related talks: acquired flat foot, natural flat foot, tibial stress fracture, shin splints, metatarsal fracture
1. Running evolved in humans for purposes of hunting over 2 million years ago, however, it wasn't until 1972 when a human named Frank Shorter won the gold medal for the United States in the Marathon that running truly became popular. The rise of Nike and other running companies similarly took off in the 70s. Today over 25 million Americans run more than 50 days a year. But a lot has changed over the last 2 million years. So lets take a look how we compare to our ancestors when it comes to running.
2. Running shoes have evolved over 4 decades to maximize comfort. Design evolution includes increasing the heel cushion and increasing the midfoot arch support. Yet there is no good evidence to suggest that these design changes have effected the incidence of injury in runners. But this type of design (referred to as "shod" because the heel is higher off the ground than the forefoot) promotes a Heel Strike pattern of running. Currently 75-80% of all long-distance runners have the Heel Strike gait pattern.
3. Despite many technological changes in shoe wear, there appears to be no change in injury rate. The most common running injuries include Patellofemoral pain (kneecap pain), IT band syndrome, Achilles tendinitis, patellar tendinitis, plantar fasciitis, and tibial stress fractures. Increased stride length is associated with tibial stress fractures. Increased loading rates is associated with plantar fasciitis.
4. Minimialist running is a counter movement to all of the shoe technology developed over the past 40 years by major athletic companies. The theory is that minimal footwear (or barefoot) promotes a change in gait pattern, whereby the forefoot or midfoot strikes the ground first (as opposed to the standard heel strike) which leads to a lighter landing and better control and therefore reduces risk of injury. Minimalist shoes are flatter (lack arch support, lack heel cushioning so that the forefoot and hindfoot are almost the same height from the ground). Minimalist Shoes promotes a FFS ( ForeFoot Strike) pattern of running. FFS has a unique style marked by increased cadence, decreased stride length, decreased ankle dorsiflexion, and increased knee flexion. Decreased stride length means the center of body mass is closer to the foot so the lever arm is less, meaning less force with the strike. Increased cadence means less force of loading with each step. Removing arch support actually allows the arch to function as a shock absorber (its natural function) and there is no evidence to suggest this leads to it wearing down over time. Impact force of FFS = 60% of body weight, while the standard heel strike running impact force = 180% body weight. The hip and knees also experience less force across them. Also one study examined 15 experienced runners trained in heel strike running that switched to FFS and showed improved running efficiency (decreased oxygen consumption). FFS running appears to decrease the "loading rate", which has been correlated with running injuries. Yet, while FFS appears to improve impact forces, it has not been correlated with meaningful changes in injury risk. FFS also has its own unique injuries, particular metatarsal stress fractures. Therefore, while biomechanics suggest FFS is superior, in reality there does not appear to be a true reduced risk of injury.
5. Take home message: FFS (forefoot strike) may reduce injuries if an athlete has been properly trained in the technique. But this running style can be done with standard or minimalist running shoes.
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