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How Does Heel-to-Toe Drop in Running Shoes Impact Heel Pain?
The importance of the latest trends and developments in athletic shoes carries over into everyday activity. We all use athletic shoes in our daily workout and activity, so the topic has great relevance to podiatric sports medicine. The more we learn about the latest trends, the better prepared we are for recommending athletic shoes to our athletes and patients. Athletic shoes provide the first line of control, cushioning, and support for the athlete. How much is performance enhancing potential versus fad?
Heel pain is among the most frequent conditions we see in our patients, and commonly, this is either plantar fasciitis (if in the plantar heel) or Achilles tendonitis (if in the posterior heel). The athletic shoe plays a critical role in both preventing injury and recovering from injury. The biggest challenges are all the variables that exist in determining the cause(s) of the injury, such as biomechanics/overload principles, type of foot strike, mileage, terrain/surface, previous injuries, age, size, cross training, etc.
We have many clinical considerations to undertake when assessing running shoes for our athletic patients. Consider the effect of preventing certain types of injuries, as well as recovering from injuries. There are biomechanical issues such as equinus, first ray motion, subtalar joint (STJ) motion, medial/lateral/anterior overload, muscle strength, balance, and limb length discrepancy (LLD) to name a few. What type of foot strike pattern does the patient have: forefoot, midfoot, or rearfoot? How does the shoe affect walking versus running mechanics? How does running shoe trends and technology effect other sports that most often involve changing directions, cutting, and stopping?
A comprehensive biomechanical and gait evaluation are critical to understanding the injury and recovery process for your patient. Gait evaluation is one of our main foundations in our biomechanics curriculum for assessing our patients’ needs in determining the effect of control, motion, and cushioning for their respective activity, be it running or other specific sports. Our visual gait evaluation is critical for evaluating the effects of the shoes we recommend in helping improve function and performance as well as orthosis treatment. Motion analysis can be very helpful in the more difficult athletes in helping assess biomechanical function.
Does Shoe Heel-to-Toe Drop Really Matter?
What is heel-to-toe drop? It is the heel height differential between the heel and the forefoot thickness of the sole (Figure 1). Heel-to-toe drop is measured in millimeters, going from 0–14 mm in running shoes. It may also be referred to as heel drop, shoe drop, shoe offset, heel differential, toe drop, pitch, and gradient.
Shoes can be divided into four heel-to-toe drop categories: 1) zero drop (0 mm); 2) low drop (1–4 mm); 3) mid drop (5–8 mm); and 4) high drop (9–14 mm). In my observation, the majority of running shoes sold are in this high drop category. I’ve found there is a general preference for shoes with lower profiles when it comes to trail running because the low drop will allow for a quicker adaptation to the terrain.
A higher drop has the potential to load the hips and knees more, while a lower drop shoe can place greater stress on the foot, ankle, and lower leg. This principle is similar to rearfoot striking versus forefoot striking. The lower the heel–toe drop, the more it will encourage striking the ground with the middle or front of the foot first. In my experience, a midfoot strike may have a lower overall impact than a heel strike, but where that stress is created is also important to understand.
Does the heel-to-toe drop of standard cushioned running shoes influence the risk of sustaining a running injury? Does the volume of running performed by a runner alter the relationship between heel-to-toe drop and injury risk? It is important to understand where the stress is created, as well as the athlete’s foot strike pattern and how much it can change with a different heel-to-toe drop.
It is important that one does not confuse heel drop with stack height (or cushioning), the amount of material between feet and the ground. They are completely independent of each other (Figure 1).
Effects of Low Drop Versus High Drop
Evidence-based studies are needed to look at the heel-to-toe drop effects on running biomechanics and injuries, as well as correlating with walking gait, as many of our patients who walk for exercise have different needs than runners do. Foot strike patterns are different in walking versus running, so the use of the athletic shoe is important in understanding the importance of parameters such as heel-to-toe drop.
