Increased tibial acceleration has been found to be an important risk factor for tibial stress fractures. Interventions aimed at reducing this variable which found a beneficial effect include the use of biofeedback in gait retraining. However, no studies have focused on the time participants take to modify tibial acceleration, therefore we aimed to find the start of a learning plateau in this study. Six participants ran on a treadmill while multisensory feedback was given. A single-subject analysis was used to characterise the learning effects. All participants changed peak tibial acceleration within the first step of running in the feedback condition. Two participants further reduced tibial acceleration to reach a plateau within 120 steps. In four of the six participants a strong effect of the feedback was still present after a week. Further research is needed to optimise the use of biofeedback in reducing the prevalence of tibial stress fractures. Full article

Athlete monitoring is a major field of interest for professional and recreational runners as well as for coaches to improve performance and reduce injury risk. The development of inertial sensors in recent years offers the opportunity to improve the number of monitored training sessions significantly. This research used a self-developed inertial sensor in conjunction with a motion tracking system and four smart bands to record the runner’s movement and extract parameters such as step numbers and frequencies. The data recorded were calibrated before it was high-pass filtered to remove gravity components from the signal. A peak detection algorithm was developed to find the number of steps, which have been further used to compare the different systems (IMU, motion capture, smart bands) and find their agreement. The results showed a very strong correlation between the IMU and the motion tracking system of r² = 0.998, and an r² = 0.996 between the IMU and one smart band. Full article

The transition from a stationary crouch on running-blocks to an erect running position is critical to success in sprint running. Three elite sprinters repeated five sprint starts on a 50 m-long instrumented running track each wearing three inertial measurement units (IMU) on both shanks. The IMU profiles and force plate data was highly consistent between runs. The increasing maximum ground force was correlated with the IMU data using a linear fit and gyroscope triggered acceleration component. Both techniques show promise (r² > 0.5). This is of significant interest to athletes and coaches using IMUs rather than a long, instrumented running track. Full article

The pervasiveness of wearable technology has opened the market for products that analyse running biomechanics and provide feedback to the user. To improve running technique feedback should target specific running biomechanical key points and promote an external focus. Aim for this study was to define and empirically test tailored feedback requirements for optimal motor learning in four consumer available running wearables. First, based on desk research and observations of coaches, a screening protocol was developed. Second, four wearables were tested according to the protocol. Third, results were reviewed, and four experts identified future requirements. Testing and reviewing the selected wearables with the protocol revealed that only two less relevant running biomechanical key points were measured. Provided feedback promotes an external focus of the user. Tailoring was absent in all wearables. These findings indicate that consumer available running wearables have a potential for optimal motor learning but need improvements as well. Full article

In order to better inform the effects of dehydration and hydration guidelines, we tested the acute effects of a 2% dehydration protocol on performance and technique of 3-point shooting (3PS) in Elite Basketball players (n = 9). The 3PS technique was monitored by using nanotechnology inertial measurement units positioned onto body joints during the exercise. When dehydrated (−2.1 ± 0.5% of body mass), 7 players experienced a slight decrease (−10.0 ± 19.6%, p = 0.16) in success rate, while RPE increased from 9.1 ± 2.6 to 13.0 ± 2.5 in euhydrated (EUH) and dehydrated (DEH) condition respectively (p = 0.003). DEH slightly altered the 3PS technique as the knee angle increased (p = 0.02) at toe-off time and the hip angle decreased during the 3PS (p = 0.01). The speed of ball release tended to be increased (p = 0.05) in DEH compared to EUH. Data from this study suggest that a 2% dehydration is tolerable for elite Basketball players, although a stronger dehydration might accentuate the effects observed. Full article

Shooting arm motions at release in one-hand set and jump basketball shots have been analyzed using a kinematic model. Set and jump shots are classified by the vertical velocity and acceleration of the shooter’s shooting-side shoulder at release. The two-dimensional three-segment model includes the vertical shooting-side shoulder velocity and acceleration. Numerical simulation investigates the effect of shoulder motion. Release backspin angular velocity can be described as a function of the vertical shoulder acceleration and the vertical fingertip acceleration relative to the shoulder. For proper backspin, jump shots require large vertical fingertip acceleration relative to the shoulder. The upward shoulder speed at release contributes to the vertical fingertip velocity relative to the shoulder for a given desired ball release speed, angle and backspin. On the other hand, upward shoulder motion does not contribute to the horizontal direction. As horizontal shot distance increases, upper arm angular speed also increases to produce the ball release conditions. Ball release with upward shoulder speed reduces the magnitudes of the upper arm, forearm and hand angular velocities. All these facts imply that the shooting arm motion in the jump shot is different from that of the set shot. Full article

To improve skill in sport activities it is essential to discern the temporal patterns of one’s own movements. Our previous motion capture experiment involving elite female softball players identified key differences in the temporal body movements between the top players and young players against fastballs/change-ups. In this paper, we found that key features could be extracted from the rotation of the pelvis and we developed a sonification feedback system with two nine-axes inertial sensors. Rotation patterns are converted into two synthesized sounds to represent the time at peak trunk rotation speed and impact time. We conducted a pilot experiment with this feedback proposal using expert and novice batters, male and female whether the participants can pace of the rotational motion in batting. As a result, this feedback approach may allow the user to alter the time of peak trunk rotation speed to more closely match the cue provided by the training sound. Full article

In the off-spin bowling grip, the ball is clamped between index and middle fingers. Spin bowlers attempt to select a spread angle between these two fingers that achieves comfort and optimises performance. The aim of this paper was to investigate whether the standard grip is superior to narrow and wide grips. The bowling performance parameters were obtained from a smart cricket ball. Smart ball data revealed that the performance parameters varied with grip type. The following parameters were optimum at the standard grip: spin rate, resultant torque, spin torque, peak angular acceleration, and peak power. The following parameters were optimum at standard and wide grips: efficiency. The following parameters were optimum at standard and narrow grips: pitch angle of spin axis. The following parameters were optimum at the wide grip: precession and the precession torque. In general, the data tended to show that the standard grip is most effective for spin bowling. However, more research is needed to confirm this result, because the precession and precession torque were optimum at the wide grip, suggesting that this may have a superior performance over the standard and narrow grips. Full article

