Track 6. Sport Biomechanics - Joint ISB Track 6.1 Sport Injuries $543

problems such as back and foot pain, but there is little in the literature to genuinely support this. Aim: The aim of this study was to evaluate the effect that wearing high-heels has on spinal motion. Methods: Ten healthy adult female volunteers, who are comfortable wearing high-heeled shoes were recruited. Walking data was acquired as subjects walked barefoot and then with their own high-heeled shoes. Shoe height was defined as the maximum height of the sole at the rear of the heel. Lumbar flexion was measured in normal stance position and during gait, through the use of a pair of ultrasonic triplet arrays (Zebris 3-D Motion Analyzer, Zebris Medical GmbH, Germany) positioned at the level of the sacrum and L1-2. A mean of three readings for each subject walking barefoot and in high heels was taken. Non-parametric assessment using the one sample sign test was used. Results: The volunteers ranged in age from 19-30 (mean 26 years), with an average height of 163cm (range 152-189cm). Heel heights ranged from 8 to 11 mm, with an average shoe size of 6.5UK (40 European). Results were individually and qualitatively compared, with intrasubject comparison of the results of barefoot and high-heeled spinal motion. The mean lumbar flexion on walking barefoot was 7.680 , and 12.40 in heels (ranges 7.3-12.20 and 9.7-160 respectively). There was a significant difference in the degree of lumber flexion in each subject between walking barefoot and in high heels (p =0.0078) Conclusion: This data demonstrates a significant difference in degree of lumbar flexion in women wearing high heels, which may correlate with postural changes.

7556 We-Th, no. 55 (P60) Analytical and computational methods to evaluate the effect of bone geometry in tibial loading response D. Subit, D. Bose, J. Ivarsson, C. Untaroiu, J. Crandall. Center for Applied Biomechanics, Charlottesville, VA, USA

The Tibia Index (TI, Mertz et al., 1993) is an injury criterion that uses combined axial compression (F) and bending moment (M) to predict midshaft tibia fracture. This criterion assumes that the tibia is a straight elastic beam: TI=F/Fc+M/M C, where F C and M C are the critical compressive force and bending moment, respectively. Injury is unlikely when TI < 1. Researchers (like Kuppa et al, 2001) have proposed revised TIs that account for the eccentricity of the load and the dynamic effect of the loading by modifying the threshold value. In all cases, the relationship between the failure and the external compressive force and bending moment was assumed to be linear. Additionally, the contribution of the regional tibia geometry to the failure location and the strain rate sensitivity was not incorporated in the formulation. The current study proposes a new TI criterion that accounts for the geometry of the tibia and the dynamic loading response. Using an analytical model based on linear beam theory, a parametric study was conducted to evaluate the sensitivity of the failure mechanism to the tibial structural properties in quasi-static loading. Fur- thermore, a geometrically accurate finite element model was implemented to account for the rate dependency of the failure criterion in dynamic loading. The results of the quasi-static analysis showed that the compressive and tensile failure stress values and the loading eccentricity were critical contributors to the tibial failure criterion. The results of the dynamic analysis showed a nonlinear dependence of the failure threshold on the compressive force and external moment.

References Mertz, H. J., (1993). Anthropometric Test Devices, in Accidental Injury: Biomechan-

ics and Prevention, edited by A. M. Nahum and J. W. Melvin, Springer-Verlag, New York.

Kuppa S, Wang J, Haffner M, Eppinger R. (2001). Lower extremity injuries and associated injury criteria. Proc. 17th ESV Conf.. Paper 457 pp. 1-15.

Track 6

S p o r t B i o m e c h a n i c s - J o i n t ISB Track

6.1 Sport Injuries 7248 Mo-Tu, no. 1 (P60) Fatigue-related changes in stance leg mechanics during soccer-related maneuvers in female soccer players G. Sanna 1,2, K.M. O'Connor 1 . 1Neuromechanics Laboratory, Department of Human Movement Sciences, University of Wisconsin, Milwaukee, USA, 2 Dipartimento di Scienze del Movimento Umano e dello Sport, Istituto Universitario di Scienze Motorie, Roma, Italy

Purpose: The increased number of women participating in sports has led to a higher knee injury rate in women compared to their male counterparts. Planting and pivoting motion is frequently linked to this injury. While this motion is present in both kicking and cutting maneuvers, knee injuries are not commonly observed during kicking. These maneuvers are regularly performed during a soccer game. In addition, fatigue and number of injuries occurring during a soccer game also seem to be correlated. The purpose of the study was to examine the fatigue-related changes in stance leg mechanics during a soccer kick and a cutting maneuver in female soccer players. Methods: Twelve female college soccer players were recruited. A soccer game fatigue level was achieved by asking them to perform a 60-minute shuttle run. Prior to and after this exercise, segmental kinematics and ground reactions were measured in a movement analysis laboratory during kicking, a 450 cutting movement, and a countermovement jump. Using these data, three-dimensional stance leg joint kinematics and kinetics and total muscular power were estimated. Jumping power output was analyzed with a repeated measures one-way ANOVA. Pre- and post-fatigue stance leg mechanics were analyzed through paired t-tests (p < 0.05). Results: Jumping power output confirmed that fatigue was induced. Post- fatigue kicking data showed augmentation of knee internal rotation which could lead to an increased risk of injury. Ankle moments and powers decreased suggesting plantar flexors fatigue which, as a consequence, could affect knee motion. Post-fatigue cutting maneuver data showed decreases in knee sagittal moment and power suggesting knee extensor fatigue. In addition, there was a greater knee abduction moment suggesting increased loading of the passive structures. Conclusions: Overall, it seems that the greater abduction angles during cutting may explain why injuries are more prevalent for cutting than for kicking.

5920 Mo-Tu, no. 2 (P60) Evaluating paddl ing per formances through force acquisitions with a specially instrumented Kayak ergometer G. Mimmi, C. Rottenbacher, M. Regazzoni. Dipartimente di Meccanica Strutturale, Universita di Pavia, Pavia, Italy

This paper presents a prototype machine working as a kayak ergometer, specially designed to closely reproduce the athletic performance during a training K1 indoor session. Drag and inertia actions on paddles are reproduced through a fan connected to the movement of the paddle-bar. The resistance action can be adjusted by regulating the air intake with a shutter, to compensate for size and weight of the paddler. Paddle action, simulated by an instrumented bar with strain gauges at both ends, pulls the rotating fan by means of ropes rolling up on pulleys. Load cells are mounted in correspondence of the bearings of the pulleys, and an encoder is mounted on the fan shaft to measure the rotational speed. This system is particularly suitable to evaluate the paddling performances and to refine the technique of strokes and style.

References [1] Smith R., Galloway M., Patton R., Spinks W. Analysing on-water rowing perfor-

mance. Sports Coach 1994; 17. [2] Barre S., Kobus J.M. Two methods to compare the efficiency of various couples

oars-oarsmen. In: 13th Conference of European Society of Biomechanics, Wroclaw. 2002; Vol. 4, pp. 583-584.

[3] Nozaki D., Kawakami Y., Fukunaga T., Miyashita M.. Mechanical efficiency of rowing a single scull. Scandinavian Journal of Medicine and Science in Sport 1993; 3.

[4] Kobus J.M., Barre S. Simulation of oars boats dynamics. Congres Europeen Marine Industrie et Simulation, Sim' Ouest Nantes, 2000.

[5] Roncin K., Kobus J.M., lachkine P., Barre S. Methodologie pour la validation du simulateur de voilier par des essais en mer, une premiere tentative. Workshop Science-Voile Ecole Navale, Brest, 2005.