health-calculator/src/sports.ts

A library to help calculate well known health-related metrics.

/**
 * @module sports
 */

enum OneRmFormula {
	Epley = 'epley',
	Brzycki = 'brzycki',
	Lombardi = 'lombardi',
	Mayhew = 'mayhew',
	OConner = 'oconner',
	Wathan = 'wathan',
	Lander = 'lander',
}

/**
 * Calculates one-repetition maximum (1RM) using various formula.
 *
 * @param {number} reps - Number of repetition of a given weight.
 * @param {number} weight - Weight being lifted for a given reps.
 * @param {OneRmFormula} formula - Formula to use.
 * @returns {number} One rep max.
 */
export function oneRm( reps: number, weight: number, formula: OneRmFormula = OneRmFormula.Epley ) : number {
	if ( reps <= 0 ) {
		throw new Error( 'reps must be greater than 0' );
	}

	switch ( formula ) {
		case OneRmFormula.Brzycki:
			return Number( ( weight / ( 1.0278 - 0.0278 * reps ) ).toFixed( 2 ) );
		case OneRmFormula.Lombardi:
			return Number( ( weight * reps ** 0.10 ).toFixed( 2 ) );
		case OneRmFormula.Mayhew:
			return Number( ( ( 100 * weight ) / ( 52.2 + 41.9 * Math.exp( -0.055 * reps ) ) ).toFixed( 2 ) );
		case OneRmFormula.OConner:
			return Number( ( weight * ( 1 + reps / 40 ) ).toFixed( 2 ) );
		case OneRmFormula.Wathan:
			return Number( ( 100 * weight / ( 48.80 + 53.8 * Math.exp( -0.075 * reps ) ) ).toFixed( 2 ) );
		case OneRmFormula.Lander:
			return Number( ( 100 * weight / ( 101.3 - 2.67123 * reps ) ).toFixed( 2 ) );
		default:
			return Number( ( weight * ( 1 + ( reps / 30 ) ) ).toFixed( 2 ) );
	}
}

enum  HRMaxFormula {
	Haskell = 'haskell',
	Inbar = 'inbar',
	Nes = 'nes',
	Oakland = 'oakland',
	Tanaka = 'tanaka',
}

/**
 * Calculates maximum heart rate (HR) of a given age and formula.
 *
 * @param {number} age - Person age.
 * @param {HRMaxFormula} formula - Formula to use.
 * @returns {number} HRmax in BPM (beats per minute).
 */
export function hrMax( age: number, formula: HRMaxFormula = HRMaxFormula.Haskell ) : number {
	if ( age < 1 || age > 124 ) {
		throw new Error( 'age must be between 1 and 124' );
	}

	switch ( formula ) {
		case HRMaxFormula.Inbar:
			return Number( ( 205.8 - ( 0.685 * age ) ).toFixed( 0 ) );
		case HRMaxFormula.Nes:
			return Number( ( 211 - ( 0.64 * age ) ).toFixed( 0 ) );
		case HRMaxFormula.Oakland:
			return Number( ( 192 - ( 0.007 * ( age ** 2 ) ) ).toFixed( 0 ) );
		case HRMaxFormula.Tanaka:
			return Number( ( 208 - ( 0.7 * age ) ).toFixed( 0 ) );
		default:
			// Haskell
			return Number( ( 220 - age ).toFixed( 0 ) );
	}
}