Technical Reference & Formulas
Complete Mathematical Implementation
Implementation Guide
This page provides copy-paste formulas and step-by-step calculation methods for all Run Analytics metrics. Use these for custom implementations, verification, or deeper understanding.
⚠️ Implementation Notes
- All times should be converted to seconds for calculations
- rTSS calculation uses Intensity Factor squared (IF²)
- Always validate inputs for reasonable ranges
- Handle edge cases (division by zero, negative values)
Core Performance Metrics
Critical Run Speed (CRS)
Formula:
CRS (m/s) = (D₂ - D₁) / (T₂ - T₁)
CRS Pace (min/km) = 16.667 / CRS (m/s)
🧪 Interactive Calculator - Test the Formula
CRS Pace (min/km):
4:17
Calculation steps:
CRS (m/s) = (3600 - 1200) / (900 - 270) = 3.81 m/s
Pace (min/km) = 1000 / 3.81 = 262 seconds = 4:22
CRS (m/s) = (3600 - 1200) / (900 - 270) = 3.81 m/s
Pace (min/km) = 1000 / 3.81 = 262 seconds = 4:22
JavaScript Implementation:
function calculateCRS(distance1, time1, distance2, time2) {
// Convert times to seconds
const t1 = typeof time1 === 'string' ? timeToSeconds(time1) : time1;
const t2 = typeof time2 === 'string' ? timeToSeconds(time2) : time2;
// Calculate CRS velocity in m/s
const crs_ms = (distance2 - distance1) / (t2 - t1);
// Calculate pace per km in seconds
const pace_per_km = 1000 / crs_ms;
// Convert to mm:ss format
const minutes = Math.floor(pace_per_km / 60);
const seconds = Math.round(pace_per_km % 60);
return {
velocity_ms: crs_ms,
pace_seconds: pace_per_km,
pace_formatted: `${minutes}:${seconds.toString().padStart(2, '0')}`
};
}
Running Stress Score (rTSS)
Complete Formula:
rTSS = (IF²) × Duration (hours) × 100
IF = NSS / Threshold Speed
NSS = Total Distance / Total Time (m/min)
🧪 Interactive Calculator - Test the Formula
Calculated rTSS:
31
Calculation steps:
NSS = 5000m / 400min = 200 m/min
FTP = 1000 / (255/60) = 235.3 m/min
IF = 200 / 235.3 = 0.850
rTSS = 0.850² × (25/60) × 100 = 31
NSS = 5000m / 400min = 200 m/min
FTP = 1000 / (255/60) = 235.3 m/min
IF = 200 / 235.3 = 0.850
rTSS = 0.850² × (25/60) × 100 = 31
JavaScript Implementation:
function calculateRTSS(distance, timeMinutes, ftpMetersPerMin) {
// Calculate Normalized Run Speed
const nss = distance / timeMinutes;
// Calculate Intensity Factor
const intensityFactor = nss / ftpMetersPerMin;
// Calculate hours
const hours = timeMinutes / 60;
// Calculate rTSS using quadratic intensity factor
const rtss = Math.pow(intensityFactor, 2) * hours * 100;
return Math.round(rtss);
}
// Example usage:
const rtss = calculateRTSS(3000, 55, 64.5);
// Returns: 65
// Helper: Convert CRS Pace to Running Speed (m/min)
function crsPaceToSpeed(crsPacePerKmSeconds) {
// Speed in m/min = 1000m / (pace in minutes)
return 1000 / (crsPacePerKmSeconds / 60);
}
// Example: CRS of 4:15 (255 seconds)
const speed = crsPaceToSpeed(255); // Returns: 235.3 m/min
Biomechanical Efficiency: Vertical Ratio
Formula:
Vertical Ratio (%) = (Vertical Oscillation ÷ Stride Length) × 100
🧪 Interactive Calculator - Test the Formula
Vertical Ratio:
7.4%
Calculation:
Vertical Ratio = (8.5 / 115) × 100 = 7.4%
Vertical Ratio = (8.5 / 115) × 100 = 7.4%
JavaScript Implementation:
function calculateVerticalRatio(oscillationCm, strideLengthCm) {
return (oscillationCm / strideLengthCm) * 100;
}
function calculateEfficiencyFactor(paceMetersPerMin, avgHeartRate) {
return paceMetersPerMin / avgHeartRate;
}
Stride Mechanics
Stride Rate (SR)
Formula:
SR = 60 / Cycle Time (seconds)
SR = (Number of Strides / Time in seconds) × 60
🧪 Interactive Calculator - Test the Formula
Cadence (SPM):
180
Calculation:
Cadence = (180 / 60) × 60 = 180 SPM
Cadence = (180 / 60) × 60 = 180 SPM
JavaScript Implementation:
function calculateCadence(stepCount, timeSeconds) {
return (stepCount / timeSeconds) * 60;
}
// Example:
const spm = calculateCadence(180, 60);
// Returns: 180 SPM
Stride Length
Formula:
Stride Length = Distance / (Step Count / 2)
Stride Length = Velocity / (Cadence / 120)
JavaScript Implementation:
function calculateStrideLength(distanceMeters, stepCount) {
// Stride length is distance / number of stride pairs (left+right)
return distanceMeters / (stepCount / 2);
