RSMI

Tool id: rsmi · Methods: direct, wen-2011

Computes the Relative Skeletal Muscle Index — appendicular muscle relative to height — and flags low muscle mass against three sarcopenia standards. Reach for it to screen for sarcopenia.

Input

Field	Type	Notes
sex	"male" | "female"	cutoffs and the estimate are sex-specific
height	{ value, unit }	cm or in
weight	{ value, unit }	kg or lb
age	number	years, 0–120
asm_kg	number | null	appendicular skeletal muscle mass from DXA
methods	string[] | "all"	defaults to "all"

Methods

• direct — asm_kg ÷ height(m)². Runs only when you provide a DXA asm_kg; otherwise it’s skipped.
• wen-2011 — always runs. Estimates appendicular muscle from height/weight/age/sex (Wen X, et al. Asia Pac J Clin Nutr 2011;20(4):551–556), then divides by height². It is an anthropometric estimate and less accurate than a DXA measurement.

Each result’s detail flags the value against EWGSOP2 (men <7.0, women <5.5), AWGS 2019 (men <7.0, women <5.4), and Baumgartner 1998 (men <7.26, women <5.45) — all kg/m².

Example

Without a DXA value, only the estimate runs:

TypeScript

import { REGISTRY } from "@almostjacked/fitness-tools";
const rsmi = REGISTRY.get("rsmi")!;
rsmi.compute(rsmi.input.parse({
  sex: "male",
  height: { value: 180, unit: "cm" },
  weight: { value: 80, unit: "kg" },
  age: 30,
}));

curl

curl -s localhost:8080/v1/tools/rsmi \
  -X POST -H 'content-type: application/json' \
  -d '{"sex":"male","height":{"value":180,"unit":"cm"},"weight":{"value":80,"unit":"kg"},"age":30}'

MCP

Call the rsmi tool with these arguments:

{
  "sex": "male",
  "height": { "value": 180, "unit": "cm" },
  "weight": { "value": 80, "unit": "kg" },
  "age": 30
}

{
  results: [
    {
      method: "wen-2011",
      value: 8.27,
      unit: "kg/m²",
      detail: { asm_kg: 26.8, below_ewgsop2: false, below_awgs: false, below_baumgartner: false },
    },
  ],
  consensus: { mean: 8.27, median: 8.27, min: 8.27, max: 8.27, n: 1 },
  skipped: [{ method: "direct", reason: "direct: requires asm_kg" }],
}

Pass asm_kg from a DXA scan to add the direct method and a consensus across both.

Call it another way

Full docs for the other protocols: HTTP API · MCP server.