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COULD PLAYING SURFACE INFLUENCES CHANGE OF DIRECTION AND PERCEIVED TRACTION PERFORMANCE IN FUTSAL?
Get PDFThe purpose of this study was to identify differences on change of direction performance, perceived traction performance and available friction coefficient between two different futsal playing surfaces. Functional test and perceived traction evaluation were performed by twenty experienced male university level soccer players using slalom course on two different playing surfaces (area-elastic:AE and point-elastic:PE). Available friction coefficient (AFC) for each playing surface was mechanically measured using a hydraulic-powered moving force platform. In the functional test, participants were found to perform significantly better on PE when compared to AE surface (p\u3c0.001). PE surface was also found to have higher perceived traction performance (p\u3c0.001). It was suggested that significantly higher AFC observed on the PE surface compared with AE surface (p\u3c0.001) may contribute to the observed findings. This study succeeded in demonstrating the performance of change of direction run was significantly influenced by the playing surface traction and frictional properties
A VALIDITY STUDY COMPARING XSENS WITH VICON
Get PDFConducting on-field measurements is warranted to investigate and reduce real-world anterior cruciate ligament (ACL) injury risk. However, validation is first warranted to ensure how Xsens relates to Vicon. The purpose of this study was therefore to compare lower extremity kinematics from Xsens with Vicon. Ten recreational ball team sport athletes (5 females, 5 males) were included, who performed isolated and dynamic movements. Strong correlations were found for movement patterns (\u3e0.7) for the isolated as well as the dynamics movements. However, absolute joint angles differ between both systems (ranging from 0.7º - 14.5º). This should be considered when using Xsens in an applied sport setting as drawing conclusions for being or not being at risk for ACL injury may depend on the system used. A major strength of this study is the inclusion of movements that are restricted to one plane and one joint as well as dynamic high-intensity movements resembling movements which occur in sports (e.g. change of direction). This analysis of methods of data collection leads to further advancement of knowledge the science of biomechanics in applied sports setting
ECCENTRIC HAMSTRING STRENGTH IN CLUB GAELIC FOOTBALLERS.
Get PDFThe purpose of this study was to investigate the eccentric hamstring strength of Gaelic footballers during the season. The Nordic hamstring exercise was used to determine maximal hamstring eccentric Torque using the Nordbord testing system™. A total of 67 players were tested in pre-season as described previously by Opar et al. (2013). Injury data was recorded directly via questionnaire from each participant. 117 players were tested in the preseason, 98 in the in-season and a combined total of 67 players tested in both in-season and pre-season and included in the study. There was no difference in eccentric torque for in both preseason (121±25 v124±27, p\u3e0.641) and late in-season (124±29 v 128±22, p\u3e0.7997) when comparing injured and non injured groups. A previous hamstring injury produced a 32.88 RR. In club Gaelic footballers pre-season eccentric strength in the Nordic exercise is not a pre-requisite for the prevention of future HSI while previous HSI is a strong risk factor
BIOMECHANICAL DIFFERENCES BETWEEN TAI-CHI PRACTICING AND ACTIVE ELDERLY DURING THE STAIR-TO-FLOOR TRANSITION
Get PDFLong-term Tai-Chi practitioners tend to have similar movement to healthy adults and exhibit movement strategies that reduce fall risk during stair-to-floor transition. We aimed to assess the differences during stair descent to ground in Tai-Chi elderly practitioners and active elderly. Fourteen regular Tai-Chi practitioners and fourteen active elderly participated. Whole-body kinematics and ground reaction forces (GRFs) were recorded synchronously by using motion analysis and a force platform. A t-test was used to test the differences between the groups. Both descent and forward walking step length and center of mass (COM) velocity, both horizontal braking and propulsive force and impulse, ankle range of motion (ROM) and total work in the sagittal plane, and maximum hip moment in the frontal plane had significant differences. Our results appear to support the benefits of long-term Tai-Chi training during the stair-to-floor transition
LANDING KINEMATICS AFTER A SPORT-SPECIFIC TASK IN TEAM HANDBALL
Get PDFCurrently, screening for ACL injury risk is mostly conducted in a laboratory setting using a drop vertical jump. There remains a lack of knowledge on lower extremity kinematics and injury risk during sport-specific landing movements. Therefore the purpose of this study was to describe the landing kinematics of elite female handball players after a jump shot in a sport-specific field test. Players’ 3D knee and trunk angles were measured using inertial sensors during landing from a jump shot. Average knee flexion at initial contact (IC) was 19.7° ± 5.9 and range of motion (ROM) was 26.2° ± 14.9. Significant between-player differences for all joint angles at IC and ROM were observed. As a variety of landing strategies were utilised, the question arises whether the drop vertical jump test in the lab setting is ecologically valid for identifying ACL injury risk in the field
