15:40   Poster Session
E-KAYAK: A WIRELESS DAQ SYSTEM FOR REAL TIME PERFORMANCES ANALISYS
Stefano Bifaretti, Vincenzo Bonaiuto, Luca Federici, Massimo Gabrieli, Nunzio Lanotte
Abstract: The performance of kayak athletes depends strongly on their paddling technique. This can be evaluated by means of video and biomechanical analysis as well as by measuring several kinematic and dynamic parameters. Kinematic parameters include speed, acceleration, intracyclic velocity, roll and pitch of the boat. Dynamic parameters include stroke frequency, force acting on paddle and foot brace, symmetry between right and left paddle, synchronization between forces. Availability of these measurements, both during the training session and after it for a more detailed analysis, can help coaches and athletes spot technical flaws and improve performance. The paper presents E-kayak, a new multichannel wireless real time data logger for race kayaks. The system includes a high frequency (10Hz) GPS receiver, a 6 DoF (three linear accelerometers and three gyroscopes) Inertial Motion Unit (IMU) and two conditioned force channels for paddle and foot brace. It synchronously acquires data from all channels, elaborates them on a microprocessor and sends them via Bluetooth to an Android smartphone placed on the cockpit of the kayak. Here a purpose-built app receives the data, stores them on a flash memory and presents some of the main parameters (time, speed, stroke frequency, force symmetry) in real time to the athlete. At the end of the training session, data can be displayed on the smartphone or downloaded to PC for further analysis. In the final release of this paper data from a training session will be presented and discussed.
ADAPTIVE SENSOR DATA ACQUISITION FOR GAIT ANALYSIS
Wolfgang Kilian, Markus Hill, Stephan Odenwald
Abstract: In this paper we present a method that uses one sensor configuration for both static and dynamic loading conditions to capture plantar pressure distribution values. We show that it is possible to develop a measurement system which is capable to capture data in different measurement ranges with equal resolution. It is possible to switch between the different required ranges in gait analyses without changing the hardware. As an example we are using a standard pressure sensor for gait analyses. In gait analysis two phases are mainly distinguished, namely stance and swing. Though, during the stance large static pressure with small changes occur, whereas in the swing a high dynamic range is needed to acquire the measured values. As stated in the literature, the pressure measurement for both phases is equally interesting. Thus, the system must be capable of measuring a small area of interest and also the full range. With analog digital converter (ADC) directly connected to a standard amplified sensor the available resolution is fixed to the maximum pressure range and the available effective resolution for smaller pressures are frequently not sufficient. To increase the measuring range resolution, it is possible to use different amplifiers. In practice, that means that the hardware needs to be replaced every time for each new measurement. We propose the use of a programmable amplifier with integrated ADC. With such devices it is possible to measure both gait phases without changing any hardware. Highly integrated solutions are already available on the market. To achieve the stated different areas of interest we are using such a three-stage amplifier - each stage with programmable gain and offset. With this solution we are able to adapt the full resolution of the measurement system dynamically to the needs of the gait analyses. In the paper we will compare a standard measurement system with our adaptive solution and show, that it is possible to advance the effective resolution without adding too much complexity to the measurement system.
AN INTELLIGENT, WEARABLE AND MODULAR SENSOR-ACTUATOR INSOLE LABORATORY
Markus Hill, Bernadett Hoena, Wolfgang Kilian, Stephan Odenwald
Abstract: In this paper we present a modular sensor system for monitoring pressure distribution, 3D-accerleration, gyroscope, temperature and humidity in a shoe insole. The intelligent sensor-actuator-insole is a newly developed product for use in medical and sport related fields. Integrated sensors record physical parameters such as acceleration and pressure while actuators stimulate areas of the foot in multiple directions. Using smart electronics, the actuators can operate in real time based on the obtained data. The combination of individual miniaturized systems, wireless data transmissions to mobile terminals and usage of rechargeable battery allow a wide field of application like fall prevention, training analysis and motion optimization. Through robust and miniaturized electronic components and wireless communication technology data can be processed in real time. Measurement data can be stored locally on the measurement device for later analysis, as well as visualized on connected mobile devices like smartphones or tablets. In addition to the application under laboratory conditions the main aim is the use of hardware and software as a mobile and easy-to-use lab. In medical field applications like gait- and running analysis outside the laboratory, wound prevention, fall prophylaxis and activity monitoring in the home environment are possible. We will show that we can attach completely different kind of sensors to the mobile measurement system without changing the main hardware. Due to the high performance of the system, the data pre-processing can already be performed on the embedded system. Because the system supports WiFi, it is possible in a very simple way to combine several of these systems together to form a sensor network. Furthermore, it is possible to transmit the collected data in a cloud. The measured data are provided in different levels of complexity. The system is able to evaluate the data automatically and provides the results to experts like doctors and coaches.
THE DESIGN AND DEVELOPMENT PROCESS FOR A NOVEL TECHNOLOGY CAPABLE OF PROVIDING A NEW SHOCK ATTENUATING SPORTS SURFACE
Alexander Walker
Abstract: Main Research Question(s) Lower limb loading rate is a major contributor to athletic injury because it represents the stress being absorbed by an athlete’s lower limbs that makes them vulnerable to stress fractures, as well as knee and ankle joint injuries. This research sought to identify a means by which the loading rate could be reduced and therefore the risk of overloading injury reduced. A sports surface that encourages elastic deformation during contact in both the horizontal anterior-posterior direction and the horizontal medial-lateral direction through a process of horizontal deformation and displacement may result in reduced foot and limb loading. This surface should maximise horizontal energy attenuation in order to reduce the risk of injury while at the same time provide satisfactory energy return to avoid player fatigue. Research Method Effective product research and development methods centre on the ways in which the activities can be effectively planned, controlled and implemented. The process can be regarded as a sequence of activities and decisions which progress a problem solving process from the initial identification of the problem, through to a final implementable design solution. The process of design is fundamentally an iterative method, which comprises the articulation of the problem which is to be solved, collecting and codifying pertinent information, the divergent exploration of potential problem solutions, convergence towards a favourable solution, and finally, the detailed implementation and optimisation of the design solution. Results, Conclusions and General Significance The creative process followed, has resulted in the design of a novel, and commercially improved modular plastic tile sports surface system. This has been realised through the development of an innovative, sustainable, shock attenuating tile and connector geometry, used in conjunction with braking-force reducing dampening elements, which aim to reduce braking forces on the surface to acceptable levels, and thus reduce the risk of athlete injury. This research is significant as currently no sports court surface exists which specifically targets horizontal force reduction as a means to reduce injury rates.
THE MOST UTILIZED ROTATION AND TRACTION MOVEMENT WHILE IN BALL-POSSESSION AMONG INTERNATIONAL FUTSAL PLAYERS
Shariman Ismadi Ismail
Abstract: The objective of this study was to identify the most utilized rotation and traction related movements among international futsal players when they are in a ball possession situation. A total of 4 matches from The AFF Futsal Championship 2014 were analyzed. The analyzed matches consist of two semifinal matches, 3rd-4th placing match and the final match. There are four indicators for rotation movement (half-trunk rotation, half-body rotation, quick-half trunk rotation, and quick-body rotation) and four indicators for traction movement (front traction, back traction, side traction, and sudden stop) that are selected to be observed in this study. Each indicator was divided into two categories, which are attacking and defensive mode. All matches were recorded using a full high definition video camera and analyzed using SportCode Elite (v. 10) and Dartfish EasyTag (v. 1.0.8) software. Two trained and experienced analysts were assigned to analyze all 4 matches. Inter- and Intra- analyst reliability study was also performed in order to examine the content validity of the data obtained. Overall results indicated that the front traction during the defensive mode is the most utilized movement, among others, while back traction during the attacking mode is the least utilized movement. Front traction during attacking mode was found to be the highest number of usage during attacking mode while sudden stop traction during defensive mode is the least utilized movement among other defensive movements. Regardless of attacking or defensive mode, results show that front traction is the most utilized movement, followed by half-trunk rotation and side traction. This study also shows that the rotation (47%) and traction movements (53%) utilized during competitive games are quite balanced. A similar result was also obtained when comparing between attacking (46%) and defensive mode distribution (53%) from overall data. Further study on futsal games should focus on the most utilized movement during competitive games to understand more about the nature of the games.
