Flex AI Workout Trainer & Log

Shown for US

• Free to download
• In-app purchases

Last verified 31 Jul 2026

Shown for US

4.6 2401 ratings · App Store

1. 5/5Best Workout App for Intermediate and Advanced Training

   I’ve been weight training for about 15 years and one of the biggest keys to success in the gym is consistency workout to workout. Flex is built exactly for this. It allows you to build your own workouts in a simple, easy to use format. There are premade workouts available for beginners but I don't think this is really the app’s strength. It remembers your last weight and set for each exercise and carries it over to the next workout. It tracks your rest (which you can customize) And if you make modifications intra-workout, you can save those for the next time as well. The stats dashboard is helpful for tracking progress, though could use some improvement and more detail. Try it out for free, but if you have an apple watch, you’ll definitely want to pay for it, the logging on the watch has changed my ability to stay focused and keep my phone away while working out. Overall an amazing app if you want a highly customizable, simple interface logging app that doesn't push a specific training style or set of workouts.

   XJRGU25 · 31 Jul 2026

2. 5/5Great App

   I’ve very often struggled to maintain a consistent workout routine without relying on a trainer. I started using this app to supplement my regular training routine. I’ve used it on days where I just wasn’t sure what to focus on, and it has helped by making it easy to target a specific muscle group or filter by equipment. The smart progression and auto tracking has really helped me see tangible progress in my training. It’s taken a lot of the effort out of planning my workouts, making actually going to the gym much easier and enjoyable. I do like how it is easy to swap out an exercise, or adjust the number of reps or weights on the fly. This has been useful when the gym is busy and I may not have access to the right equipment, it makes it really easy to adapt a workout. The animations and descriptions of what to do in an exercise are also really helpful. I would recommend this to anyone who struggles to track and maintain a consistent workout plan.

   ~(0_0~) ZombieGhost · 31 Jul 2026

3. 5/5Great 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.

   Karmma333 · 31 Jul 2026

4. 4/5Barebones but with Style

   Was hospitalized last fall and lost 20 lbs where I was previously in fantastic shape, so was looking for anything to help make getting back into the gym as easy as possible as becoming more aware of the progress I lost felt demoralizing. This app caught my eye due to its gorgeous interface. Seriously, one of the sleekest designs I have ever used and combined with the smart progressive algorithm this has helped me make serious progress I didn’t consider possible. My criticisms: You are going to have to log an awkward amount of progress into the app before the smart progressive algorithm gets what you’re doing. It’ll drastically lowball the weight you can lift until you get tired of 95 for top sets and manually change it and then recommend weight much higher than you can do with good form. This in hand with your only other option for workout progressions as the “Inheritance” option in settings doesn’t give you great options other than to switch to an app such as Bolt (“inheritance” is admittedly a cool name for saying “there’s no algorithm, log it all manually”) or to put in weeks of work before the algorithm works itself out. Otherwise you’ve got a great option for a workout app and one I’ll probably stick with for a long time to come! Obviously if you want the best results find a trainer but I personally feel no shortage of features for the free version I use, the developers obviously care about their users and understand the difference between paid-for-features that make the experience better and the often seen progress-paywall features for apps of this kind.

   Liam Bull · 31 Jul 2026

5. 4/5Good for detailed tracking

   Great for saving workouts whether these are cardio, calisthenics, or strength training. The app has a bank of exercises to choose from and if needed, you can create custom ones. You can group exercises into supersets and set rest times between reps. Also, if competition and point systems motivate you to exercise, then this app is for you! You earn points for every workout and can unlock achievements for more points. If you really want to unleash your competitiveness, view the rankings. It’ll really humble you. I left off a star because it’d be more convenient if I could add workouts anytime like the MyFitness App, which allows you to manually fill out the date and time for any previous day. I like this because sometimes I forget to track workouts and this app (at least the free version) doesn’t allow you to add a workout to a previous day.

   wakeup2 · 31 Jul 2026

Privacy

Accessibility

No accessibility labels collected yet.