If your fitness app needs to show which muscles an exercise or workout hits, you’re choosing between five approaches: pre-rendered images, SVG highlighter libraries, Lottie animations, building your own renderer, or an interactive runtime asset. We’ve written deep dives on several of these; this page is the map that connects them, with every option we know of in one table.
(Disclosure: the last category is ours, at Fitness Visuals. Everything else here is free or someone else’s, and several of those are the right choice for plenty of apps.)
The whole landscape in one table
| Option | Detail level | Transitions | Body models | Platforms | Cost |
|---|---|---|---|---|---|
| Pre-rendered images | One muscle group per image | None | Whatever you export | All | Free (your time) |
| react-native-body-highlighter | ~25 broad regions | Instant snap | Male + female | React Native | Free (MIT) |
| react-body-highlighter | Broad regions | Instant snap | Same models, web port | React (web) | Free (MIT) |
| flutter_body_atlas | Individual muscles | Instant snap | One model | Flutter | Free (CC BY artwork) |
| bodyheatmap | 60+ body zones | Instant snap | One model | Flutter | Free (MIT) |
| Lottie muscle packs | Fixed clips, not state | Plays animations | Varies by pack | All | Free to ~$ |
| DIY (CustomPaint / Canvas / Skia) | Unlimited | Anything you build | Your design budget | Your platforms | Weeks of work |
| Rive muscle heatmap (ours) | Individual muscles | Animated | Male + female | Flutter, SwiftUI, Android, React, RN | $30 / $50 one-time |
Category by category
Pre-rendered images are the v1 answer: an exported image per muscle group, shown on the exercise detail page. Zero dependencies, and completely fine until you need combinations, at which point the required image count explodes and you move on.
SVG highlighter librariesare the workhorse category: free, quick to integrate, runtime-composable. The React Native side has a clear default in react-native-body-highlighter; Flutter’s field is younger, with flutter_body_atlas the best free anatomy and bodyheatmap better suited to zone-level pain tracking. They share the genre’s ceilings: snap transitions, discrete intensity buckets, and mostly single-gender models. We’ve compared them in depth for React Native and Flutter.
Lottie packs(on marketplaces like IconScout, or dedicated libraries like Vector Fit Exercises) are decorative animations, excellent for exercise demo clips and celebrations, wrong for a heatmap, because a Lottie clip can’t react to your app’s state. The full reasoning is in our Rive vs Lottie breakdown.
Building your own with CustomPaint, Canvas, or Skia buys unlimited control at the price of weeks of engineering plus the part teams underestimate: anatomy artwork that looks right from two views, at multiple intensities, for two body shapes.
Interactive runtime assets move the state machine into the asset itself. Ours is built in Rive: muscles animate between states, intensity is a runtime input, male and female shapes are included, the advanced version adds four runtime-settable colors and tap-to-identify, and one .riv file serves every platform. Basic is $30, advanced $50, one-time with a lifetime license. The Flutter wrapper is open source and the playground runs in your browser, so the evaluation costs nothing.
Choosing in three questions
- Do you need combinations of muscles at runtime? No: pre-rendered images. Yes: keep reading.
- Is a static diagram with snap-changes good enough? Yes: pick the SVG library for your platform from the table. No: keep reading.
- Animated, themable, gendered, cross-platform? Build on canvas if it’s your product’s centerpiece and you have design capacity; otherwise buy the asset and spend the weeks on your actual product.
For the fuller requirements checklist, including the exercise-to-muscle data layer that every one of these approaches needs and none provides, start with our guide to showing worked muscles. And if you find an option this page is missing, tell us , we’d rather keep this map complete than comfortable.