MODELING OF THE PERFORMANCE AND BIOMECHANICS IN THE 100M DASH: COMPARISON OF THE WORLD AND EUROPEAN RECORDS
Tiago Barbosa, Pedro Forte, Daniel Marinho, Victor Reis
Abstract: The aim was to model the performance and biomechanics of the World and European records at the 100m dash in Athletics. At the time of this research, the World record was hold by Usain Bolt (Jamaica, 1.96m, 94kg) with 9.58s (wind: +0.9m/s) and the European record 9.86s (wind: +0.6m/s) by Francis Obikwelu (Portugal, 1.95m, 80kg). The modelling of the performance was done based on a quasi-physical model that includes the drive term (start), propulsive term (rate of deceleration), velocity term (maximal speed) and drag term (resistance). The speed-time or speed-distance raw-data was retrieved online. The biomechanical assessment included the measurement of the kinematics from video analysis (contact time, flight time, stride frequency, stride length) and the estimation of the kinetics based on a spring-mass model (change in the centre of mass vertical displacement, change in the leg’s length, maximal ground reaction force, vertical stiffness, leg stiffness) for every 20m splits. Mann-Whitney U rank tests and Cohen’s d were also run to compare both races. Obikwelu showed a slower start (drive term) and Bolt a lower rate of deceleration over the race (propulsive term). The drive term took 2-3 extra meters for Obikwelu. The velocity and drag terms were higher for Bolt. On the event of no wind, Bolt would have had delivered the time of 9.62s and Obikwelu 9.89s. Bolt showed a higher stride frequency (P=0.03, 2.33≤|d|≤2.51), stride length (P=0.02, 4.22≤|d|≤3.46) but shorter contact time (0.01≤P≤0.14, 0.84≤|d|≤5.77) than Obikwelu. The ground reaction force was higher for the Jamaican over most of the race (0.01≤P≤0.02, 0.13≤|d|≤5.72; Bolt:3.68-4.23BW; Obikwelu:3.65-4.06BW). Obikwelu displayed higher changes in the body vertical displacement by 0.5cm and leg’s length by 5-10cm. The vertical (0.02≤P≤0.04, 1.46≤|d|≤11.55) and leg (0.02≤P≤0.03, 1.43≤|d|≤10.64) stiffness were higher for Bolt over most of the race but the last 20m split. Based on this approach it is possible to deliver useful and comprehensive information on the sprinters’ performance and main determinants a few minutes after the end of the race. E.g., in comparison to Obikwelu, Bolt showed a more efficient reutilization of elastic energy and neuromuscular response that was due to his kinematic behaviour, both having an impact on the performance delivered.
ANALYSIS OF THE AERODYNAMICS BY EXPERIMENTAL TESTING OF AN ELITE WHEELCHAIR SPRINTER
Tiago Barbosa, Pedro Forte, Jorge Morais, Eduarda Coelho
Abstract: The aim was to compare the aerodynamics of an elite wheelchair racer, keeping different body positions. The subject was a male wheelchair sprinter competing in the T52 category being at the time of this research an European medallist at the 100m event and ranked 2nd in the world. The coast-down technique was selected as experimental procedure to assess the aerodynamics. The wheelchair racer was invited to perform 3 sets of 8 repetitions at different speeds, randomly assigned. He was advised to perform one lap on the track per repetition, reaching the end of the last curve, before the finish line, should stop performing stroke cycles so that the speed decay would be measured by Doppler-effect (Stalker Pro, Stalker Radar, Texas, USA). The 3 sets were done keeping the: (i) torso in the upright position on the wheelchair; (ii) torso in the racing position (i.e. trunk bended in the horizontal position) and neck in hyperextension (so that the trailing edge of the helmet would be pointing backwards); (iii) racing position but the neck in flexion (i.e. trailing edge of the helmet pointing upwards). Surface area of the racer plus chair was measured by a photogrammetric technique (UD Ruler, AVPSoft, USA). It was computed the effective surface area (ACd), power to overcome drag (Pd) at his national record pace in the 400m (6.298m/s) and coefficient of rolling friction (CR). The ACd in the upright position, racing position with helmet pointing upwards and backwards was 0.1747, 0.1482 and 0.1456m2 , respectively. The CR was 0.00119, 0.00489 and 0.00618 for the upright position, helmet pointing upwards and backwards, respectively. The Pd was 26.62, 22.59 and 22.19W for the same positions, as well. This makes that in comparison to the racing position with helmet pointing backwards, the power was 1.75% higher having the trailing edge pointing upwards and 16.64% in the upright position. As a conclusion, the resistance acting upon the sprinter is different according to his position on the chair. Slight changes in the head position over the race can affect by almost 2% the power output. So, athletes should beware of this, keeping a good body alignment all the time.
AN ASSESSMENT OF POSTURAL SWAY IN BALLET DANCERS DURING FIRST POSITION, RELEVÉ AND SAUTÉ WITH ACCELEROMETERS
Christopher Hinton-Lewis, Elle McDonough, Gene Moyle, David Thiel
Abstract: Classical ballet is a performance art where unintentional and uncontrolled movement degrades the aesthetic. Vertical torso movement can induce body tilt. Postural sway was measured in pre-professional ballet dancers when performing simple vertical movements. 47 pre-professional dancers (5 males and 42 females, mean age in years = 19.2, SD= ± 1.3) on a full time undergraduate dance program were asked to stand in first position and perform a demi-plié, a relevé and a sauté. These movements were performed in a continuous cycle undertaken 15 consecutive times. The first 5 cycles were undertaken as practice. The second set of 5 cycles were recorded with the arms held in Bras bas, with the final 5 having the arms held in 5th position (rounded arms placed above the head). Accelerometers were attached to the lumber spine (L4) and thoracic spine (T1-T2). The tilt during the demi-plié prior to the sauté and relevé increased significantly for both arm positions. The male participants preparative angle change was much larger than the female participants (p = 0.07). No significant angle change was observed between the Bras bas and arms in 5th position for the sauté but the change is significant for the relevé (p = 0.007). Exaggerated forward tilt is undesirable both aesthetically and biomechanically. Small accelerometer sensors on the spine can allow self-monitoring practice of these basic classical ballet movements.
DEVELOPMENT OF A PARAGLIDE CONTROL SYSTEM FOR AUTOMATIC PITCH STABILIZATION TO INCREASE THE PASSIVE SAFETY
Julian Obergruber, Lars Mehnen
Abstract: Paraglider wings tend to collapse when entering a low angle of attack. Since a collapse destroys the airfoil and restricts the controllability as well as ability to carry a mass, the resulting state is endangering the life of the paraglider pilot. Therefore the aim of this project was to develop a stabilization system, which is able to automatically stabilize the pitch axis/movement of a paraglider wing in order to avoid critical angles of attack, hence decreasing the risk of a resulting front collapse. The movements of the paraglider are measured using a 6 DOF-sensor and a microcontroller unit. This system detects the orientation angles (yaw, pitch, roll) and the rotation rate of the pitch axis. It is located at low end of the C-risers of the paraglider (attachment point of lines connected to the wing). Increased forward pitch movements (overshooting), are being detected during flight and critical pitch values activate two linear actuators located in the harness of the pilot, pulling the D-risers (lines that can be used to control the angle of attack similar to the brake lines) of the paraglider wing to a predefined length at the correct moment and until the overshooting is stabilized. This automatically prevents critical flight situations without the need of the pilot's intervention. To evaluate the system artificially induced overshooting manoeuvres with and without the stabilization system were induced and pitch values were compared. The results showed a distinct influence of the system on the pitch behaviour of the wing. An effective stabilization of the pitch axis of a paraglider wing could be shown. This project should be regarded as a feasibility study for an electronic stabilization system for paragliders. It could be shown that with such systems it is possible to increase the safety of paragliding pilots.
