Pacewright’s engine is an optimizer. Every time it plans your week, it looks at the realistic options and picks the one that scores best for you. That raises an obvious question: best by what measure? What makes one week “better” than another?

This article is the answer. It’s the scorecard the engine optimizes against.

There’s no single “right” week

There is no universally correct training week, and most apps won’t say so out loud. Two good coaches will hand the same runner two different plans, and both can be defensible. “Better” is a judgment call, built from competing priorities that have to be weighed against each other.

So Pacewright makes that judgment explicit. The science is published and open — anyone can read the same research. What’s ours is the specific way we weigh it: the scorecard below. That synthesis is the part of Pacewright that’s genuinely ours. But unlike a black box, it’s never hidden from you. Every number on the scorecard is named, and every workout shows how it added up.

The five things that make a week fitter

The core of the score is fitness, measured the same five ways your Run Fitness Index already shows you:

  • Aerobic — your easy-pace engine, the base everything else is built on.
  • Speed — your ability to run fast, from threshold work up to VO2max efforts.
  • Endurance — how far you can go, and how well you resist fatigue late in a run.
  • Consistency — whether you’re training regularly, week after week.
  • Recovery — whether you’re absorbing the work instead of digging a hole.

When the engine scores a candidate week, it estimates how much that week would move each of these five dimensions, then weighs them by your goal. This is the key idea: a better week depends on what you’re training for.

A marathon leans hard on aerobic base and endurance, because that’s what the distance demands. A 5K leans on speed, because that’s the lever. Someone running to lose weight or stay healthy is best served by consistency above all — the plan that works is the one they’ll keep doing. The five dimensions don’t change. How heavily each one counts does, and it shifts with your goal. (The detail behind these dimensions lives in the science articles on polarized intensity,1 training load,5 pacing,3 and the fitness-fatigue balance.4)

It’s not only about fitness

A week that maximized raw fitness gain and nothing else would be reckless. So the scorecard has more on it than the five fitness dimensions:

  • Safety comes first, and it isn’t negotiable. Before the engine scores anything, it throws out every option that breaks a hard safety limit: a single run that jumps far beyond your longest recent run,2 a weekly total that climbs faster than your current mileage allows, too little recovery between hard days, a long run that’s too large a share of your week. What you report after a run — how hard it felt, whether you’re sore — feeds the same limits.5 The optimizer only ever chooses from weeks that are already safe. No score can buy its way past that.
  • Specificity, as your race approaches. Far from a race, general fitness matters most. Close to it, race-specific work counts for more. The scorecard shifts with the calendar.
  • Does it look like a coach wrote it? A pure number-chaser can produce technically-optimal weeks that look bizarre — hard the day after hard, erratic patterns no human coach would prescribe. The engine carries a penalty for that, so “optimized” stays sensible and legible.5

How the engine uses the scorecard

For each of your run days, the engine considers the workouts that are safe and appropriate, scores each candidate week against everything above, and picks the highest. Then it shows you the result: which factors mattered most, and what the runner-up was. “We chose a tempo run today. It scored highest for your half-marathon goal, mostly on threshold and endurance. An interval session was allowed, but it scored lower because your recent load is already elevated, so the recovery cost tipped it.”

The scorecard does two jobs at once: it’s how the engine decides, and it’s how it explains that decision to you.

Why it’s ours, and why we still show you

We could keep the scorecard secret and ask you to trust the output. We won’t. The published science belongs to everyone, the way we weigh it into a better week is ours, and the result is laid open for you to read anyway. Proprietary and opaque is the norm in this industry. Proprietary and explained is the standard we hold ourselves to.