Comparison

FLEX Stronger vs Train.Red APP

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

FLEX Stronger

This app revolutionizes weight training by syncing with a sensor to provide real-time performance feedback. Track, manage, and review your training like elite athletes, with automated workouts and group training options. It offers detailed metrics, video recording with data overlay, and a community feature for sharing and downloading workouts.

Highlights
  • Real-time performance feedback
  • Velocity-based training (VBT)
  • Automated workouts
  • Group training for up to three people
  • Video recording with synced data
  • 1RM prediction
  • Workout creation and sharing
Features
Read full description

Revolutionise the way you train and prepare in the weights room! The FLEX Stronger app syncs to a FLEX barbell sensor to deliver real-time feedback straight to your device. Track, manage and review training performance just like elite and professional athletes right across the globe, through the Major Leagues, UFC, Premier League and Olympic institutes. Developed by the team at GymAware, FLEX packages everything we learned from delivering gold standard products to the pro ranks into the only VBT system developed specifically for individual use. The smartest system on the market, FLEX automates your entire training experience. Select an exercise. Load some weight. Lift. Completely wireless. No calibration, adjustments or exercise creation required. Perfect for individual athletes, remote coaches and personal trainers. *Performance Metrics & Targets* Precise and immediate feedback on Mean and Peak Velocity, Mean and Peak Power, Distance, Height, Eccentrics, Position and live bar path tracing. Set targets on key performance metrics to benchmark effort across your session. *Group Training* Add other lifters into your session for group training with up to three people. Complete regular training, pre-programmed workouts or even the 1RM prediction with your group. Training partners who complete sessions with you can collect and store their data in their own profiles once the session is done. Training partners can be added or removed from sessions at any time. *Video Mode* Switch to video mode and record your set with synced data overlaid on the saved file. Send to friends, coaches or share online. Handsfree start and stop. Set your device up and lift. Your video will start, stop and crop to capture the set you just completed. *Automated Workouts* Complete workouts that step you through the entire program, from exercise and weight changes to targets and rest times. *Create, Share and Download Workouts* Create custom workouts directly in the app. Let FLEX run you through your new program, or share them via our Community feature with training partners or clients using FLEX. Looking for inspiration, download sessions from any of your connections in Community and complete them yourself. Set targets based on their results and compete and compare over the same workout. *1RM Predictions* Use the automated 1RM prediction protocol to gauge current strength and readiness levels without an actual 1RM attempt. *Multitasking* There are no limits in the FLEX app. Start regular sessions and add in training partners, or start a pre-programmed workout. Background the app and switch on your favourite tunes. Browse your historical results in the middle of your training sessions. Whatever you need is accessible any time. *Community* Create connections in the FLEX community so you can browse their training history, download sessions (complete with their results), send workouts, train in groups. View session data live as it is uploaded set by set, and interact with fist bumps and comments directly on the platform. *Store and Review* All your data is stored and reviewable in History right in your app. Data is securely backed upon our servers and retrieved on your device at any time.

About

Train.Red APP

This app monitors muscle oxygen saturation to provide real-time physiological insights for athletes and coaches. It helps optimize performance, track recovery, and analyze training data with actionable metrics.

Highlights
  • Muscle oxygen saturation monitoring
  • Real-time physiological insights
  • Performance and recovery tracking
  • Workout analysis and data export
  • Team/organization structure
  • Live data overlay
Read full description

