Trajectory or rate

A desired direction and pace of change across time, where the slope matters more than any snapshot.

Cleared to run again after injury, you're staring at your old training log and its intoxicating peak: 40-mile weeks. Setting that as the target is exactly how comebacks fail, because the danger isn't the destination mileage. It's the speed of the climb back to it. Snapshots can look fine while the slope is quietly breaking you.

A trajectory or rate is the reference shape for change over time: a desired direction and pace, where the slope matters more than any single observation. Use it when adaptation, recovery, growth, or transition is the real phenomenon. For the comeback: increase weekly running volume no faster than your individually tolerated progression, while next-day symptoms stay stable. The goal each week isn't a number; it's a controlled rate of increase with the symptom check as the governor. What changes: you evaluate weeks by "is the slope right?" instead of "am I back yet?", which is the question that actually predicts staying healthy. Three warnings from the spec: rates depend on baselines, so early gains flatter you; progress slows naturally, so don't read deceleration as failure; and short noisy windows can manufacture fake trends. Skip this shape when a hard endpoint genuinely rules, like a race date; then the trajectory serves the deadline, not the reverse.