The purpose of this study was to quantify the functional roles of the whole-body’s joint torques including fingers’ joints in the generation of ball speed and spin during baseball fast-ball pitching motion. The dynamic contributions of joint torque term, gravitational term, and motion-dependent term (MDT) consisting of centrifugal force and Coriolis force, to the generation of the ball variables were calculated using two types of models. Motion and ground reaction forces of a baseball pitcher, who was instructed to throw a fastball into the target, were measured with a motion capture system with two force platforms. The results showed (1) the MDT is the largest contributor to ball speed (e.g., about 31 m/s prior to ball release) when using 16-segment model, and (2) the horizontal adduction torque of pitching-side shoulder joint plays a crucial role in generating ball speed with conversion of the MDT into other terms using a recurrence formula. Full article

Batting cage pitching machines are widely used across the sports of baseball and softball for training and recreation purposes. The balls are specifically designed for the machines and for the environment to ensure high durability and typically do not have seams. Polymeric foam balls are widely used in these automated pitching machines for batting practice in a cage environment and are similar in weight and size compared with the regulation balls used in leagues. The primary objective of this paper is to characterize the polymeric balls and their interaction with the pitching machine. The paper will present measured ball properties and measured relationships between various pitching machine parameters such as wheel speed, and the ratio of wheel speeds on the ball exit velocity and rotation. This paper will also characterize some of the effects of wear on the baseballs and wheels from their prolonged use. Full article

Models of fatigue are based on physiological parameters such as Critical Power (CP) and Anaerobic Work Capacity (AWC). CP is a theoretical threshold value that a human can generate for an indefinite amount of time and AWC represents a finite expendable amount of anaerobic energy at intensities above CP. There is an increasing interest in developing mathematical models of energy expenditure and recovery for athletic training and human performance. The objective of this research is to propose and validate a model for recovery of AWC during a post exertion recovery interval of cycling. A cycling ergometer study is proposed which involves a VO_2max ramp test to determine gas exchange threshold, a 3-min all-out intensity test to determine CP and AWC, and exertion-recovery interval tests to understand recovery of AWC. The results will be used to build a human in the loop control system to optimize cycling performance. Full article

Using multiple cameras with force platforms is a classical and popular method for gait analysis. However; it is difficult to measure natural walking; because the subjects have to adjust their steps to place on the force platform. This study proposes two rigid body linked segment models to estimate the joint force and ground reaction force without force platform. In order to validate the accuracy of the models; the authors compared their kinetic parameters with those of classical model. The results showed that the proposed models could estimate the ground reaction force and the joint force with high accuracy (less than 10% in the third quartile on all axes). In addition; using the center of pressure from force platform could also estimate the joint torque with high accuracy. These results suggest that we can analyze the gait without force platform; if the center of pressure is provided in the future. Full article

Two wind tunnel experiments were carried out to investigate the drag acting on a tandem bike. One experiment involved measurement of the drag acting on two full-scale human models on a tandem. These two human models can pedal the tandem. In the other experiment, two oscillating cylinders were used as a simplified model of the legs of the pilot and the stoker. These were arranged to represent the legs of the riders on a tandem. Measurements of the drag on this model were made. It was found that the drag decreases when the crank angle of the stoker’s pedal is delayed with respect to the pilot’s pedal. Full article

Brake induced heating has become more difficult to control as bicycle component mass has been reduced. High-power braking with insufficient cooling or thermal capacitance can create excessive temperatures, boiling brake fluid, performance degradation, and damage. To better understand component heating, a disc braking dynamometer has been constructed with a motor driven disc, hydraulic braking, and a miniature wind tunnel. Disc temperatures are studied for various braking scenarios using infrared techniques and thermocouples. A transient, numerical, MATLAB, lumped parameter thermal/mechanical model is created to predict the impact of key design parameters on braking performance and to understand the heat loss mechanisms from the brake system components. Computational fluid dynamics (CFD) simulations are used to estimate the disc surface convective cooling coefficients for the model. The final model provides transient temperature predictions based on bicycle velocity and braking power, and successfully matches dynamometer experimental data. Full article

Previous studies have shown how finite element analysis (FEA) can be used to support designers and frame builders in the selection of butted tubes to tune the stiffness and strength behaviour of steel bicycles. The aim of this paper was therefore to analyse the effects of tube butting on the stiffness, stress distribution and energy absorption behaviour of bicycle frames using numerical simulations. Butted tubes were shown to provide a highly effective means to decrease mass whilst producing a disproportionately small change in stress compared with a straight gauge tubeset with a maximum material condition although there was no added benefit in terms of stiffness or strain energy. Conversely, decreasing the wall thickness produced an increase in stress at the tube ends that was disproportionate to the change in mass. This work can now be extended to analyse a fuller set of butted profiles for a range of tube types. Full article

Predictive dynamic simulation is a useful tool for analyzing human movement and optimizing performance. Here it is applied to Olympic-level track cycling. A seven degree-of-freedom, two-legged cyclist and bicycle model was developed using MapleSim. GPOPS-II, a direct collocation optimal control software, was used to solve the optimal control problem for the predictive simulation. The model was validated against ergometer pedaling performed by seven Olympic-level track cyclists from the Canadian team. The simulations produce joint angles and cadence/torque/power similar to experimental results. The results indicate optimal control can be used for predictive simulation with a combined cyclist and bicycle model. Future work needed to more accurately model an Olympic cyclist and a standing start is discussed. Full article

Descend technique and performance vary among elite racing cyclists and it is not clear what slower riders should do to improve their performance. An observation study was performed of the descending technique of members of a World Tour cycling team and the technique of each member was compared with the fastest descender amongst them. The obtained data gives us guidelines for rider specific feedback in order to improve his performance. The bicycles were equipped with a system that could measure: velocity, cadence, pedal power, position, steer angle, 3D orientation, rotational speeds and linear accelerations of the rear frame and brake force front and rear. From our observation study, the brake point and apex position turned out to be distinctive indicators of a fast cornering technique in a descent for a tight, hairpin corner. These two indicators can be used as feedback for a slower rider to improve his descend performance. Full article

