Össur (Germany)

Intense training, along with the advent of new materials and technology available for development of prosthesis, are allowing amputee athletes to reach greater success in sport. To improve run performance, trans-tibial amputee athletes strive to improve efficiency of movement, which in part, is attributed to the amount of rebound provided through their prosthetic. The popular carbon fiber Ossur running foot, Flex Run, is manufactured with nine specific categories of stiffness, each with a difference in the coefficient of restitution. Currently, guidelines are provided by the manufacturer for fitting the appropriate running foot stiffness to the athlete based on body mass and fitness. PURPOSE: To objectively quantify run efficiency based on the energy cost of different running feet. METHODS: A sub- 3:10 marathon BK runner (age 40 yr, body mass 74.5 kg and ht.175 cm) participated in a treadmill run GXT to Max VO2 (62.2 mL/kg-m-1) starting at 187.6 m/min with increments of 13.4 m/min every 3 min. AnT was determined from the max GXT at 262.6 m/min (52.4 mL/kg-m-1or 87% max VO2). The subject completed three randomly assigned double blind trials at AnT with three consecutive categories of running foot stiffness. The running foot stiffness categories included one standard category recommended by the manufacturer (S), as well as one category above (S+) and one below (S-) the standard. RESULTS: The following data were obtained: Ve (106.4, 108.5, & 113.4 L/m), HR (164, 159, 165 b/m) and VO2 (58.5, 57.6 & 59.5 mL/kg-m-1) at S-, S, and S+ trials, respectively. All trials resulted in the same 186 foot strikes/min and the same stride length. His energy cost was 4.4%, 2.8%, and 6.2% greater than the ACSM prediction equation for S-, S, and S+ trials, respectively. Although the athlete reported the greatest comfort during the S+ trial, his VO2 was elevated 3.2% above the S trial. CONCLUSION: The prosthesis does not appear to offer any advantage in terms of efficiency. The evaluation of additional subjects and running speeds are necessary to effectively quantify running efficiency attributed to prosthetic running foot stiffness.