Friday, July 6th, 2012 16:05 - 17:35 BRUGES/ BELGIUM, 4-7 TH JULY 2012 463 the anatomical position with the use of the e-Zone software and also with the use of 3D body scanning techniques. Symmetry in the sagittal plane was assumed and only the right upper and lower limbs were measured in both cases. A front and side view photograph was taken simultaneously for the requirement of the e-Zone method and the radii of each elliptical cylinder was measured from the photographs with manual digitizing. The digitizing process was repeated five times to establish reliability. In parallel, a 3D laser scanner (Hamamatsu®) was employed to create an accurate 3D representation of the swimmer’s body. The model was then edited and seg- mented with the use of Rhinoceros® software whereas the segment volumes were measured with the use of the Magics® software. Results The volume of the WB was computed to be 74230.90 cm3 with the eZone method and 76613.90 cm3 with the 3D scanning technique. The head and neck volume was overvalued by 3.7% whereas the core, the right upper and lower limb were undervalued by 3%, 2.7% and 4.5% respectively. Discussion The findings of this study demonstrate that the volume of the full body was undervalued. These findings suggest that the estimates of segment mass and the location of the WBCM could have been affected. Further investigation of the accuracy of the e-Zone method with a greater number of participants and of both genders is necessary to draw a safe conclusion. Also, the effect of the WB volume measurement error in the location on the WBCM should be investigated. References Deffeyes J & Sand- ers R, (2005). In, Wang Q (Ed.): Proceedings of the XVII International Symposium on Biomechanics in Sports. Beijing, China. Pp. 749-752. Jensen, R.K. (1978). Journal of Biomechanics, 11, 349-358. SPRINT RUNNING MECHANICS: A CASE STUDY OF A WORLD-CLASS ATHLETE Morin, J.B., Bourdin, M., Edouard, P., Peyrot, N., Samozino, P. Laboratoire de Physiologie de l'Exercice SPRINT RUNNING MECHANICS: A CASE STUDY OF A WORLD-CLASS ATHLETE Morin, JB.1, Bourdin, M.2, Edouard, P.1, Peyrot, N.3, Samozino, P.4 1: LPE, University of Lyon (Saint Etienne, France), 2: LBMC, University of Lyon (Lyon, France), 3: DIMPS, University of La Réunion (Le Tam- pon, France), 4: LPE, University of Savoy (Le Bourget du Lac, France) Introduction To date very few experimental data have been obtained directly on world-class sprinters. The recent validation of a sprint instrumented treadmill (Morin et al., 2010) allowed us to introduce the concept of effectiveness of force application throughout sprint acceleration and to show its relationship with 100-m performance in non- specialists (Morin et al., 2011). We tested here our recent hypothesis that the forward orientation of the resultant force onto the ground was better related to sprint performance than its magnitude, in a population including a sub-10 s individual. Methods The biomechanics and field 100-m performance of a world-class sprinter (WCS, 2011 best times of 9.92 s and 19.80 s on the 100-m and 200-m, respectively) were tested and compared to those of three national-level sprinters (NLS), and nine physical education students (PE). Subjects performed 6-s sprints on an instrumented treadmill during which horizontal, vertical and resultant ground reaction forces (GRF), and belt velocity were continuously recorded and used to compute linear force-velocity relationships. An index of the force orientation effectiveness (DRF) was also computed as the slope of the linear relationship between the decrease in the ratio of contact-averaged horizontal-to-resultant GRF and the increase in velocity (Morin et al. 2011). A 100-m field sprint was also performed with performances were recorded with a radar. Results WCS differed by more than 2 SD from the NLS and 2 to 4 SD from the PE for the slope of his force-velocity relationship (~25 % more oriented towards velocity muscular qualities), his ability to orient the resultant GRF forward during acceleration (~43 % better DRF) and his step frequency (~5 % higher, resulting only from a lower contact time). Contrastingly, he did not differ from NLS and some of the PE for the magnitude of resultant force produced. Discussion The main mechanical determinants characterizing this WCS were (i) a “ve- locity-oriented” force-velocity profile, likely explained by (ii) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration. Despite similar resultant force capabilities compared to NLS and PE, the WCS showed a better forward orientation of the resultant force onto the ground during acceleration, which confirmed our recent hypothesis that what matters to acceleration and sprint performance is more the orientation of the resultant force than its magnitude. References Morin JB, Samozino P, Bonnefoy R, Edouard P, Belli A. (2010) J Biomech, 43, 1970-1975. Morin JB, Edouard P, Samozino P. (2011). Med Sci Sports Exer, 43, 1680-1688. STRONG POSITIVE CORRELATIONS WERE FOUND BETWEEN MUSCLE ACTIVATION AND BREASTSTROKE SPEED MEAS- URED WITH 3D AUTOMATIC TRACKING Olstad, B.H., Zinner, C., Cabri, J., Haakonsen, D., Kjendlie, P.L. 1: NSSS (Oslo, Norway), 2: GSU (Cologne, Germany), 3: VUC (Toensberg, Norway) Introduction A limited number of studies have investigated the muscle activation during breaststroke swimming through the use of sur- face electromyography (sEMG). No previous studies have investigated kinematic variables in human swimming using motion capture (mo-cap) 3D with automatic tracking (AT). The aim of this study was therefore to investigate the relationship between muscle activation in eight different muscles and swimming velocity at five different efforts. Methods Four swimmers (one male, world championship medalist and three females, one Olympic medalist, one national medalist and one national finalist) performed one trial of 20m breaststroke at the speeds of 60%, 70%, 80%, 90% and 100% of maximum effort. During each trial the velocity of the swimmers right trochanter major and the muscle activation in biceps brachii, triceps brachii, trapezius (pars descendens), pectoralis major (pars clavicularis), rectus femoris, biceps femoris, tibialis anterior and gastrocnemius were recorded over three stroke cycles. Each stroke cycle started when the heels were fully pulled up, flexed and ready to kick. 3D images with AT were recorded from ten underwater mo-cap cameras (Oqus Underwater, Qualisys, Gothenburg, Sweden). The cameras recorded spherical markers (diameter of 19mm) fixed to the swimmers suit using cyan LED light. The muscle activity was recorded using waterproof electrodes and active sensors from (Plux Ltda, Lisbon, Portugal) and recorded according to (Olstad et al., 2011). Results Pearson’s correlations was used to assess the relationship between the average velocity of trochanter major (representing hip speed) at the five different velocities with the average sEMG during the three stroke cycles. Strong positive and significant relationships were found for tibialis anterior r=.756 (p<0.001), biceps femoris r=-.666 (p<0.001), pectoralis major (pars clavicularis) r=.666 (p<0.001), biceps brachii r=.641 (p<0.002), triceps brachii r=-.622 (p<0.01). Positive but insignificant relationship was found for rectus femoris r=.448. Moderate positive and insignificant relationships was found in gastrocnemius r=.311. In trapezius (pars descendens) weak and insignificant relationship was found, r=-.028. Discussion The study showed a strong and significant rela- tionship between muscle activation in five different muscles and average swimming velocity over five different speeds. It showed that velocity can be tracked using 3D AT and therefore opens up new possibilities for conducting kinematic analysis in swimming with 3D AT combined with measuring muscle activity through the use of sEMG. References Olstad, B. H., Cabri, J., Zinner, C., Nunes, N., & Kjendlie, P. L. (2011). SEMG measurements on land and in water prior to and after 60-90 minutes of submersion (swimming) are highly reliable. Portuguese Journal of Sport Sciences, 11 (Suppl. 2), 763-765.