There are many factors that influence endurance running performance. There is general agreement that the most important factors appear to be:

* high maximal oxygen uptake: VO2 max

* ability to sustain a high percentage of VO2 max (fractional utilisation of VO2 max)

* excellent running economy, that is largely determined by:

1. training intensity
2. body size, body weight, thin legs, maximum calf circumference
3. age
4. stride length
5. cadence
6. ground reaction forces

Age is associated with a reduction of VO2 max, stride length and frequency, muscle strength and the ability to sustain training intensity and volume without injury. Regardless, remarkable performance is still possible including a sub-3 hour marathon at age 70.