Running Mechanics: Challenging the Forefoot Striking Stereotype
What is a stereotype? If you ask the Cambridge dictionary it’ll tell you that a stereotype is, “a set idea that people have about what someone or something is like, especially an idea that is wrong”. In the endurance running world we have plenty of stereotypes that we may have heard of. For example; you should aim for 180 strides per minute, polarized training is the best type of training, or one shouldn’t increase their mileage by more than 10% in consecutive weeks. I think it’s safe to say I’ve provided enough evidence in previous posts to suggest that we shouldn’t take these claims at face value – and it’s interesting to me that the world of academia and the world of practice often fuel one another. For example, a coach may recognize that his athletes with quicker cadence are better runners than those with slower cadence, so he enlists the help of an academic/researcher to study this phenomenon. This academic finds that the better runners run at 180spm and reports back to the coach. Now the coach, his/her network as well as the academic’s network all believe that 180spm is the way to go. Today I’m going to be covering another stereotype: Forefoot Striking (FFS) is the optimal foot strike pattern for endurance runners.
I can’t remember exactly when I first heard about FFS in running but I remember attending a lecture as a student about the topic. There was a guest lecturer in my class who was busy doing research about the benefits of FFS in running. We had to go outside and run around the fields barefoot and using a purposeful FFS. I remember thinking, “damn this feels so unnatural and uncomfortable. I feel like I’m stopping myself”. “Should my heel ever touch to ground? Help!”. Ever since that day I’ve been hearing more and more about forefoot running and how we should all be running with a FFS pattern (for those of you who haven’t heard about this, it means initial contact with the ground should be on the balls of your feet rather than on your heels or midfoot i.e. toe-heel-toe as opposed to heel-toe). Maybe I was doing it wrong, maybe I still am (I later tried shifting to FFS and experienced terrible hip pain), but one thing is for sure – I’m not convinced about this FFS business. As such, I’m writing a two part blog comparing the proponents of FFS and rearfoot striking (RFS). At the end of this series I’ll give you my final thoughts on the argument, but for now what does the science surrounding FFS say?
Arguments for FFS
I am going to paraphrase some of the work and findings of recent research done on FFS by several researchers below. I’ll state the title, authors, and year published before summarizing their work and at the end I’ll conclude everything in my own opinion. Some of the content may seem repetitive, but this is important because it will help us understand the main benefits of FFS. Remember that all of their researchers have done their own empirical research often using large study samples and normally making them run in FFS and RFS conditions – these are their findings:
“Why forefoot striking in minimal shoes might positively change the course of running injuries” (Davis, Rice and Wearing, 2017):
Humans evolved as bipedal walkers and started running barefoot around two million years ago. Two million years is a helluva long time ago, especially when keeping in mind that only 10,000 years ago were primitive shoes first designed and used. Furthermore, modern cushioned running shoes have only truly started developing in the last 50 years. This speaks to the mismatch theory of evolution which suggests that the majority of health problems in today’s society (including a reported annual running injury incidence of up to 80%) owes to the rapid and accelerated change in several factors including; environmental changes, food changes, pollution, and increasing levels of inactivity. In other words, our human bodies are not able to keep up with the rate of change in modern life, and so our running mechanics adaptations (shifting to a largely rearfoot striking (RFS) species) are mismatched with what we are evolved to do. Simply put, we didn’t evolve to run as RFS and because of factors like fancy shoes we are now running that way – possibly leading to high injury incidence.
If we observe modern humans who run barefoot, we will see that they tend to strike using a FFS pattern (particularly on hard surfaces) to reduce the force (and subsequent soreness) acting through the heel. Barefoot runners have stronger arches of the foot and bigger musculature in their feet than shod runners because they don’t have the added support of a fancy shoe and have therefore adapted to have stronger arches. Barefoot runners also have optimized lower limb stiffness (neither too stiff nor too slack as both can lead to injuries) because they have heightened sensory input available (direct skin on running surface contact) as opposed to shod runners.
Forefoot runners and rearfoot runners experience similar peak ground reaction forces but the vertical loading rate (force running up the leg) is steeper (more jarring) for rearfoot runners. These vertical loading rates are directly related to injury as both muscles and bones are vulnerable to injury at high loading rates. Evidence has been found that suggests transitioning from a RFS to a FFS can reverse chronic injuries such as compartment syndrome and patellofemoral pain (see more below) likely due to decreased instantaneous vertical load rates of approximately 20%. Lastly, 3 key anatomical features’ functions are enhanced when using a FFS compared to a RFS namely;
- Heel pad
- Plantar fascia
- Achilles tendon
The heel pad provides less shock reduction than we might think and has a poor protective function compared to the fibroadipose tissues of the forefoot which has a higher stiffness and thus dissipates force much better than the heel pad. This function means FFS might actually be more well suited to attenuate mechanical loads than RFS. Your plantar fascia (think the arch under your foot), function to store and release energy but they need to be stretched under load in order to do so. FFS provides a greater stretch of the fascia and as such returns more energy for forward propulsion than RFS making for a more efficient runner. The achilles tendon also stores and returns energy (around 95% of stored energy is returned), however under RFS the achilles tends to lose it’s stored force upon ground contact. This force is maintained in FFS and FFS runners can produce a much stronger toe-off than RFS runners.
