# Flex AI Workout Trainer & Log vs Muscle Booster Workout Tracker

Flex AI Workout Trainer & Log and Muscle Booster Workout Tracker both sit at 4.6 stars, but that hides the real split: 69% of Flex AI Workout Trainer & Log's written reviews are positive against 43% of Muscle Booster Workout Tracker's. Muscle Booster Workout Tracker's advantage is ratings volume (138K vs 2.4K) and chart position (#62 vs unranked). On price, rating, 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 Muscle Booster Workout Tracker sells 16 in-app purchases, starting at $9.99 per 7 days. Whichever you choose, the download price is not the number that matters.

On the App Store both sit at effectively the same score — 4.6 for Flex AI Workout Trainer & Log against 4.5 for Muscle Booster Workout Tracker. That said, the two scores are not equally well evidenced: Muscle Booster Workout Tracker has 138K ratings behind it against 2.4K, so its average is the more settled of the two. Written reviews are what separate them: 69% of Flex AI Workout Trainer & Log's written reviews are positive against 43% of Muscle Booster Workout Tracker's.

Flex AI Workout Trainer & Log ships an update every 9 days, Muscle Booster Workout Tracker every 2 weeks. The most recent releases landed on September 23, 2026 and September 24, 2026 respectively.

## The numbers

| Metric | Flex AI Workout Trainer & Log | Muscle Booster Workout Tracker |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.6 (2.4K ratings)](https://appshunter.io/ios/app/flex-ai-workout-trainer-and-log/id1446354547/reviews)** | [4.5 (138K ratings)](https://appshunter.io/ios/app/muscle-booster-workout-tracker/id1446447749/reviews) |
| Number of ratings | 2.4K | **138K** |
| Positive reviews | **69.3% of reviews** | 43.5% of reviews |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | **Every 9 days** | Every 2 weeks |
| Monetization | Freemium | Free with in-app purchases |
| Best chart rank | — | **#62** |
| Size | 574 MB | 574 MB |
| Requires iOS | 18.0 | **17.0** |
| Devices | iPhone, Apple Watch | iPhone, Apple Watch |
| Age rating | 17+ | 17+ |
| Developer | [Flex Artificial Intelligence Inc.](https://appshunter.io/developer/1446354546) | [WELLTECH APPS LIMITED](https://appshunter.io/developer/1450265454) |

## 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


### Muscle Booster Workout Tracker

[App page](https://appshunter.io/ios/app/muscle-booster-workout-tracker/id1446447749)

**Currently charting:** #62 Top Grossing · Health & Fitness, #123 Top Free · Health & Fitness (US App Store)

This app acts as a personal trainer, creating customized workout plans for muscle gain, weight loss, or recovery. It offers a vast library of exercises and challenges for home or gym, adapting to your available equipment and goals.

**Highlights:** Personalized workout plans, 1000+ exercise library, Home and gym workouts, Calisthenics and weight loss plans, Workout timer and audio tips, Equipment-based plan creation, Muscle recovery guidance

**Features:** macOS Compatibility, Apple Watch app, Vision Pro support

**In-app purchases (16)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 1 Week Subscription | $9.99 | per 7 days |
| 1 Week Subscription | $9.99 | per 7 days |
| 1 Week Subscription | $14.99 | per 7 days |
| 1 Month Premium | $14.99 | per month |
| Muscle Booster | $14.99 | per month |
| Muscle Booster Workout Premium | $19.99 | per month |
| 1 Month Subscription | $19.99 | per month |
| 1 Month 22.99 with 7-day free trial | $22.99 | per month |
| 1 Month Subscription | $24.99 | per month |
| 3 Month Subscription | $29.99 | per 3 months |
| 3 Month Premium | $39.99 | per 3 months |
| 3 Months Subscription | $39.99 | per 3 months |
| 1 Year Premium | $59.99 | per year |
| Muscle Booster Premium | $59.99 | per year |
| 12 Month Subscription | $79.99 | per year |
| Premium Bundle | $29.99 | one-time |

**What reviewers like**

- 🚀 Great workouts
- 👍 Easy to follow
- 👍 Variety of exercises
- 🚀 Customizable plans
- 👍 Helpful for beginners

**What reviewers complain about**

- 🐛 Buggy app performance
- 🔒 Lack of free trial
- 💰 Expensive subscription
- 👎 Limited gym equipment options
- 👎 Repetitive exercises

**Reported bugs**

- Workouts not logging properly
- App freezing and crashing
- Sync issues with Apple Watch
- Inaccurate exercise counting
- Inability to contact customer support

**Requested features**

- Ability to track progress and weights
- Better integration with Apple Health
- More personalized meal plans
- Ability to customize workout schedules
- Audio/voice guidance during workouts


## 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 Muscle Booster Workout Tracker free?

Muscle Booster Workout Tracker is free to download, with in-app purchases available.

### Which has better reviews, Flex AI Workout Trainer & Log or Muscle Booster Workout Tracker?

Flex AI Workout Trainer & Log is rated higher. Flex AI Workout Trainer & Log averages 4.6 out of 5 from 2.4K ratings, while Muscle Booster Workout Tracker averages 4.5 from 138K ratings.

### Do Flex AI Workout Trainer & Log or Muscle Booster Workout Tracker have ads?

Neither Flex AI Workout Trainer & Log nor Muscle Booster Workout Tracker shows ads.

### Which is updated more often, Flex AI Workout Trainer & Log or Muscle Booster Workout Tracker?

Flex AI Workout Trainer & Log ships an update every 9 days, and Muscle Booster Workout Tracker every 2 weeks. Most recently, Flex AI Workout Trainer & Log was updated on September 23, 2026 and Muscle Booster Workout Tracker on September 24, 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.*