COMPARISON OF 'PLAIN CONDITIONS' AND 'CLOSE-TO-REALITY CONDITIONS' FOR EVALUATION OF BIOMECHANICAL LOAD SPECTRA OF HANDBALL SHOES
Dominik Krumm, Anne Gläser, Gert Schlegel, Stephan Odenwald
Abstract: The purpose of this paper was to compare two different testing conditions during the acquisition of biomechanical load spectra for handball shoes. Subjects performed two typical handball activities, i.e. feints and jump shots, either under ‘plain conditions’ (group I) or ‘close-to-reality conditions’ (group II). While subjects of group II performed their tasks with a handball and an obstacle in front of them that simulated a defense player, subjects of group I performed their tasks without any additional items. In total, 19 experienced amateur handball players provided written informed consent and participated. Kinematics and kinetics were recorded using an optoelectronic measurement system and a force plate. Biomechanical load spectra, which can be used to synthesize mechanical simulations for characterization of handball shoes, were evaluated from normalized vertical ground reaction forces, forefoot bending angles and temporal spatial parameters. Statistical tests such as one-way analysis of variance were conducted to test for significant differences between both groups. The results showed that the mean of maximum vertical ground reaction forces between both groups was significantly different for feints (2.2 body weight vs. 2.5 body weight) and jump shots (2.7 body weight vs. 3.1 body weight) with higher values for group II. The maximum bending angles during feints were not significantly different (17.6° vs. 17.2°), whereas the angles during jump shots were significantly different between both conditions (32.2° vs. 22.2°). In conclusion, subjects of group II showed higher effort in performing their tasks compared to subjects of group I. Therefore, the authors suggest that the acquisition of biomechanical load spectra should be performed under real conditions or at least ‘close-to-reality conditions’.
PARAMETRIC ANALYSIS OF THE INFLUENCE OF ELASTOMERIC FOAM ON THE HEAD RESPONSE DURING SOCCER HEADING MANOEUVRE
Mohd Hasnun Arif Hassan, Zahari Taha
Abstract: Soccer is a unique game that permits the purposeful usage of the head in directing the ball. A lot of studies have coupled heading in soccer with brain trauma injury. This has led to the introduction of various protective headgears for soccer players. Nonetheless, studies have shown that these headgears are only beneficial in head-to-head impact, but none are useful in reducing the risk of sustaining a brain injury due to a soccer heading manoeuvre. The purpose of this study is to evaluate the influence of an elastomeric foam on the head response due to soccer heading manoeuvre by means of the finite element analysis. Validated FE models of soccer ball and human head were used to perform FE analysis of soccer heading. A layer of soft foam was added on the forehead to represent the protective headgear. The foam was defined using hyperfoam material model. A parametric study was conducted to investigate the impact of each material coefficient and foam density on the head response due to soccer ball heading. The results obtained show that an elastomeric foam alone is not able to mitigate the impact caused by soccer heading. Further work on the design of the headgear is needed to look for an optimal impact mitigation strategy.
SEAT OPTIMIZATION FOR SINGLE HANDED PARALYMPIC SAILING BOAT
Karen van Stein Callenfels, Martijn van der Ent, Monique Berger
Abstract: Abstract PURPOSE: The aim of this study was to optimize the seat for the skipper of a 2.4mR, a Paralympic class sailing boat (single-hander). Primarily, the seat was designed for a man with diastrofic dysplasia, a disorder of cartilage and bone development. This 39 year old man has a short stature with very short arms and legs and joint deformities which restrict movement. The skipper’s main tasks are handling the rudder and the mainsheet using small ropes with his hands and pedals with his feet. He is sitting on a seat attached to the floor of the boat, while his body is positioned facing the bow of the boat. The combination of movements of the boat and tasks during sailing resulted in a constantly changing instability of the body. This might declare some of the injuries (pain in hips, knees and shoulders) that were called. The design goal for the seat was to find an optimum in body stability and range of motion during sailing. METHODS: An analysis of the possible movements of the skipper and the boat was made using a mock-up of the frontal and sagittal plane. A movement analysis of sailing was made in three boat conditions: 1. boat heeling 32° (sailing close hauled); 2. No boat heeling (reaching), bodyweight in front of the seat; 3. No boat heeling (reaching), bodyweight at the back of the seat. A biomechanical analysis was made in order to estimate the forces on the body. An iterative design process was followed which resulted in different prototypes and finally in a new seat. RESULTS: The main requirement on the seat is that it should prevent sliding on the seat in the frontal plane, especially in condition 1. Then, a friction coefficient of 0,63 is needed. Three prototypes have been build and tested. The final design consists of an aluminum three sided seat and a backrest which stabilizes the body. The seat can slide 19 cm forwards and backwards. CONCLUSION: The third prototype has been tested in the lab and on the water. Freedom of movement and stability were enhanced. The prototype is further developed and applied for different paralympic sailers and sailboats.
PERFORMANCE ANALYSIS IN STRENGTH TRAINING: AN INNOVATIVE INSTRUMENTATION
Zahari Taha, Chei Ming Lee, Nizam U Ahamed, Saju Joseph, Syed Faris S Omar
Abstract: In strength training, performance of the athletes varies according to different objectives of the training. In this study, the performance of the athlete in strength training is defined as the torque and power generated to lift given loads. Electromyography (EMG) is utilized during the performance assessment to prevent muscle injuries. In the past few years, athletic and clinical testing on performance analysis and enhancement have traditionally taken place in laboratory due to low portability of the equipment. With the rapid development in electronics miniaturization, instrumentation for such data acquisition can be constructed in mini and micro scale. Miniaturized instrumentations are designed to be unobtrusive to athletes’ movement during performance analysis and enhancement. On the other hand, correlation between muscle activity and real-time data for performance assessment is critical for coaches and physiologists. With the help of a miniaturized system that has the ability to correlate the muscle activity with performance, fatigue, impulse and total energy expenditure, coaches and physiologists can plan the most suitable training for athletes in order to achieve higher performance. In conclusion, this study focuses on the miniaturized instrumentation for the analysis of athletes’ performance in strength training.
CORRELATION BETWEEN ARCHERS’ ARM MOVEMENT WHILE SHOOTING AND THEIR SCORES
Zahari Taha, Jessnor Arif Mat-Jizat, Edin Suwarganda, Syed Faris Syed Omar
Abstract: In archery, the most critical time is a few seconds before the release of the arrow because the trajectory of the released arrow is dependent on the movement of the archer’s arms in the release phase. An archer use’s two hands while drawing a bow, one hand to push on the bow riser and the other to pull the string. The archer’s performance can be quantified through the analysis of the movement of both the archer’s arms while releasing the arrow. In this paper, a study of the arm movement of an archer while shooting using recurved bow is presented. In the experiments, university level archers shot six arrows per frame and each archer shot three frames each whilst wearing a dedicated small sized accelerometer in both arms. The generated data, in terms of linear acceleration, was streamed in real time to a computer wirelessly via Bluetooth. The sampling rate of the accelerometer was about 15Hz. The forward-reverse, up-down, left-right motion of both arms as well as the score and the position of the arrow of each shot were recorded. A high score category is when an archer shot ten, nine, and eight points while three, two, and one points score is a low score category. The analysis of the data showed a correlation between the archers’ arm movement and their score. Although the arm movement generated a similar displacement pattern for a higher score and a lower score, a high bow arm’s movement in transverse plane upon releasing the string may lead to a lower score.
PRELIMINARY INVESTIGATION OF AN INNOVATIVE DIGITAL MOTION ANALYSIS DEVICE FOR BADMINTON ATHLETE PERFORMANCE EVALUATION
Zahari Taha, Mohammad Syawaludin Hassan, Hwa Jen Yap, Wee Kian Yeo
Abstract: Badminton is a sport that requires the combination of several different physical features. At a professional level, the sport demands excellent fitness criteria namely the player’s aerobic stamina, agility, strength, speed as well as precision. This study fundamentally entails the development of an innovative training system that incorporates technology that could improve the athlete’s performance. This system uses a combination of two Kinect, and relevant sensors that are required to capture essential parameters for badminton analysis such as the motion detection, as well as the acceleration of the player. The training system can be used by the coach and/or biomechanics to analyse the performance of the athletes. The motion detection of the athlete is captured by means of Kinect skeleton tracking algorithm that tracks up to 20 joints of the body including their x-axis, y-axis and z-axis coordinates. The kinematics of the upper limb are required to evaluate the skeleton tracking by the Kinect. An external device (a miniaturised Bluetooth, 6 DoF accelerometer and microprocessor) attached at the right-hand wrist is used to measure the motion of the hand. The data are transferred via Bluetooth to an Android-based tablet device. The skeleton’s angular acceleration obtained from the tracking algorithm is found to be in good agreement with the measurements taken from the accelerometer. In addition, the acceleration results acquired from the device attached to the wrist shows promising results in enabling pattern recognition of different badminton strokes.
