The Distance Trap

You ran 20 miles this week. Proud of that volume, right?

Here's the problem: that 20-mile number tells you almost nothing about the training stress your body actually experienced.

Compare these two weeks:

Week A:

Monday: 5 miles easy
Wednesday: 5 miles easy
Saturday: 10 miles long run (easy)
Total: 20 miles, zero hard efforts

Week B:

Monday: 5 miles easy
Wednesday: 5 miles with 3 × 5-minute VO2Max intervals (hard)
Saturday: 5 miles easy
Total: 15 miles, 15 minutes at high intensity

Which week created more training stress? The 20-mile week or the 15-mile week with intensity?

Most athletes would guess the 20-mile week. They'd be wrong.

Week B, despite being 5 miles shorter, creates significantly more physiological stress because the intensity is so much higher. Your body needs different recovery. Your adaptations will be different. Your performance gains will be different.

This is why distance is a terrible metric for measuring training. It doesn't account for intensity, and intensity is what triggers adaptation.

Introducing Training Stress Score (TSS)

Training Stress Score is a mathematical metric that combines duration and intensity into a single number representing total training stress.

The formula is:

TSS = (Duration in hours) × (Intensity Factor) × 100

Where Intensity Factor is your average effort as a percentage of your functional threshold.

The result? A single number that tells you how much stress that workout created.

Examples:

Easy 1-hour run at 70% max effort = 45 TSS
Moderate 1-hour run at 85% max effort = 67 TSS
Hard 45 minutes with 4 × 3-minute VO2Max intervals = 75 TSS

Notice something? The 45-minute hard session creates more training stress than a 1-hour easy run. The metric captures what distance misses.

Why TSS Changes Everything

When you track TSS instead of just distance, training becomes quantifiable and predictable.

You know that you can sustain roughly 800-1000 TSS per week without overtraining. Go above that, and recovery suffers. Go below 600 TSS, and you're not creating enough stimulus for adaptation.

A properly periodized training plan manipulates TSS strategically:

BASE Phase: Build volume at lower intensity. Target 600-700 TSS/week.

BUILD Phase: Introduce intensity. Increase to 800-900 TSS/week.

PEAK Phase: Maintain TSS near capacity. Target 900-1000 TSS/week.

TAPER Phase: Reduce TSS to 40-50% of peak. Target 400-500 TSS/week.

This is the science of periodization. And it's invisible if you're only tracking distance.

The Recovery Revolution

Here's where TSS gets magical: it tells you how recovered you actually are.

Imagine you planned a hard workout with a target TSS of 85. You get out there, and it feels easy. You complete it with an actual TSS of 55.

What does that tell you? Your fitness has improved. You're handling the same workout stimulus with less effort. Your aerobic capacity is climbing.

A smart training system (like CADENCE) sees this and makes immediate adjustments. Next week's workout increases in intensity to maintain the targeted 85 TSS.

You're always training at the right intensity for your current fitness level—never too easy, never excessive.

How CADENCE Uses TSS

When CADENCE generates your weekly plan, every workout has a target TSS. The app learns what your body can handle:

Can you handle 1000 TSS per week? CADENCE pushes you there.
Can only handle 700 TSS? The plan scales back.
Recovering faster than expected? Intensity increases.
Struggling? Volume adjusts downward.

You're not estimating your fitness or guessing at your capacity. The data guides every decision.

At the end of the week, CADENCE shows you:

Total TSS accumulated
TSS distribution (percentage at each intensity zone)
Recovery indicators
Readiness for next week's training

You see, in real numbers, exactly how much training stress you handled and how well you recovered.

The Bottom Line

Stop measuring training by miles or kilometers. Start thinking in terms of stress and recovery.

A 5-mile run can be either a 30-TSS recovery session or a 75-TSS hard effort. The difference isn't in the distance—it's in the intensity and the adaptation it triggers.

CADENCE tracks this for you automatically. Every workout shows you the exact stress it creates and how it impacts your overall training load. You'll understand, for the first time, exactly what's driving your fitness progress.

Ready to train smarter than distance? Start your free trial and see your training in numbers that actually mean something.

What Is Training Stress Score (TSS) and Why It Matters More Than Distance