Toe Spring And Plantar Fasciitis

 

Ever wonder why so many people other than runners are getting plantar fasciitis? It may be because of the amount of 'toe spring' in your shoes.

You may have already noticed this in your running (or other) shoes, most of them seem to have 'toe spring'. Toe spring is how much the front of the shoe is curved upwards. This curve allows your foot to roll off the front of your foot more easily compared to wearing flatter soled shoes.

Hence, the toe spring allow your foot muscles to work less hard when you are walking or running. The more toe spring in the shoe, the less work your feet have to do.

However, this may lead to weaker foot muscles according to research (Sichting et al, 2020).Weaker intrinsic foot muscles may increase your chances of sustaining injuries like plantar fasciitis.

In the research which includes famed Harvard evolutionary biologist / barefoot running researcher, Daniel Lieberman, had subjects walk on a specially designed treadmill that had force plates and infrared cameras to measure how much power was put into each step.

The subjects walked barefoot in four different pairs of custom made sandals. The sandals had varying angles of toe spring from 10 to 40 degrees. These ranges of curvatures were designed to be similar to modern footwear.

Sandals were chosen as they allowed the researchers to see the exact motion of the subjects' feet as they walked. The different degrees of toe spring can be filmed to see how they affected their gait with special attention paid to the metatarsophalangeal (MTP) joints at the base of their toes. This is where the toe bones join to the foot bones.

The results showed that the more the shoes curved up front, the less propulsive force was generated with their MTP joints. This means that your intrinsic foot muscles are working less to maintain stability when you move making walking and running easier. However, it also decondition your foot muscles over time, making them weaker and not able to protect other structures in your foot.

Weaker intrinsic foot muscles make one more susceptible to conditions like plantar fasciitis as people rely on their plantar fascia to do what the intrinsic muscles normally do. This may also explain why people get injured if they transition too quickly minimalist type barefoot style running shoes.

Many of my patients who do not run with plantar fasciitis have been told to wear more 'supportive' and comfortable shoes while outside or even at home. This may be worse as their intrinsic foot muscles continue to weaken.

This is why shoes with more toe spring are popular because they are more comfortable and prevent your feet from tiring. This is great in a race and it may be why most racing shoes have a lot of toe spring (see picture below).

More research needs to be done with toe spring and foot injuries as other elements of footwear like stiffer soles and amount of cushioning can impact how our intrinsic foot muscles work.

So what should a runner do? Some physiotherapists and podiatrists often suggest doing intrinsic foot exercises like towel scrunching or pulling your toes toward your heel.

I suggest going barefoot more often. Either at the beach, or when you're at the playground with your kids. In Singapore we are generally barefoot while we're at home. That's better than wearing shoes with lots of toe spring at home. 

While training, look for running shoes with little or no toe spring when you train. 

For my patients who have plantar fasciitis, I tell them to wear flat slippers like Havaianas to minimize the effect of toe spring and for their intrinsic foot muscles to get stronger. 

That is totally different from what some other physiotherapists or podiatrists may suggest. Of course, I also treat plantar fasciitis differently from them.

Reference

Sichting F, Holowka NB, Hansen OB and Lieberman DE (2020). Effect Of The Upward Curvature Of Toe Springs On Walking Humans. Sci Reports 10, 14643. DOI: 10.1038/s441598-020-71247-9.

Asics Metaracer Tokyo - a racing shoe with lots of toe spring