EXPERIMENT OF AERODYNAMIC FORCE ON A ROTATING SOCCER BALL
Sungchan Hong, Ryosuke Nobori, Keiko Sakamoto, Masaaki Koido, Masao Nakayama, Takeshi Asai
Abstract: In recent study, trajectory analysis and wind tunnel experiments were used to glean information for comparing the non-spin aerodynamics of various soccer balls. However, for rotating soccer balls, only a few studies are available which present aerodynamic force coefficients. In some of these studies only Magnus data is given, as the drag coefficient was strongly increased by the flow interference of the driving rod. As all of them show, to a great extent, support interference due to the penetration by shafts or by wires at the ball equator, and as the results disagree among each other, the measured force coefficients as a function of Reynolds number and spin parameter cannot be considered as reliable. Such data are, however, needed to gain a better understanding for ball trajectories encountered in today's game of soccer. The experimental set-up used to determine the aerodynamic coefficients of non-rotating and rotating soccer balls for a broad range of Reynolds numbers and spin parameters, with soccer ball halves replacing the hemispheres. The experimental arrangement consisted of a prototype model soccer ball (diameter 220 mm) mounted on an L-shaped sting.
DEVELOPMENT OF A NEW METHOD FOR MEASURING QUASI-STATIC STIFFNESS OF SNOWBOARD WRIST PROTECTORS
Caroline Adams, David James, Terry Senior, Tom Allen, Nick Hamilton
Abstract: The upper extremity is frequently reported as the most common injury site in snowboarders. During falls snowboarders often put their arms out to cushion their fall. This can result in a compressive load being applied through the carpals which coupled with hyperextension can lead to wrist sprains or fractures. In an effort to reduce the incidence and severity of such injuries, a call has been made to implement an international standard that specifies minimum requirements wrist protectors should meet. EN 14120:2003 prescribes requirements that roller sports wrist protectors should meet and has been identified as a starting point for a snowboarding specific standard. This paper critiques the EN 14120:2003 test and describes a new method for testing the stiffness of wrist protectors. The proposed bending test in the standard is fundamentally flawed. The standard deems that guards are suffciently stiff if the hand angle is between 35°-55° when 3Nm is applied, however using the test method prescribed in the standard angles greater than 45° cannot be measured. Furthermore the standard does not provide sufficient dimensions for the test prosthesis, nor does it take into consideration parameters such as strapping tightness and loading rate. The newly developed method utilises a bespoke rig mounted to a uniaxial test machine (Instron 3367) enabling the application of a quasi-static load at a constant rate (200mm/min). The prosthesis arm is mounted to the rig and wrist protectors fitted to the arm at a consistent strapping tightness. The bending moment is applied to the wrist by transferring the load from the uniaxial load cell via a galvanised wire rope through a low friction pulley. The hand movement is measured throughout the test to determine the wrist extension angle across a range of bending moments. The bending moment is calculated based on the load cell output. The developed test provides a new and repeatable way to determine the stiffness of snowboarding wrist protectors.
MAINTENANCE OF ARTIFICIAL TURF – PUTTING RESEARCH INTO PRACTICE
Prateek Sharma, paul fleming, Steph Forrester, Jon Gunn
Abstract: Artificial turf is successfully utilised around the world for many sports and many levels of performance and competition requirement. Enhanced quality assurance systems for elite and community (UK) level demand effective maintenance programmes to ensure adequate play performance, with increasing regulation. Past research is, however, very limited in this important aspect of artificial turf science. Practical experience has been relied on to develop a range of maintenance techniques to sweep, clean, replace and repair artificial turf carpets and infills. However, validation of these techniques is yet to be comprehensively undertaken and reported. The authors have collaborated with an industry maintenance provider on a 4 year research programme, focussed on measuring the effectiveness of common maintenance practice. This paper presents an overview of the most important outcomes. The data presented describe the findings of detailed studies into power-sweeping, decompacting, and decontamination, and describes their specific effects against the backdrop of temporal pitch monitoring of changes in play performance over several years. These field data provide a unique insight into the short-term and long-term benefits of intervention processes. The data permit quantitative analysis of key issues such as: the build-up of contamination that clogs infill and can lead to flooding; infill compaction under player loading and how this affects the system hardness; and how loss of fibre resilience influences ball roll behaviour. These mechanisms and their mitigation are discussed in light of the developing understanding of the science of artificial turf sport surface system behaviour. The results demonstrate that, for example, the monthly power-brushing of a surface may effectively reduce the rate of build-up of contamination by more than 1% per year. This alone can potentially add several years’ life to a sand-filled pitch before more costly deep cleaning or removal the contaminated infill is required. The paper concludes with a series of recommendations for practice, and areas for further research.
DESIGN AND DEVELOPMENT OF A NOVEL NATURAL TURF SHEAR STABILITY TESTER
Frazer Anderson, Paul Fleming, Kathryn Severn, Paul Sherratt
Abstract: The stability of natural Rugby Union pitches continues to be a recurring problem at all levels of the game. The effects of poor stability are seen when the pitch surface shears under player loading, creating unsightly divots and an uneven and potentially injurious surface. This observed instability is a real concern for many stakeholders, from the groundsmen through to the revenue generating television companies, and is arguably increasing due to greater sports popularity, more intensive use of natural turf pitches and advances in player physical conditioning. However, perhaps surprisingly, currently there exists no objective quantitative mechanical test method for assessing the shear stability of the natural turf, prior to games being played. This paper presents the findings from a (ongoing) research study into the design and development of a prototype turf stability apparatus – ‘Turf Tester’. The key aim was to measure the natural turf resistance to shearing using realistic loading magnitudes and directions that simulate player(s) interaction. The test method developed was also required to be utilized for routine commercial use and was required to be easy to operate, easy to interpret and, be repeatable and portable. The paper details the observed failure mechanisms of natural turf under (rugby) player loading, the test method design, and presents the results of the prototype apparatus trialed on a range of types of turf construction at venues used for the 2015 rugby world cup. In addition, data was collected at each venue for full agronomic classifications and a suite of the industry standard play performance tests. The combined data from the 13 venues provided a powerful data set to evaluate and refine the prototype apparatus, and has provided validity of its conceptual design. Useful correlations have been drawn between the Turf Tester and conventional surface tests such as rotational traction and pitch hardness. The findings show the influence of many factors on pitch turf shear stability, including pitch construction, grass health and root depth, specific materials used such as sand/clay, moisture influence, and the comparison between modern hybrid systems that include polymeric fibre reinforcement.
TOWARDS SAFER HELMETS: CHARACTERISATION, MODELLING AND MONITORING
Luca Andena, Francesco Caimmi, Lidia Leonardi, Aldo Ghisi, Stefano Mariani, Francesco Braghin
Abstract: Bike and ski helmets are mainly made up of two layers: the external shell and the foam liner. The foam liner, typically made of expanded polystyrene (EPS) or polypropylene (EPP), is asked to provide energy absorption in case of impacts. Standard helmet design requires the foam to maximize this energy absorption, thus achieving large deformations (up to 25% in compression) while maintaining the stress level below a threshold value. To optimize the helmet construction in terms of foam composition, structure and density, reliable numerical models are required, which in turn need to be fed with accurate experimental data. A characterisation of several foams was performed, including EPS and EPP having varying densities, under tensile and compressive stress states at varying strain rates. Typical mechanical parameters (elastic moduli and plateau stress in compression, Poisson’s ratio) were compared with literature data and applicability of existing models to experimental results was discussed. A marked strain rate dependence – very important for impact applications – was accurately described using the Nagy phenomenological model. The foam microstructure was investigated using scanning electron microscopy (SEM) to assess structural changes before and after compression. The aforementioned mechanical features were then adopted in a rate-dependent constitutive law for crushable foams, to model the shock attenuation properties of helmets and validate the approach against available data. Finally, a microelectromechanical system based in-helmet wireless micro monitoring system was developed and inserted in a helmet prototype. The system is capable of acquiring impact load spectra, providing valuable information to investigate generic impacts with varying angles and energy. In particular, it can monitor the effect of repeated micro-impacts on the residual energy absorption characteristics of the foam.
