Introduction The construction of the Nike Vaporfly 4% shoe has led to the widespread incorporation of Advanced Footwear Technology (AFT) in modern running shoe design, characterised by the innovative use of a curved carbon fibre plate that significantly enhances propulsion and cuts down on energy costs (Frederick, Citation2022). Different carbon fibre-reinforced composite materials, like low curvature plates (LCP) and high curvature plates (HCP), adjust the ankle push-off moment by either increasing or decreasing it through changes in the lever arm (Farina et al., Citation2019). Despite the emphasis on longitudinal bending, the impact of horizontal scrolling on sports biomechanics, particularly considering the ubiquitous running motions such as foot eversion and calf internal rotation (Nigg et al., Citation2020), remains insufficiently researched, highlighting a key area for further investigation in the context of elite runner performance. Purpose of the study: This study aimed to investigate the effect of the horizontal construction of carbon fibre plate on the biomechanics of the lower limbs compared to regular racing plate, which will benefit the industrial utilisation of shoe producers in light of improving running performance for elite runners. Methods: Thirteen male runners (mean (SD) age: 35.03 (1.7) years, height: 1.75 (0.26) m, weight: 63.14 (22.65) kg, BMI: 20.19 (1.38) kg/m2) with the foot size of US (9 ± 0.5) were instructed to run with each test shoe on the instrumented treadmill (Bertec, Columbus, OH, USA) at 4 m/s. Participants were identified as rearfoot strike runners and had a minimum weekly running mileage of 50 km and were capable of running 10 km in less than 40 minutes. Experimental plate (PHC: plate with horizontal curvature, PWHC: plates without horizontal curvature). GRF and kinematics of 10 consecutive running strides were collected by vicon and force plate (C-Motion Inc., Ontario, Canada; AMTI, Watertown, MA, USA). Statistics were processed by SPSS (24, IBM Corp., Armonk, NY, USA). Shapiro-Wilk tests were adopted for normality distribution. Paired t-tests was used to assess the characteristic value. The statistical significance alpha levels were set to < 0.05 for all statistical tests. Results: Shapiro-Wilk tests revealed that 100% of biomechanical variables and 100% of perception variables were normally distributed (both p > .05). There was no significant difference between these two kinds of shoes in spatiotemporal parameters and shoes longitudinal bending stiffness (LBS). What`s more, the horizontal curvature around forefoot also did not led to the significant different at propulsion force. Concerning metatarsophalangeal joint(MTPJ) angles during running, compared to PWHC, a smaller Peak MTP internal rotation angle and MTP range of motion (ROM) in the sagittal plane were found in that of PHC (all P<.05). As for running during push-off phase, the peak ankle eversion angle, peak ankle eversion velocity and ankle ROM in the frontal plane of PHC were significantly lower than those of PWHC (all p<.05). For kinetic variables, PHC presented a smaller ankle eversion moment relative to that of PWHC during running stance (P<.05). Discussion and conclusion: The relationship between MTPJ ROM and the LBS of running footwear has presented conflicting findings. While previous research suggested that MTPJ ROM in the sagittal plane decreases as LBS increases (Hunter et al., Citation2019), our study offers a different perspective. Mechanical and biomechanical evaluations revealed that PHC actually restricted MTPJ ROM similarly to PWHC despite possessing the same LBS (p<.05). This indicated that even mild changes in the horizontal curvature of carbon plates can significantly influence joint movements. The stability and support offered by marathon shoes, particularly in adjusting the horizontal curvature of plates, is critically important. Such changes impact joint motion in the frontal plane during running. Noteworthy is the observed reduction in navicular bone height by approximately 5 mm following a half marathon, which in turn diminishes the mechanical energy of running (Fukano et al., Citation2018). Our study highlights positive effects, such as PHC shoes resulting in decreased peak ankle eversion angles, velocities, and reduced ankle ROM compared to PWHC (both p<.05). In terms of lower limb joint kinetics, our research confirms that neither PHC nor PWHC instigate significant changes in sagittal plane joint work, a finding consistent with earlier studies. Previous observations noted no proximal shift in joint work after extended runs among rearfoot-striking, well-trained athletes (Melaro et al., Citation2021). This underscores the preservation of biomechanical efficiency regardless of plate type. Moreover, the use of PHC in running shoes presents fewer ankle eversion moments than PWHC during the running stance (P<.05). For elite runners, integrating horizontal carbon fibre plate curvature into racing shoes provides distinct advantages in terms of stability and support, facilitating enhanced performance and reducing the risk of injury during long distance running.
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