}
// Example (1000m, 800 steps):
const strideLength = calculateStrideLength(1000, 800);
// Returns: 2.50 meters per stride
Velocity from SR and DPS
Formula:
Velocity (m/s) = (SR / 60) × DPS
JavaScript Implementation:
function calculateVelocity(strideRate, dps) {
return (strideRate / 60) * dps;
}
// Example:
const velocity = calculateVelocity(70, 1.6);
// Returns: 1.87 m/s
Stride Index (SI)
Formula:
SI = Velocity (m/s) × DPS (m/stride)
JavaScript Implementation:
function calculateStrideIndex(velocity, dps) {
return velocity * dps;
}
// Example:
const si = calculateStrideIndex(1.5, 1.7);
// Returns: 2.55
Performance Management Chart (PMC)
CTL, ATL, TSB Calculations
Formulas:
CTL today = CTL yesterday + (TSS today - CTL yesterday) × (1/42)
ATL today = ATL yesterday + (TSS today - ATL yesterday) × (1/7)
TSB = CTL yesterday - ATL yesterday
JavaScript Implementation:
function updateCTL(previousCTL, todayTSS) {
return previousCTL + (todayTSS - previousCTL) * (1/42);
}
function updateATL(previousATL, todayTSS) {
return previousATL + (todayTSS - previousATL) * (1/7);
}
function calculateTSB(yesterdayCTL, yesterdayATL) {
return yesterdayCTL - yesterdayATL;
}
// Calculate PMC for series of workouts
function calculatePMC(workouts) {
let ctl = 0, atl = 0;
const results = [];
workouts.forEach(workout => {
ctl = updateCTL(ctl, workout.tss);
atl = updateATL(atl, workout.tss);
const tsb = calculateTSB(ctl, atl);
results.push({
date: workout.date,
tss: workout.tss,
ctl: Math.round(ctl * 10) / 10,
atl: Math.round(atl * 10) / 10,
tsb: Math.round(tsb * 10) / 10
});
});
return results;
}
// Example usage:
const workouts = [
{ date: '2025-01-01', tss: 50 },
{ date: '2025-01-02', tss: 60 },
{ date: '2025-01-03', tss: 45 },
// ... more workouts
];
const pmc = calculatePMC(workouts);
// Returns array with CTL, ATL, TSB for each day
Advanced Calculations
CRS from Multiple Distances (Regression Method)
JavaScript Implementation:
function calculateCRSRegression(distances, times) {
// Linear regression: distance = a + b*time
const n = distances.length;
const sumX = times.reduce((a, b) => a + b, 0);
const sumY = distances.reduce((a, b) => a + b, 0);
const sumXY = times.reduce((sum, x, i) => sum + x * distances[i], 0);
const sumXX = times.reduce((sum, x) => sum + x * x, 0);
const slope = (n * sumXY - sumX * sumY) / (n * sumXX - sumX * sumX);
const intercept = (sumY - slope * sumX) / n;
return {
crs: slope, // Critical running velocity (m/s)
anaerobic_capacity: intercept // Anaerobic distance capacity (m)
};
}
// Example with multiple test distances:
const distances = [100, 200, 400, 800];
const times = [65, 150, 340, 720]; // in seconds
const result = calculateCRSRegression(distances, times);
// Returns: { crs: 1.18, anaerobic_capacity: 15.3 }
Intensity Factor from Pace
JavaScript Implementation:
function calculateIntensityFactor(actualPaceMinKm, thresholdPaceMinKm) {
// Convert pace strings "mm:ss" to seconds if necessary
const actualSecs = typeof actualPaceMinKm === 'string' ? timeToSeconds(actualPaceMinKm) : actualPaceMinKm;
const thresholdSecs = typeof thresholdPaceMinKm === 'string' ? timeToSeconds(thresholdPaceMinKm) : thresholdPaceMinKm;
// IF is Threshold Pace / Actual Pace (faster pace = smaller seconds value)
return thresholdSecs / actualSecs;
}
// Example:
const if_value = calculateIntensityFactor("4:45", "4:15");
// Returns: 0.895 (running at 89.5% of threshold)
Pace Consistency Analysis
JavaScript Implementation:
function analyzePaceConsistency(segments) {
const paces = segments.map(kilometer => kilometer.distance / kilometer.time);
const avgPace = paces.reduce((a, b) => a + b) / paces.length;
const variance = paces.reduce((sum, pace) =>
sum + Math.pow(pace - avgPace, 2), 0) / paces.length;
const stdDev = Math.sqrt(variance);
const coefficientOfVariation = (stdDev / avgPace) * 100;
return {
avgPace,
stdDev,
coefficientOfVariation,
consistency: coefficientOfVariation < 5 ? "Excellent" :
coefficientOfVariation < 10 ? "Good" :
coefficientOfVariation < 15 ? "Moderate" : "Variable"
};
}
// Example:
const segments = [
{ distance: 100, time: 70 },
{ distance: 100, time: 72 },
{ distance: 100, time: 71 },
// ...
