Impact of Increasing Mileage on Running Economy

The following in an expert from Owen Andreson’s fantastic book Running Science, pp.326-327 on the Impact of Increasing Mileage on Running Economy:

One of the most popular strategies for enhancing running economy is actually quite a weak stimulus for upgrading economy especially when economy is measured at competitive speeds. Many runners believe that the strategy of increasing the weekly distance run, or volume, is a powerful way to become more economical, but scientific research fails to support this contention.

In classic work conducted by Finnish exercise scientists in 1999, one group of runners increased weekly running volume from 45 to 70 miles (72-113 km) while a second group remained at 45 miles (72 km) per week and added explosive training to their program. The group that added volume failed to enhance economy at all, while the explosive group improved economy significantly by approximately 3 percent.

Download a pdf of the Study: Explosive-strength training improves 5-km running time by improving running economy and muscle power

This Finnish research is quite revealing, giving researchers and runners a clear picture of a key mechanism by which running economy can be improved. In the study, the runners who added explosive training shortened foot-strike time as a result of the high-speed training; the change in foot-strike time was tightly correlated with the gain in economy. In effect, after explosive training, the runners’ feet needed to be on the ground for less time per step to maintain a specific velocity.

This reduction in contact time apparently reduces the oxygen cost per step and thus enhances economy. It is difficult to see why increasing the overall distance run would produce a similar effect. When distance is increased significantly, a large portion of the additional volume is conducted at submaximal intensities, the kinds of speeds that do not require a shortening of foot-strike time. Thus, the nervous system does not learn to regulate a quicker foot-strike; on the contrary, a pattern of slower running and more lethargic reaction of the feet with the ground may be locked in to the neuromuscular system, hurting economy at competitive velocities.

Source: Running Science, Anderson, pp. 326-327