Introduction: In 2017, the Nike Vaporfly 4% running shoes were first released to the public (Ortega et al., Citation2021). Some studies have shown that carbon-plated running shoes change the mechanics of the lower limb joints (Hoogkamer et al., Citation2018), and excessively increased bending stiffness may induce discomfort or hinder the performance benefits (Roy & Stefanyshyn, Citation2006). Purpose of the study: The purpose of this study is to explore the influence of special carbon plate structure on the elite runners` lower limb biomechanics during running. Methods: Fifteen elite male marathon runners (mean (SD) age:34.23 (9.15) years, height:1.68 (0.04) m, weight:59.37 (4.59) kg) joined in this research. They wear two different carbon running shoes, one pair of shoes with normal forward bending stiffness in the forefoot (NFBS), one pair of shoes with a 20% reduction in forward bending stiffness in the forefoot (LFBS), and the two pairs of shoes have similar reverse bending stiffness in the forefoot). Participants were free from injury for at least one year before this study. All participants had been confirmed in foot size (size US9 ± 0.5). All the subjects were instructed to run with each test shoe on the instrumented treadmill (1000 Hz, Bertec, Columbus, USA) at 4 m/s. They were identified as rearfoot strike runners and had a minimum weekly running mileage 60 km. NFBS/LFBS footwear, the maximum value of the forward force of the forefoot: 293.2 N/232.5N, the maximum value of the reverse force of the forefoot: 310.8 N/304.2N). Kinematics of 10 consecutive running strides were collected by Vicon (200 Hz, Oxford Metrics Ltd., Oxford, UK). Statistics were processed by SPSS (24, IBM Corp., Armonk, NY, USA). Shapiro-Wilk tests were adopted for normality distribution. Paired t-test was used to assess the characteristic value. The statistical significance alpha levels were set to <0.05 for all statistical tests. Results: The results showed that the footwear with LFBS significantly increase the range of motion of the metatarsophalangeal joint (MTPJ) during the propulsion phase time (p<.05). Meanwhile increased the peak MTPJ dorsiflexion angle during the propulsion phase time (p<.05). LFBS compared to the NFBS not significantly affect the ground contact time and the propulsion phase time (p>.05). Meanwhile not significantly affect the propulsion force (p>.05). Discussion and conclusion: The two experiment shoes only differ in the forward bending stiffness of the forefoot, while parameters such as shoe weight are similar. LFBS compared to the NFBS increased MTPJ range of motion during the propulsion phase time. The increased MTPJ range of motion may allow the toes to bend normally and suitable for more runners (Roy & Stefanyshyn, Citation2006). LFBS can maintain the same athletic performance and reduce the load on the lower limb joints, making it suitable for more runners. Meanwhile, it may be the future development direction of running shoes.
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