In recent years, carbon fiber has been slowly incorporated into many high-performance running shoes, eg. Alphyflys, Vaporflys, Carbon X. Many athletic shoe's companies utilize the advantages of carbon fiber proven to reduce energy expenditure during running. If energy reduction is available through implementing the carbon fiber, could this technology be incorporated into normal, everyday shoes? A long-term goal would be to target the elderly population to walk faster at a lower energy requirement with a simple footwear intervention. Our research question focuses on how different thicknesses of carbon fiber changed foot joint angles during a typical walking gait cycle. Through use of a biplane fluoroscopy (i.e., x-ray) system, bone motion was captured inside of the shoe to analyze foot joint angles. One participant (N=1, F, 21) walked across the biplane fluoroscopy under four different conditions: barefoot, shod, shod with 1.6 mm carbon fiber, and shod with 3.2 mm carbon fiber. Analysis of joint angles for the metatarsophalangeal joint (i.e., toe), midtarsal joint (i.e., arch), and ankle were conducted through use of the Kinovea software. We hypothesized that increasing shoe stiffness via carbon fiber insoles would cause the: 1) toe joint to decrease dorsiflexion [toe will bend less] 2) arch will decrease plantarflexion [arch will be flatter] 3) ankle will increase peak dorsiflexion [foot will be raised up more]. Overall, the results found comparing Shod vs Carbon 3.2 mm supported the hypothesis: 1) toe decreased dorsiflexion by 18.5Â° 2) arch decreased plantarflexion by 2.3 Â° 3) ankle increased dorsiflexion by 2.96Â°. The research utilized a novel state-of-the-art method via high-speed X-rays to analyze foot motion inside of the shoe during walking. This data is meaningful in helping further the development of footwear for people of all ages with goals to reach new athletic records, walk with less energy requirement, and wear a more comfortable shoe.