Jan 29, 2015Freeing the Foot
As running barefoot and with minimalist shoes has taken off, new research is uncovering the pros and cons of the practice, as well as how to shed shoes safely.
By Dr. Daniel Cipriani
Daniel Cipriani, PhD, PT, is an Associate Professor in the Department of Physical Therapy at Schmid College of Science and Technology at Chapman University, where he teaches courses in biomechanics and kinesiology. He can be reached at: [email protected] or follow him on Twitter @danielcip3.
The popularity of barefoot running has once again reared its dirty foot. From competitive track and field athletes to weekend warriors, more and more runners want to feel the earth underneath them while they train. This “trend” actually has a long history.
When the running fitness craze took off in the 1960s, a small but very dedicated group opted to run without shoes. This practice gained international attention after the barefoot running success of athletes such as Abebe Bikila (1960 Olympic gold medalist in the marathon) and Bruce Tulloh (1962 European Championships gold medalist in the 5000 meters).
Two decades later, the world was captivated by Zola Budd (1985 and 1986 World Cross-Country champion) who mainly ran barefoot. Her success revitalized the notion that running shoeless might have performance benefits, and many gave it a try in the mid to late 1980s.
In recent years, there has been another push to trade running sneakers for bare soles thanks in part to the book Born to Run by Christopher McDougall, published in 2009. McDougall argues that the human species is engineered for long distance running (hunters would run their faster prey into a fatigued state to allow capture without the use of weaponry) and compares the incredible distance running performances of today’s athletes to current-day tribes in Mexico and Africa who run either barefoot or in nothing more than a sandal. McDougall likens barefoot running to a sense of freedom and liberation from modern-day constraints.
Another significant factor contributing to the growth in popularity of barefoot running is the development of “minimalist” style shoes (such as Vibram’s FiveFinger, New Balance’s Minimus, and Sockwa’s G2/G3). These have allowed runners to try near-barefoot training without risking injury to the plantar surface of the foot. Current research suggests that running in a minimalist shoe not only replicates the mechanics of barefoot running, but may be more efficient.
Thus the big question arises: Is barefoot and minimalist running better than shod running (with shoes)? Is it more efficient? Is it safer? Thanks to the research of epidemiologists, biomechanists, and sports medicine specialists, we are much closer to answering these questions–although there is still more research to be done.
Before we can even begin to compare the pros and cons of each style, it is important to understand the mechanics of running with shoes vs. without. Running barefoot and in minimalist shoes involves a different technique than running with traditional shoes. This results in differences in foot position at initial landing, stride length, cadence, knee flexion, and ground reaction forces.
All barefoot runners and most minimalist shoe runners land using the midfoot or forefoot portion as the primary contact area on initial impact. Unlike shod runners, the heel touches the ground barely, rarely, or not all. Landing this way, the athlete’s ankle begins contact with the ground in a position of slight plantarflexion. The vast majority of shod runners, on the other hand, land with the ankle neutral or slightly dorsiflexed and with the heel as the first point of contact.
Mid/forefoot landing requires the use of a shorter stride and a higher cadence compared with the traditional heel-strike runner. This leads to slightly greater knee flexion of mid/forefoot strikers, particularly during the stance component of running.
In looking at ground reaction forces, it has been demonstrated that the mid/forefoot striker experiences a reduced impact force at initial contact. This is due to the action of the ankle joint, which undergoes a rapid dorsiflexion motion to absorb the impact with the ground. The heel-strike runner absorbs this force through very limited subtalar joint eversion and knee flexion, resulting in a higher and more rapid impact force.
However, it is important to note that the overall peak ground reaction forces are very similar between a heel-strike runner and a forefoot-strike runner. The slight difference is that the forefoot runner does not have an initial spike in ground reaction force. INJURY RISK
It’s no secret that injury risk for runners is high and many who have parted with their traditional shoes are seeking a way to lower their chances of injury. Research on injury rates for shod runners is bountiful, showing that 75 percent of these athletes will sustain some form of injury. Because mid/forefoot strikers experience less impact on initial contact with the ground, it seems to follow that this should reduce the prevalence of injury.
A recent survey study performed on military personnel examined this idea and suggests that midfoot and forefoot striking might be a way to protect against injuries. In a sample of 900 runners, the authors found that those who self-reported to be mid/forefoot strikers (69 percent) had less injuries than those who self-reported as heel strikers (31 percent). Unfortunately, self-report of striking style is highly unreliable, with other research showing that nearly 70 percent of runners who claim to be mid/forefoot strikers are actually heel-strike runners. Another study examining more than 1,000 marathon runners, which videotaped their running form at a mid-point location in the race, noted that over 90 percent landed on their heels.
