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14:40   Adaptive sports; device design Chair: Jos Oberdorf 14:40 20 mins INFLUENCE OF WEIGHTED CUFFS ON GROUND REACTION FORCES IN RUNNING OF AN ELITE UNILATERAL UPPER EXTREMITY AMPUTEE ATHLETE Stefan Litzenberger, Franziska Mally, Steffen Willwacher, Björn Braunstein, Anton Sabo, Gert-Peter Brüggemann Abstract: Due to their opposing movement the swinging arms are said to not have a major contribution to the overall motion of running [1],[2]. However, missing one upper extremity limb can lead to significant asymmetries [3],[4]. In the present study it was investigated what influence weighted cuffs, which are added to the missing limb, have on the ground reaction forces in running of an elite unilateral upper extremity amputee athlete. One elite athlete (PB 400m: 0:48,45, PB 800m:1:50,92) currently classified as T47 by the International Paralympic Committee due to missing his right forearm participated in this study. The subject had to perform several runs on a 100m Tartan track with a velocity of 8 m/s (high race speed) without and with wearing two differently weighted cuffs (0.5 kg and 1 kg) applied to the elbow of the impaired limb. Ground reaction forces (GRFs) were captured with a frame rate of 1000Hz using four floor-level mounted Kistler force plates aligned consecutively along the running track. Mean vertical and horizontal GRFs were calculated over 100% of stance phase duration and statistical data was evaluated for maximum and minimum values. Patterns of vertical GRFs did not differ dramatically whereas the maximum vertical force revealed a highly significant and significant difference between left and right foot when running with heavy or no additional weight respectively. Running with the light weighted cuff did not reveal a significant difference between the two sides. No significant differences could be found when comparing the maxima of each side when running with different weights. The different weights lead to no significant differences in anteroposterior GRFs at all. Although no differences were revealed when comparing maximum mediolateral GRFs while running with different added weights, all conditions showed highly significant asymmetries between left and right foot. Minimum values of mediolateral GRFs did not show significant differences between the three weight conditions as well. Significant and highly significant differences between left and right food could be observed without any and with heavy weight. References: [1] Hinrichs, R. N. (1987). “Upper Extremity Function in Running. II: Angular Momentum Considerations.” In: International Journal of Sport Biomechanics 3, pp. 242–263. [2] Hinrichs, R. N., P. R. Cavanagh, and K. R.Williams (1987). “Upper Extremity Function in Running. Part I: Center of Mass and Propulsion Considerations.” In: International Journal of Sport Biomechanics 3, pp. 222–241. [3] Litzenberger, S., Mally, F., Willwacher, S., Braunstein, B., Sabo, A., & Brüggemann, G-P. (2015). Ground Reaction Forces in Elite Upper-Limp Amputee Running. in: Congress of the International Society of Biomechanics (ISB): Abstract book (S. 1095-1096). International Society of Biomechanics in Sports. [4] Mally, F., Litzenberger, S., Sabo, A. (2015), Kinematics of Elite Unilateral Below-elbow Amputee Treadmill-running - A Case Study, Procedia Engineering (112) 2015, pp. 449-454 15:00 20 mins EFFECT OF DIFFERENT MOUNTING ANGLES OF PROSTHETIC FEET DEDICATED TO SPRINTING ON REACTION FORCES Stefan Litzenberger, Anton Sabo, Franz Fuss Abstract: Prosthetic sprinting feet made of carbon fibre reinforced plastics for transtibial amputee athletes are widely used by hobby athletes and in professional competition. However, so far only little work has been done to assess static and dynamic properties of prosthetic feet dedicated to sprinting. Only few different parameters (energy return and vibration, respectively) have been examined, results are not generally applicable and do not take different mounting angles of the prostheses onto the shaft into account. During the intended measurements two sprint prostheses (Otto Bock Sprinter feet (Duderstadt, GER) with low (S1) and mid stiffness (S3), respectively, used for athletes with low (approx. 55kg) and mid (approx 80~kg) bodyweight (high activity level, used in Paralympic sports)) are tested on a motor driven static test bench under different loading and mounting conditions. Additionally different attachment brackets (0, 5 and 18 degree) are used which allow different mounting angles between shaft and prosthetic foot. Although the mounting angle does not directly influence the foot's mechanical properties it is considered to highly affect the direction of the reaction forces during loading and unloading. These forces are measured on the attachment point using a three dimensional load-cell (ME-Messsysteme GmbH, Hennigsdorf, GER). Force is applied in several steps from zero up to an estimated 4 times bodyweight (BW) of the vertical forces for the intended user. As this is a static test the motor will be stopped for several seconds after reaching each single force level. After having reached the maximum test force an unloading sequence will be done using the same step width as for loading. Results will show the differences in reaction force amplitudes and direction and will allow predicting the effect of different mounting angles on the athlete. NOTE: This work is still in progress, no detailed results are available yet. 15:20 20 mins OPTIMIZATION OF THE DESIGN OF A DISCUS FOR PEOPLE WITH DISABILITIES Kazuya Seo, Naoki Takahashi, Koichi Kawabata, Toshihito Mitsui Abstract: Discus throwers develop and adjust their skills depending on the discus that is being used. The optimal skill is applicable to the discuses used in their training and those used in competitions. However, their performance could be maximized if their skill and their equipment were optimized simultaneously. Here, the objective function for optimization is the flight distance. Longer flight distance is better. Fourteen design variables are considered. Eight of the fourteen are concerned with the skill of the thrower. They determine the launch conditions, which are controlled by the thrower when he or she throws. The other six variables are concerned with the design of the equipment. These are the dimensions of the discus (width, thickness, radius of the metal rim and diameter of the flat center area on each side), the moment of inertia about the transverse axis and finally the mass of the discus. In our previous studies, we developed techniques for simultaneously optimizing the design of a discus and the throwing skill. It was found that the world record might be possible if their skill and their equipment were optimized simultaneously. In this study, this technique is applied to the design of a discus for people with disabilities (Paralympians). As the movements of persons with impairments are very limited when compared with Olympians, the optimized discus size for Paralympians should be different from that for Olympians. The objective of this study is to determine the optimized discus size for Paralympians. It was found that the optimized discus for a Paralympian has less width and greater thickness when compared with the commercially available discus for women.