# Flexbound

> Flexbound is a smart workout notebook for lifting, yoga, Pilates, barre, HIIT, cardio, and mixed training. Write in your own words; deterministic math builds plans and trends with AI kept to the margins.

Flexbound is a notebook-first workout and nutrition app for iOS supporting lifting, yoga,
Pilates, barre, HIIT, steady cardio, home training, full-gym training, and mixed weeks.
Key differentiator: every number (calories, macros, TDEE, estimated 1RM, volume, progression)
comes from versioned deterministic calculators citing peer-reviewed sources. AI may only write
and explain. It is architecturally prevented from producing numbers or decisions.

The core notebook is free (unlimited journaling, deterministic parsing, backup/sync).
Pro adds sourced nutrition estimates, weekly reviews, workout plans, and unlimited history.

## Core pages

- [Home](https://flexbound.app): what Flexbound is, feature overview, early access
- [Features](https://flexbound.app/features): real iOS-framed app screens and the product loop
- [Training plans](https://flexbound.app/features/training-plans): how equipment-aware plans are built across movement styles
- [Training styles](https://flexbound.app/training-styles): lifting, yoga, Pilates, barre, HIIT, and cardio-only plan pages
- [Methodology](https://flexbound.app/methodology): the decision architecture and how AI is kept out of the math
- [Comparisons](https://flexbound.app/compare): sourced comparisons with leading calorie and workout apps
- [Guides and tools](https://flexbound.app/guides): workout journal guides, printable logs, calculators, and glossary
- [About and editorial standard](https://flexbound.app/about): sourcing, review, corrections, and publisher information
- [Pricing](https://flexbound.app/pricing): free vs Pro comparison
- [FAQ](https://flexbound.app/faq): common questions, straight answers
- [Support](https://flexbound.app/support): help and contact

## Science library

Documentation of the exact rules and formulas the app runs, with peer-reviewed citations:

- [Progressive overload & double progression](https://flexbound.app/science/progressive-overload): How Flexbound decides when you add weight: the rep-target gate, repeating missed prescriptions, and smallest-practical increments.
- [Estimated 1RM: the Epley formula and its limits](https://flexbound.app/science/estimated-1rm): The exact formula behind every e1RM in the app, why we chose it, and the rep ranges where the estimate is trustworthy.
- [Weekly training volume & the recovery guardrail](https://flexbound.app/science/training-volume): Why plans start near 10 hard sets per muscle per week, the dose-response evidence, and the 20% volume-jump caution.
- [Adaptive TDEE from your own logs](https://flexbound.app/science/adaptive-tdee): Mifflin-St Jeor as the starting estimate, then energy-balance math over confirmed intake and weight trend. No AI guessing.
- [Protein targets that match the evidence](https://flexbound.app/science/protein): Where Flexbound’s per-pound protein targets come from, by goal, and why more isn’t automatically better.
- [RPE and RIR: measuring effort you can log](https://flexbound.app/science/rpe-and-rir): What reps-in-reserve actually measures, the evidence lifters can estimate it, why every planned set ships with an RIR target, and where self-rated effort breaks down.
- [Deload signals, pain flags & minimum-dose weeks](https://flexbound.app/science/recovery-and-deloads): The thresholds that trigger a deload suggestion, how recurring pain notes change prescriptions, and training through busy weeks.

## Workout journal guides and tools

- [Complete workout journal guide](https://flexbound.app/workout-journal): what to record, how to write useful notes, and how to review training
- [Food and workout journal guide](https://flexbound.app/food-journal): keeping food and training on one page, complete-day grading, and honest estimates
- [Home strength training guide](https://flexbound.app/home-strength-training): what each piece of equipment unlocks, the vertical-pull problem, and progression without plates
- [Printable workout log template](https://flexbound.app/workout-log-template): a print-ready strength session sheet with effort, pain, and next-session fields
- [One-rep max calculator](https://flexbound.app/tools/one-rep-max-calculator): Epley e1RM calculator with rep-range confidence
- [Macro calculator](https://flexbound.app/tools/macro-calculator): calories and macros from Mifflin-St Jeor, activity multipliers, and goal-based protein, with every step documented
- [Weekly training volume calculator](https://flexbound.app/tools/training-volume-calculator): direct and secondary hard sets per muscle
- [Strength training glossary](https://flexbound.app/glossary): 26 plain-English definitions with methodology links

## App comparisons

- [Flexbound vs MyFitnessPal](https://flexbound.app/compare/myfitnesspal): Choose MyFitnessPal for database breadth and mature scanning tools. Choose Flexbound if you want food and lifting notes to begin as your own words, with sources and uncertainty left visible.
- [Flexbound vs MacroFactor](https://flexbound.app/compare/macrofactor): MacroFactor is the closer fit if nutrition coaching is your main goal. Flexbound is for lifters who want adaptive calories, training progression, and the messy context of a real notebook in one place.
- [Flexbound vs Cronometer](https://flexbound.app/compare/cronometer): Choose Cronometer when micronutrient depth is the priority. Choose Flexbound when you care more about connecting a practical food log to lifting, recovery, and progression.
- [Flexbound vs Hevy](https://flexbound.app/compare/hevy): Choose Hevy for structured set logging, routines, rich gym stats, and a social layer. Choose Flexbound for free-form notes, private context, and recommendations you can trace back to a rule.
- [Flexbound vs Strong](https://flexbound.app/compare/strong): Choose Strong for a mature, focused workout logger with timers, templates, charts, and wearable support. Choose Flexbound when the note itself matters as much as the set table.
- [Flexbound vs Fitbod](https://flexbound.app/compare/fitbod): Choose Fitbod when you want the app to generate the session and teach the movements. Choose Flexbound when you want to steer the training and inspect the rule behind every recommendation.

## Blog

- [How long should a lifting session be? Shorter than the guilt says](https://flexbound.app/blog/how-long-should-a-lifting-session-be): What the time-efficiency research actually supports for session length, the exact trim order that protects results in 30 and 45 minute workouts, and why "not enough time" is a programming problem, not a dedication problem.
- [How to choose a workout tracker: seven questions that actually decide it](https://flexbound.app/blog/how-to-choose-a-workout-tracker): Most workout app comparisons list features. This is the decision framework instead: seven questions about input style, data ownership, honesty, and coaching that sort every tracker on the market, including ours.
- [How Flexbound estimates calories without lying to you](https://flexbound.app/blog/calorie-estimates-without-lying): Every macro tracker shows you precise-looking numbers built on uncertain assumptions. Here is what honest nutrition estimation looks like: sources, serving assumptions, and confidence grades on every number.
- [Double progression: the simplest loading scheme that actually works](https://flexbound.app/blog/double-progression-guide): A complete guide to double progression: the rep-range method behind most real-world strength progress, when to use it, and the mistakes that stall it.
- [Why your workout log should be written, not tapped](https://flexbound.app/blog/why-your-workout-log-should-be-written): Dropdown-and-picker workout trackers optimize for the database, not the lifter. The case for a written training log and what software should do underneath it.

## Legal

- [Privacy](https://flexbound.app/privacy)
- [Terms](https://flexbound.app/terms)
- [Delete account](https://flexbound.app/delete-account)

Contact: suolaraketti@proton.me