PLANTARFLEXOR ELECTROMECHANICAL DELAY: INFLUENCE OF CONTRACTION TYPE AND MUSCLE-TENDON UNIT LENGTH
Get PDFElectromechanical delay (EMD) is an important determinant of explosive neuromuscular performance. Factors such as muscle contraction type and initial muscle-tendon unit (MTU) length influence this delay period. The aim of this study is to compare differences in EMD from plantar flexors across different contraction modes and MTU lengths. EMD of physically-active individuals (n = 14) was assessed during a series of twitch and explosive isometric plantarflexions across different MTU lengths. For involuntary and voluntary explosive conditions, EMD tended to decrease while the MTU length increased from plantarflexion to neutral/dorsiflexion. No significant differences in EMD were observed between neutral and dorsiflexion MTU lengths. These results have implications for sporting performance where the ability to rapidly produce muscular force is crucial
THE BALL ORIENTATIONS USED BY PLACE KICKERS AT THE 2019 RUGBY WORLD CUP AND THEIR ASSOCIATIONS WITH KICK SUCCESS
Get PDFThe outcomes of place kicks can have a large impact on Rugby Union match results. This study investigated the ball orientations used in place kicking and their potential implications for success. All 416 place kicks from the 2019 Rugby World Cup were grouped into one of three ball orientation categories, and predicted odds of success were calculated for each category using a binomial logistic regression which accounted for situational factors known to affect performance outcome. Kicks taken using a slanted orientation (n = 152) had the greatest odds of success (90.0%) when taken from the mean tournament distance (29.7 m), compared to a near vertical (n = 116) orientation (84.4%), and near horizontal (n = 148) orientation (86.8%). A further investigation into the impact characteristics associated with each ball orientation is required to better understand the relative merits of each
DIFFERENCES IN REACTION FORCE-TIME CHARACTERISTICS EXPERIENCED BY FEMALES WHEN RUNNING ON A TRACK AT DIFFERENT SPEEDS
Get PDFElite collegiate runners are susceptible to sustaining lower extremity stress related injuries. Ground reaction forces (GRFs) were analyzed to understand differences in mechanical loading at steady state 5.5 and 7 min/mile paces. We hypothesized GRF magnitudes would increase with speed while horizontal GRFs during braking would be unique to each participant. GRFs, inertial measurement units, and high speed video were collected during outdoor over ground running. Group differences were observed that were not always significant within participant. As speed increased, average horizontal GRF during braking (-0.25 to -0.29 BWs) decreased while peak vertical GRF increased (2.75 to 2.91 BWs). The unique pattern of the sagittal plane resultant GRF orientation was maintained during initial braking phase which may indicate this orientation is a nervous system control priority
ESTIMATION OF GROUND REACTION FORCES DURING RUNNING USING INERTIAL MEASUREMENT UNITS AND ARTIFICIAL NEURAL NETWORKS
Get PDFThe purpose of this study was to develop a system to estimate ground reaction forces during running using inertial measurement units and artificial neural networks. Kinematics of the pelvis and feet and ground reaction forces were measured using an inertial measurement system developed by Casio and Kistler force plates from seventy-nine runners (57 males and 22 females). Two long short-term memory based neural networks were used to estimate the instants of foot-strike and toe-off, and anteroposterior and vertical ground reaction forces from the triaxial accelerations and angular velocities measured by inertial measurement units fixed to the pelvis and foot of support leg. Although there are some limitations due to the small sample size, the results of this study showed the potential of estimating the ground reaction forces during running using a small number of inertial measurement units and artificial neural networks
EFFECT OF MENTAL DEMAND ON KNEE FORCES IN PROFESSIONAL YOUTH SOCCER PLAYERS
Get PDFSoccer is one of the most popular sports all around the world. It is an injurious type of sport with a focus on lower extremities and high psychological pressure during matches. The stressor is linked with injuries and an increased musculoskeletal loading. This study investigates the influence of cognitive stress on the load profile of the knee joint. Twelve professional youth soccer players performed highly dynamic runs with and without additional cognitive stress. The runs were analysed with a musculoskeletal simulation software. The data analysis shows no difference in knee joint reaction loading under additional mental stress compared to the baseline. Yet running times are significantly lower in the baseline. While there is no increase in the joint loads, the running times indicate an altered movement behaviour when the subjects are exposed to additional mental demand