that's your agreement to the updated terms. If you don't agree, stop using the app and delete your account.

12. The boring legal bits

• Governing law and where disputes go. These terms, and any dispute about them or about JST Fitness, are governed by the laws of the State of Florida, United States, without regard to its conflict-of-laws rules. Any such dispute that ends up in court must be brought in the state or federal courts located in Florida, and you and the developer both agree those courts are the place for it.

If you are a consumer, this does not take away any right you have under the law of the country or state you live in, including any right to bring a claim there.

• Severability. If any part of these terms turns out to be unenforceable, the rest of them still stand.
• No waiver. Not enforcing something once doesn't mean it can't be enforced later.
• Entire agreement. These terms and the Privacy Policy are the whole agreement between you and JST Fitness about the app.
• Third-party services. The app relies on services run by other people — Supabase for accounts and sync, Google's Health Connect and Play Store, Open Food Facts for barcode lookups, and Have I Been Pwned for the password safety check. Their own terms apply to them, and none of them are controlled from here.

13. Contact

Questions, bug reports, security issues, or anything about these terms:

[email protected]