What’s inside
The adaptive workout planner and smart gym tracker that connects progressive overload, five strength periodisation models and recovery-aware training—powered by on-device machine learning, not chatbots.
PROGRESSION
Flux is a progressive overload tracker that advances your weights and reps automatically. Use double progression (rep ranges first, then load) or linear progression so you’re always training at the right intensity. 1RM entry and calculation from performance keep your numbers honest. No spreadsheets—the app handles progression so you can focus on lifting.
READINESS
Fatigue-based training is at the core of Flux. The app tracks systemic fatigue and per-muscle recovery so each session is tuned to how you actually feel. Subjective recovery and optional HealthKit data (sleep, HRV, RHR) feed into readiness. Flux includes fatigue modulation: live volume and intensity adjustments so you train hard when you’re ready and back off when you need to. It’s the workout app that changes based on sleep and recovery.
STRATEGY
Choose Adaptive Block, Daily Undulating (DUP), Linear, Weekly Undulating (WUP) or Manual when generating a strength routine. The model shapes sets, reps, load, rest and effort targets. Managed progression follows completed training, not a fixed number of calendar days, with safety recovery when needed.
Move through adaptive phases, vary workout or weekly emphasis, follow a structured Linear build, or hold an eligible Manual phase. To change models, generate a new routine. Routine Library programmes keep their authored progression, and HIIT keeps its timed prescription.
HEALTH CONTEXT
HRV workout adjustments can use Apple Health data you choose to share. Available sleep, resting heart rate and HRV readings add recovery context to daily volume targets. Apple Health is optional: you can use Flux without sharing Health data, and data-dependent insights show only what is available. ML Readiness Simulation predicts RPE and adherence before you lift.
EQUIPMENT
The custom gym equipment filter makes every workout fit your setup. Create profiles for home gym, commercial gym, or limited equipment (e.g. hotel or minimal kit). The app selects exercises only from what you have, so you get a personalized lifting program that’s actually doable. Perfect for home gym owners and anyone who doesn’t have a full commercial setup.
ADAPTATION
When progress stalls, Flux acts as a plateau breaker. Included Plateau Interventions use goal shifts, exercise swaps, and intensity boosters so you’re not stuck on the same plan. The Exploration Engine uses bandit-driven variety to prevent stagnation, and Adaptive Pathing learns which movements drive your progress while balancing favourites with the variety you need. Smart exercise selection gets more personal the more you use it.
THE COMPLETE APP
Offline workout saving: completion confirms after your workout and final feedback save successfully on your device, without waiting for cloud acknowledgement. Signed-in backup can sync later when the app has connectivity; a local save is not a completed cloud backup.
Clearer Routine Details: Overview brings workouts and progress together, Settings groups the available controls, and saved programmes with an available template also have a Guide. See clearer phase and cycle displays, planned muscle volume for the programme phase you’re viewing, and more of your exercise history.
Also included: strength, hypertrophy and powerbuilding workouts; custom exercises; favourites; supersets; Weekly Check-In coaching; effort calibration; training insights; optional signed-in cloud backup; and more reliable Lock Screen and Dynamic Island timers.
Every feature is available during the 14-day Full Access trial and with Lifetime Unlock or eligible existing access. Read the Flux 8.5.1 release highlights →
Download free for iPhone and iPad. Try every feature for 14 days with no payment, subscription or automatic charge. After the trial, training requires a one-time Lifetime Unlock or eligible existing access.
Download Free on the App Store