Every training system needs a way to measure how much work you’re doing. Some use miles. Some use heart rate zones. Some use proprietary “training effect” scores that nobody can explain.

Pacewright uses a formula you can calculate in your head.

The Formula

Training Load = Duration (minutes) × RPE (1-10)

That’s it. A 45-minute easy run at RPE 4 produces a load of 180. A 30-minute tempo at RPE 7 produces a load of 210. The tempo was shorter but harder — and the training load reflects that.

This approach — called session RPE — was validated by Foster and colleagues and is now one of the most widely used training load metrics in sports science. It correlates strongly with heart rate-based methods but doesn’t require any equipment. You need a clock and an honest answer to “how hard was that?”

Why Not Heart Rate? Why Not Pace?

Heart rate is affected by caffeine, heat, dehydration, stress, sleep, and medication. The same effort produces different heart rates on different days, making it an unreliable load measure unless you control for everything else.

Pace measures speed, not effort. Running 8:30/mile on a cool flat road and running 8:30/mile uphill in 90°F heat are radically different efforts — but pace calls them equal.

RPE captures what you actually experienced. It automatically accounts for hills, heat, fatigue, illness, stress, and every other variable that affects how hard a run feels. That’s why Pacewright uses it as the foundation of everything.

How Load Becomes Safety

A single session’s load is useful on its own. Tracked over time, it becomes the input to every limit Pacewright applies.

Pacewright tracks your load over time, weighting recent runs more heavily than old ones, so the picture reflects what you’ve been doing lately rather than months ago. That picture describes your training. It doesn’t decide anything by itself. Three limits do that. Your DIAL reading is drawn from the same picture.

Your longest recent run sets the ceiling on your next one. Pacewright won’t prescribe a session that jumps far beyond the longest run you’ve genuinely done in the last month. This is the best-supported injury predictor we have in runners specifically. In the largest study of runners to date, covering 5,205 runners and 588,071 recorded sessions, a run that exceeded the runner’s longest run of the previous 30 days by more than 10% was associated with overuse injury. Every band of excess the study measured carried elevated risk.2

Your weekly volume has a ceiling, and so does how fast it grows. How much you run in total matters, and how fast that total climbs matters too.

Your own reports can override both. RPE, soreness, and how a run actually felt are inputs, not decoration. Tell Pacewright an easy run felt hard and the plan responds, whatever the arithmetic says.

All of it flows from Duration × RPE. The simple formula is what the rest is built on.

Are You Training the Right Amount?

Those same signals produce one reading: your DIAL, short for Dose In Adaptive Limits. It answers a single question — am I training the right amount? — by placing you on one axis between the least you can do and still improve and the most you can safely handle.

  • Dial it up — you have room to grow.
  • Dialed in — you’re in a productive range.
  • Dial it back — ease off.

DIAL pairs with your Run Fitness Index. RFI tells you how fit you are. DIAL tells you whether you’re loaded right. It’s a reading, not a gate: it tells you about the amount, and the three limits above are what actually hold.

What About Rest Days?

Rest days contribute a load of zero, and that zero matters. The moving average includes rest days in its calculation, which lowers your recent load and gives your body credit for recovery. Taking a rest day isn’t just “not training.” It’s lowering the load you carry into the next run, and it’s what makes room for the next hard one.

This is why Pacewright mandates minimum rest days. They’re not wasted time — they’re load management.