How Long Does Your Running Shoe Last?

Picture from Run Repeat

Ever wondered how long before you need to change your running shoes? A bit of history on midsole technology. Previously, the midsoles in running shoes were all made with ethylene-vinyl acetate (or EVA). Then Adidas managed to secure (Adidas bought the technology from BASF) their Boost midsole out of thermoplastic polyurethane (TPU) in 2013 which led to many marathon world records falling. In 2017, Nike's super shoe, the Vaporfly, was made of polyether block amide (PEBA) and it is still the current dominant midsole.

Previous anecdotal evidence and hearsay suggest EVA midsole running soles tend to last between 300 to 500 miles (480 to 800 km). There was an older study supporting this information (Cook et al, 1985). The researchers measured shoes shock absorption at frequent intervals between 0 to 500 miles. 

A machine was used to simulate running impact as well as 2 vounteers who actually ran 500 miles (pictured above). The 2 human volunteers show similar patterns compared to the machine (see diagram). Human testing showed that EVA midsole shoes retained 80 percent of shock absorption after 150 miles (240 km) and 70 percent after 500 miles (800 km). The curve then flattens out between 300 to 500 miles which is probably where we get shoe lifespan information from.

More recently, a bunch of researchers teamed up with the brand On and manufactured prototype running shoes that were almost identical (Rodrigo-Carranza et al, 2023). One had the new PEBA super foam while the other had the traditional EVA midsole. 

Shoe testing from Rodrigo-Carranza et al (2023)

Both versions also had a curved carbon fiber plate. They tested the shoes before and after 280 miles (448 km). 22 runners performed a running economy test to measure how much energy they used at a given pace, once in fresh shoes, once with pre-worn shoes. The researchers themselves actually ran 280 miles (448 km) in each pair of shoes to pre-wear them for the research!

The researchers found that the new super foam did lose their powers quicker. In fact they were no better than the traditional EVA midsole when they did. A key finding was that energy consumption while running with the new PEBA midsole shoe was 1.8 percent less than using the new EVA shoe. This strengthens the case that the super foam itself is more important ingredient since both versions of the prototypes had carbon plates in them.

Another key finding was that after 280 miles (448 km), there was no significant difference between the 2 shoes. The EVA did not lose anything while the PEBA super foam shoe got 2.2 percent worse. Please note that not all PEBA foams are created equal. On's super foam may not be totally similar to Nike's and other brands.

I have not converted to super shoes yet as I do not like them stacked too high. Moreover, I currently only run 2-3 times a week and I rotate between 2 to 3 pairs of shoes with EVA and TPU midsoles. I run in them until they start to feel "flat". It is relatively easy to feel especially if one of my other newer pairs still feels supportive by comparison. I usually retire that "flat pair" from running but will still use them for walking. If you're using the PEBA foam super shoes, you may have to change them earlier.

If you are interested, have a look at Run Repeat, where infomation on a huge range of high performance super foams are available. The author, Carlos Sanchez runs 100 km a week and has run three sub 3 hours marathons. Sanchez suggests that shoe foams take more than 24 hours to 'recover' and some foams recover faster than others so you may want to rotate your running shoes to maximise comfort and shoe life.

References

Cook SD, Kester MA and Brunet ME (1985). Shock Absorption Characteristics Of Running Shoes. AJSM. 13(4): 248-253. DOI: 10.1177/036354658501300406

Rodrigo-Carranza V, Hoogkamer W, Gonzalez-Rave JM et al (2023). Influence Of Different Midsole Foam In Advanced Footwear Technology Use In Running Economy And Biomechanics In Trained Runners. Scan J Med Sci Sp. DOI: 10.1111/sms.14526