# Weightlifting

> An Olympic weightlifting simulator. A planar multibody lifter, the IWF Technical and Competition
> Rules & Regulations 2025, three referees and a full competition with the 2025 tie-break.

## What is modelled
The lifter is a serial chain - foot, shank, thigh, trunk - plus a telescoping arm link whose length
is a generalised coordinate. That last piece is the point: the arm's length is actuated, so the
lifter can push the bar away from the shoulder and therefore the shoulder away from the bar. Airborne,
that is the only thing available, and it moves the lifter down exactly as much as it moves the bar up,
weighted by their masses.

## Two derived results
- The bar in the deepest receiving position a lifter's joints allow sits at 67.8 per cent of stature.
  Standing with it locked overhead it is at 109.6 per cent. The gap of 41.8 points of stature is
  covered by standing up under the bar, not by lifting it. Published measurements: catch 67-69 per
  cent, standing hold 107-110, peak 69.6-76.
- The double knee bend is a consequence of balance. Ask only for a hip height and a trunk angle with
  the whole system's centre of mass over the mid-foot, and the knees re-bend by 8.9 degrees against a
  published 8.28-12.07. Take the barbell out of the balance and the re-flexion disappears entirely.

## What this model does NOT reproduce
- The bar does not loop back toward the lifter. Published 3.6-7 cm; this model 0.0.
- The arm force in flight is about 700 N against a published 150; peak ground reaction 2.5 times
  system weight against a published 1.4-1.8.
- The snatch comes out at 0.95 of the clean & jerk instead of the published 0.821.
- A left-right symmetric receiving position cannot represent a split jerk.

## Three rulebook corrections
- The minimum barbell increment is one kilogram everywhere, records included (TCRR 6.6.2, 6.6.3, 8.1).
- A tie is NOT broken on bodyweight. It goes to whoever reached the total first (TCRR 6.8.2).
- The competition platform is 10 cm high (TCRR 3.3.2.2), not the 150 mm the IWF's own summary page
  still shows.

## Files
- index.html - the app, with every substantive claim in static markup
- js/dyn.js - a planar multibody solver, checked against four closed forms
- js/lift.js - the lifter, the poses, the phases and the adjudication
- js/rules.js - the IWF rulebook as implemented
- js/provenance.js - every constant and claim, tagged and sourced
- CREDITS.txt - the documents, the tally, and what the model gets wrong