The impact of toe spring and foot strike angle on forefoot running biomechanics: a finite element analysis

The surge in popularity of running has led to a multitude of designs in running shoe technology, notably, there is an increasing trend in toe spring elevation. However, the impact of this design on foot structures during running remains an essential exploration. To investigate the effects of toe spring on the foot during forefoot running, we employed finite element simulation to create two sole models with different toe spring heights (6.5 cm and 8 cm) and ground contact angles (5°, 10°, and 15°). We established and validated two foot-shoe coupling models and compared stress variations in metatarsal bones and the big toe under identical loading and environmental conditions. Higher toe spring resulted in lower peak stress and reduced stress concentration in metatarsal bones. The fourth and fifth metatarsals exhibited increasing stress trends with ground contact angle, with the fifth metatarsal experiencing the most significant stress concentration. In the case of low toe spring, stress on the fifth metatarsal increased from 15.917 MPa (5°) to 27.791 MPa (15°), indicating a rise of 11.874 MPa. Conversely, the first metatarsal showed lower stress, indicating relative safety but reduced functional significance. Moreover, higher toe spring running shoes exerted less pressure on the big toe, with an increasing trend in stress on the big toe with an increase in ground contact angle. Shoes with a higher toe spring design result in reduced pressure on the big toe. Therefore, it is advisable to avoid landing angles greater than 15° to prevent stress fractures resulting from repetitive loading.