1. Running economy measures oxygen use at a given pace.
   Running economy refers to the amount of oxygen consumed at a given running velocity. It is a critical determinant of endurance performance and reflects the interplay between biomechanical efficiency and physiological function. Unlike maximal oxygen uptake (VO2 max), which measures aerobic capacity, running economy represents how efficiently that capacity is used.
2. Efficient runners use less oxygen for the same speed.
   A runner with good economy needs less oxygen to hold a given pace, which means less energy wasted, reduced fatigue, and better performance over time. In fact, two runners with similar VO₂ max values may perform very differently due to variations in running economy [1].
3. Multiple factors influence running economy.
   Several factors influence running economy, including muscle effort, stride length, ground contact time, and posture. These factors determine how much energy the muscles must generate to produce movement.
4. Elastic energy plays a major role.
   More efficient runners are able to take advantage of the elastic recoil of their tendons, essentially reusing stored energy from each step. This reduces the workload on the muscles and lowers oxygen demand [1].
5. Coordination and control improve efficiency.
   How well your nervous system controls and coordinates movement, timing, rhythm, and balance can influence how economical your stride is. When your body moves smoothly and uses that “spring” energy well, your muscles don’t have to work as hard, thereby allowing you to run farther or faster with the same effort.

Reference:

1. Saunders PU, Pyne DB, Telford RD, Hawley JA. Factors Affecting Running Economy in Trained Distance Runners. Sports Medicine. 2004;34(7):465-485. https://link.springer.com/article/10.2165/00007256-200434070-00005