The Algorithm
How Pacewright makes decisions. ACWR, plan adaptation, race predictions, weather adjustments — every formula explained.
12 articles
How Pacewright Builds Your Training Plan
Pacewright uses published sports science — not a black box — to build your plan. Every decision is based on real research, and we show you exactly why each workout is in your plan.
Missed Workouts: The Safe Reschedule Rules
When you miss a run, Pacewright doesn't guilt you — and it doesn't cram the work into tomorrow. Some workouts get rescheduled, some get dropped, and some are never 'made up.' Here are the actual rules.
Volume Caps: Why Pacewright Will Not Let You Run Too Much
Your weekly mileage, your longest run, and your week-to-week increases all have limits — and those limits change based on where you are. Here's the math behind the guardrails.
How Weather Affects Your Pace (And How Pacewright Adjusts for It)
Heat, humidity, and altitude measurably slow you down — and the effect is bigger than most runners expect. Here are the actual numbers, and how Pacewright uses them to keep your targets honest.
ACWR: The Safety Number Behind Every Workout
Your acute:chronic workload ratio tracks how fast your training is ramping up. It's the primary guardrail Pacewright uses to keep you in the safe zone — and we're transparent about what the research does and doesn't prove.
Why Pacewright Changed Your Workout (And What It Means)
Pacewright doesn't change your workout arbitrarily. Every modification has a specific reason, and the app tells you exactly what it is.
Race Predictions: How Pacewright Estimates Your Finish Time
Pacewright uses up to three mathematical models to predict your race time — and always gives you a range, not a single number. Here's how each model works and why the range matters.
Grade-Adjusted Pace: Why Your Hill Run Was Actually Faster Than You Think
Hills make you slower. But they also make you fitter. Grade-adjusted pace tells you what your hilly run would have been on flat ground — and the answer might surprise you.
"Why This Workout Today?" The Decision Tree
Every day, Pacewright decides what you should run. Here's the exact logic it follows — from periodization to safety checks to the final prescription.
Training Load: How Pacewright Measures How Hard You Are Working
Duration times RPE. That's it. No heart rate monitor required, no pace data needed. Here's why this simple formula works — and how Pacewright turns it into the safety system that protects you from doing too much.
Why Pacewright Shows You Ranges, Not Exact Numbers
Single-number predictions create false confidence. Ranges are honest. Here's why Pacewright always gives you a window rather than a target.
What Pacewright Ignores (On Purpose)
Every feature Pacewright doesn't have is a deliberate decision. Here's what we chose not to build — and why.