DEVELOPMENT OF A PROGAMMABLE HUMAN SWAY SIMULATION APPARATUS
Otto Hofstätter, Peter Breyer, Patricia Kafka, Anton Sabo
Abstract: Force and pressure sensors are commonly used in systems to measure balance and postural sway. When it comes to biomechanics in sports trainers and therapists often rely on those measurement methods to set up rehabilitation and performance enhancement exercises. To proof sensor reliability and comparability of various systems, a programmable human sway simulator (PHSS) apparatus was developed to enable standardized and reproducible human-like load simulations. The apparatus can be used to test computerized dynamic posturography (CDP) systems, instrumented balance and training systems or any static sensor of that kind. Results from CDP systems provide information for more efficient and focused athlete’s coordination training. Due to the variety of CDP instruments on the market the question arises, whether these systems provide reliable results. With the PHSS apparatus impartial comparison of these systems will be possible. For the test procedures it is required to create predefined sway patterns with varying loads to simulate human mass from kids to adults. These loads have to be applied over footprints representing the human forefoot and heel. The conceptual design of the PHSS was performed using reliable industry standard components for rapid production. The operating PHSS simulates the moving human mass via four separated DC-Motors in order to record indicators of the tested system such as center of pressure (COP), range of motion (ROM) and applied load frequency. Besides that, the PHSS includes a monitoring of motor positioning to retrieve operation indicators for self-check and calibration. With all that, the PHSS allows direct comparison of CDP systems that record GFR or verify the long term precision of sensors as a quality assurance tool. This enables higher standards for training and testing systems and more precise conclusions about human balance abilities and training conditions.
EXPLORING DIFFERENT TECHNICAL SOLUTIONS OF THE INTERFACE BETWEEN THE HAND, RACKET AND THE RIM IN WHEELCHAIR TENNIS
Jorine Koopman, Monique Berger, Aldo Hoekstra, Sonja de Groot
Abstract: Purpose In wheelchair tennis propulsion of the wheelchair is different for both hands, since the athlete has to hold a tennis racket in one hand. Differences in propulsion technique, i.e. forces and timing, have been found between propelling the wheelchair with and without a racket in the hand (de Groot et al, 2015 submitted). Optimizing the coupling of the hand with the racket to the rim is expected to lead to performance improvement Therefore, the purpose of this study was to explore different technical solutions for the interface between the hand, racket and the rim in order to optimize propulsion technique during wheelchair tennis when holding a racket. Methods A limited literature study has been done on the interface between the hand, racket and the rim. Qualitative interviews were held with (sub)top Dutch tennis players and trainers to gain insight in their technique. Video analysis of training and tennis matches of (sub)top Dutch tennis players were made to acquire knowledge of the hand and racket positions. A list of requirements and several ideas were developed. Different prototypes of (a part of) a rim were 3d printed and tested in laboratory settings. Results The literature study showed an increase of effectivity of propulsive force by creating a larger contact area and increased friction; different textures and/or materials can create an increased friction. The video analysis showed a variety of racket positions between players and within players at different speeds. Five different design spaces were explored: push rim, wheel, the tire, the hand and the racket. Prototypes with a larger contact area and/or different material showed higher isometric peak forces. Conclusion This study shows different technical solutions for the interface between the hand, racket and the rim, which will improve propulsion technique during wheelchair tennis. The technical solutions are; different shape of the rim and/or using textures and/or materials with high friction coefficient on the rim and/or hand. References de Groot S, Bos F, Koopman J, Hoekstra A, Vegter R, Effect of holding a racket on propulsion technique of wheelchair tennis players. Scandinavian Journal of Medicine & Science in Sports 2015 (submitted).
CALIBRATION OF A PRESSURE SENSOR SYSTEM FOR RUGBY STUD IMPACTS
Bodil Oudshoorn, Marcus Dunn, Heather Driscoll, David James
Abstract: In rugby union, laceration injuries can occur from players stamping on opponents in the ruck. For measuring the stud-skin interaction during this movement, pressure sensors can be used. Literature on pressure sensor calibration techniques highlights the need to perform calibration at the appropriate impact dynamics (Cazzola et al. 2013; Halkon et al. 2012). The expected pressure range and the rate of loading are both required for effective calibration, although the latter is rarely considered. This study aims to identify an accurate calibration procedure for rugby stud impacts and to report on kinetic and kinematic measurements from the stamping event in the ruck. As a pilot study, seven experienced rugby players were asked to simulate the stamping motion on a force plate. The peak force and rising time (10-90% of time needed to reach peak force) were identified for each stamp. Peak force varied from 1.2 to 5.4 BW and rise time from 6 to 20 ms. This information provided the range in which the sensors need to be calibrated. For the calibration procedure, the pressure sensors were mounted on top of a force plate and were impacted with a 5kg drop hammer from varying drop heights. Rise time was controlled with different types of foams between the impact hammer and pressure sensors. Subsequently, the calibrated pressure sensors were mounted on top of an anthropomorphic test device and rugby players simulated stamping movements that typically occur in the ruck. Impact speed of the foot and pressure data was measured during these trials. This study describes appropriate calibration procedures for the use of pressure sensors in simulated stamping in rugby and reports on expected pressure ranges and impact speeds. This information will be used to inform testing methods for analysing stud laceration injury risk . Cazzola, D., Trewartha, G. & Preatoni, E., 2013. Time-based calibrations of pressure sensors improve the estimation of force signals containing impulsive events. Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology, 228(2), pp.147–151. Halkon, B. et al., 2012. Development of a test methodology for the assessment of human impacts in sport. Procedia Engineering, 34(0), pp.813–818.
THIRD GENERATION ARTIFICIAL PITCH QUALITY IN COMMERCIAL ASSOCIATION FOOTBALL CENTRES
Jim Emery, Heather Driscoll, Andrew Barnes, David James
Abstract: Small sided football is the most popular and fastest growing area of adult football in the UK with an estimated 1.5m adults playing every week. The sport's popularity has led to an influx of commercial football centers offering organized 5, 6 and 7-a-side leagues on third generation artificial pitches. The range of quality and maintenance of these pitches is not fully understood despite the established links between surface quality, player performance and injury. Currently researchers and manufacturers use national governing body standards as guidelines for quality; however, many commercial centers are not approved by governing bodies and therefore are not obliged to meet these criteria. In this paper we characterize the quality of 23 pitches at five, UK based, commercial football centers using portable, low cost methods including; the FIFA rotational resistance test, the Clegg Impact Hammer and an infill depth probe. This paper describes the range of qualities observed, alongside maintenance procedures and usage statistics. To the authors knowledge this is the first study that characterizes commercial football center pitches. Twenty-two of the 23 pitches met the FIFA 1 star guidelines for rotational resistance (25 - 50 Nm), however, mean Clegg Impact Hammer readings are high (208 G), suggesting surface compliance in commercial centers falls outside FIFA standards. Within pitch variance was common at all centers and was an order of magnitude higher in some pitch comparisons. These findings have two practical implications; 1) pitch quality and maintenance at commercial centers is highly variable across and within pitches, 2) the harder surfaces and the high levels of variability found in commercial football centers suggests that players require footwear researched and designed specifically for these conditions.
INVESTIGATING THE RELATIONSHIP BETWEEN PHYSICAL PROPERTIES OF A FOOTBALL AND PLAYER PERCEPTIONS
Benjamin Thompsett, Andy Harland, Jonathan Roberts
Abstract: Football being one of the most popular sports globally sees the emergence of new ball products and technologies on a regular basis, with the governing body FIFA having set a standard to ensure consistency between products. Despite this, differences are commonly perceived between footballs. The aim of this study was to evaluate players’ perceptions in relation to direct and objective measurements of footballs. A paired comparison method was used to evaluate players’ perceptions of hardness and weight during passing and shooting exercises of three individual FIFA Approved footballs. Direct measurements of mass and Shore A hardness were obtained as well as quasi-static stiffness values and diameter normal compression ratios during kicking robot impacts. Players perceived with significance, differences between the footballs in respect to hardness for the passing exercise. No initial trends were seen between perceptions of hardness and weight and direct measurements of hardness and mass. An emerging trend between perceptions of hardness and weight and objective measurements of quasi-static stiffness and high-speed impact diameter normal compression ratio was seen suggesting players’ perceptions of hardness and weight are more complicated than purely direct measurements of mass and hardness.
