Startup idea: AI Video Diagnosis of Your Movement Pattern
One person can't do a lunge in any variation after a hundred tutorials; another hasn't activated their left glute in Bulgarian split squats for a year. Generic tutorials don't fix their case.
Get the PRD prompt, $9.99 Market: $1.8M in 3 years
r/xxfitness · Sep 14, 2026 – Oct 14, 2026 · 60 upvotes
Unable to do lunges. At all
Read the thread · 84 comments
AI Video Diagnosis of Your Movement Pattern is a startup idea for gym-goers and people who train at home. One person can't do a lunge in any variation after a hundred tutorials; another hasn't activated their left glute in Bulgarian split squats for a year. Generic tutorials don't fix their case. A thread in r/xxfitness drew 60 upvotes and 84 comments between Sep 14, 2026 – Oct 14, 2026. People get by with Online coaches and Form-check subreddits, and that still leaves this job open. Hotness is 3.10, Warm. Real but moderate pain. Some willingness to pay. The thread drew 60 upvotes and 84 comments. Gaps in existing tools. Needs integrations or data deals. A first version is a hard build, about 5+ weeks, priced between $10 and $49 a month and charged as a subscription. The pain, the source, the alternatives, the scope notes, and the questions on this page are free to read and free to build from. The agent starter prompt is the paid part. The first slice is on the page. One credit unlocks the rest, to paste into a coding agent, download as Markdown, or send as a private link.
Who has it
Gym-goers and people who train at home.
- Gym-goers
- People who train at home
- B2C
- Global
- r/xxfitness
What people use now
2 options, and the gap between them.
Online coaches
Form-check subreddits
Real gaps in the existing tools.
AI Video Diagnosis of Your Movement Pattern is built for the part these leave undone.
A way through
An app where users upload video of a movement and AI pinpoints the asymmetry or compensation in their body, with targeted corrective exercises.
MVP scope
The first version, in 6 weeks.
- 00 Goal
The one job
Upload a clip of your lunge or split squat and get told which compensation your body makes, plus targeted fixes.
- 01 Weeks 1–2
The core
Let users upload a video of a movement.
- 02 Weeks 3–4
The follow-through
Use AI to pinpoint the asymmetry or compensation in their body, and give targeted corrective exercises.
- 03 Weeks 5–6
How it ships
As a phone app, before any desktop or web version. AI does the core work, and people can check what it produced.
- — Not in v1
Left out on purpose
Replacing online coaches. Version one does the one job above and stops there.
How it could charge
The business model, at a glance.
- Model
- Subscription
- Price
- $10–49 a month
- Buyer
- PeopleAn individual or household pays
- Region
- Global
Hotness
Why it scores 3.10.
Real but moderate pain. Some willingness to pay. The thread drew 60 upvotes and 84 comments. Gaps in existing tools. Needs integrations or data deals.
60 upvotes 84 comments r/xxfitness Sep 14, 2026 – Oct 14, 2026 verified Oct 14, 2026 Thread ↗
Weights: pain 25%, willingness to pay 20%, demand 20%, gap 15%, ease 10%, recency 10%. Recency is recomputed every build. The source report’s 1–10 score is not shown.
Market size · estimate
How big this could get
A bottom-up estimate for AI Video Diagnosis of Your Movement Pattern: real customer counts × a realistic price. Not a forecast.
$924M a year
7.7M members · 10% of US gym and studio members
$180M a year
1.5M members · app-store reach in the US
$1.8M a year
15,000 members · 1% of the reachable segment in three years
What that means
15,000 members at $10/mo = $1.8M ARR
Medium confidenceHow we estimated this
- Base: 77,000,000 US gym and studio members.
- Has the problem: 10% (assume 10% want form feedback).
- Revenue per member: $120 per year ($10/mo).
- Reachable: 20% (app-store reach in the US).
- Three-year capture: 1% of the reachable segment.
TAM = customers with the problem × revenue per customer. SAM = the part an early product can reach. SOM = a conservative three-year share of SAM. Bars use a log scale. Shares marked “assume” are our judgment, not measured.
Take it to a build
Build AI Video Diagnosis of Your Movement Pattern with an agent, or with us.
Agent starter prompt
$9.99 / 1 credit
A full PRD written for a coding agent: scope, data model, screens, edge cases, and the first week of tasks for this idea.
- Copy it straight into Claude Code, Cursor, or Codex.
- Download it as a .md file you keep.
- Send your bot a private link that refreshes every seven days.
# Agent starter prompt: AI Video Diagnosis of Your Movement Pattern You are a senior product engineer. Build only the product described in this document. If a detail is missing, choose the smallest option and write it down in the README. Do not invent a second product, a marketplace of marketplaces, or a growth hack. ## Product Name: AI Video Diagnosis of Your Movement Pattern One line: Upload a clip of your lunge or split squat and get told which compensation your body makes, plus targeted fixes. Shape: Mobile app AI stance: AI-native Region for v1: Global Hotness (context only, not a requirement): 3.10 (warm). Real but moderate pain; some willingness to pay; thread engagement 60▲/84💬 (demand 3/5); gaps in existing tools; needs integrations or data deals. ## Problem One person can't do a lunge in any variation after a hundred tutorials; another hasn't activated their left glute in Bulgarian split squats for a year. Generic tutorials don't fix their case. Who feels it: Gym-goers and people who train at home.
The first slice is above. The rest unlocks for 1 credit and is never in this page’s HTML.
Credits work on both sites. On Business Ideas to Build the same credit unlocks the business plan and growth playbook for AI Video Diagnosis of Your Movement Pattern.
Or we build it
Your first version, shipped by our team.
A working product in your repo, built from this PRD. You own the code.
$1,000 scoping fee, credited toward the build.
Equity instead of cash is an application, not a checkout →Questions
Is this idea already taken?
People already use Online coaches, Form-check subreddits. Those options do not do the job in the solution above. The idea is free to build. Nothing here is an exclusive claim.
How hard is a first version?
Hard. A tight MVP is about 6 weeks (5+ weeks), assuming the regulated or partner-gated parts are stubbed. The paid prompt turns that into tasks.
Who would pay, and how?
The audience is gym-goers and people who train at home. Charge a subscription, and test a price between $10 and $49 a month. Willingness to pay is one input to Hotness, not a promise that someone will buy.
Can I use the evidence?
Yes. Build the product. The thread title is a short excerpt with a link, not a quote we are putting in someone's mouth. Exact post dates and verbatim lines are added only after a manual check. Ideas are suggestions, not medical, legal, or financial advice.
The sister site keeps a business plan and a growth playbook for the same pain. The business-plan version