Influence of Carbon-fiber Shoes on Outdoor Running Biomechanics as Assessed with Wearable Sensors.

Carbon-fiber shoes feature a stiff yet lightweight curved carbon-fiber plate embedded in the sole and a resilient midsole foam. These shoes create spring-like rebounding effect that has proven to decrease energy consumption and enhance athletic performance. To date, most biomechanics research on carbon-fiber shoes has been laboratory-based. The purpose of our study was to compare running biomechanics in competitive runners wearing carbon-fiber shoes or traditional shoes using wearable sensors on an outdoor composite track. Ten elite runners (9F, 1M) who consistently ran over 30 miles per week and owned a pair of carbon-fiber shoes participated. The experiment consisted of three 40-meter run trials in carbon-fiber shoes and three trials in traditional running shoes. The self-selected speed was held constant between the two conditions. Two Inertial Measurement Units (IMUs) were strapped on subject's right foot and tibia to measure biomechanical parameters including tibial acceleration, eversion velocity, stance time, stride frequency, sagittal plane angular velocity of the foot at toe-off, and sagittal plane angular acceleration of the foot during propulsion. A paired sample t test was used to compare between shoe conditions. Sagittal plane angular acceleration of the foot during propulsion was significantly greater in the carbon-fiber shoes, 8774.4±4348.2 deg/sec 2, compared to 7492.9±3495.0 deg/sec 2 for traditional shoes (P=0.01, Cohen's d=0.513). Additionally, sagittal plane angular velocity of the foot at toe-off approached significance (carbon-fiber: 953.1±227.9deg/sec, traditional: 881.0±216.1deg/sec, P=0.082, Cohen's d=0.326). No other differences were noted. Carbon-fiber shoes create a more efficient toe-off by providing greater propulsive acceleration during push-off.