WHAT IS SLOWING ME DOWN? ESTIMATION OF RIDING RESISTANCES DURING CYCLING
Daniel Meyer, Gideon Kloss, Veit Senner
Abstract: Introduction: Electric bicycles are getting more important as a mean of transportation. One of the biggest issues of electric bicycles is their limited range and the inaccurate prediction of their residual range. Detailed knowledge of the cyclists’ fitness, the type of electric bicycle and the environmental resistances is necessary in order to estimate the residual range accurately. In this paper we focus on the environmental resistances and present a new model to estimate the current riding resistances while cycling. Riding resistances include resistances from slope as well as rolling and wind resistance. Methods: First, we derived a multiple linear regression model to calculate the current rolling resistance by using the current velocity of the bicycle and the vibration at the handlebars. To derive the model, we performed experiments on three different surfaces. A cyclist rode on an electric bicycle on the test tracks on five different, mostly windless days with different velocities. During the experiments power output at the pedals and velocity were measured. Additionally, vibrations at the handlebars were measured using a smartphone. Then, a curve consisting of the mathematical representations of rolling and wind resistance was fitted to the data and the rolling coefficients of the surfaces and the drag coefficient of bicycle and cyclist were estimated. Mean amplitude of the acceleration at the handlebars was calculated for each test ride and each surface. From this data the multiple linear regression model to estimate the rolling coefficient was derived using velocity and vibration as predictors. Results: Mean amplitude of vibration increases with velocity and is higher for surfaces with higher rolling resistance. Combined with a wind speed sensor kit, the system can be used to measure the riding resistances during cycling. To validate the model outdoor experiments with an electric bicycle were performed. We believe that this system can help improve the estimation of the residual range of electric bicycles by providing more detailed information of the environment. Additionally, the system can be used to map cycling paths and the information can be provided to other users, therefore increasing the information available.
RETHINKING THE SAFETY OF JOCKEY HELMETS: A STATISTICAL COMPARISON OF DIFFERENT COMPOSITE LAMINATE HELMET SHELLS
Fuernschuss Bernd, Everson Kandare, Anton Sabo, Toh Yen Pang
Abstract: Jockeys are exposed to higher risk of serious head injuries in the event of a fall while riding. Therefore helmets are vital to protect jockeys from head injuries. Carbon fibre has been widely used in sports and personal protective equipment, which includes helmets, due to its lightweight and strong mechanical properties. The aim of the research was to manually produce jockey helmet shells using carbon fibre, and then the helmet was subjected to a series of laboratory impact tests. The impact tests were performed in accordance to the requirement of AS/NZS2512.3.1: 2007 (Australian/New Zealand Standard, 2007). Four different shell types were produced with the same material. They were differed in the number of layer (four and five layers) and pattern (two and four patterns). Three shells were produced for each variation and resulted in a total number of 12 shells. All shells were autoclave cured under the same conditions (2 hours at 180°C under 0.7 MPa pressure). Guided free fall drop tests of 1.5m were conducted on flat anvil with a rigid head form. Peak deceleration of each shell sample was recorded for comparison. Each shell was tested on four impact sites (side, front, rear and crown). A thin layer of foam was placed between the shell and the rigid head form to avoid direct contact. Differences between the shell samples were assessed using a one-tailed t-test with pair samples (p=0.05). The Gaussian and Mean curvatures of the impact sites were also measured for a better understanding of the impact behaviour. It was expected that the four pattern as well as the five layer variations perform better due to the more accurate lay-up. Results showed no significant differences between the layer and the pattern, but the two patterned shell with the five layers showed the best overall performance during the standard impact test.
MAIN CONTRIBUTORS TO THE BASEBALL BAT HEAD SPEED CONSIDERING THE GENERATING FACTOR OF MOTION-DEPENDENT TERM
Sekiya Koike, Kohei Mimura
Abstract: Motion-dependent term (MDT), which consists of centrifugal force, Coriolis force and gyro moment expressed in the equation of motion for a multi-link system, plays significant roles in the generation of tip speed in high speed swing motion. A phenomenon caused by the MDT is usually called as ‘whip-like effect’ and ‘kinetic chain’. Since baseball batting is one of high speed swing motion manipulating a bat with both hands, it is important to make clear the generating factor of MDT and main contributors to the generation of bat head speed. The purpose of this study was to quantify main contributors to the bat head speed considering the generating factor of MDT. A player with a bat was modelled as linked sixteen-rigid segments. The equation of motion for the whole-body and bat was obtained by considering modelling errors. Kinetic data of each hand was obtained by using an instrumented bat equipped with 28 strain gauges. A recurrence formula with respect to the generalized velocity vector consisting of angular and linear velocity vectors of all segments was derived by combining two equations, such as the equation of motion for the system and an equation of difference approximation with respect to generalized acceleration vector. Contributions to the generation of the bat head speed without use of MDT were calculated from the recurrence formula with use of experimental data. Five collegiate baseball players, participated as subject, hit a teed ball as strong as possible. The kinematic and kinetic data were measured with motion capture system with 3 force platforms and the instrumented bat. The results showed that abduction and extension torques about knob-side shoulder joint and forward rotation torque about torso joint are the main contributors to the generation of bat head speed among subjects. Main contributors to the generation of bat head speed are knob-side shoulder joint torques and torso joint torque.
DEVELOPMENT OF A NEW EXPERIMENTAL PROTOCOL FOR ANALYSING THE RACE WALKING TECHNIQUE BASED ON KINEMATIC AND DYNAMIC PARAMETERS
Giuseppe Di Gironimo, Teodorico Caporaso, Domenico Maria Del Giudice, Andrea Tarallo, Antonio Lanzotti
Abstract: In race walking, more so than in any other athletic event, technique is strictly determined by competition rules. This study aims to develop a new protocol for analysing the race walking technique in order to improve the biomechanical efficiency and to recognize objectively infringements of competition rules in according to International Association of Athletics Federations (IAAF). One Italian national team athlete has conducted twenty test runs in laboratory conditions. It is elaborated a specific marker set based on Davis’ protocol. A motion capture system (340 Hz) integrated with force platforms (680 Hz) has recorded both kinematic and dynamic patterns. Data analysis have concerned the evaluation of the knee flexion-extension and the loss of ground contact (i.e. the flight phase) for detecting infringements, and the angles of pelvis, hip, ankle, elbow, step and temporal components of gait for assessing the biomechanical efficiency. Comparing results with others studies of specialized literature, which differ in methods and the experimental protocol (e.g. SAFLo, CAST) it is found a substantial coherence. The experimental protocol developed can thus objectively improve the knowledge of race walking technique and it could be a valuable tool to assist athletes, trainers and judges in a better way. However, this is just a first step toward an application “on field”.
DEVELOPMENT OF A NOVEL PORTABLE TEST DEVICE TO MEASURE THE TRIBOLOGICAL BEHAVIOUR OF SHOE INTERACTIONS WITH TENNIS COURTS
Daniel Ura, Matt Carré
Abstract: Establishing the characteristics of player-court interaction in tennis is a key challenge. The governing body of tennis (International Tennis Federation) is responsible for setting the rules and maintaining the standards of the sport, and therefore needs a system to quickly assess courts around the world and rate them according to the player interaction. Despite many years of research, there still remains opportunity for significant improvement of a realistic portable device for this application. The interaction between the player and the court is a complex problem determined mainly by player, surface and shoe parameters that can be broken down further as: the range of player movements (e.g. push-off and sliding); a variety of surfaces (e.g. clay, acrylic and grass); different shoes properties (e.g. material and tread geometry). These combinations generate different levels of friction that relate to both playing performance and safety. This paper presents the observations, findings and design methodology of a mechanical portable device to improve the understanding of tennis shoe-court interactions and allow courts to be measured and monitored. Case studies of biomechanical player testing (kinetics and kinematics) and examination of how the tribological mechanisms change with different parameters (e.g. shoe orientation, contact area, roughness, shoe temperature), were combined in the design of a novel robust portable device capable of simulating the key aspects of the player-court interactions. This study also has wider implications for other human-surface interactions, to enhance grip performance and/or reduction of injuries due to slips, trips and falls.