A smaller study looking at a sample of very select competitive runners (36 heel strikers and 16 forefoot strikers) found a two to three times greater incidence of injury in the heel-strike runners compared with mid/forefoot strikers. While these results are certainly promising, the small number of subjects and highly specific sample makes it difficult to apply these findings to all runners.
One theory to explain the possible reduction in injury risk relates to the differences in ground reaction forces. As mentioned earlier, mid/forefoot landing eliminates the initial spike in ground reaction force that is seen with heel-strike runners. Advocates of barefoot running postulate that this initial impact is a cause of injury in shod runners. However, research has not found any relationship between ground reaction forces and injury risk (primarily stress fractures) in runners. A study examining the correlation between these forces and the incidence of stress fractures in runners found no substantial differences. In addition, the bulk of the ground reaction forces (shod or barefoot) occur during the full loading and propulsive aspects of running, which are similar between the running styles. Unfortunately, there have not been any studies to date examining ground reaction forces and the multitude of injuries observed in runners, including tendonitis around the foot, ankle, and knee, as well as anterior knee pain.
Barefoot enthusiasts have also speculated that running shoes impede foot proprioception and reduce foot strength, which could leave the athlete more susceptible to injury. However, there is no research to support or refute these anecdotal claims. Nor is there any research to support the notion that greater foot strength contributes to injury prevention.
Overall, running shoes have not yet been shown to increase or decrease injury risk. In fact, the rate of running injuries reported in the literature has not changed over the past 40 years, despite all of the advances made to sneakers. There are a few biomechanics studies that suggest a modern running shoe might contribute to the pronation motion at the foot, rather than control for this motion. And since excessive relative pronation is associated with injury risk, there is certainly a need for further research to test this theory.
Although we know a great deal about the injury prevalence in shod runners, we do not know the rates or types of injuries of barefoot runners, due to the lack of research on the topic. Beyond the obvious plantar foot skin injuries, anecdotal evidence reports an increased risk for metatarsal stress fractures and Achilles tendonitis. However, it is not clear if the incidence rate of these injuries is less or greater than that of shod runners.
The good news is that research is starting to pick up on barefoot running. In March, a team of researchers reported they found that running on the ball of the foot places greater stress on the metatarsals and could potentially lead to stress fracture development. MRIs revealed that runners transitioning to minimalist shoes had greater increases in bone marrow edema in their feet and more stress injuries than those in sneakers. PERFORMANCE QUESTIONS
Beyond injury risk, many athletes want to know if there are any training or performance benefits to going minimal or barefoot. Those who have made the switch often say they feel they are running faster and getting a better workout. Many also report feeling less “beat up” after a run. However, research has yet to find anything to back this up.
In terms of energy cost, limited research on this topic has found no significant differences between barefoot and shod running. The benefit of less mass (no weight of the shoe) during barefoot running is lost because of greater muscle work from using the ankle plantarflexor muscles (the gastrocnemius and soleus) to absorb the initial impact and produce propulsion.
Running in a minimalist shoe, however, does provide a slight energy advantage. The same research that examined energy cost between shod and barefoot runners also included a group with minimalist shoes, which were found to be the most efficient, albeit by only a slight amount. It is possible that the shoe material, along with the running mechanics, contributed to this advantage. Still, the energy advantage did not translate into improved performance.
Another area to examine is temporal and spatial differences, since the mid/forefoot landing results in a shorter stride and a higher cadence compared with the traditional heel-strike runner. Barefoot/minimalist shoe runners often report feeling less stressed while training by taking shorter, faster strides. But we do not know if this translates into improved performance.
One possible advantage is the fact that, as speed of running increases, the tendency to run on the midfoot or forefoot also increases. At speeds approaching sprinting, the runner will use an entirely forefoot landing style. Thus, training in a minimalist shoe would likely help prepare a runner to develop faster running form.
A recently published study refuted the notion that all barefoot runners land on the ball of the foot, finding that increased speed leads to adopting a forefoot running style, while runners landed on their heels while going slowly. This supports the notion that faster running is facilitated by forefoot landing mechanics, but that barefoot running does not always translate to forefoot landings.
MAKING THE TRANSITION If your athletes want to make the switch to barefoot running or minimalist shoes, how can you help? First, figure out if the move is right for them. Although there is a lack of research to indicate who is best suited for barefoot running, it is safe to suggest that any current runner likely has the potential to train in a minimalist shoe or even barefoot.