A new approach is introduced to evaluate the potential drag reduction by skin suit design in speed sport. The approach relies upon local flow information measured in the wake of a cyclist mannequin. Lagrangian Particle Tracking is employed to measure the distribution of time-average streamwise velocity in a cross-plane of 30 × 100 cm² behind the stretched leg of the rider at a range of Reynolds numbers (0.4 × 10⁵ < Re < 2.4 × 10⁵). The expected Reynolds number effect is observed: a general wake narrowing at increasing speed. Unexpected local effects are also identified, which may be due to local variations in geometry of the rider’s leg. The conservation of momentum within a control volume containing the leg is used showing that the aerodynamic drag of the rider’s leg can be decreased by application of surface roughness. This outcome is validated by repeated measurements using zigzag tape on the legs’ surface. Full article

With the advent of commercially available virtual reality (VR) hardware, immersive experiences can be created to simulate competitive performance environments. Simulators can provide novel ways for fans to engage with otherwise unattainable performance situations. Furthermore, simulators can also have clear advantages for elite athletic training by controlling the perceptual inputs, measuring the kinematic based outputs, measuring how the athlete is interacting with the created environment, and providing concurrent audio-visual-haptic feedback. When engineering a virtual simulation system, fundamental design considerations include; hardware selection, software design, user safety, and the provision of performance factors. This paper provides a case study into the design considerations of engineering a track cycling simulator for the 2018 Commonwealth Games Velodrome. The experience utilises a stationary exercise bike (Wattbike, 2016 Pro) transmitting performance data wirelessly, via the ANT+ protocol, to a PC connected to an Oculus Rift VR projecting the audio-visual simulated environment. The simulator has been tested on a large reference group to evidence the design decisions. The design processes have been generalized to create an operational framework to aid the creation of future VR sports simulators. Full article

Aerodynamic drag is a key determinant of cycling performance. The distribution of yaw angles that a cyclist experiences is equally important. Analysis and presentation of aerodynamic data in cycling, generally, has not combined these two effects. A theoretical derivation of a probability density function for yaw angle weighting, based on the theory of Wind Averaged Drag is presented. The weighting function allows for functional variation of yaw distribution according to road and wind speed as well as the visual representation of yaw distribution applied to graphical wind tunnel data. A normalised average of the weighted curve combines both drag and yaw angle data into a single value which is essential for performance modelling. This approach provides a more intuitive way to view and interpret yaw angle data and aerodynamic performance. This has the potential to standardise performance analysis in the industry and improve athletes’ understanding of complex aerodynamic phenomena. Full article

Many cyclists use online-maps for planning their routes, however, only little information is known about the road surface of different cycling paths, farm or public roads. Cyclists prefer road surfaces fitting the type of bike they are using for a specific ride (e.g., time trial, road, MTB, cyclocross, gravel bike). Often riders upload their ride data including GPS, heart rate (HR) or power (P) on platforms like Strava or Garmin Connect. In this research we tried to evaluate whether it is possible to (1) evaluate the road surface quality using a 3D accelerometer mounted on the bicycle’s fork (f = 500 Hz) and whether (2) results of similar quality can be achieved using the accelerometer of a smartphone (f = 100 Hz) placed in the cyclist’s pocket. For data acquisition a cyclist rode on a cyclocross bicycle on three different road surfaces (cobblestones, gravel and tarmac) with three different speeds (10, 20 and 30 km/h) and three different tire pressures (3, 4 and 5 bar). Data of both measuring systems were analyzed using machine learning algorithms. Results showed that road surfaces could be predicted with more than 99% accuracy with the accelerometer and with more than 97% with the smartphone-data. Full article

An aerodynamic study was conducted on eleven high-end ‘aero-road’ helmets with the aim of determining whether a helmet can simultaneously have low drag and efficient cooling. The aerodynamic drag of each helmet was measured using a custom-built cycling manikin at a velocity of 40 km/h with a yaw angle range of 0° to ±25° and at velocities of 50 and 58 km/h at 0° yaw. Thermal testing of the cooling abilities of each helmet was conducted with a custom-built heated mannequin headform, which incorporated 36 thermocouples embedded within its surface. Contour plots of the temperature distributions over the head were created together with images obtained by a thermal camera. The results demonstrate that all the aero-road helmets are generally as cool as each other, however, there can be significant differences in the aerodynamic drag. Full article

The objective of this work was to assess the effectiveness of cycling gloves and handlebar tape in reducing the vibration transmitted to the cyclist’s hands in the classic “hoods” position for shock-type excitation at the front wheel on a bicycle treadmill. Three pairs of conditions were tested on a single participant: (1) With gloves vs. no gloves, no bar tape; (2) With bar tape vs. no bar tape, no gloves; (3) With gloves and bar tape vs. no gloves and no bar tape. We have shown that a rider can expect a small but significant drop in the level of transmitted power and energy through the handlebars when wearing a standard pair of road cycling gloves. If bar tape is used however (both with and without gloves), there is a significantly larger drop in the level of transmitted power and energy through the handlebars. Full article

the wind tunnel at the SportsTech Research Centre at Mid Sweden University (MIUN, Ostersund) was opened in 2015 for sports technology research. It is dedicated to analysis of equipment performance and garment development and suitable for roller skiing, running and cycling. The aim of this work was to develop and apply a full-scale method to investigate the aerodynamic behaviour of a cyclist facing front and cross wind at different yaw angles (from 0° to 30°) and speeds. To reach this goal, a rotating structure supported by a force platform was constructed. It includes a set of rollers on which fully unrestrained cycling is possible. The method was applied to the comparison of three wheelsets (differing in material, height and shape of the rim, number and shape of spokes) in terms of drag and side aerodynamic forces during a cyclist’s ride at 30 km/h, while keeping all the other factors constant. Resulting curves allowed estimating differences of 4% and 9% when applied to a recent time trial competition with supposed wind conditions. Full article