VACUUAIR – A NEW TECHNOLOGY FOR HIGH PERFORMANCE INFLATABLE STAND UP PADDLEBOARDS
Stefan Klare, Andreas Trapp, Joaquin Parodi, Veit Senner
Abstract: Stand up paddleboarding (SUP) became a rising sporting activity over the last decade. The main categories of the sport can be distinguished into: Leisure, Fitness, Race, Wave, Yoga and River/Touring. Especially the categories Fitness, Race and Wave require high performance SUPs for sportive success. In here the term “high performance” refers to “high bending stiffness” and “precise shape” of the surfboard/SUP. SUPs have a length of about 8 to 14 feet, which causes plenty of inconvenience while travelling with the equipment. A solution to the travelling problem can be found in inflatable SUPs (iSUPs). ISUPs use the socalled Dropstitch technology, invented by the U.S. military. However the fabric did not work sufficiently to keep their boats stiff enough [1]. Dropstitch is a three-dimensional fabric; fibers connect an upper and lower layer, which leads to a flat shape when inflating the object. The Dropstitch material does solve the transportation problem, but the technology is not suitable for high performance SUPs due to the insufficient possibility of forming any camber line. Further, as the fibers, which connect the upper and lower layer, are perpendicular to these layers, the Dropstitch material is not providing high enough bending stiffness. Thirdly iSUPs in Dropstitch construction have one air chamber only, thus buoyancy cannot be guaranteed when the iSUP is damaged. This can lead to dangerous situations for the sportsman. The VacuuAir-technology (patent pending, [2]) presented in this manuscript solves all previous described problems for iSUPs. The technology is characterized by a two-chamber system: A high-pressure chamber defines the shape and a vacuum-chamber increases the stiffness and guarantees buoyancy. The tubular high-pressure chambers enable the desired high performance shape. The vacuum chambers surround these tubes and are filled with granule. When applying the vacuum the granule is compressed and hard regions are formed, which increases the stiffness. Because of the floating property of the granule, buoyancy can be guaranteed even if both chambers are punctured. In this manuscript, we will explain the structure of the VacuuAir technology and the Dropstitch technology as well as the consequences regarding shape, safety, pumping effort and packing size. We show a comparison of the bending stiffness of iSUPs in a Dropstitch construction versus iSUPs in a VacuuAir construction.
COMPARATIVE ANALYSIS OF MODERN RACING BICYCLE WHEELS AERODYNAMIC USING CFD
Matteo Pogni, Nicola Petrone
Abstract: In bicycle racing, improving aerodynamic performance is extremely important, because drag is the main source of losses when cycling, therefore it is necessary to improve the bicycle's components, which account of about 33% of the total drag, mainly the wheels and the frame. The aim of this research is to evaluate and compare the aerodynamic performance of racing bicycle wheels by means of CFD numerical steady state models
A STUDY OF DIMPLE CHARACTERISTICS ON GOLF BALL DRAG
Harun Chowdhury, Bavin Loganathan, Firoz Alam
Abstract: Dimples on the golf ball have significant effect on its aerodynamic properties as well as the flight trajectory. The aerodynamic of golf ball is still not fully understood in spite of a significant number of published data in the open literature. Most studies were conducted using the wind tunnel testing and Computational Fluid Dynamics (CFD) simulation. This paper examines the aerodynamic effect of dimple depth on golf balls. 3D printing technology was used to manufacture 10 balls with various dimple depths. RMIT Aero Wind Tunnel was used to measure the drag forces over a range of wind speeds. It was found that the drag coefficients of these balls varied significantly due to varied dimple geometry. The results showed that the balls with deeper dimples had least drag compared to smoother balls.
SMART CARBON FIBRE BICYCLE SEAT POST WITH LIGHT AND SENSOR INTEGRATION
Joerg Kaufmann, Henning Rabe, Nicole Siebert, Peter Wolf, Holger Cebulla, Stephan Odenwald
Abstract: The development of high-performance sports equipment is nowadays focused on lightweight structure designs with integrated functions. One example is the A.L.D.-Technology for floating sports equipment such as snowboards (1). Even in cycling more and more manufacturers prefer to use fibre reinforced plastics (FRP) in their frames and further bicycle parts. During the manufacturing of the FRP-components it is possible to integrate flat and flexible electronics and sensors such as stitched strain gauges into the fibre layup. Seat posts made of aluminium with integrated LEDs for taillight already exist, but the LEDs must be applied subsequent to the manufacturing process, thus damaging the structure to some degree. The new innovative seat post presented here is made of carbon fibre reinforced plastic (CFRP) and contains LED lights as well as sensors for ambient light and acceleration, which are integrated into the laminate structure during the manufacturing process. In that way a highly functional smart light weight seat post with fully integrated taillight can be realized. The seat post can be designed with several layers of carbon braided structures, which can drape around the single LED lights with a minimum influence on the mechanical properties and resulting in a high class carbon optic. Due to the integrated sensors, the seat post will detect the motion of the bike and the illuminance to activate the taillight when it is needed. The thresholds for acceleration and ambient light can be programmed also using a timer function, so that the lighting stays constant even in discontinuous lighting conditions (for example due to traffic lights at night) but will turn on when it is needed and stay off in a daytime ride. A prototype with all integrated sensors and electronics could successfully put into operation (see Figure 1). One limitation of FRP seat posts is that there is still no elegant solution to connect the saddle with the seat post without using a mast topper. Some additional research is needed here. The main innovation and advantage of the new smart and lightweight seat post is the automated activation of the taillight without intervention of the rider. This guarantees maximum safety and comfort especially while biking through tunnels or underpasses. A second advantage is the nearly unaffected performance because of a minimal additional weight as well as no aerodynamic disadvantages resulting from external lighting, which allows the use of the new seat post in high-performance bicycle disciplines in training and competition.
VIDEO-ANALYSIS OF PLAYER’S KINEMATICS IN RUNNING OUT OF BOUNDARIES IN ASSOCIATION FOOTBALL FIELDS.
Antonio Lanzotti, Gianluca Costabile, Giuseppe Annino, Giuseppe Amodeo, Stephan Odenwald
Abstract: The risk of injury following a player's impact with objects in sport facilities is a growing problem, as shown by serious accidents that happen when players have head impacts with obstacles and barriers installed around the play area. At present, no experimental data are available about the kinematics of football (soccer) players during a running-out of playing areas. Experimental tests on a sample of 14 skilled football players, aged between 17 and 19 years, were conducted to investigate athletic performances in common gaming actions of running, considered potentially-damaging when they occur near the boundary lines of the regular pitch. In the current research, a player’s motion was captured with a high-frequency camera and kinematic data were video-analysed. The experimental trials resulted in kinematic data plots, characterised by a decelerating trend of the speed versus the distance covered by the players during the required movements. A section at the starting point and three sections at consecutive distances (a total amount of four sections in correspondence of 0 m and consecutive 1.5 m, 2.5 m, 3.5 m on the lane covered by players) of the decelerating trends of data were analysed. Findings of this pilot study should be useful for the improvements of passive safety in sports fields, allowing to correlate the potential impact energy of players with the installation distances of protective devices.
