Source: https://guthlabs.ai/docs/instruments/one-rep-max-calculator-epley-brzycki/implementation/

instrument implementation / implementation-contract

# One-Rep Max Calculator (Epley/Brzycki) implementation

A source-bound implementation contract for One-Rep Max Calculator (Epley/Brzycki); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-235

**Effect**: Computation or source lookup only

## Input and validation requirements

The Brzycki formula has an unhandled division-by-zero input at exactly 37 reps. The calculator must reject reps = 37 rather than emit Infinity, NaN, or an invalid training table. Negative-weight interpretation is also ambiguous unless input validation or an absolute-magnitude convention is specified.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "weight": 100,
    "weight_unit": "kg",
    "reps": 5,
    "formula_choice": "Epley",
    "table_percentage": 0.8,
    "sets": 5,
    "reps_per_set": 5
  },
  "expected_outputs": {
    "estimated_1RM": 116.6666667,
    "estimated_1RM_unit": "kg",
    "table": {
      "scheme": "5x5",
      "percentage": 0.8,
      "load_per_set": 93.3333333,
      "load_unit": "kg"
    }
  },
  "working": "1RM = 100 × (1 + 5/30) = 100 × (1 + 0.1666667) = 100 × 1.1666667 = 116.6666667 kg. Training load = 116.6666667 × 0.80 = 93.3333333 kg per set."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/one-rep-max-calculator-epley-brzycki/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/one-rep-max-calculator-epley-brzycki/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/one-rep-max-calculator-epley-brzycki/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`