The lower the heel-to-toe drop of the shoe, the more forefoot and midfoot strike occurs during running, and a greater potential to increase runner cadence. The low drop also allows for more ankle flexion during landing, as the ankle functions as a spring to better absorb impact. This can place greater stress on the foot, ankle, and lower leg. The low drop shoe could help with iliotibial band (ITB), hip, knee, and gluteal pain as ankle is taking up more of the force. The high drop allows for rearfoot strike due to the elevated heel position, which helps with high impacts on the heel when it hits the ground. This high heel drop may help with heel and calf injuries in the runner. I find that the high drop has a higher knee flexion moment, and has the potential to load the hips and knee more. In regard to heel-to-toe drop on influence of foot strike, runners were more likely to run with forefoot strike in minimalist shoes when compared to regular running shoes, although most continued to rearfoot strike, in my experience observing runners in our Motion Analysis Research Center at Samuel Merritt University.
There appears to be an adaptation period, I’ve noticed, when changing a heel drop to zero drop, much like going from using traditional running shoes and going to barefoot running.
When deciding on a running shoe, several key points to keep in mind aside from heel-to-toe drop, include comfort, foot strike pattern, injury history, terrain, and distance. Heel-to-toe drop is only one piece of the puzzle.
There is a lack of evidence that a shoe’s drop affects overall injury rates. Heel-to-toe drop can be important if you have a history of injury to certain sites or some key bodily characteristics. In general, a shoe with a higher drop will be easier on the lower leg—foot, ankle, Achilles, calf—while directing more stress to the knees and hips. A lower-drop shoe will typically spare the knees but put more stress on the lower leg. What that means in terms of drop will vary greatly from runner to runner, depending on not only the history of injury, but also on speed, foot strike pattern, flexibility, strength, and more. A small or nonexistent drop encourages a more natural foot and ankle motion, as well as a more evenly distributing impact forces.
Why Does Heel-to-Toe Drop Exist?
Running shoes of 50 years ago did not really have a heel-to-toe drop component. Almost all shoes were flat or almost flat (and had a low stack height). That started to change during the first running boom of the 1970s, thanks to two related developments. First, a broader cross section of the population, including many previously non-athletic individuals, took up running. Second, in an effort to make running more comfortable for more people, shoe companies developed more cushioned midsoles. Putting additional cushioning in the heel compared to the forefoot was an effort to help reduce stress on calf muscles and Achilles tendons.
In general, a shoe with a higher drop will be easier on the lower leg while directing more stress to the knees and hips.1 In contrast, a shoe with a lower drop will typically spare the knees but put more stress on the lower leg.
Do Running Shoes Cause or Prevent Injury?
Another limitation of studies on running shoes and injury is that they tend to focus on one aspect of shoe design, such as heel-to-toe drop. However, any given shoe contains a multitude of features. A thickly cushioned shoe can have the same drop as a lower, firmer model. Two shoes could have similar midsole firmness, but vary greatly in width, height, and drop.
Most experts disagree with runners on the role of shoes in injury. A 2020 review in the Journal of Athletic Training looked at four decades of research on shoes and injury. They concluded, “footwear does not cause injury.”2
Richert and colleagues found that a 4 mm heel-to-toe led to increased vertical loading rate and maximum ankle moment and a decreased maximum knee moment compared to 8 mm and 12 mm heel-to-toe.1 In addition, there were differences in ankle and knee kinematics between running in shoes and running barefoot. A lower heel-to-toe drop mainly altered the kinetics of the ankle and knee. Authors noted running with a low heel-to-toe drop did not lead to similar lower limb biomechanics as barefoot running.3
Mo and colleagues studied heel-toe drop on running kinematics and kinetics and perceived footwear comfort of runners in standard cushioned shoes, finding significant effects in rearfoot strikers as far as foot strike angle, stride length, and cadence.4 A greater foot strike angle was indicated during running in 8-mm drop shoes compared with 4-mm, although authors noted the reduction was not sufficient to cause foot strike pattern transition towards a midfoot/forefoot strike pattern. Stride length in 8-mm shoes was significantly larger than in 12-mm shoes. The authors noted shoe models with a standard heel stack height demonstrated the isolated effects of heel–toe drop on running biomechanics. Authors concluded that the lower heel-toe drop of standard cushioned shoes may reduce foot strike angle and increase stride length during running.
Sun and colleagues reviewed 7 articles different performance-related variables in drop in runners.5 Shoes with higher drops were related to increased knee adduction, knee excursion, knee flexion at midstance, stance time and reduced tibial acceleration, initial ankle plantarflexion, initial knee extension angle. For running mechanics, authors found shoes with higher drops increased net knee flexion moment in the push-off, but reduced net joint ankle flexion moment during the braking phase.
