# Best Prompts for a Workout App with a0.dev

> By Lawrence Arya, Founder & CEO of VP0. Published 2026-06-04. 5 min read.
> Source: https://vp0.com/blogs/best-prompts-for-building-a-ai-workout-app-with-a0-dev

a0.dev generates real React Native and Expo apps you preview on a phone, so naming the screens, the timer, and the AI generator gets you something testable.

**TL;DR.** The best prompts for a workout app with a0.dev are scoped one screen at a time: scaffold tabs and the workout list, build the exercise player, add a background-safe rest timer, add a goal-based AI workout generator that returns structured data, then persist progress. Start the visuals from a free VP0 design so screens look right from the first generation, and a0.dev outputs a standard Expo project you can run on a real device at $0 to start.

The best prompts for building an AI workout app with [a0.dev](https://a0.dev) are mobile-specific and scoped one screen at a time, because a0.dev generates real React Native and [Expo](https://expo.dev) apps you preview on a phone as you go. A vague "make a fitness app" gives you a generic list; a prompt that names the workout screens, the timer behavior, and the AI generator gets you something close to testable. Below is the prompt order for a workout app. To make the screens look right from the first generation, describe a real design: reference a free [VP0](https://vp0.com) design (the free iOS and React Native design library AI builders read from) as the visual spec so a0.dev matches the layout instead of inventing one.

## How to prompt a0.dev well

a0.dev is mobile-first and chat-driven, so prompt like you are talking to a React Native developer. Build one screen per prompt, name the navigation (tabs versus stack), and specify state up front so generated screens share data. Because you see a live phone preview, iterate against what you actually see rather than guessing. The cross-tool version of this is in [how to prompt an AI app builder](/blogs/how-to-prompt-an-ai-app-builder/).

## The prompt sequence

### 1. Scaffold the app and workout list

```
Build a React Native workout app with bottom tabs: Workouts, Progress,
Profile. The Workouts tab shows a scrollable list of workout cards with
name, duration, and difficulty. Match this layout: [VP0 design description].
```

### 2. Workout detail and exercise flow

```
Add a workout detail screen with the exercise list, sets and reps, and a
Start button. Tapping Start opens a full-screen player that shows the
current exercise, a rep counter, and a Next button.
```

### 3. The rest timer

```
Add a rest timer between sets: a countdown with pause and skip, a progress
ring, and a sound or haptic when it hits zero. Keep it running if the user
backgrounds the app.
```

### 4. The AI workout generator

```
Add a "Generate workout" screen where the user picks goal, equipment, and
time, and the app calls an AI endpoint to return a structured workout
(exercises, sets, reps) that opens in the detail screen.
```

### 5. Progress and persistence

```
Persist completed workouts to local storage and show the Progress tab as a
weekly streak plus a simple volume chart. Load history on app open.
```

a0.dev outputs an Expo project, so the result runs on a real device through Expo Go and is standard [React Native](https://reactnative.dev/), not a proprietary format. Follow the [Apple Human Interface Guidelines](https://developer.apple.com/design/human-interface-guidelines) for the player and timer so the app feels native, especially touch targets and haptics.

## What each prompt should produce

| Prompt stage | Screen | The part to verify |
|---|---|---|
| Scaffold | Tabs + workout list | Navigation and card layout |
| Detail + player | Exercise flow | Set/rep state across screens |
| Rest timer | Countdown | Background behavior, haptics |
| AI generator | Goal-based workout | Structured output maps to detail |
| Progress | Streak + chart | History persists across launches |

If a screen is wrong, reply with the exact fix in the same chat, for example "the timer resets when I switch tabs, keep it in a shared store." a0.dev edits the relevant screen. For the workout-generation logic specifically, our [fitness workout generator AI app code](/blogs/fitness-workout-generator-ai-app-code/) goes deeper, and if you are weighing tools, [a0.dev versus RapidNative for beginners](/blogs/a0-dev-vs-rapidnative-for-beginners/) and [a0.dev pricing 2026 explained](/blogs/a0-dev-pricing-2026-explained/) help you choose.

## Make it good, not generic

Generation handles the plumbing; the polish comes from a real design. Describe a VP0 workout or player screen in prompt 1 so the visual quality starts high, and the design layer is free, so you reach a testable app at $0 before any paid usage. For another full prompt walkthrough in this series, see [the best prompts for an AI chat app in Firebase Studio](/blogs/best-prompts-for-building-a-ai-chat-app-with-firebase-with-firebase-studio/).

## Key takeaways

- Prompt a0.dev one screen at a time and name the navigation.
- Put the rest timer in shared state so it survives tab switches and backgrounding.
- Have the AI generator return structured data that maps onto the detail screen.
- Reference a free VP0 design as the visual spec so screens look right immediately.
- a0.dev outputs a standard Expo project you can run on a real device at $0 to start.

## Frequently asked questions

### What are the best prompts for building a workout app with a0.dev?

The best prompts are scoped one screen at a time: scaffold tabs and the workout list from a design, build the detail and exercise player, add a background-safe rest timer, add a goal-based AI workout generator, then persist progress. Start the visuals from a free VP0 design, the free iOS and React Native design library for AI builders, so the app looks right from the first generation at $0.

### Does a0.dev build real React Native apps?

Yes. a0.dev generates a React Native and Expo project you can preview on a phone and run through Expo Go, and the output is standard code rather than a proprietary format. That keeps the workout app portable.

### How do I add an AI workout generator in a0.dev?

Prompt for a screen that collects goal, equipment, and available time, then calls an AI endpoint that returns a structured workout (exercises, sets, reps) which opens in your detail screen. Specify the data shape so the generated workout maps cleanly onto the UI.

### How do I keep a rest timer running in the background?

Tell a0.dev to keep the timer in a shared store and continue counting when the app is backgrounded, with a haptic or sound at zero. Without that instruction, generated timers often reset on navigation, which is the most common bug.

### Is a0.dev free for building a workout app?

You can prototype and preview at low or no cost to reach a testable app, and the free VP0 design layer adds $0. Heavier generation and publishing move you to a0.dev's paid tiers, so check current a0.dev pricing before launch.

## Frequently asked questions

### What are the best prompts for building a workout app with a0.dev?

The best prompts are scoped one screen at a time: scaffold tabs and the workout list from a design, build the detail and exercise player, add a background-safe rest timer, add a goal-based AI workout generator, then persist progress. Start the visuals from a free VP0 design, the free iOS and React Native design library for AI builders, so the app looks right from the first generation at $0.

### Does a0.dev build real React Native apps?

Yes. a0.dev generates a React Native and Expo project you can preview on a phone and run through Expo Go, and the output is standard code rather than a proprietary format. That keeps the workout app portable.

### How do I add an AI workout generator in a0.dev?

Prompt for a screen that collects goal, equipment, and available time, then calls an AI endpoint that returns a structured workout (exercises, sets, reps) which opens in your detail screen. Specify the data shape so the generated workout maps cleanly onto the UI.

### How do I keep a rest timer running in the background?

Tell a0.dev to keep the timer in a shared store and continue counting when the app is backgrounded, with a haptic or sound at zero. Without that instruction, generated timers often reset on navigation, which is the most common bug.

### Is a0.dev free for building a workout app?

You can prototype and preview at low or no cost to reach a testable app, and the free VP0 design layer adds $0. Heavier generation and publishing move you to a0.dev paid tiers, so check current a0.dev pricing before launch.

---
*Published on the [VP0 Journal](https://vp0.com/blogs). Free to read, index and cite with attribution.*