With that said, individuals who have extremely flat feet (excessive pronators) should pay particular care with progression to a barefoot style of running. An individual with a “high arch,” however, is already somewhat programmed to the stress of forefoot landing and might make this transition a bit more readily. Regardless, the best plan is a gradual, careful progression from a heel-strike to a forefoot-strike running form.
To begin, instead of tossing away traditional running shoes, athletes should slowly introduce barefoot or minimalist running to their training. This allows the athlete time to develop different movement skills associated with midfoot and/or forefoot striking while running. It also gives the skin on the bottom of the foot the time necessary to adapt to these new forces. Frequent barefoot walking before beginning barefoot running is a great place to start.
It is also important to explain the changes in running form. The athlete will need to adopt a short stride and high cadence while remaining in a more upright running posture. This will require slightly greater knee flexion prior to initial contact. The athlete will need to consciously avoid heel strike, attempting to land with the foot flat on the ground or biased toward the forefoot.
These form changes will place a much greater mechanical demand on the metatarsals and metatarsal heads, as well as the Achilles tendon and calf musculature. Preparatory activities to condition the foot and calf musculature can include backward running and uphill running. Backward running has been shown to improve function of the calf muscles, and it requires a forefoot landing pattern and greater knee flexion at initial contact. Training on a treadmill or track are the safest environments for this form of running. Running and walking briskly uphill requires a forefoot strike pattern, greater knee flexion, shorter stride, and greater muscle effort of the calf musculature, as well.
Before the athlete takes off with no shoes, he or she should try wearing true minimalist shoes such as the Vibram FiveFinger sock or Sockwa’s G2/G3 shoe-socks for a period of time. Beginning with some form of foot protection, while avoiding the feel of traditional shoes, might improve the athlete’s transition to a forefoot striker and eventually barefoot runner.
The final step is to condition the skin on the bottom of the foot to withstand the abrasive forces encountered with ground contact. This will likely require several months of gradual dosage of fully barefoot running. Again, barefoot walking is a sensible place to start.
Recommendations range from 10 to 15 minutes of barefoot running three days a week, to exposure of five to 10 minutes a day, gradually increasing barefoot running time at a rate of 10 percent per week. And of course, selecting the safest terrain for barefoot running, free of litter and debris, as well as training with sufficient daylight to see the running surface are critical.
Most important to remember is that, regardless of footwear, the predominant risk factors for injury remain excess mileage and training errors. Too many miles puts athletes at greater risk for injury, and any runner (particularly a novice) is at increased risk when training is not conducted properly. In fact, any major change, whether it is an increase in distance or speed work or running on new terrain, ups the chance of injury.
Sidebar: Feeling the Floor While most of the discussion on minimalist shoes is about how they affect runners, it is interesting to speculate how they might impact athletes in other sports. One question is whether they provide an athlete with improved proprioception.
Consider the dancer, who performs highly dynamic activities in minimal footwear. These athletes complete demanding foot-to-ground movements including jumping, landing, twisting, and spinning. Interestingly, they demonstrate a significantly lower incidence of injuries to the knee, particularly the ACL, when compared with court sport athletes.
It could be argued that because dancers choreograph their movements, they are well prepared for every jump and landing. However, research has demonstrated that the difference in landing styles between men and women basketball players (leading to higher rates of ACL injuries in females) does not exist between dancers. Female and male dancers exhibit similar hip and knee movement when landing, which protects the knee from injury.
Could it be that training in a minimalist shoe or barefoot provides athletes with improved proprioception and foot-knee-hip interactions compared with athletes who train and compete in standard athletic shoes? Research on this hypothesis would be interesting.
Sidebar: Footwear Overview
Type: Traditional Features: – Heel material thicker than forefoot material (heel rise) – Supportive heel counter and longitudinal arch – Heavier in weight Common Brands: Asics, Saucony, New Balance, Mizuno, Nike, adidas
Type: Minimalist shoe Features: – Heel material equal in thickness or slightly thicker than forefoot material (less than 4 mm difference) – Minimal or no supportive materials in heel or arch area – Lightweight (6-8 oz) Common Brands: New Balance Minimus, Mizuno, Saucony
Type: “Barefoot” footwear Features: – Sock-like with no heel wedge – Thin, abrasion-resistant sole – Fits like a sock Common Brands: Vibram FiveFingers, Sockwa G2/G3 or Amphibean