A novel measurement system, the Ring of Fire, is deployed which enables the aerodynamic drag estimation of transiting cyclists. The system relies upon the use of large-scale stereoscopic PIV and the conservation of momentum within a control volume in a frame of reference moving with the athlete. The rider cycles at a velocity of approximately 8 m/s, corresponding to a torso based Reynolds number of 3.2 × 10⁵. The measurements upstream and in the wake of the athlete are conducted at a rate of 2 kHz within a measurement plane of approximately 1000 × 1700 mm². The non-dimensional, ensemble-averaged streamwise velocity fields compare well to literature and the ensemble-averaged drag area shows a rather constant value along the wake with an uncertainty of 5%. A comparison with wind tunnel force balance measurements shows discrepancies which may be partly attributed to the bike supports and stationary floor in the wind tunnel measurements. The 25% drag difference measured between a rider in upright and time-trial position, however, matches literature well. Full article

The bicycle, being unstable at low speed and marginally stable at high speed, is sensitive to lateral perturbations. One of the major lateral perturbations is crosswind, which can lead to accidents and fatalities. Here we investigate the effect of crosswind on the lateral dynamics and control of the bicycle in a wide range of forward speeds and various crosswinds, by means of computer model analysis and simulation. A low dimensional bicycle model is used together with experimentally identified rider control parameters. The crosswind forces are obtained from a recent experimental study. Analysis and simulation show that crosswind decreases the stability of the bicycle and is clearly a safety issue. Full article

The objective of this research is to model the expenditure and recovery of Anaerobic Work Capacity (AWC) as related to Critical Power (CP) during cycling. CP is a theoretical value at which a human can operate indefinitely and AWC is the energy that can be expended above CP. There are several models to predict AWC-depletion, however, only a few to model AWC recovery. A cycling study was conducted with nine recreationally active subjects. CP and AWC were determined by a 3-min all-out test. The subjects performed interval tests at three recovery intervals (15 s, 30 s, or 60 s) and three recovery powers (0.50CP, 0.75CP, and CP). It was determined that the rate of expenditure exceeds recovery and the amount of AWC recovered is influenced more by recovery power level than recovery duration. Moreover, recovery rate varies by individual and thus, a robust mathematical model for expenditure and recovery of AWC is needed. Full article

According to syllabi of ballroom dancing, the sway is explained as the inclination of the body towards the inside of the turn. This explanation is questionable and a more adequate explanation is given based on a mechanical analysis with a new concept of inclination and bending sways. First, the sway mechanism is explained as the balance of the inertia force and the inclination using one-element model. Further a two-element model is introduced including both the inclination and the bending effects. The model explains the control and stability of sway. The sway process is classified into three stages, and the change of the inclination and bending with time is demonstrated by the analysis. The understanding of sway mechanism improves the dancers’ swing movements. Full article

Kendo is one of the most ancient swordsmanship arts in Japan. The aims of this study are to develop and test an innovative smart Kote glove for assisting the Kendoka to distinguish scoring from non-scoring Kote (wrist) strikes. An in-house developed pressure sensing platform was utilized to develop the smart Kote glove. Ten kendo practitioners, comprising of five Dan (black belts equivalent) and five Kyu (lower level/ungraded of both genders), participated in this study. The results showed significant differences between Dan and Kyu participants in both accuracy and sharpness of the strikes. Dan grade participants showed higher percentage of hitting the target comparing to Kyu grade (92% and 75% respectively). The percentage of scoring was also significantly higher in Dan (78%) than in Kyu (37%) grades. The average impact force of scoring by Dan grade (1159 ± 379 N) was higher than by Kyu grade (852 ± 429 N). Full article

Natural rise and fall movement represents typical characteristics of the swing dances in ballroom dances. The rise and fall movements are analyzed in the mechanical point of view in the presentation. The biomechanics of the rise and fall movements were analyzed in terms of the potential energy and the velocity of the body. Some basic figures of Waltz are taken as examples with application suggestion to the other dances. A sinusoidal function is employed for vertical and horizontal movements in the analysis featuring the natural swing movement of the dancer’s body. The height of center of gravity of dancer and its vertical acceleration are quantitatively exhibited in graphs for each basic movement of the figures of these dances. It is shown that the maximum height in the movement depends on each figure in each dance and that it is limited by the acceleration analysis regardless of dancer’s height or weight. Full article

In rock climbing, finger strength is directly related to performance. Here, a novel device is described to enhance finger strength training or aid in rehabilitation of finger injuries. The device incorporates load cells into an existing hangboard to measure finger force, record it and display it to the athlete in real time. The device was characterized for accuracy, linearity, hysteresis and repeatability, and found to have a resolution of ±01.5 N, sample rate of 10 Hz, and linearity of 0.9998. Preliminary athlete trials of the device verified its ability to more accurately record training exertion, that biases exist between the right and left hands of climbers and that this real-time performance feedback can improve training quality. Full article

A smart cricket ball was used to investigate the influence of increased spin rate on the bowling performance parameters. In three spin bowlers, the performance parameters were compared before and after increasing the spin rate. The first bowler increased the spin rate by 22%, decreased the normalised precession the angle at which the spin rate vector moves into the torque vector—the lower the more efficient), and increased the torque, angular acceleration and power, showing an improvement in all performance parameters. The second bowler showed no improvement in any performance parameters. The third bowler increased the spin rate marginally, but insignificantly; but improved the normalised precession dramatically (reducing it by 50%). The research results suggest that the mere intention to improve the spin rate changes bowling technique in way that optimises normalised precession, even if the spin rate does not actually increase. Full article

