# Domain: Mike Mentzer's Heavy Duty

hito is a Heavy Duty training tracker.

- Source of doctrine: `doc/Mike_Mentzer_Heavy_Duty_I.md` (HD1). Every domain
  decision must be justified against it.
  - It is copyrighted local reference material, gitignored, and never committed.
- On conflict between a design choice and the doctrine:
  1. The doctrine wins, or
  2. The conflict is raised explicitly.

## Principles that bind the model

- **Intensity is categorical, not scalar.**
  - A working set is taken to momentary muscular failure; that *is* its
    definition (HD1, "The Intensity Factor": the only accurate measures are 0%
    at rest and 100% at failure).
  - Going further is qualitative — `Beyond_failure`: forced reps, negatives,
    rest-pause, static hold.
  - Never introduce a numeric "intensity score".
- **Recovery produces growth; the gym only stimulates it.**
  - Stimulation is immediate; production is not (HD1, "The Economics of Growth
    and Recovery": recovery precedes growth).
  - Recovery is systemic and time-based — any hard workout gates the next one.
- **Volume beyond the minimum is harmful.**
  - One working set per exercise is nominal; three sets per muscle is the ceiling.
  - The net negative effect of each extra set increases geometrically.
  - Rising volume is a diagnostic warning — never an achievement or a progress
    target.
- **Progressive overload is the progress signal.**
  - Progress = an increase in reps, weight, or both; one extra rep counts.
  - Reps are an *outcome*, never a target — a set ends at failure, not at a
    number. The prescribed band only calibrates load.
  - Raise the load once twelve reps are reached, by 10-20%, so failure returns
    inside the band.
  - Note the slack: a 6-10 band is not breached at eleven.
- **Brief, infrequent, intense.**
  - Shorter sessions at equal or better overload are favourable.
- **Focus over novelty.**
  - Exercises come from a curated catalog.
  - Substitutions are limited to author-specified whitelists, which a routine
    may only narrow.

## Encoding rules

- Prefer making an illegal training state unrepresentable over validating it at
  runtime.
- Deviations from doctrine (training early, extra volume) must be *possible* but
  never *silent*:
  - Require an explicit acknowledgement.
  - Retain that acknowledgement.
- Keep plan and record distinct:
  - Prescription/routine vs logged workout.
  - Prescription vs progression (plan vs observation).
- The logbook records; it never interprets.
  - Judgement belongs to one module.
  - Invariants belong on plans, which are authored — not on history, which is
    observed.
  - A log that refuses to state what happened is worse than one recording an
    error.
- On a stall, the answer is never more work.
  - No remedy may add volume or frequency.
  - Doctrinal remedy (HD1, "Regulating Volume and Frequency"): after two weeks
    of no progress, take a week off, then *reduce* volume and frequency —
    drop sets and add rest days.