Runners! How important is having multiple pairs of shoes?

There's a study that says runners who rotate shoes have a 39% less risk of injury

http://www.runnersworld.com/injury-prevention-recovery/study-backs-rotating-shoes-to-lower-injury-risk

You've probably been told that running in two or more pairs of shoes throughout the week can lower your risk of injury. According to a first-of-its-kind study, you've probably been told correctly, as runners who rotated among multiple models during the 22-week study had a 39% lower risk of running injury than those who almost always ran in the same shoes.

Researchers in Luxembourg gathered information on training volume, injury rate, cross-training, shoe usage and other variables from 264 adult recreational runners. During the 22-week study, 87 of the 264 runners suffered at least one running-related injury, which the researchers defined as "a physical pain or complaint located at the lower limbs or lower back region, sustained during or as a result of running practice and impeding planned running activity for at least one day."

Of the 264 runners, 116 were classified as single-shoe wearers; runners in this group did 91% of their mileage in the same shoe, and ran in an average of 1.3 pairs of shoes during the study. The other 148 were classified as multiple-shoe wearers; runners in this group tended to have a main shoe, which they wore for an average of 58% of their mileage, but they rotated among an average of 3.6 pairs of shoes for their training during the study.

Once they crunched the numbers, the researchers found that the multiple-shoe wearers had a 39% lower risk of injury during the study period than the single-shoe wearers.

The researchers wrote that this could well be because different shoes distribute the impact forces of running differently, thereby lessening the strain on any given tissue. Previous research has shown, and runners have long intuitively felt, that factors such as midsole height and midsole firmness create differences in gait components such as stride length and ground reaction time.

As the researchers put it, "the concomitant use of different pairs of running shoes will provide alternation in the running pattern and vary external and active forces on the lower legs during running activity. Whether the reduced [injury] risk can be ascribed to alternation of different shoe characteristics, such as midsole densities, structures or geometries cannot be determined from these results and warrants future research."

Supporting this idea of reducing injury risk by varying tissue loads, the researchers also found that runners who reported more cross-training had a lower incidence of injury.

"Multiple shoe use and participation in other sporting activities are strategies leading to a variation of external and internal loads applied to the musculoskeletal system that could have a beneficial effect on [running injuries]. Although speculative, it could be that any training paradigm that limits excess repetitions will decrease the risk of [running injuries], especially overuse injuries," the researchers wrote.

The research was published in the Scandinavian Journal of Medicine & Science in Sports.