# Flex AI Workout Trainer & Log vs Booty Builder

The clearest difference is in-app purchases: Booty Builder at none against Flex AI Workout Trainer & Log's 8. Booty Builder also leads on review sentiment (100% vs 69%) and iOS requirement (16.6 vs 18.0). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Flex AI Workout Trainer & Log sells 8 in-app purchases, starting at $12.99 per month. Booty Builder asks for nothing beyond the download.

Both ship on a similar rhythm, roughly every 9 days. The most recent releases landed on October 12, 2026 and October 7, 2026 respectively.

## The numbers

| Metric | Flex AI Workout Trainer & Log | Booty Builder |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.6 (2.4K ratings)](https://appshunter.io/ios/app/flex-ai-workout-trainer-and-log/id1446354547/reviews)** | — |
| Number of ratings | **2.4K** | — |
| Positive reviews | 69.0% of reviews | **100.0% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 9 days | Every 9 days |
| Monetization | Freemium | **Free** |
| Size | 574 MB | 4 MB |
| Requires iOS | 18.0 | **16.6** |
| Devices | iPhone, Apple Watch | iPhone, iPad |
| Age rating | 17+ | 4+ |
| Developer | [Flex Artificial Intelligence Inc.](https://appshunter.io/developer/1446354546) | [ADAM LEWIS HUNT](https://appshunter.io/developer/1786412845) |

## What reviewers say

### Flex AI Workout Trainer & Log

[App page](https://appshunter.io/ios/app/flex-ai-workout-trainer-and-log/id1446354547)

This app uses AI to provide personalized workout plans and real-time form feedback for weightlifters. It tracks progress, offers adaptive progression, and includes motivational features like leaderboards and streaks. It's designed for all experience levels, from beginners to pros.

**Highlights:** AI personal trainer, Real-time form feedback, Personalized workout plans, Adaptive progression, Strength tracking, Community leaderboards, Apple Watch integration

**Features:** Family Sharing, Apple Watch app, Vision Pro support

**In-app purchases (8)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium Subscription Monthly | $12.99 | per month |
| Premium Plus Monthly | $29.99 | per month |
| Premium Plus Family Monthly | $69.99 | per month |
| Premium Yearly Subscription | $79.99 | per year |
| Premium Plus Yearly | $191.99 | per year |
| Premium Plus Family Yearly | $499.99 | per year |
| 1 Month Free Premium | Free | one-time |
| Lifetime Free Premium | Free | one-time |

**What reviewers like**

- 🚀 Detailed workout tracking
- 👍 Customizable workouts
- 🔒 Comprehensive exercise library
- 💡 Helpful progress tracking
- 👍 Clean and intuitive interface

**What reviewers complain about**

- 🐛 Glitches and bugs
- 💰 Expensive premium subscription
- 🔒 Limited functionality without premium
- 🐛 Inconsistent rest timer
- 🐛 Workout data loss

**Reported bugs**

- App crashes on iOS 16 update
- Inability to log workouts on previous days
- Inconsistent syncing between app and Apple Watch

**Requested features**

- Offline workout mode
- Ability to save and reuse custom workout plans
- Muscle group targeting and analytics
- Social features and community integration


### Booty Builder

[App page](https://appshunter.io/ios/app/booty-builder/id6739646754)

Embark on a 4-week squat challenge to build strength and sculpt your glutes. Choose from various squat targets tailored to your fitness level, track progress with daily and weekly milestones, and stay motivated with a distraction-free interface. This ad-free app offers a straightforward path to a stronger, healthier you.

**Highlights:** 4-week squat challenge, Multiple squat targets, Progress tracking, Daily and weekly milestones, Intuitive design, Ad-free experience

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Flex AI Workout Trainer & Log free?

Flex AI Workout Trainer & Log is free to download, with in-app purchases available.

### Is Booty Builder free?

Booty Builder is free to download, with no in-app purchases.

### Do Flex AI Workout Trainer & Log or Booty Builder have ads?

Neither Flex AI Workout Trainer & Log nor Booty Builder shows ads.

### Which is updated more often, Flex AI Workout Trainer & Log or Booty Builder?

Flex AI Workout Trainer & Log ships an update every 9 days, and Booty Builder every 9 days. Most recently, Flex AI Workout Trainer & Log was updated on October 12, 2026 and Booty Builder on October 7, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*