Author(s): LIU, L., HANJUN,LI., Institution: BEIJING SPORT UNIVERSITY, Country: CHINA, Abstract-ID: 2066

INTRODUCTION:
Incorporating carbon plates into running shoes to enhance marathon performance has become prevalent. While plate geometry, elasticity, and longitudinal bending stiffness are well-documented, limited research examines how plate length alters specific biomechanical parameters. Sprinting studies demonstrate that Y-shaped plates increase sagittal ankle range of motion, whereas full-length plates restrict metatarsophalangeal dorsiflexion. We hypothesized that altering plate length modulates joint excursion, thereby affecting lower extremity work and metabolic cost—i.e., running economy. This study aimed to investigate whether increased carbon plate length restricts joint kinematics, alters lower extremity work, and consequently increases energy expenditure.
METHODS:
Seven male rearfoot strikers(shoe size 41, VO₂max ≥50 ml/kg/min)completed testing in both full-length and half-length carbon plate shoes. (1) Running economy was assessed using gas analysis(Cosmed K4b², Italy)at 16 km/h, with energy expenditure calculated as EE=16.89 VO₂+4.84 VCO₂. (2) Biomechanical testing employed an 8-camera motion capture system(Qualisys Oqus 12, 200Hz, Sweden),force platforms(Kistler 9281CA, 1000Hz, Switzerland), and timing gates(PT Master 124, SmartSpeed, Canada)to monitor 16 km/h velocity.Five valid trials were collected per shoe. Marker trajectories were processed in Qualisys Track Manager, exported to Visual 3D for modeling,filtered (Butterworth, 13.3Hz cutoff), and analyzed using Euler angles for joint kinematics and inverse dynamics for net joint moments.Joint work was calculated as the product of net moment,angular velocity, and time.Statistical analyses were performed in R Studio using paired-samples t-tests.
RESULTS:
Joint Range of Motion:Ankle maximum dorsiflexion differed significantly between conditions(half-length: 23.17°±4° vs. full-length: 20.63°±4.09°; t[6]=4.63, p<0.01). Metatarsophalangeal dorsiflexion showed no difference(t[6]=-1.95, p=0.09). Work: Ankle positive work(half-length: 0.060J±0.01J vs. full-length: 0.064J±0.01J; t[6]=-2.58, p=0.04) and metatarsophalangeal positive work(half-length: 0.004J±0J vs. full-length: 0.008J±0J; t[6]=-2.83,p=0.03)differed significantly. Angular Velocity: Metatarsophalangeal extension velocity was lower in half-length shoes(231.43°/s±54.16°/s vs. 288.01°/s±54.16°/s; t[6]=-3.2, p=0.02). Metabolic Cost: Energy expenditure was higher in half-length shoes(16.872W/kg±1.75W/kg vs. 16.365W/kg±2.17W/kg; t[6]=2.67, p=0.036).
CONCLUSION:
(1)Full-length plates significantly restricted ankle dorsiflexion (p<0.01);(2)This restriction increased ankle and metatarsophalangeal positive work (p<0.05) with reduced extension velocity, indicating elevated mechanical loading; (3) Via the force-velocity relationship, full-length shoes improved muscle efficiency through elastic energy storage, resulting in lower energy expenditure (p=0.036), achieving an optimized balance between biomechanical constraint and metabolic economy.