];
const analysis = analyzePaceConsistency(segments);
// Returns: { avgPace: 1.41, stdDev: 0.02, coefficientOfVariation: 1.4, consistency: "Excellent" }
Fatigue Detection from Stride Efficiency
JavaScript Implementation:
function detectFatigue(segments) {
// Compare Vertical Ratio of first and last segments
const firstSegment = segments[0];
const lastSegment = segments[segments.length - 1];
const ratioIncrease = lastSegment.verticalRatio - firstSegment.verticalRatio;
return {
startRatio: firstSegment.verticalRatio,
endRatio: lastSegment.verticalRatio,
increase: Math.round(ratioIncrease * 10) / 10,
fatigueLevel: ratioIncrease < 0.2 ? "Minimal" :
ratioIncrease < 0.5 ? "Moderate" :
ratioIncrease < 1.0 ? "Significant" : "Severe"
};
}
// Example:
const segments = [
{ verticalRatio: 7.2 }, { verticalRatio: 7.3 }, { verticalRatio: 8.1 }
];
const fatigue = detectFatigue(segments);
// Returns: { startRatio: 7.2, endRatio: 8.1, increase: 0.9, fatigueLevel: "Significant" }
Data Validation
Workout Data Quality Checks
JavaScript Implementation:
function validateWorkoutData(workout) {
const issues = [];
// Check for reasonable pace ranges (3:00-8:00 per km)
const avgPaceSecs = workout.totalTime / (workout.totalDistance / 1000);
if (avgPaceSecs < 180 || avgPaceSecs > 480) {
issues.push(`Unusual average pace: ${Math.round(avgPaceSecs)}s per km`);
}
// Check for reasonable Vertical Ratio (4% - 15%)
if (workout.avgVerticalRatio < 4 || workout.avgVerticalRatio > 15) {
issues.push(`Unusual Vertical Ratio: ${workout.avgVerticalRatio}%`);
}
// Check for reasonable cadence (120-220 SPM)
const avgCadence = calculateCadence(workout.totalSteps, workout.totalTime);
if (avgCadence < 120 || avgCadence > 220) {
issues.push(`Unusual cadence: ${Math.round(avgCadence)} SPM`);
}
// Check for missing segments (gaps in time)
if (workout.segments && workout.segments.length > 1) {
for (let i = 1; i < workout.segments.length; i++) {
const gap = workout.segments[i].startTime -
(workout.segments[i-1].startTime + workout.segments[i-1].duration);
if (gap > 300) { // 5 minute gap
issues.push(`Large gap detected between segments ${i} and ${i+1}`);
}
}
}
return {
isValid: issues.length === 0,
issues
};
}
// Example:
const workout = {
totalDistance: 2000,
totalTime: 1800, // 30 minutes
totalStrides: 800,
segments: [/* kilometer data */]
};
const validation = validateWorkoutData(workout);
// Returns: { isValid: true, issues: [] }
Helper Functions
Time Conversion Utilities
JavaScript Implementation:
// Convert mm:ss to seconds
function timeToSeconds(timeString) {
const parts = timeString.split(':');
return parseInt(parts[0]) * 60 + parseInt(parts[1]);
}
// Convert seconds to mm:ss
function secondsToTime(seconds) {
const minutes = Math.floor(seconds / 60);
const secs = Math.round(seconds % 60);
return `${minutes}:${secs.toString().padStart(2, '0')}`;
}
// Convert seconds to hh:mm:ss
function secondsToTimeDetailed(seconds) {
const hours = Math.floor(seconds / 3600);
const minutes = Math.floor((seconds % 3600) / 60);
const secs = Math.round(seconds % 60);
return `${hours}:${minutes.toString().padStart(2, '0')}:${secs.toString().padStart(2, '0')}`;
}
// Examples:
timeToSeconds("1:33"); // Returns: 93
secondsToTime(93); // Returns: "1:33"
secondsToTimeDetailed(3665); // Returns: "1:01:05"
Implementation Resources
All formulas on this page are production-ready and validated against scientific literature. Use them for custom analytics tools, verification, or deeper understanding of running performance calculations.
💡 Best Practices
- Validate inputs: Check for reasonable ranges before calculating
- Handle edge cases: Division by zero, negative values, null data
- Round appropriately: CTL/ATL/TSB to 1 decimal, sTSS to integer
- Store precision: Keep full precision in database, round for display
- Test thoroughly: Use known-good data to verify calculations