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Stiffness Index defined as the slope of relation between torque and lengthening of tissues, and Young Modulus Index as the index of material property were determined. The lengthenings of tissues were evaluated by B mode ultrasound images, during passive dorsiflexion for muscle tissues, and during isometric voluntary contractions for tendinous tissues. Two-dimensional kinematic analysis of race pace running was also applied with high speed VTR. RESULTS AND DISCUSSION Morphological variables related to length and cross sectional area have no significant difference between HPG and NPG. The mechanical properties related to only tendinous tissues showed significant differences between HPG and NPG. The Stiffness Index and Young Modulus Index of tendinous tissues of HPG were more compliant by 40% (p0.01) and by 41% (p0.01) than those of NPG, respectively. However, no significant difference was observed in Induces of muscle tissue. The difference of not only Stiffness Index but also Young Modulus Index in tendinous tissues imply the difference in its material properties between HPG and NPG, which is originated in biomaterial composition like collagen type. In addition, HPG and NPG did not demonstrate significant difference in many kinematic variables such as joint angle changes and step frequencies, while HPG showed 8% larger step length, 12% shorter contact time, and 32% faster maximal angular velocity of plantar flexion in late contact phase significantly (p0.05).
References Saltin B, Larsen H, Terrados N, Bangsbo J, Bak T, Kim CK, Svedenhag J, Rolf CJ. (1995) Scand J Med Sci Sports, 5, 209-21.
MEASUREMENT OF THE AERODYNAMIC DRAG OF TEXTILES WITH A NOVEL DEVICESchindelwig, K., Hasler, M., Van Putten, J., Knoflach, C., Nachbauer, W.
University Innsbruck Introduction In the past years, high speed sports such as speed skating, cycling and skiing were extensively studied from the aerodynamic point of view (Chowdhury et al., 2010; Oggiano et al. 2009). A number of authors previously studied how surface roughness affects the drag of cylinders. The acquisition of the drag data was always carried out in wind tunnel experiments. One important drawback of wind tunnel measurements is the high costs. In this study results of a novel measurement device allowing exact and economic studies are presented. Method The linear measurement system primarily consists of a 25 m long guidance beam and a cylinder with a height of 60 cm and a diameter of 15 cm mounted on a carriage. The carriage runs on the beam on a guideway on four rollers and is moved by a high torque electro motor via light fibre cables. The linear guidance system is located in a cooling chamber that can be adjusted in the range of -30°C to 30°C. The distance from the cylinder to the carriage is 40 cm. The horizontal forces between the carriage and the cylinder are measured with two load cells and the position of the carriage is determined by an inductive length measuring system. The cylinder was covered with 2 different textiles. The drag force on the cylinder was measured at velocities from 5 to 20 m/s with a step size of 1 m/s with the linear measurement system and in an aeroacustic wind tunnel (Audi, Ingolstadt, Germany). Every textile was tested 10 times at each speed with the linear measurement system to also assess the reliability of the system and 2 times in the wind tunnel.
Results There is a good agreement between the wind tunnel data and the linear measurement system. The mean range of the 10 linear measurements is +/-3.6%. The reliability of the linear system was high with a correlation of 0.92. The range of the calculated cd value at the different velocities was +/-2.4% with the linear system. In the wind tunnel experiments drag forces at the relevant velocities were in the range of +/-10%. Discussion The results of this work show that it is possible to determine the drag coefficient exactly with the new system. Especially at low velocities it is advantageous compared to automotive wind tunnels given the large velocity range required for the latter. Therefore in future it will be possible to analyze the effects of textile surfaces on the drag coefficient with a new, exact and economic method. References Chowdhury, Alam F, Subic A. (2010) Proc. Eng. 2, 2517-2522 Oggiano L, Troynikov O, Konopov I, Subic A, Alam F. (2009) Sports Eng. 12, 1-12
THE EFFECT OF PLAYING LEVEL AND ENGAGEMENT METHOD ON FORCES GENERATED IN RUGBY SCRUMMAGINGPreatoni, E., Stokes, K.A., England, M., Trewartha, G.
