A study titled "Heel-to-toe drop of running shoes: a systematic review of its biomechanical
effects" aimed to analyze the impact of heel-to-toe drop (HTD) values on running biomechanics.
What is heel-to-toe drop?
For those of you who are not aware of HTD, it is defined as the sole height difference between the rearfoot and forefoot, as shown by the photo to the right. It should not be confused with stack height which is the height of the sole (i.e the top line on the photo).
Due to the high incidence of running there has been an obsession with the commercial market and researchers to tinker with footwear and running styles to reduce this risk. One trend that many people thought offered a solution was barefoot running which has been shown to reduce impact forces compared to wearing shoes. However, it was later found that this was just due to the change in running technique when not wearing shoes, which was a shift to forefoot strike pattern (landing on the front of your foot), as apposed to a heel strike which is more common when wearing shoes. However, it was later shown that there was no difference in injury risk when a runner ran with a forefoot strike with or without shoes.
There is some evidence that a lower HTD changes the foot strike pattern to a fore foot strike and therefore can decrease injury risk in recreational runners. Therefore this study wanted to clarify the specific effects caused by different Heel-to-Toe Drop values of running shoes on bio-mechanical variables in endurance runners.
The Study
The study is a systematic review, which means it conducts a search of the major online databases to find all the studies related to the topic and using their data and findings together to form a conclusion. A systematic Review is considered the highest form of evidence.
Twelve studies were included, with only one being a randomized control trial of 'good' quality. The studies covered various kinematic and kinetic variables, with HTD ranging from 0 to 16 mm. Most of the studies used force plates to calculate their data.
Surprisingly, the study concluded that HTD did not significantly affect: ground contact time or ground reaction forces, flight time, stride frequency, stride length, or any of the joint kinematics of the ankle, knee, and hip. However, it was stated that there are more than twenty additional footwear characteristics may influence running biomechanics which could be negating the changes the HTD makes.
These other variables are:
Taken from Hoitz (2020)
However, there was some weak evidence to support the hypothesis that the foot strike pattern changes towards a greater forefoot strike with HTD 0mm shoe compared to HTD 8–10mm shoe.
Therefore, when choosing what shoes to train in, basing your decision solely on HTD ratio may not be adequate. You should consider all the other aspects of the shoe. I personally like to wear a mixture of different shoes to give my feet variety rather than receiving the same forces each run. I also find that as long as the shoe is comfortable and made with good quality materials, then it should be fine to add to your crammed shoe cupboard.
It is also important to remember to stop using your shoes once they have worn out as they will no longer give the same support, I switch shoes between 400-600 miles depending on the shoe and what I use them for.
James McMurray
Sport and Exercise Health Sciences BSc
Physiotherapy BSc
References:
Celso Sánchez-Ramírez, Codi Ramsey, Valentina Palma-Oyarce, Eduardo Herrera-Hernández & Esteban Aedo-Muñoz (2023) Heel-to-toe drop of running shoes: a systematic review of its biomechanical effects, Footwear Science, 15:2, 77-101, DOI: 10.1080/19424280.2023.2180542
Fabian Hoitz, Maurice Mohr, Michael Asmussen, Wing-Kai Lam, Sandro Nigg & Benno Nigg (2020) The effects of systematically altered footwear features on biomechanics, injury, performance, and preference in runners of different skill level: a systematic review, Footwear Science, 12:3, 193-215, DOI: 10.1080/19424280.2020.1773936