A wingsuit gives the human body an airfoil-like shape to fly in the sky. The paper proposes a holistic design approach combining the fluid mechanical simulation of the function with appropriate CAE-software for the generation of pattern cuttings. A parametric CAD model of the flyer wearing a wingsuit is created enabling easy changes in its posture and the wingsuit geometry. The flow simulation is set up using a commercial CFD code. Since there is no database available for the flow around a wingsuit, validation is conducted for a delta wing. This configuration is close to a wingsuit in terms of geometry and flow regime, but simpler and with sound experimental data available. Boundary conditions, mesh and selected turbulence model are validated with this configuration and experience gained about parameters of the solution process. Due to the computational link between CAE and CFD it’s possible to accelerate the development of wingsuits. Full article

Active fabrics providing better comfort of the garments and footwear rapidly become an essential part of our life. However, only limited information about the performance of such fabrics is commonly available for the garment and footwear designers, and tests are often done only with the final products. Thus development of the objective testing methods for the fabric assemblies containing microporous membranes and garments using them is one of the important topics. Garment tests in the climate chamber when exercising in windy and rainy conditions with a set of temperature and humidity sensors placed over the body allow comparing manufactured garments for thermal and humidity comfort. To allow for better material testing a new laboratory setup was developed for studying the dynamics of the humidity transport through different fabrics at realistic conditions in extension of the existing ISO test procedure. Present paper discusses the experimental procedures and first results acquired with new setup. Full article

The thermophysiological function of clothing influences athletic wellbeing and performance, particularly in outdoor endurance activities such as triathlon. However, there is very little existing research on the performance of triathlon suits relative to thermophysiological function of the wearer. This pilot study provides a benchmark for triathlon suit performance and insights into improving the suit design and material engineering. The study assessed the thermal and breathability attributes of 6 triathlon suits and concluded that while both of the attributes were similar overall, they varied in different body zones due to different design, construction and materials. Local thermal and evaporative performance were affected by fabric construction; double fabric layering in the stomach panel; the number, size, shape and material structure of rear pockets; cycle crotch pad size, shape and thickness; and panel design. The results of this study show the importance of garment design, construction and materials for the best thermal and evaporative resistance attributes of sportswear. Full article

This study is designed to understand post-exercise comfort perceptions by exploring the relationship between users and garments. Influenced by new technologies from fibres, manufacturing techniques, and surface coatings athletic apparel is changing. These technologies can influence the quality of daily pursuits, and by assessing psychological and physiological responses to physical activity, it’s possible to optimise garment performance. To that end, this paper presents a qualitative and quantitative analysis of thermal regulation and comfort perceptions within a controlled laboratory environment. A group of eleven healthy athletic female participants performed a twenty-minute high-intensity interval training running session (HIIT) and subsequent transition activity period. Participants had vitals monitored and were periodically prompted with specific questions to gauge their perceptions of effort, temperature, exertion, and comfort. The results suggest that perceptual differences are minor when evaluating apparel design during high-intensity exercise, and perhaps the efforts of garment design optimization would be best placed in an immediately subsequent activity type. Full article

The interaction between footwear and the pitch surface is an important aspect for successful performance and injury prevention in futsal. We aimed to investigate shoe-surface interaction of non-marking and multi-studded outsole designs. Five university players were recruited to perform two futsal specific movements (front translational traction-FTT and side translational traction-STT). A motion capture system including an embedded force plate covered by a synthetic material for futsal pitch, were utilized to collect the ground reaction force components. During FTT and STT, the multi-studded outsole was characterized by significantly higher mean peak traction forces. Moreover, although there were no significant differences in peak coefficient of traction between the two types of futsal shoes during STT, the multi-studded outsole tended to produce marginally higher peak coefficient of traction during FTT. It can be concluded that the multi-studded outsole design is prone to generate higher traction force and coefficient of traction. Full article

In competitive association football, wearing electronic performance and tracking system (EPTS) devices was approved in 2015. Safety concerns regarding their use have been raised; however, research and understanding is limited. Recently, FIFA has taken steps to assess possible injury mechanisms associated with wearing EPTS devices. This study identifies potential injury scenarios in football and associated impact energies. EPTS device use was first surveyed by questionnaire and semi-structured interviews. Unexpected, backward falls were highlighted as potential injury scenarios. An anthropomorphic test device (ATD), wearing a mock-EPTS device, was dropped onto 3G turf. Impact energy was 142.4 ± 42.1 and 5.8 ± 4.0 J whilst wearing and not wearing mock-EPTS devices respectively. Results indicate that wearing EPTS devices markedly increased impact energy experienced at the upper-back during falls. Further investigation into possible injury mechanisms (e.g., EPTS device shape and/or contact-area) of skin laceration and/or contusion risk, is warranted. Full article

The drag and lift of footballs have been mainly measured by wind tunnel tests. In the present study, computational fluid dynamics (CFD) and the lattice Boltzmann method were used to visualise the wakes of spinning and non-spinning footballs and analyse the dynamics of the observed vortex structures. The dominant vortex structures in the wakes of the footballs were determined to be large-scale counter-rotating vortex pairs. The fluctuation of the vortex pair for the spinning football was also estimated to be smaller and more stable than that for the non-spinning football. Although the presence of an unstable, large-scale counter-rotating vortex pair in the wake of a non-spinning ball has been previously observed in wind tunnel tests, the present study particularly found that the dominant vortex structure of a spinning ball was a stable, large-scale counter-rotating vortex pair. Full article

Football is one of the most popular sports in the world. It is played by a diverse set of people, from little kids to professional athletes, who possess a large range of physical abilities and skill. One of the most important pieces of equipment is the football itself. This paper examines the physics behind the optimal football pressure as a function of ball speed, touch and force of kick, considering the vibration and dynamics of the football as it is kicked. It was observed that the pressure of a football plays a significant role in the dynamic interaction between the ball and foot. A low-order nonlinear lumped mass dynamic model of kicking foot and ball with mass, stiffness and damping was proposed and equations of motion were derived. Simulations were conducted and the optimal football pressure between 0.138 bar (2 psi) and 0.965 bar (14 psi) was proposed considering a multi-objective DIRECT optimization. Full article