About this app The official app for the Train.Red muscle oxygen sensors, the new metric for performance. To move, your muscles need energy. The most efficient way to get this energy requires oxygen. We measure the oxygen saturation in your muscles to help you improve. Not every athlete has a team of scientists helping them with their physiological data, we measure data from your muscle and translate this into useable insights, in real-time. - Monitor your physiological power and perform easy exercise tests as an endurance athlete. - Know when your muscle is fully recovered and ready for the next set when doing strength. What’s more? - Cloud functionality to allow workout analysis at home, even when you perform in the gym. - A Team/organisation structure that allows multiple athletes to use the sensors. - Actionable insights after your training or scientific analysis with access to raw data. - Live view with data overlay to match measured fatigue with movement patterns. - Muscle States, Protocols, Dashboard, Training Menu, Muscle Stress Score, and much more. How to start with Train.Red: Create a user profile and connect your sensor. No sensors yet? The Train.Red app requires the Train.Red sensors for full functionality (https://train.red/). Connected your FYER or PLUS? Nice, you are ready to BE AHEAD. What does Train.Red do for me: Whether you’re an athlete, coach, scientist, physio, or anyone involved in sport, Train.Red has something to offer you. Simply because your muscles play a key role in human movement. We track your muscle oxygenation, more specifically, the hemoglobin concentration changes. The Train.Red sensors measure: - SmO2, Muscle Oxygen Saturation (%) - O2Hb, Oxyhemoglobin (mM) - Hhb, Deoxyhemoglobin (mM) - Thb, Total hemoglobin (mM) - HbDiff, the Hemoglobin Difference (mM) If this sounds like Abracadabra, no worries. We display the oxygen saturation in your muscle live and use the other metrics to provide you with actionable insights in real-time. Our AI and advanced analysis options translate this data into 5 different muscle states showing you if your muscle is recovering, or approaching its limits. If this physiological data sounds familiar, perfect. We allow exporting your data to .csv or .fit files for an in-depth analysis of all your data. Every single training session is stored in our cloud and can be analyzed or exported afterward. How do I use Train.Red? The Train.Red sensor is a light-based wearable that you wear directly on your skin. You’re free to place the sensor anywhere on your body but know that this is a hyperlocal metric that will only tell you something about the exact location you place the sensor. We recommend wearing the sensor on a primary involved locomotor muscle, a place on your body that is active during the activity you’re performing. e.g. on your thigh during cycling or squats, the middle part of your upper leg during running, or on your lower arm during climbing. Of course, you are free to use more than one sensor! You can connect up to 4 sensors simultaneously and measure multiple areas at once. You’re not bound to this smartphone application. The Train.Red hardware is integrated into 3rd party apps allowing you to easily synchronise your data from multiple sources. Train.Red sensors can be connected to most Wahoo’s, Garmin’s, Suunto’s and several other devices. More information can be found on our website https://train.red/

Screenshots

FLEX Stronger4 screens
Train.Red APP4 screens

Verdict

The call

The clearest difference is rating: Train.Red APP at 5.0 against FLEX Stronger's 4.4. FLEX Stronger's advantage is ratings volume (8 vs 1). On price, update cadence, ads and in-app purchases there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

Train.Red APP holds the better App Store score, 5.0 against 4.4. That said, the two scores are not equally well evidenced: FLEX Stronger has 8 ratings behind it against 1, so its average is the more settled of the two.

UpkeepUpdate frequency

FLEX Stronger ships an update monthly, Train.Red APP every 3 weeks. The most recent releases landed on August 6, 2026 and July 30, 2026 respectively.

Scorecard2 real differences · 8 level
FLEX Stronger versus Train.Red APP: the parameters behind the verdict, then further details
ParameterFLEX StrongerTrain.Red APP
PriceFreeFree
Rating4.4 (8 ratings)5.0 (1 ratings) — better
Positive reviews71.4% of reviews—
Number of ratings8 — better1
Update frequencyMonthlyEvery 3 weeks — better
AdsNoNo
In-app purchasesNoNo
MonetizationFreeFree
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS12.0 — better13.0
Further details — not scored
Size83 MB101 MB
Age rating17+4+
DeveloperKinetic PerformanceTrain.Red B.V.

Customer experience

FLEX Stronger

All ratings8 ratings
Positive87.5%
Neutral0.0%
Negative12.5%
Written reviews7 reviews
Positive71.4%
Neutral14.3%
Negative14.3%

Train.Red APP

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

None

FLEX Stronger

No in-app purchases

None

Train.Red APP

No in-app purchases

Questions

Is FLEX Stronger free?
FLEX Stronger is free to download, with no in-app purchases.
Is Train.Red APP free?
Train.Red APP is free to download, with no in-app purchases.
Which has better reviews, FLEX Stronger or Train.Red APP?
Train.Red APP is rated higher. FLEX Stronger averages 4.4 out of 5 from 8 ratings, while Train.Red APP averages 5.0 from 1 ratings.
Do FLEX Stronger or Train.Red APP have ads?
Neither FLEX Stronger nor Train.Red APP shows ads.
Which is updated more often, FLEX Stronger or Train.Red APP?
FLEX Stronger ships an update monthly, and Train.Red APP every 3 weeks. Most recently, FLEX Stronger was updated on August 6, 2026 and Train.Red APP on July 30, 2026.

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