University of Bath Introduction The scrum is an important phase of the rugby union game. During the scrum, players experience very peculiar biomechanical demands (high forces coupled with unstable balance) and repetitive mechanical stresses (Milburn, 1990; Preatoni et al., 2013), which may be a factor for both acute injuries and chronic degeneration of the spine. Since physical condition and technique likely play a fundamental role for both performance and injury prevention, the aim of this study was to analyse the effects of playing level and engagement conditions on forces generated in scrummaging. Methods Force measures were analysed as a function of: 6 playing levels (International, Elite, Community, Academy, Women and School), and 5 different engagement conditions (Hit&Hold, 3-Stage, FoldIn, 7+1 and 5+3). The different engagement conditions were designed in part to modify the loading conditions on players. Thirty-four teams participated in the study and performed 4-8 machine scrummaging trials for each of the 5 engagement conditions. A commercial scrum machine (Dictator, Rhino Rugby, UK), equipped with a bespoke force measurement system (Preatoni et al., 2012) measured the compression, lateral and vertical forces generated by the scrum pack. A set of parameters was selected to analyse applied forces in the subsequent phases of the engagement, from initial shock absorption to the sustained push. A mixed design ANOVA was used to assess main effects between and within groups and the playing level-engagement condition interaction. Results During the shock-absorption phase: (i) peaks of force (in all three directions) were lower in the FoldIn engagement than in the other conditions, and (ii) International and Elite teams produced higher peak compression forces than the other categories. For example, peak compression force ranged between 8.6 (2.0) kN for International and 4.2 (0.8) kN for School in the FoldIn engagement, and between 16.5 (1.4) kN for International and 8.7 (0.1) kN for Women in the Hit&Hold. Sustained compression force ranged between 8.53 (0.69) kN (International, 5+3) and 4.37 (0.15) (Women, 3Stage), with greater sustained push for International and Elite, and the FoldIn engagement producing higher sustained compression force than the other conditions (significant for 3-Stage and 5+3). Discussion This study provides a more comprehensive picture of the influence of playing levels and engagement conditions on contemporary scrummaging biomechanics. It also informs practitioners and governing bodies about biomechanical factors that may influence performance and injury prevention. References Milburn PD. (1990). J Sports Sci, 8, 47-60. Preatoni E et al. (2012). P I Mech Eng P - J Sports Eng Tech, 226(3/4), 266-273. Preatoni E et al. (2013).
Scand J Med Sci Spor, DOI:
10.1111/sms.12048. Acknowledgement Research funded by the International Rugby Board
THE EFFECTS OF GRADED SLOPES AND WALKING SPEED ON LOWER EXTREMITY MUSCLE ACTIVITYGierlinger, G., Christian, J., Schwameder, H.
University of Salzburg Introduction Walking on graded slopes requires exertion of greater forces across lower extremity joints. In the course of walking downwards, the knee joint absorbs up to 70 percent of the total negative work. This work is predominantly performed by the leg extensor M.
quadriceps which is also expressed in the increasing tractive patella tendon and quadriceps force. When walking uphill, the rates of the performed work are equally balanced by the ankle, knee and hip joint (Schwameder et al., 2005). Despite increased attention to effects of inclination on human gait during the last years, many questions remain unresolved. On this account, this study has the main purpose of shedding further light on the muscular response to walking on various inclination levels and increased walking speed. Methods Twentysix healthy male students with average age, height and weight of 25.4 (±2.5) years, 178.9 (±6.5) cm and 75.4 (±9.2) kg respectively, volunteered to complete this study. All participants were instructed to walk up and downhill on a treadmill at 4, 8 and 12 degrees and at walking speeds of 1.0 and 1.3m/s. Muscle activity was recorded of tibialis anterior (TA), soleus (SO), medial gastrocnemius (GA) and vastus (VA), medial (SM) and lateral hamstring (BF), rectus femoris (RF) as well as gluteus maximus (GL). Gait characteristics were obtained with Novel® Pedar insoles. Data was processed with a custom written Matlab® code and statistically analysed applying one-way ANOVA with repeated measures (Bonferroni, α=0.05). Results Significant differences were observed between ascending and descending inclination levels for all muscles regarding both mean activity and burst duration. During upslope walking, the mean activity of all muscles significantly and progressively increased from 4 to 12 degrees. GA revealed a significantly delayed activity onset and consequently decreased burst duration. With regard to BF, VA, RF and GL a significantly delayed offset and therefore increased burst duration was detected. However, when walking downwards the activity of BF set on significantly earlier while VA and RF revealed a tremendous increase in burst duration. The mean activity of VA and RF increased significantly at -8 and -12 compared to walking level. Between the walking speeds no significant differences were observed whether in terms of burst duration nor mean activity. Discussion The findings of the present study are in accordance with previously done research (Lay et al., 2007). It can be concluded that the extensor muscles namely SO, RF, GL, GA and VA responded most to the increase in inclination. TA, SM and BF however, served as co-contractors of the respective joints. When walking downhill, only the knee extensors absorbed the downwards moving body while the early onset of GA and BF evidently increases knee joint stability. References Lay A, Hass C, Nichols T, Gregor R. (2007). J Biom, 40(6), 1276-1285. Schwameder H, Lindenhofer E, Müller E. (2005). Sports Biom, 4(2), 227-243.