For an athlete to make an appropriate decision and successfully perform a skill, they need to perceive opportunities for action by visually exploring their environment. The head movements that support visual exploration can easily and accurately be recorded using Micro-Electro-Mechanical Systems (MEMS) Inertial Measurement Units (IMU) in research and applied settings. However, for IMU technology to be effective in applied settings, practitioners need to be able to communicate data to coaches and players. This paper presents methods of visualising and communicating exploratory head movement data, with the aim of giving a better understanding of (a) individual differences in exploratory action, and (b) how IMUs can be used in applied settings to assess and monitor visual exploratory action. Full article

The kick skill and its analysis are important in Soccer. To detect impact point by using virtual impact model is aim of this study. The virtual impact model was made as a surface composed of virtual markers. As the result, mean coordinate values of impact point were below; straight (Lateral: −24.0 ± 5.6 mm, Horizontal: 152.7 ± 8.4 mm, Vertical: 52.3 ± 4.0 mm), curve (Lateral: −35.6 ± 4.8 mm, Horizontal: 151.6 ± 13.7 mm, Vertical: 47.5 ± 5.2 mm), knuckle (Lateral: −33.3 ± 9.0 mm, Horizontal: 140.8 ± 10.7 mm, Vertical: 52.1 ± 2.7 mm). According to comparison of coordinate value of each trial, mean point of straight was near the center line of foot on instep, mean point of curve was located on inside of foot, mean point of knuckle was near the foot joint. We revealed difference of impact point and showed trajectory of impact point. Full article

Golfers aim to hit the golf ball correctly and maximize its displacement. It is necessary to predict shaft movement during a golf swing via simulation in order to determine the appropriate shaft for each individual golfer’s swing. Our previous study simulating golf club movement during the golf swing demonstrated 3D club movement via a finite element method simulation model with shaft flexibility. In this study, we added torque, taking into account the combination of grip acceleration and club head centroid, to the simulation model. In order to determine the influence of the torque, we then compared the measured and simulated results of shaft deflection and club head kinematics [HS (club head speed), Path (path angle), AA (attack angle), and FA (face angle)]. There was no significant torque influence for HS, AA, or shaft deflection. However, the Path and FA simulations were close to the measured values. Full article

Wearable inertial sensor systems are an upcoming tool for self-evaluation in sports, and can be used for swing analysis in golf. The aim of this work was to determine the validity and repeatability of an inertial sensor system attached to a player’s glove using a radar system as a reference. 20 subjects performed five full swings with each of three different clubs (wood, 7-iron, wedge). Clubhead speed was measured simultaneously by both sensor systems. Limits of Agreement were used to determine the accuracy and precision of the inertial sensor system. Results show that the inertial sensor system is quite accurate but with a lack of precision. Random error was quantified to approximately 12%. The measurement error was dependent on the club type and was weakly negatively correlated to the magnitude of clubhead speed. Full article

A long-held assumption in golf research is that the driver-ball impact is accurately modelled as a collision between two free bodies, i.e., the clubhead is not attached to the shaft. The purpose of this work was to examine the validity of this assumption using multibody simulation and motion capture technology. Ten elite golfers were recruited to participate in a motion capture experiment to validate a Rayleigh beam model of a flexible club. Using the six degree-of-freedom motion of the grip as an input to the model, the simulated shaft deflections showed good agreement with the experiment. An impact model based on volumetric contact was integrated with the flexible club model and was used to compare the launch conditions of free-body and full-club impacts. Analysis of the launch conditions revealed that the shaft creates a stiffening effect that resists clubhead rotation during contact, corresponding to an increase in ball speed and suppression of the gear-effect relative to free-body impacts. The results demonstrate that shaft dynamics cannot be treated as negligible when evaluating driver impact mechanics. Full article

A two degree of freedom hand-grip model was developed and simulated with a golfer downswing model, which contained an experimentally validated flexible shaft model. Experimental modal analysis was performed on a golf club to derive frequency response functions for both fixed-free and hands-free boundary conditions. Simulated frequency response functions were generated with the developed grip model to impose a hands-free boundary condition. Direct collocation using GPOPS-II was utilized to optimize the swing model with and without the grip model. An increase in clubhead velocity and decrease in shaft deflection was observed with the grip model implemented. In addition, the direct collocation approach resulted in similar joint angle trajectories, shaft deflection patterns, and joint torque profiles to those reported in the literature. Full article

Advances in golf club performance are typically based on the notion that golfer biomechanics do not change when modifications to the golf club are made. The purpose of this work was to develop a full-swing, forward dynamic golf drive model capable of providing deeper understanding of the interaction between golfer biomechanics and the physical properties of golf clubs. A three-dimensional biomechanical model of a golfer, a Rayleigh beam model of a flexible club, an impact model based on volumetric contact, and a spin-rate dependent aerodynamic ball flight model are used to simulate a golf drive. The six degree-of-freedom biomechanical model features a two degree-of-freedom shoulder joint and a pelvis to model the X-factor. It is driven by parametric joint torque generators designed to mimic muscle torque production, which are scaled by an eccentric-concentric torque-velocity function. Passive resistive torque profiles fit to experimental data are applied to the joints, representing the resistance caused by ligaments and soft tissues near the joint limits. Using a custom optimization routine combining genetic and search-based algorithms, the biomechanical golf swing model was optimized by maximizing carry distance. Comparing the simulated grip kinematics to a golf swing motion capture experiment, the biomechanical model effectively reproduced the motion of an elite golf swing. Full article

The objective of this study was to construct a finite element model for a carbon fiber reinforced plastic club shaft, and to investigate the effects of the torsional stiffness of the shaft on the dynamic behavior of a golf club during the swing. Mechanical properties of the shaft with orthotropic elasticity were determined using the rule of mixture which was defined by a volume fraction of fiber and resin. Swing simulations were conducted using club models with different torsional stiffness. The effect of the torsional stiffness on the clubhead alignment at impact tended to be stronger with the impact velocity of the clubhead due to the centrifugal force acting on the head. This indicates that the clubhead alignment at impact tends to be subject to effects of the timing of the impact, which depends on the relationship between the ball position and the impact velocity in addition to the mechanical properties of the shaft. Full article

