Running economy
The amount of oxygen your body uses to run at a given, submaximal pace.
Why it matters
Running economy is a better predictor of race performance among runners with similar VO2 max than almost any other single physiological measure.
What it means
Better economy means less oxygen consumed at the same speed. Cadence, vertical oscillation, ground contact time, and elastic tendon return all influence economy. Because economy is trainable through form changes as well as fitness changes, small, consistent adjustments to stride mechanics can meaningfully lower the energy cost of a given pace over a training block.
Related reading
The complete guide to running form analysis