A FINITE ELEMENT ANALYSIS OF A HUMAN FOOT MODEL FOR SIMULATING NEUTRAL STANDING ON GROUND
Zahari Taha, Muhammad Syukur Norman, Syed Faris Syed Omar, Edin Suwarganda
Abstract: The objective of the paper is to develop a finite element analysis of a human foot model to study the dynamic behaviour and the internal loading conditions during neutral standing on planar ground. The paper was done also to simulate the foot structure which later being used to assist in the design of shoe insole for future research. Finite element model of human foot was generated and the loading condition during neutral standing was used to evaluate the stress distribution. The comprehensive stress distribution of the human foot model subjected to several loading conditions can be specified by a computational model. The method of the research is a computational tomography data of the bone and soft tissue structures of a human foot were developed into a 3-D finite element foot model. An analysis was conducted to simulate the loading condition of human foot during neutral standing. A commercialize CAD software package was used to generate the boundary surfaces and the solid models of all model components. The numerical stress analyses for neutral standing of the foot model was done using commercialize finite element software package. The total deformation, von-Mises stress, and von-Mises strain of the 3-D foot model were acquired. A peak pressure was seen at the first metatarsal, fifth metatarsal, and under the heel. The plantar deformation and the von-Misses stress distribution of the neutral standing foot model were seen similar to the finite element foot model of the previous literatures. The present study offers a prior computational model, which capable of estimating the comprehensive plantar pressure and bone stress distributions and was intended to expose new approaches for the development of custom-made insoles.
A NEW CONTACT MAT WIRELESS SYSTEM FOR ESTIMATING VERTICAL JUMP HEIGHT
Giuseppe Annino, Vincenzo Bonaiuto, Luca Federici, Massimo Gabrieli, Nicola Silvaggi
Abstract: Vertical jump test is one of the most prevalent method of assessment on sport performance. The Jump height is highly correlated with leg extensor muscles power. From almost 40 years the contact mat has been used to evaluate the jump height, through the flight time, ensuring an effective scientific validity. From it invention (Bosco C., 1978) the contact mat, with metal bars equally arranged over its entire surface, has been remained unchanging just to date. The aim of this study was to evaluate concurrent validity of the new contact mat (Wi-Jump, Weiss.s.r.l. , Rome, Italy), built replacing the metal bar with another conductive tissue on the surface, with force plate measurements for estimating vertical jump height. Five subjects performed (three times for each test) maximal squat jumps, countermovement jumps and continuous jumps for 5s. Flight time and contact time of vertical jump performed on a force platform were correlated with those provided by the Wi-Jump to examine its concurrent (criterion-related) validity. Intraclass correlation coefficient (ICCs) for validity was very high. A systematic negligible difference was observed between force plate and Wi-Jump in flight time and contact time. The results obtained from this study show a significant concurrent validity of Wi-Jump for the flight and contact time measurement. In conclusion, the new conductance device is legitimate to assess vertical jump height and leg extensors muscle power. The latter estimate using both flight and contact time.
PIV MEASUREMENT OF A FLYING TABLE TENNIS BALL
Yasufumi Konishi, Hiroyuki Okuizumi, Tomoyuki Ohno
Abstract: There seems to be some differences between wind tunnel test and flight test on the ball aero dynamics. The reason of the difference seems to come from an acceleration and deceleration or unsteady motion at the flight test. In order to confirm the differences, PIV measurements around a flying table tennis ball are conducted. Because a weight of a table tennis ball is very light, the deceleration rate is high compared to other ball games. The high speed camera which frame rate is 10,000, is used to capture the instantaneous motion around the flying ball. The imaging region is 210mm×210mm. The Reynolds number is around 65,000 which correspond with a smash in the table tennis ball games. A coordinate transformation to the ball fixed coordinate system well captured the wake motion of non-rotating and rotating ball. It is observed that at non-rotating condition, the averaged wake velocity field of the ball is symmetric. On the other hand at rotating condition, it is asymmetric to show the Magnus effect. These observations quantitatively agree with the wind tunnel test.
CHARACTERIZATION OF MAPLE AND ASH MATERIAL PROPERTIES AS A FUNCTION OF WOOD DENSITY FOR BAT/BALL IMPACT MODELING IN LS-DYNA
Joshua Fortin-Smith, James Sherwood, Patrick Drane, David Kretschmann
Abstract: In response to a perceived increase in multi-piece failures (MPFs) in professional baseball bats, the Office of the Commissioner of Baseball implemented changes to the Wooden Baseball Bat Specifications (WBBS) in December of 2008. These changes introduced bat-supplier regulations that outlined strict quantitative requirements for wood quality and instituted a third-party inspection of professional wooden baseball bats for the 2009 season. An additional change to the WBBS for the 2010, 2011, and 2012 seasons targeted increasing the density of the wood used to make maple bats, thereby increasing the minimum breaking strength of the wood allowed for these bats. By the completion of the 2014 season, these changes had driven a 65% reduction in MPFs relative to the 2008 season. It is hypothesized that the level of multi-piece failures can be further reduced if regulations on the allowable geometries of the taper region for the bats used by MLB teams are implemented. To assist in developing credible LS-DYNA finite element models of wood baseball bats that could be used to explore the relationship between bat profile and bat durability, a comprehensive experimental program was conducted to characterize the mechanical behaviour of maple and ash woods for the range of densities used to make Major-League quality baseball bats. The test program included four-point bend testing to determine elastic moduli and strength and Charpy testing to determine strain to failure as a function of strain rate. The material parameters were calibrated by completing finite element simulations of the Charpy tests in LS-DYNA using the MAT_WOOD material model. This paper will describe the experimental characterization program, summarize the material parameters and present a comparison of the finite element simulations to the Charpy testing.
NUMERICAL PREDICTIN METHOD OF MECHANICAL CHARACTERISTICS OF FORMED RUBBER USING HOMOGENIZATION FEM ANALYSIS
Akitaka Nomoto, Hiroki Yasutaka, Sho Oketani, Akihiro Matsuda
Abstract: In this study, we proposed an evaluation method of foamed rubber considering the mechanical characteristics of rubber matrix and its microstructure using homogenization method. In order to realize the evaluation method, the microstructure of the foamed rubber is assumed to the periodic structure with hole, and a FEM code for hyperelastic material was developed based on homogenization theory. Furthermore, compression test of the rubber specimen reproducing FEM model was conducted to verify the validity of analysis code. Foamed rubber has complex microstructure made by foam molding of matrix. The microstructure consists of struts and walls. The struts and the walls bend when foamed rubber is compressed. Therefore, foamed rubber has good shock-absorbing characteristics in addition to good formability and lightweight. For that reason, foamed rubber is widely used for shoe soles and so on. The mechanical characteristics of foamed rubber are determined by the mechanical characteristics of rubber matrix and its microstructure. While suitable design of foamed rubber used for each product is required, the mechanical characteristics of foamed rubber have usually been evaluated with material test using prototypes under the assumption to be homogeneous material. Thus, an evaluation method using a numerical analysis considering the microstructure would be an effective method to improve quality, performance and productivity. In order to establish the evaluation method, 2-dimensional finite element analysis code were developed in this study. The microstructure of the foamed rubber is assumed to the periodic structure with hole. Therefore, homogenization theory was applied to the developed analysis code. The rubber matrix was assumed to have incompressible hyperelasticity which was represented by the Mooney-Rivlin model. The material parameters of rubber matrix were identified from the tensile test results. Compression test of the rubber specimen reproducing FEM model was conducted to verify the validity of analysis code. Porosity was reproduced by adjusting the diameter of the pores. The analysis result showed good agreement with the compression test result in the low strain region.
AN INNOVATIVE HANGBOARD DESIGN TO IMPROVE FINGER STRENGTH IN ROCK CLIMBERS
Michael Anderson, Mark Anderson
Abstract: In elite rock climbing, finger strength is critical, and is directly related to performance. A hangboard, composed of sets of artificial climbing grips to hang from, is often used by climbers to improve their finger strength. While some research has studied training protocols for climbing, virtually no published research exists addressing the specific enhancement of training equipment to improve training effectiveness. Here we seek to show that hangboard design, especially novel features included in the Rock Prodigy Forge hangboard increases the effectiveness of hangboard training. Recently, this hangboard was developed through an iterative process leveraging modern CAD/CAM techniques. This enabled design engineers to optimize the hangboard for improved training benefit and reduced injuries. As a result, several innovative features were added to the design including: (a) equation-driven grip edge profiles, (b) drafted pockets, (c) novel grip designs, (d) improved grip geometry, and (e) improved texture, among other features. The Forge was tested by experienced climbers, and 92% assessed it as more effective than other training tools, with 91% of users able to train harder without fear of injury relative to other training methods, and 86% reporting improved climbing performance. This is a significant and unique result for the sport of climbing.