The following considers lift and drag measurements of 13 production golf ball models propelled through still air in a laboratory setting. The balls travelled at speeds ranging from 18 m/s to 91 m/s and spin ranging from 1500 rpm to 4500 rpm. Speed sensors measured the speed and location of the balls at three locations from which the coefficient of lift and drag were found. The sensors were sufficiently close (3.81 m to 5.08 m) so that the lift and drag effects were nearly constant. Lift and drag were observed to depend on speed, spin rate, and ball model. The difference in the drag coefficient between the ball models were relatively large (>0.1) at low speed (Re < 10⁵), and smaller (<0.05) at high speed (Re > 10⁵). The lift coefficient had a non-linear dependence on spin (fit with a 2nd order polynomial). A trajectory of each ball model was found from the measured lift and drag response. Carry distance varied by 18 m over the models considered here and was not strongly correlated with ball cost. Full article

The influence of the location of the center of mass (cm) of the putter head, relative to the shaft, on golfer applied kinetics at the grip was investigated. Participants made 12 attempts at a straight up-hill (2.2° slope) 8 ft putt with half of the attempts executed using a PING Anser 4 toe-hang putter (TH) and half with an Anser 5 face-balanced putter (FB). The net torque applied by the golfer, acting about the long axis of the shaft, was significantly greater in magnitude with the TH putter in comparison to the FB putter. The TH putter was also associated with a higher angular velocity about the shaft and a more open face at impact. These findings may have important implications for fitting the style of putter to a particular stroke or individual golfer as golfer applied kinetics would be strongly associated with the ‘feel’ of a putter. Full article

A two-part experimental study was conducted in order to better understand how the delivered face angle and club path of a golf club influences the initial launch direction of a golf ball for various club types. A robust understanding of how these parameters influence the ball direction has implications for both coaches and club designers. The first study used a large sample of golfers hitting shots with different clubs. Initial ball direction was measured with a Foresight Sports camera system, while club delivery parameters were recorded with a Vicon motion capture system. The second study used a golf robot and Vision Research camera to measure club and ball parameters. Results from these experiments show that the launch direction fell closer to face angle than club path. The percent toward the face angle ranged from 61% to 83%, where 100% designates a launch angle entirely toward the face angle. Full article

The forgiveness of golf putters is traditionally achieved through weight distribution. Higher MOI (moment of inertia) putters will show less ball speed loss on impacts away from the sweet spot. A very large MOI putter, however, may not be desired by a golfer due to weight or appearance. The relationship between ball speed and impact location is affected by the mass properties of the putter (i.e., CG location, mass, moments of inertia, products of inertia) and the putter face. It has been shown that certain face properties, such as milling patterns, grooves, or soft inserts, can have small effects on ball speed. This paper proposes a method to normalize the ball speed on laterally miss-hit putter impacts using a “model-specific” milling pattern of variable depth and pitch, resulting in the largest possible region of the face providing consistent putt distances, thus improving performance given the average player’s impact pattern. Full article

Golf clubs are often evaluated by many methods to determine their performance. For drivers in particular, the primary performance indicator is ball speed, which is directly related to distance. Golf club manufacturers make many claims about how extra ball speed is achieved. For example, these may include: design features, face thickness, materials, center of gravity location, and moments of inertia. This paper proposes a new method to evaluate the performance of golf clubs from a single metric. With the benefits of modern launch monitors, accurate impact location data can be captured very efficiently. Using this, along with COR (coefficient of restitution) map testing, the Expected Value of COR can be calculated for a golfer or population of golfers. The “Expected COR” metric takes into account many engineering properties of a particular club that affect ball speed, along with the impact variation of the golfer, to give a single score for rating. Full article

Putting accounts for more shots in a round of golf than any other type of play. The percentage of putts holed decreases as putt length increases, because golfers struggle to achieve a consistent range and direction. Range variation has been partly attributed to the ball striking the club face away from the central plane of the putter face. Tests have shown a 30 mm off-centre impact can reduce the roll distance of a putt by 13%. In this paper, changes in mass distribution of the putter body and the addition of a flexible striking surface are considered. Physical testing and Finite Element Analysis are used to produce a club design with more consistent roll distance. Redistribution of mass reduced the roll distance variation across the clubface. Combining this with a flexible impact surface reduced the variation between a central impact and one 20 mm from center to just 1%. The proposed design could significantly reduce distance variation; aiding golfers in holing putts. Future work will optimise the design and validate through physical prototyping. Full article

In April 2017, a foiling Optimist dingy designed entirely by students, was successfully tested under standard sailing conditions in the waters outside Gothenburg. In order to achieve take of wind speeds as low as 6 m/s, a stiff and lightweight design of the dinghy and its foiling components was necessary. There have been few successful attempts to make an Optimist foil in a stable manner, as such there were no standards or recommendations available for the design. Therefore, a simulation driven structural design methodology for hydrofoils, centreboards, centreboard-to-hull connections, and necessary hull reinforcements using sandwich structures was adopted. The proposed design was then manufactured, allowing for a significantly stiffer hull and a 20% decrease in weight over a conventional Optimist. Excluding the rig and sail, the final weight came to 27 kg. Full article

Advanced materials such as metal alloys, carbon fibre composites and engineered polymers have improved athlete performances in all sporting applications. Advances in manufacturing has enabled increases in design complexity and the ability to rapidly prototype bespoke products using additive manufacturing also known as 3D printing. Another recent fabrication method widely used by medical, electronics and armaments manufacturers is particulate injection moulding. This process uses exact quantities of the required material, in powder form, minimising resource and energy requirements in comparison to conventional manufacturing techniques. The process utilises injection moulding techniques and tooling methods developed and used in the plastics industry. It can produce highly complex component geometries with excellent repeatability and reduced cost where volume manufacturing is required. This is especially important when considering materials such as titanium that are not only expensive in comparison to other metals but are difficult to process by regular machining and fabrication methods. This work presents a review of titanium use in the sporting sector with a focus on sporting devices and equipment. It also proposes that the sports engineering sector could increase performance and enable improvements in safety by switching to design methods appropriate to processing via the particulate injection moulding route. Full article