BIOMECHANICAL DETERMINANTS OF LONG-STANDING ADDUCTION-RELATED GROIN PAIN IN FOOTBALL PLAYERS.Kloskowska, P.1, Morrissey, D.1, Alty, J.2, Graham, J.1, Malliaras, P.1, Woledge, R.1 1: Queen Mary University of London, 2: Reading FC Background: Long-standing adduction-related groin pain (LSARGP) is common (Weir et al., 2011b). In football LSARGP accounts for 12%of all injuries (Ekstrand and Hilding, 1999, Werner et al., 2009). It is associated with high recurrence and prolonged time off sport (Weir et al., 2011a). Muscle activation and kinematic strategies in LSARGP are not well understood. The aim of this research was to better understand the kinematics and muscle activation in professional and amateur footballers with LSARGP. Methods: 20 professional (10 unilateral pain) and 19 male amateur (9 unilateral pain) footballers were recruited. Surface electromyography (sEMG) and 3D motion capture (CodaMotion) were applied during standing hip flexion (SHF). Analysis focused on gluteus medius (GM) versus adductor longus (AL) muscle activation ratio and kinematics of the hip joint in early, middle and end phase of SHF while standing on a symptomatic leg.
Results: GM vs AL ratio was significantly (p0.01) decreased in amateur but increased (p=0.02) in professional symptomatic athletes compared to matched control groups. Kinematic analysis of professionals with LSARGP showed increased abduction compared to control group, while symptomatic amateurs were more internally rotated and flexed compared to control group. Discussion: Opposite results in symptomatic professionals and amateurs might be explained by differences in rehabilitation. Professionals have access to treatment that might be focused on gluteal muscles, whereas amateurs may not all have rehabilitation and adopt alternative strategies to maintain pelvic stability. The results might also be explained by study limitations as participants were not matched nor controlled for symptoms chronicity or level. These findings have implications for rehabilitation of athletes with groin pain. References: EKSTRAND, J. & HILDING, J.
1999. The incidence and differential diagnosis of acute groin injuries in male soccer players. Scand J Med Sci Sports, 9, 98-103. WEIR, A., DE VOS, R. J., MOEN, M., HOLMICH, P. & TOL, J. L. 2011a. Prevalence of radiological signs of femoroacetabular impingement in patients presenting with long-standing adductor-related groin pain. Br J Sports Med, 45, 6-9. WEIR, A., JANSEN, J. A., VAN DE PORT, I. G., VAN DE SANDE, H. B., TOL, J. L. & BACKX, F. J. 2011b. Manual or exercise therapy for long-standing adductor-related groin pain: a randomised controlled clinical trial. Man Ther, 16, 148-54. WERNER, J., HAGGLUND, M., WALDEN, M. & EKSTRAND, J. 2009. UEFA injury study: a prospective study of hip and groin injuries in professional football over seven consecutive seasons. Br J Sports Med, 43, 1036-40.
08:30 - 10:00 Oral presentations OP-PM13 Molecular Biology [MB] 3