Proper TSS calculation

src/index.ts

@@ -1,10 +1,11 @@
 import * as fs from "fs";
-import { averageIntensity } from "./average-intensity";
-import { normalizedIntensity } from "./normalized-intensity";
+import { averageIntensity } from "./averageIntensity";
+import { normalizedIntensity } from "./normalizedIntensity";
 import { parse } from "./parser";
 import { tokenize } from "./tokenizer";
 import { totalDuration } from "./totalDuration";
 import { tss } from "./tss";
+import { tss2 } from "./tss2";
 
 const filename = process.argv[2];
 
@@ -33,3 +34,10 @@ console.log(
     normalizedIntensity(workout.intervals) * 100
   ).toFixed()}%`
 );
+
+console.log(
+  `TSS: ${tss2(
+    totalDuration(workout.intervals),
+    normalizedIntensity(workout.intervals)
+  )}`
+);

src/tss2.ts

@@ -0,0 +1,16 @@
+// Training Stress Score formula from Training and Racing with a Power Meter:
+//
+// TSS = (s * W * IF) / (FTP * 3600) * 100
+//
+// s - duration in seconds
+// W - power in watts
+// IF - intensity factor (power / FTP)
+//
+// Derive a formula without power values, using intensities alone:
+//
+// TSS = (s * (FTP * IF) * IF) / (FTP * 3600) * 100
+// TSS = (s * IF * IF) / 3600 * 100
+
+export const tss2 = (duration: number, intensity: number): number => {
+  return ((duration * intensity * intensity) / 3600) * 100;
+};