Introduction
As a species, humans have evolved from running barefoot for survival. Footwear has also evolved over the past 10,000 years into modern-day cushioned running shoes. Despite the technological advances in running shoes, it is estimated that up to 80% of runners sustain a running-related injury (RRI) in a given year. This high incidence rate of injuries leads researchers to question whether our modern-day running shoes are contributing to RRIs and if humans should be running barefoot, like our ancestors. Researchers in the article, Barefoot Running: Biomechanics and Implications for Running Injuries, look at the biomechanics of barefoot running compared to minimalist shoes and modern-day running shoes and their implications on RRIs.
Running Mechanics in Modern-Day Running Shoes
The modern-day running shoe has a dual-density midsole, elevated cushioned heel, arch support, stiff heel counter, and an array of other features proposed to help foot function and reduce the likelihood of sustaining a RRI. When wearing these shoes, it is estimated that 75% of runners land on their heel or rearfoot strike (RFS), 24% land with foot-flat or mid-strike (MFS), and 1% land on the ball of their foot in a forefoot strike (FFS). Landing with a RFS causes high loading rates through the lower extremity while FFS has a reduced loading rate force at impact.
Running Injuries in Modern-Day Footwear
The majority of runners who wear modern-day shoes are RFS (75%). The authors reported mild and moderate RRIs occurred 2.5 times more frequently in RFS than in FFS. Higher vertical loading rates at impact and abnormal mechanics are thought to contribute to injury risk. Vertical loading rates have been shown to be higher in RFS runners with a history of tibial stress fractures, patellofemoral pain syndrome (PFPS), and plantar fasciitis. The knee is the most common site of running injuries, followed by the lower leg, foot, and upper leg. PFPS, iliotibial band syndrome, tibial stress syndrome/fractures, plantar fasciitis, and Achilles tendinitis are typically among the most common injuries reported. There are also reported cases on anterior compartment syndrome due to hypertrophy of the anterior shin muscles in RFS runners.
Barefoot Running Mechanics
Barefoot running is associated with a FFS, shorter stride length, and higher cadence compared to modern-day footwear runners. Contrary to the belief that the medial longitudinal arch will fall in barefoot runners, studies show there is actually shortening of the arch over time in FFS runners. Hindfoot eversion, knee flexion, knee adduction, and hip external rotation moments were also reduced when running without shoes. With a FFS, there are greater loads through the posterior calf musculature as well as increased stress on the metatarsal heads. In addition, the act of being barefoot appears to allow for more sensory input to the neuromuscular system and static balance has shown to be better when standing barefoot compared to when wearing socks.
Barefoot/Minimalist Shoes
The authors reported on studies which looked at the striking pattern of runners wearing a minimalist shoe. One study reported that runners actually landed in greater dorsiflexion and exhibited greater vertical load rates and tibial shock compared with a modern-day running shoe. Another study looked at a transition of 14 runners into a minimalist shoe. Of the 14 runners, 10 of them began the training program landing with an RFS pattern. After 6 weeks of training, all runners landed less dorsiflexed, but surprisingly, five of them still remained RFS runners. Without the sensory feedback between the sole of the foot and the surface of the ground, the runner may not have the complete neural cueing to convert to a FFS. Minimal footwear, like barefoot running, offers no foot support, thereby increasing the demand on the foot and ankle musculature. Another study following minimalist shoe runners showed a significant increase in the cross-sectional area of some of the intrinsic and extrinsic muscles of the foot and ankle, an indication of strengthening.
Barefoot/Minimal Footwear Running Injuries
The top reason that runners choose to switch to barefoot/minimal footwear is to avoid future injury. However, the most prevalent barrier to barefoot/minimal footwear running reported in the literature was fear of possible injury. In fact, there is little evidence that proves injury risk is increased in barefoot and minimal footwear running. There have been reported cases of metatarsal stress fracture in barefoot/minimal footwear runners and there is also an increased likelihood of calf strains and Achilles tendonitis due to the nature of FFS and increased loading in the posterior calf. It is true however that the foot is exposed when barefoot and thus more vulnerable to cuts, bruises, and abrasions.
Transitioning to a Minimalist Shoe
One of the biggest theoretical risk factors in barefoot running is doing too much, too quick, too soon. Habitual RFS runners wearing modern running shoes with 10 to 14 mm elevated, cushioned heels should not abruptly change their footwear to zero drop while maintaining their current mileage. It is imperative to follow a program that transitions runners slowly to the use of minimal footwear and the adoption of a mild FFS pattern. The most common problem associated with transition is soreness in the lower leg and foot. The authors conclude that while it appears that runners plagued with injury may benefit from switching to a barefoot strike, there is less justification for injury-free runners to change running mechanics. It is also unknown how barefoot running may affect those with special foot conditions, such as bunions, severe diabetes, or neuromas.
Future Research
There is currently a significant amount of knowledge that is not known about barefoot running. Future studies need to address differences between FFS in modern-day footwear vs barefoot running, who is appropriate for barefoot running, what are the best ways to transition to barefoot running to minimize injury risk, are there less injuries in barefoot runners vs. runners who wear modern-day shoes, and what are the long-term effects on bone and joint health. Well controlled, large-scale, prospective injury studies are needed to determine whether shedding our shoes while we run is truly good for our health.
Conclusions and Implications for Physical Therapy First
One could argue that running with heavily cushioned shoes is unnatural and may contribute to the high rate of injuries that runners experience today. Clearly there are well documented biomechanical differences between barefoot and RFS running. The injury risk associated with barefoot however running is largely unknown. At Physical Therapy First, our clinicians are trained to perform gait evaluations and will use this knowledge to offer footwear and training suggestions on a case-by-case basis. If you are a runner with frequent pain and/or want to improve your performance, you could benefit from an evaluation by one of our therapists to keep you training at your healthiest.
Reference:
Altman, A., Davis, I. (2012). Barefoot Running: Biomechanics and Implications for Running Injuries. American College of Sports Medicine. Vol. 11, Number 5 (244-250).