BRIDGING THE GAP
RESEARCH and PRACTICALITY
When to Retire Running Shoes
There is much debate in the running community about when the day has come to retire that loved pair of running shoes. Running shoes are important equipment in running, regardless of the runner’s fitness level, for shoes help enable proper running biomechanics. When a shoe becomes worn out and the cushioning degrades, running in the shoes can become harmful to the feet, ankle, knee and hip joints and to overall health. Though wear will vary for the terrain, mileage and regularity of runs, it is imperative to be conscious of the state and age of running shoes.
As running shoes deteriorate their stability and cushioning are impacted. A 2008 study by Wong, Candelaria, and Smith investigated if the cushioning of a running shoe had a significant impact on the biomechanics of runners (1). Twenty-four runners participated in a 20m sprint in both worn and new running shoes. The researchers found runners not only had better stance times when wearing new running shoes, but when they wore the worn running shoes the participants altered their running form to compensate for the instability of the degraded shoes. The runners did not lean forward as much from their hips in an attempt to relieve impact on their front toes. As a result, this caused the runners to have a reduced ankle dorsiflexion and increased impact in plantar flexion (1). If the ankle’s dorsiflexion is severely inhibited it can lead to serious injuries in the knees, glutes, and even shoulders. In addition, increases in plantar flexion can increase impact on the fascia, which can cause plantar fasciitis, an extremely painful injury to the bottom supporting structures of the foot.
An earlier study by Taunton et al. focused on training routines of elite runners and what methods used during training helped to minimize injuries (2). Their results stipulated that the age of a running shoe was instrumental in preventing injuries for long distance runners. The runners found it beneficial to replace the running shoe after the cushioning in the shoe had been worn down.
Though research supports replacing old, degraded running shoes, the exact time or point a shoe becomes ill-equipped can be ambiguous. Sports medicine studies have yet to investigate if there is a finite mileage or time when a running shoe should be replaced. This is because the degradation of a running shoe is dependent on many factors including the runner themselves, tier biomechanics, foot pronation, mileage, and frequency of use. A common practice is to replace shoes every 250 to 500 miles – a wide range with some going even longer. Another practice is to purchase and use two pairs during each stage and alternate between the pairs every other run. Suggestions to keep in mind when considering replacing running shoes are the visible condition of the sole and shoe, judging how the shoes feel when running in them, and, if any abrupt running related injuries have occurred. While budget may be an influencing factor, getting in a few extra runs may not be worth the long-term psychological and physical costs of an injury.Written by Jennifer Clark with Eric Sternlicht, Ph.D., Occidental College, Los Angeles, CA.