A randomized controlled trial by Malisoux and colleagues showed that the drop of standard cushioned running shoes did not modify injury risk overall.6 In contrast, the authors noted low-drop shoes could pose more of a hazard for regular runners, while occasional runners seemed to prefer low-drop shoes to limit injury risk.
Zhang and colleagues found the heel-to-toe drop of running shoes can influence the running pattern and loading on the lower extremity joints.7 Running in shoes with large drops significantly increased the knee extension moment and decreased the ankle eversion moment during the standing phase. The authors suggest that running shoes with large drops may be disadvantageous for runners with knee weakness but may offer an advantage to runners with weak ankles.
Moody and colleagues sought to determine if runners accustomed to running in traditional footwear would change their running mechanics when first wearing footwear with a lower heel to toe differential and with no footwear.8 The authors found running barefoot will cause a faster stride rate in runners, decrease ground time, and decrease vertical oscillation.
Closing Thoughts
More evidence-based research is needed to investigate the effects of heel-to-toe drop in relation to injuries and prevention, which is challenging when taking into account all the biomechanical variables of running.
Leading sports medicine practitioners apply the more targeted approach by looking at individuals’ injury histories. Two current best practices in this regard are to have runners with a history of knee injuries gradually transition to lower-drop shoes. Doing so should shift some of running’s impact forces from the knees to the calves, Achilles tendons, and other lower-leg areas. Conversely, runners with chronic calf and Achilles issues might benefit from shoes with a greater heel-to-toe differential to move some impact forces to the knees.
Shoes should not be seen as cure-alls or the sole cause of injuries, but as part of an overall approach to avoiding and preventing an injury. Most running injuries result from low-grade, repetitive strain that eventually pushes a body part past its breaking point. Finding the shoes that help you run with your best form is a start, because doing so should mean how you absorb impact forces matches what your body is best suited for. Rotating among different models of shoes should mean more variation in how those impact forces are distributed.
Cross-training is another way to change the stresses on your body. So too are running on different types of surfaces, running at a variety of paces, varying your topography, and having day-to-day variety in distance and intensity.
Dr. Dutra is an Assistant Professor at the California School of Podiatric Medicine at Samuel Merritt University, Oakland, CA. He serves as a podiatric team podiatrist for Intercollegiate Athletics at University of California, Berkeley, CA. He is a Past President and Fellow of the American Academy of Podiatric Sports Medicine. Dr. Dutra is the Past Vice Chair of the Joint Commission on Sports Medicine and Science and he is a Clinical Director for the Special Olympics of Northern California Healthy Athletes Fit Feet Program.
References
1. Douglas S. What heel-to-toe drop is, and why it matters. Zappos. Available at https://www.zappos.com/c/what-is-heel-to-toe-drop
2. Malidoux L, Theisen D. Can the “appropriate” footwear prevent injury in leisure-time running? Evidence versus beliefs. J Athl Train. 2020; 55(12):1215–1223.
3. Richert FC, Stein T, Ringhof S. The effect of the heel-to-toe drop of standard running shoes on lower limb biomechanics. Footwear Science. 2019; 11(1):1-10
4. Mo S, Lam WK, Ching ECK, Zhang JH. Effects of heel-toe drop on running biomechanics and perceived comfort of rearfoot strikers in standard cushioned running shoes. Footwear Sci. 2020; 12(2):91–99
5. Sun X, Lam WK, Zhang X, Wang J, Fu W. Systematic review of the role of footwear constructions in running biomechanics: implications for running-related injury and performance. J Sports Sci Med. 2020 Mar; 19(1):20–37.
6. Malisoux L, Chambon N, Urhausen A, Theisen D. Influence of the heel-to-toe drop of standard cushioned running shoes on injury risk in leisure-time runners: a randomized controlled trial with 6-month follow-up. Am J Sports Med. 2016 Nov; 44(11):2933–2940.
7. Zhang M, Shi H, Liu H, Zhou X. Biomechanical analysis of running in shoes with different heel-to-toe drops. Appl Sci. 2021; 11(24)12144.
8. Moody D, Hunter I. Ridge S, Myrer W. Comparison of varying heel to toe differences and cushion to barefoot running in novice minimalist runners. Int J Exerc Sci. 2018; 11(1):13–19.
