FitnessJS

FitnessJS is a library of exercise physiology and healthcare equations for transforming basic health data. FitnessJS compiles bodybuilding competition formulas, aerobic performance models, and body composition equations so developers don't have to track them down themselves.

Written in TypeScript and published with full type definitions, ESM, CommonJS, and UMD builds.

Resources

• Website
• Home
• Enums
• Balance
• Cardio
• Composition
• Convert
• METs
• Model
• Sport
• Strength
• Test Protocols

Installing

Note: FitnessJS is not published to the npm registry, unpkg, or jsDelivr. Until then, install it directly from GitHub as shown below.

npm (from GitHub)

npm install git+https://github.com/dpfens/fitnessjs.git#v3.0.0

npm will clone the tag and run the package's prepare script automatically, which builds dist/esm, dist/cjs, dist/types, and dist/bundle for you so no manual build step is needed. Swap #v3.0.0 for another tag, branch, or commit as needed.

Once installed, it's used exactly like a registry package and supports both module systems out of the box:

// ESM
import { ... } from 'fitnessjs';

// CommonJS
const { ... } = require('fitnessjs');

TypeScript type definitions will be included (no @types package needed). Each domain of the library will also be importable individually, keeping your bundle limited to only what you use:

import { ... } from 'fitnessjs/anthropometry';
import { ... } from 'fitnessjs/cardiovascular';
import { ... } from 'fitnessjs/composition';
import { ... } from 'fitnessjs/conversion';
import { ... } from 'fitnessjs/models';
import { ... } from 'fitnessjs/sport';
import { ... } from 'fitnessjs/strength';
import { ... } from 'fitnessjs/utilities';

Script tag (direct download)

For direct browser use without a bundler or package manager, download the built bundle from the latest GitHub Release and include it in your markup. The UMD build exposes a global Fit namespace:

<script src="fitness.umd.min.js"></script>
<script>
  // Available as the global `Fit`
  Fit.someFunction();
</script>

Or the unminified version, useful for debugging:

<script src="fitness.umd.js"></script>

From source (manual build)

If you'd rather clone and build the repo yourself instead of installing via npm:

git clone https://github.com/dpfens/FitnessJS.git
cd FitnessJS
npm install
npm run build

This produces the same dist/esm, dist/cjs, dist/types, and dist/bundle output described above, which you can import directly, e.g. import { ... } from './dist/esm/index.js'.

Usage

A few quick examples to give you a taste of what's available. See the wiki for the full API.

Anthropometry

Estimate body landmarks from height

import { Segment } from 'fitnessjs/anthropometry';

const segment = new Segment(180); // body height in cm

segment.height_shoulders(); // height of the shoulders off the ground
segment.shoulder_width();   // shoulder width
segment.hand_length();      // wrist-to-fingertip length

Cardiovascular

Max heart rate & training zones

import { cardiac } from 'fitnessjs/cardiovascular';

const astrand = new cardiac.Astrand();
const maxHR = astrand.predict(34); // estimated max HR for a 34-year-old

const targetHR = cardiac.karvonen(0.7, 60, maxHR); // 70% intensity, resting HR of 60

Models

Predict race performance

import { aerobic } from 'fitnessjs/models';

// 10K (10,000m) finished in 40 minutes (2400s)
const riegel = new aerobic.Riegel(10000, 2400, aerobic.Riegel.RUNNINGMEN);

const halfMarathonTime = riegel.time(21097.5); // estimated half-marathon time, in seconds

Strength

Estimate 1RM & compare lifts across body weights

import { Gender } from 'fitnessjs';
import { estimate1RM, Compare } from 'fitnessjs/strength';

// Estimate a 1-rep max from a set of 8 reps at 100kg
const oneRM = estimate1RM('Brzycki', Gender.Male, 28, 8, 100);

// Compare the lift across body weights using the Wilks coefficient
const athlete = new Compare(Gender.Male, 83); // 83kg lifter
const wilksScore = athlete.wilks(oneRM);

Support

Please raise potential bugs on Github.