Midsole hardness altered selected lower-limb kinematics, navicular height, vertical loading rate, and muscle activation during running in children; however, these acute differences do not indicate functional superiority of any of the tested hardness conditions.
Maximum ankle sagittal angle decreased significantly as midsole hardness increased during running in children.
Hip sagittal range of motion decreased significantly with increasing midsole hardness during running.
Navicular height was significantly higher under medium and hard midsole conditions compared to the soft midsole condition.
Vertical average loading rate (VALR) was significantly higher under the hard midsole condition compared to the soft midsole condition.
Tibialis anterior (TA) and lateral gastrocnemius (LG) relative muscle contributions were lower under the hard midsole condition than under the soft midsole condition.
Semitendinosus (ST) relative muscle contribution was higher under the hard midsole condition than under both soft and medium midsole conditions.
Gluteus maximus (GM) activation and relative contribution were highest under the medium midsole condition.
The study enrolled 30 healthy boys and used a within-subject repeated-measures design to assess running biomechanics across three midsole hardness conditions.
The authors concluded that acute biomechanical differences observed across midsole hardness conditions do not indicate functional superiority of any single hardness.
This research suggests that the hardness of a running shoe's midsole — the cushioning layer between the foot and the ground — meaningfully changes how children's bodies move and which muscles they use when running. In a study of 30 healthy boys, researchers tested three midsole hardness levels (soft, medium, and hard) and found that harder soles were associated with reduced ankle and hip movement, a higher arch position (navicular height), and increased impact loading rates — meaning the feet experienced faster force build-up during each step. Different muscles were also recruited differently depending on shoe hardness, with harder soles reducing demand on the calf and shin muscles while increasing hamstring involvement, and medium-hard soles producing the greatest activation of the gluteus maximus (buttock muscle). This matters because children's bones, muscles, and joints are still developing and may be more sensitive to the mechanical forces generated during activities like running. Shoe design choices could therefore influence movement patterns and muscle development during a critical growth period. This research suggests that midsole hardness is not a neutral design feature — it changes how a child's body responds to running in measurable ways. However, the researchers were careful to note that finding differences does not mean any one shoe hardness is better or worse for children. The study only measured immediate, short-term effects during a single running session, and did not track whether these differences led to better performance, injury prevention, or any long-term outcomes. Further research following children over time would be needed to understand whether midsole hardness choices have lasting effects on health or development.
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Upload Your LabsYe Z, Xuan B, Li F, Chen K, Chen Y, Zhou Z, et al.. (2026). Modulation of Lower Limb Biomechanics and Muscle Activation by Midsole Hardness in Children During Running.. Journal of foot and ankle research. https://doi.org/10.1002/jfa2.70211