business

Verdict

Submitted 5/21/2026, 6:33:21 AM · Completed 5/21/2026, 6:45:31 AM

5.5
pivot
The idea

Built a browser tool that visualizes muscle activation and scores form on any workout clip. Looking for signal.

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Hey r/SideProject, Origin: I've been watching r/formcheck posts go back and forth with feedback and figured maybe I could build a tool that handles at least the measurable parts in a consistent way. Here's what came out: [https://formfit.web.app](https://formfit.web.app/) What it does 1. You upload a clip. 2. The app breaks the clip apart frame-by-frame and runs pose detection on sampled frames. This is the wait. You get a progress bar and can choose how densely to sample (10/15/20/30 fps; 15 is the default and takes \~6 s of compute per 1 s of source video). 3. When processing finishes, you get a playback view: the original video plus a skeleton overlay tracking your body, alongside a side panel showing 24 muscles with per-frame activation intensity. If you tagged the clip as a back squat with a camera angle, you also get a form report below the body diagram: · Rep count · Depth · Forward lean · Hip drive timing · Lockout · Heel stability · Tempo Each metric is scored good / borderline / bad against published coaching thresholds (Rippetoe, Schoenfeld 2010, IPF). To be clear: the muscle panel and form report come from precomputed data, not live inference during playback. The expensive work happens once up front, and playback is essentially a smooth lookup against cached data, with linear interpolation between cached samples so the skeleton glides instead of clicking frame-to-frame. How it actually works (honest breakdown) The only AI/ML in the pipeline is a pretrained Google pose detection model, BlazePose Lite (33 keypoints) via TensorFlow.js running in the browser. Everything downstream is classical computation I wrote: · Keypoint smoothing: exponential moving average against the previous frame · Muscle activation: joint angular velocity (dθ/dt across consecutive samples), capped and mapped to extensor or flexor groups for each joint per anatomical specs. No learning, no neural net, just kinematics. · Postural-load term: when a joint is held in a loaded range with low angular velocity (example: bottom of a wall sit), the prime mover scores isometrically so the muscle reads engaged during holds, not just during motion. · Rep detection: peak finding on the smoothed hip-Y signal with a prominence threshold to ignore noise, plus a time-based gap floor so it works regardless of chosen sample fps. · Form scoring: each metric (depth, lean, hip drive, etc.) has a hardcoded threshold pulled from coaching literature, with the citation visible in the report. Stack: · TypeScript + Vite · TensorFlow.js for the pose model · Firebase Hosting No backend, no auth, nothing leaves your tab. Caveats, read before trying · Muscle activation works on any clip / movement. Form scoring is back-squat-only for now. Deadlift, bench, OHP, etc. are visible in the picker as disabled "Soon" tiles. · Nothing is hard-tuned yet. The form thresholds came from books and review papers, not from validating against a labeled dataset of real lifters. The activation math is physics-derived, not learned. Anywhere it disagrees with reality, the math is the suspect. · Processing time is real. First upload of a clip processes locally on your machine at roughly \~6 seconds per second of source video at the recommended 15 fps. A 20-second clip takes roughly 2 minutes. · The trade-off is no server and your video never leaves your browser/device. · Mobile or tablet works best. Desktop browser works too, but hardware varies. · This is a side project, not a product. What I'm asking the room This is more of an "is there signal here?" post than a launch. Specifically: · Is this something worth further exploring. Thanks! Roast it, suggest things, or just try a clip and tell me what felt off.
TRIZ inventive level: 3/5· Principles: parameter changes, mechanical interaction
Synthesis verdict
**Pivot**. The idea has a clear value proposition for fitness enthusiasts and coaches, with strong monetization potential due to its privacy-first approach and high margins. However, critical risks exist, including regulatory and licensing exposure, platform dependency, and a non-paying user base. The current implementation's reliance on client-side processing may lead to performance issues on lower-end devices. To mitigate these risks, it's essential to validate the product with coaches and athletes, refine the muscle activation math, and explore alternative monetization paths. The strongest signal is B2B2C: personal trainers and online coaches need scalable form review, and the privacy-first architecture is a differentiator.

Strengths

  • Strong monetization potential due to clear value proposition and high margins
  • Privacy-first approach is a differentiator in the market
  • High demand for asynchronous form feedback among coaches and athletes

Weaknesses

  • Regulatory and licensing exposure due to Google-owned BlazePose model
  • Platform dependency risk with TensorFlow.js and BlazePose Lite model
  • Non-paying user base and high churn rate due to compute-heavy client-side load

Best angle

Refine the product by validating with coaches and athletes, and explore alternative monetization paths to mitigate critical risks and create a scalable business model.

Panel verdicts

Viability

meta/llama-4-maverick-17b-128e-instruct

8.0

The project's feasibility hinges on the team's ability to refine and expand the existing classical computation algorithms and pre-trained model integration.

The idea is technically feasible for a solo or 2-person team to build within 4-12 weeks. The existing prototype demonstrates a clear understanding of the technical requirements, leveraging pre-trained models and classical computation. The use of TensorFlow.js and Firebase Hosting simplifies the development process. The most complex part, pose detection, is handled by a pre-trained model. However, expanding form scoring to other exercises and refining the muscle activation math may require additional development time. The current implementation's reliance on client-side processing may lead to performance issues on lower-end devices, but this trade-off allows for a serverless architecture. Overall, the project's technical complexity is moderate, and the team can likely build upon the existing foundation.