“Muscle activity and kinematics of forefoot and rearfoot strike runners” (Ahn, et al. 2014)
Habitually barefoot runners are predominantly FFS (or midfoot strikers) while habitually shod runners are predominantly RFS. FFS runners experience no impact peak and have a lower loading rate however FFS runners are less common because of the introduction of the modern running shoe with a cushioned heel. Humans used to run with FFS (evolution argument) which reduced the vertical forces on landing and also improved storage and release of energy by the elastic structures of the foot (fascia) and lower leg (achilles tendon). FFS generally have shorter stride lengths and faster cadence with a subsequent quicker ground contact time – most likely because their knees are slightly more flexed on initial contact with the ground. FFS runners tense their calf muscles earlier than RFS runners before initial contact in order to stiffen the ankle and resist the ground reaction forces acting against the ankle resulting in lower amounts of force acting within the ankle resulting in more stability. Simultaneously, the earlier activation of these muscles increases the capacity of the passive structures (mentioned above) to store elastic energy and resulting in an increased force output. FFS runners subsequently activate these muscles for longer which may result in an increased energetic cost per stride however this is likely counteracted by having lighter/more minimalist shoes or even running barefoot as well as by the increased energy return from the foot arch, achilles tendon and calf muscles..
40 runners of all levels were asked to run barefoot on a treadmill and with neutral running shoes on a treadmill (at different speeds) without being told to run. An equal percentage of runners (27.5%) ran either RFS or FFS regardless of whether they were barefoot or shod, while the remaining 45% ‘shifted’ from RFS when shod to FFS when barefoot. FFS tended to plantarflex (point their toes) before initial contact while RFS dorsiflexed (toes curled up) while shifters moved from a dorsiflexed position while shod to a plantarflexed position when barefoot. This once again suggests that the natural evolution of humans was to be a FFS pattern prior to the invention of running shoes. However, those shifting to a FFS from a RFS should do so carefully and over a period of months.
“The effects of forefoot striking, increasing step rate, and forward trunk lean running on trunk and lower limb kinematics and comfort” (dos Santos et al. 2016):
Approximately 95% of distance runners are RFS while a FFS pattern is related to a decreased risk of running injury most likely due to reduced loading rates and peak impact on ground contact. Patellofemoral joint stress (knee stress) is reduced in FFS runners most likely owing to less peak knee flexion during the stance phase which reduces knee joint contact forces (and subsequent stress) by almost 20%. Faster cadence often associated with FFS also decreases the amount of force acting on the knee significantly. The knee and ankle joints are positively affected by shifting from a RFS to a FFS as the reduced flexion of the knee joint on initial contact and during the stance phase may reduce stress on the knee joint. However, the subsequent increased amount of plantar flexion at the ankle joint results in increased calf muscle and intrinsic foot muscle activity which means any transition to FFS should be done in conjunction with strength training and take place over a long period of time because it is highly taxing of these muscles.
“Is the foot striking pattern more important than barefoot or shod conditions in running?” (Shih, Lin & Shiang, 2013)
Shod FFS have a significantly lower loading rate compared to their RFS counterparts, but barefoot runners should avoid RFS at all costs. FFS land with the ankle in a plantarflexed position while RFS land in a dorsiflexed position (same as above). This plantar flexion provides an additional benefit of cushioning or shock absorption on initial contact which implies that habitually shod runners will have a greater shock absorption capacity when changing from a FFS to a RFS. The knee is more flexed on initial contact in FFS runners compared to RFS which results in a shorter stride length and higher cadence. FFS runners’ calf muscles work harder and as such are at a elevated risk of injury. Runners shifting from a RFS to a FFS pattern are at risk of overstriding when FFS and as such need to bend their knees slightly more on impact or reduce their stride length in order to avoid injury. There should be a due process in switching from RFS to FFS.
From what I can tell, there are a few main proponents for a FFS pattern in endurance runners. Seemingly the passive structures of the foot (fascia, arches, tendons and musculature) benefit from this striking pattern (they are both protected, and enhanced) by landing on the balls of the feet. In addition this is commonly accepted as the way that our ancestors ran and we are evolved to run in this manor. This may have something to do with injury prevention as both the average and maximal vertical loading rate are increased with RFS compared to FFS resulting in a higher likelihood of musculoskeletal injury. Runners who have shifted from a RFS to a FFS have shown to have reduced injury rates or symptoms while also producing more force per stride which results in an improved running economy. Perhaps I’ve been unfair in my assessment of FFS and, to be fair to all of the authors above suggesting that it is the most optimal/beneficial foot strike pattern, almost all the authors above say that the shift should take place over many months and it is not without risks. Perhaps I just wasn’t managing that shift correctly? I did try and ramp up the kays safely and slowly, but hey maybe I was overstriding or not bending my knees enough on initial contact. Maybe I was maintaining a similar stride length and frequency and all I needed to do was shorten the length and up my cadence and I wouldn’t have experienced the pain that I did. It seems from the work of Shih, Lin and Shiang (2013) that I wouldn’t have needed to change to my shoes to a minimalist type shoe in order to gain the benefits of FFS so it must’ve been something to do with the biomechanics of my change or the speed at which I made the shift.
Next week time I’m going to tackle all of the research that states that FFS is not the optimal pattern for endurance runners and perhaps even present some evidence that will make you think twice before making the shift. Perhaps after that I will be in a position to reassess whether or not I (and readers out there) should make the shift to a FFS pattern. Let me know if you have any comments or thoughts by posting below. Have you made the shift? How was the transition? Has becoming a FFS runner improved your performance and kept you injury free? I’d love to know!