# Flex AI Workout Trainer & Log vs Workout Builder

The clearest difference is ratings volume: Flex AI Workout Trainer & Log at 2.4K against Workout Builder's 20. Flex AI Workout Trainer & Log also leads on rating (4.6 vs 4.3). On price, review sentiment, update cadence and ads there is nothing between them.

Both are free to download. Flex AI Workout Trainer & Log sells 8 in-app purchases, starting at $1.99 per month and Workout Builder sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

Flex AI Workout Trainer & Log holds the better App Store score, 4.6 against 4.3. That said, the two scores are not equally well evidenced: Flex AI Workout Trainer & Log has 2.4K ratings behind it against 20, so its average is the more settled of the two. Written reviews complicate that: 69% of Flex AI Workout Trainer & Log's written reviews are positive against 71% of Workout Builder's, so the app with the better star average is not the one people write more warmly about.

Flex AI Workout Trainer & Log ships an update every 9 days, Workout Builder fortnightly. The most recent releases landed on September 26, 2026 and July 26, 2026 respectively.

## The numbers

| Metric | Flex AI Workout Trainer & Log | Workout Builder |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.6 (2.4K ratings)](https://appshunter.io/ios/app/flex-ai-workout-trainer-and-log/id1446354547/reviews)** | [4.3 (20 ratings)](https://appshunter.io/ios/app/workout-builder-send-to-watch/id6450721774/reviews) |
| Number of ratings | **2.4K** | 20 |
| Positive reviews | 69.3% of reviews | **71.0% of reviews** |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | **Every 9 days** | Fortnightly |
| Monetization | Freemium | Free with in-app purchases |
| Size | 574 MB | 1 MB |
| Requires iOS | 18.0 | **17.0** |
| Devices | **iPhone, Apple Watch** | iPhone |
| Age rating | 17+ | 4+ |
| Developer | [Flex Artificial Intelligence Inc.](https://appshunter.io/developer/1446354546) | [Matthew Palmer](https://appshunter.io/developer/669856153) |

## 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 | $1.99 | per month |
| Premium Plus Monthly | $2.99 | per month |
| Premium Yearly Subscription | $9.99 | per year |
| Premium Plus Family Monthly | $9.99 | per month |
| Premium Plus Yearly | $19.99 | per year |
| Premium Plus Family Yearly | $49.99 | 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


### Workout Builder

[App page](https://appshunter.io/ios/app/workout-builder-send-to-watch/id6450721774)

Design personalized fitness routines on your iPhone, then seamlessly transfer them to your Apple Watch. Supports a wide range of activities from running and cycling to yoga and strength training, with options for simple goals, advanced intervals, and paced efforts.

**Highlights:** Create custom workouts on iPhone, Send workouts to Apple Watch, Supports running, cycling, swimming, yoga, HIIT & Strength interval training, Boxing and skipping interval options, Goal-based workouts, Advanced interval workouts, Paced workouts

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Workout Builder Premium | $9.99 | one-time |


## 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 Workout Builder free?

Workout Builder is free to download, with in-app purchases available.

### Which has better reviews, Flex AI Workout Trainer & Log or Workout Builder?

Flex AI Workout Trainer & Log is rated higher. Flex AI Workout Trainer & Log averages 4.6 out of 5 from 2.4K ratings, while Workout Builder averages 4.3 from 20 ratings.

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

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

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

Flex AI Workout Trainer & Log ships an update every 9 days, and Workout Builder fortnightly. Most recently, Flex AI Workout Trainer & Log was updated on September 26, 2026 and Workout Builder on July 26, 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.*