Monetization

mistralai/mistral-medium-3.5-128b

8.0

Monetize via tiered subscriptions targeting serious lifters and coaches, leveraging privacy and zero-server costs for high margins.

The idea has strong monetization potential due to its clear value proposition for fitness enthusiasts, coaches, and athletes. The tool automates form analysis—a high-value, time-consuming task—using a lightweight, privacy-first approach (no backend, no data retention). Pricing could follow a freemium model: free for low-resolution/short clips (e.g., 10s max, 10fps) with watermarked outputs, and a subscription ($10–20/month) for HD, longer clips, higher sampling rates (30fps), and access to additional lifts (deadlift, bench, etc.). A one-time purchase ($50–100) could unlock lifetime access for casual users. Channels include direct-to-consumer via a landing page, partnerships with fitness influencers, and integrations with apps like Strong or MyFitnessPal. Gross margins are high (~80–90%) since compute happens client-side, and cost-to-serve is near-zero post-development. Unit economics are favorable: at $15/month, even 1,000 subscribers yield $180k ARR with minimal overhead. Risks include competition from established players (e.g., TrainHeroic, Kinovea) and the need to validate form thresholds with real-world data to build trust.

Risk

openai/gpt-oss-120b(fallback #1)

2.0

Regulatory/legal exposure, fragile Google‑dependent tech stack, and a non‑paying user base will kill this project within six months.

The moment you ship this thing it will implode for three brutal, concrete reasons. First, regulatory and licensing landmines: you’re pulling a Google‑owned BlazePose model into a browser app and then doing heavy‑weight processing on user‑generated video. Even though the data never leaves the tab, any accidental leak, telemetry, or even the model’s EULA breach will trigger GDPR, CCPA, or Google’s own licensing enforcement, forcing an immediate shutdown or costly legal battles. Second, platform dependency risk: the entire pipeline hinges on TensorFlow.js and the BlazePose Lite model staying publicly available and unchanged. Google can yank the model, alter the API, or impose fees at any time, instantly breaking the core functionality and leaving you scrambling for a replacement you have no expertise to implement. Third, pure churn and zero‑budget reality: the target market—home gym hobbyists—won’t pay for a tool that stalls for minutes per clip on a phone. Without a clear monetization path, you’ll attract only free‑riders, the app’s compute‑heavy client‑side load will drive users away, and you’ll have no cash to cover Firebase hosting or future development. Within weeks the user base will evaporate, and you’ll have no runway to survive.

Market

moonshotai/kimi-k2.6(fallback #1)

7.0

The real market is coaches who need scalable form review, not consumers who won't tolerate 2-minute waits for 20-second clips.

The demand signal is real but fragmented. r/formcheck and r/weightroom represent ~500k+ engaged users, with adjacent communities (CrossFit, powerlifting, Olympic lifting, physiotherapy, online coaching) pushing total addressable into low millions. The unmet need is clear: asynchronous form feedback is bottlenecked by coach availability and consistency. Competitors exist (WL Analysis, Barbell Logic app, Coach's Eye legacy, newer AI tools like Perch, Spleeft, Metric VBT) but most target institutional/B2B or require hardware. The consumer gap—affordable, private, no-hardware form analysis—is genuinely open. However, critical risks: (1) Processing time (~6s per 1s video at 15fps) creates friction that kills retention for casual users; (2) Squat-only scoring limits repeat engagement; (3) Browser-only local compute caps quality vs. cloud competitors; (4) No clear monetization path yet—coaches might pay for client tools, consumers resist subscriptions for single-lift tools, and one-time purchases underperform in fitness apps. The strongest signal is B2B2C: personal trainers and online coaches need scalable form review, and your privacy-first, no-upload architecture is a differentiator in an era of AI skepticism. The muscle visualization is compelling for engagement but unverified against EMG or established biomechanics. Recommendation: validate with 10-15 coaches on whether they'd use this for client intake or async programming; their willingness to pay $20-50/month would de-risk faster than consumer metrics.

Competition

qwen/qwen3.5-397b-a17b(fallback #2)

4.0

Static, physics-based heuristics cannot compete with data-driven machine learning models that improve via network effects from a growing user base.

The fitness technology market is saturated with established players who have already solved the core value proposition of automated form analysis with superior data moats. Primary competitors include Home Workout AI (and similar mobile-first apps like Fitbod or Freeletics which integrate form tracking), specialized computer vision startups like Zone7 or Hudl Technique used by professional coaches, and the ubiquitous human alternative: certified personal trainers or knowledgeable peers on platforms like Reddit itself. The critical flaw in this venture is the reliance on hardcoded, literature-based thresholds rather than a proprietary, labeled dataset. While the 'privacy-first, browser-only' approach is a valid differentiator for privacy-paranoid users, it severely limits the product's ability to learn and improve. Competitors collecting server-side data can refine their models across millions of lifts, whereas this tool remains static and potentially inaccurate due to the lack of empirical tuning against real-world variance. Furthermore, the friction of a 6x processing time ratio (6 seconds compute per 1 second video) on client-side hardware creates a poor user experience compared to cloud-optimized or real-time mobile solutions. The differentiation is real in terms of architecture (local-only), but it is not durable because it sacrifices accuracy and speed—the two metrics that actually matter to an athlete correcting their form. Without a feedback loop to validate and adjust the 'physics-derived' math against actual human performance, the tool risks providing confident but incorrect advice, which is dangerous in a business context.

Synthesized by meta/llama-3.3-70b-instruct · 66.7s