Flex - Fitness Training 4+

Lose Weight, Build Muscle

Flex Artificial Intelligence Inc.

    • 4.7 • 1.3K Ratings
    • Free
    • Offers In-App Purchases


A free trainer in your pocket. Lose weight or build muscle.

Personalized workout plans
Or build your own
Achieve any fitness goal
Top workout routines & plans built by personal trainers
For any difficulty level

Our goal is to create a healthier world.
Follow us on instagram @flex.ai to join the community!

• Basic workout programs
• Build or customize your own program and freestyle workouts
• Workout guide to log and improve upon your performance each session
• Share your plans and workouts to other people
• View your progress and stay consistent: workout calendar, exercise stats, streak, bodyweight tracker, calories tracker, steps tracker, workout notifications
• Auto Progression: Flex automatically increases or decreases the difficulty of your exercises in your program based on past performance

Flex Premium:
• Logging on the Apple Watch app
• Unlock Premium programs
• Unlock Premium freestyle workouts
• Premium workout experience: music integration, plate calculator, etc.
• Advanced editing/building tools

Flex is the free, simple, and engaging app that does the planning and tracking so that you can just focus on your workouts and achieve your goals. Flex can automatically increase or decrease the difficulty of your exercises in your program based on past performance.

Hundreds of workouts and programs for you. Find and use the most effective workouts and programs designed by personal trainers, tailored to your goal and whether you workout at the gym or at home.

Forget about researching exercises, programs and keeping track of all your progress. Flex handles that and makes working out more engaging with features like streaks and progress charts.

Freestyle workouts:
Whatever your time commitment, physical goals, experience, or access to equipment, Flex has the right workouts for you. Choose any combination of equipment, goals, muscles worked or quick freestyle workouts.

Already have a fitness program you use or want to customize your own?
Edit one of our programs or build your own into Flex with the custom plan builder.

Real-Time Workout Guide:
Flex’s workout guide will lead you through your workout step by step, telling you which exercises to do, how to do them, how long to rest for optimal results and notifying you when you need to start your next set. You also have the spreadsheet view where you can fully modify your workout on the fly. Move around exercises, change exercises, add/remove sets. Control your music without leaving the app thanks to native Spotify and Apple Music integrations.

You can't improve what you don't measure. With Flex, you can track:

How consistently you’re exercising with the calendar feature
Your total calories burned daily, calculated from workouts/steps/BMR
Your bodyweight over time
Your steps with a 10k daily goal via the Apple Health integration
Your exercise progress with the exercise stats
Your workout history

An even easier way to workout with Flex Apple Watch:
Use the Flex apple watch app to log sets and complete workouts without needing to constantly check your phone. Sync your data and close your activity rings.

What’s New

Version 1.16

One Rep Max
Minor Apple Watch updates
LOTS of bug fixes

Ratings and Reviews

4.7 out of 5
1.3K Ratings

1.3K Ratings

Karmma333 ,

Great Work Out app for Gym and At Home!

I have been through my fair share of work out apps, everyone of which limits what I can do and what types of work outs I can create for ME, so I wasn’t expecting much from Flex when I saw it advertised thinking it was like others but decided to try it out. I was pleasantly surprised when I saw I can create my own work out’s however many that it, my own work out plan. They let you completely customize and decide what you are going to be doing with your own work outs for free. They do provide work outs themselves and plans but you have to pay for some of them which is only expected. For someone who has a work out plan in their mind and just need the structure for said plan this app is perfect.

minarjuman ,

If you have a terrible memory, this is for you.

This app is amazing. Throughout my workouts, I would always forget which set I’m on. This app allows you to click on complete after every set while also allowing you to create your own workouts (besides the ones they already have). It has amazing offers and the prices are very reasonable for a college student on a budget!!

I love how with every single workout, a short video is added with instructions. It shows which muscles the workout hits AND the side muscles. I truly couldn’t find such information on any other platform— neither could I from coaches.

On a side note, I do think it would be REALLY really cool if the app had an option to take pictures of yourself with a reminder set optionally as to have every gym related things in one app and simply for progress. As for myself, I can never have such pictures placed in my camera roll for fear of something happening to them.

I really wish I knew about this app sooner. Would’ve saved me so much trouble with remembering my sets!!

mprub4 ,

Many glitches

This app is useful but I am finding many glitches that interrupt and confuse me during my workouts. For starters, the rest times are never consistent. When I set my rest time to thirty seconds, sometimes it’ll choose to default back to two minutes and other times thirty seconds. I also find that the app skips over many of my exercises. Also, when I pause a timed exercise, the app will randomly choose to resume the workout and I’ll come back to the app to find that I “missed” several minutes of workouts, and I have to skip back to where I had left off. Other times, during a timed exercise the exercise will end as if the time was up, even though I still had time left. I really want this app to work, and I still find it useful but it becomes very frustrating while I’m working out.

Developer Response ,

Hi there! Most of these issues will be fixed in the update coming out by next week. Do you mind pressing “report an issue” button in the profile page in app so we can investigate your issues and make sure they’re being resolved? Thanks!

App Privacy

The developer, Flex Artificial Intelligence Inc., indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Linked to You

The following data may be collected and linked to your identity:

  • Health & Fitness
  • Contact Info
  • Identifiers
  • Usage Data
  • Diagnostics

Privacy practices may vary, for example, based on the features you use or your age. Learn More


  • Family Sharing

    Some in‑app purchases, including subscriptions, may be shareable with your family group when Family Sharing is enabled.

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