Foams are commonly used for cushioning in protective sporting equipment. Volumetrically compressing open-cell polyurethane foam buckles cell ribs creating a re-entrant structure—set by heating then cooling—which can impart auxetic behaviour. Theoretically, auxetic materials improve impact protection by increasing indentation resistance and energy absorption, potentially reducing sporting injuries and burdens on individuals, health services and national economies. In previous work, auxetic foam exhibited ~3 to ~8 times lower peak force (compared to its conventional counterpart) under impacts adopted from tests used to certify protective sporting equipment. Increases to the foam’s density and changes to stress/strain relationships (from fabrication) mean Poisson’s ratio’s contribution to reduced peak forces under impact is unclear. This work presents a simple fabrication method for foam samples with comparable density and linear stress/strain relationship, but different Poisson’s ratios ranging between 0.1 and −0.3, an important step in assessing the Poisson’s ratio’s contribution to impact force attenuation. Full article

Current research of auxetic materials highlights its potential as personal protective equipment for sports apparel with enhanced properties such as conformability, superior energy absorption and reduced thickness. In contrast, commercially available protective materials have proven to be problematic in that they inhibit movement, breathability, wicking and that molded pads are prone to saddling. Foam components are embedded within personal protective equipment for sports apparel, where protective material is positioned at regions of the body frequently exposed to injury of the soft tissue through collision, falls or hard impact. At present, the impact resistance of auxetic open cell polyurethane foam and some additively manufactured auxetic structures have been established, and processes for manufacturing curved auxetic materials as well as molding methods have been developed. Despite this, auxetic materials have not yet been applied as personal protective equipment for sports apparel in current research. This paper argues that there is scope to investigate auxetic materials potential for enhanced wearer functionality through properties of synclastic curvature and biaxial expansion. Full article

In 2003, the BMW Group developed a longboard called “StreetCarver”. The idea behind this product was to bring the perfect carving feeling of surf- and snowboarding on the streets by increasing the maneuverability of classical skateboard trucks. The outcome was a chassis based on complex kinematics. The negative side effect was the StreetCarver’s exceptional high weight of almost 8 kg. The main reason for this heaviness was the choice of traditional metallic engineering materials. In this research, modern fiber reinforced composites were used to lower the chassis’ mass by up to 50% to reach the weight of a common longboard. To accomplish that goal, carbon fibers were placed along pre-simulated load paths of the structural components in a so-called Tailored- Fiber-Placement process. This technology allows an angle-independent single-roving placement and leads not only to the reduction of weight but also helps to save valuable fiber material by avoiding cutting waste. Full article

Optimisation of wheelchairs for court sports is currently a difficult and time-consuming process due to the broad range of impairments across athletes, difficulties in monitoring on-court performance, and the trade-off set-up that parameters have on key performance variables. A robust design approach to this problem can potentially reduce the amount of testing required, and therefore allow for individual on-court assessments. This study used orthogonal design with four set-up factors (seat height, depth, and angle, as well as tyre pressure) at three levels (current, decreased, and increased) for three elite wheelchair rugby players. Each player performed two maximal effort sprints from a stationary position in nine different set-ups, with this allowing for detailed analysis of each factor and level. Whilst statistical significance is difficult to obtain due to the small sample size, meaningful difference results aligning with previous research findings were identified and provide support for the use of this approach. Full article

The aim of the work was the kinematic analysis of pushing technique of four wheelchair rugby players using a stereophotogrammetric motion capture system. The four players presented an increasing level of ability expressed by their wheelchair rugby classification point. An original contribution of the work is the fact that exercises were recorded on an inertial drum ergometer with players using their own game wheelchair. The ergometer inertia was tuned to reproduce the linear inertia of each player: subjects performed sprint tests without additional resistance and Wingate tests. The Initial Contact and Hand Release values at the wheel were recorded for each test in the early stages and at the end. The shoulder flexion/extension angle and the elbow flexion angle were plotted against each other to highlight a tendency to a synchronous joint kinematics with increasing classification points. Full article

The objective of this study was to evaluate an optimum structure for a rugby wheelchair by estimating the muscle force during forward linear operation of the wheelchair using an inverse dynamics analysis. The simulation model was represented by restraining the contact area between the frame and seat of the wheelchair and the body model. Three body model variations were constructed with different degrees of disability. Wheelchair models were also constructed by varying the range of camber angle, wheel diameter and axle positions, respectively. The effects of the design parameters for the wheelchair on the muscle force were investigated. As a result, the axle position had the strongest effect on the muscle force of the upper limbs, and it is effective to lower the axle position for reducing the muscle force required. This implies that the adjustment of the axle position leads to a reduction in risk of injury occurrence. Full article

This work was included in a wider project oriented to the improvement of residual neuromuscular skills in disabled athletes playing wheelchair rugby: the wheelchair rugby Italian national team was involved and tests allowed to analyse the impact loads on a rugby wheelchair frame. The frame of a rugby wheelchair offensive model, made by OffCarr Company, was instrumented with four strain gauge bridges in four different points. Then, three test types were conducted in laboratory: two static calibrations with the application of known loads, the first with horizontal load and the second with vertical load, and a dynamic horizontal calibration, impacting against a fix load cell in order to validate the results of horizontal static calibration. Finally, a test session took place in the field with the collaboration of two team players. The test consisted in voluntary frontal impacts between the two players, starting from 6 meters distance each other. The opponent of the instrumented wheelchair was a defender. From this test, the value of the horizontal load received by the frame in the impact instant was quantified. Moreover, also the vertical load acting on the wheelchair during the rebound of the player after the hit was evaluated: these informations were useful to the wheelchair frame manufacturer for the proper static, impact and fatigue design. Full article

A high prevalence of shoulder injuries exists across the wheelchair using populations. To maintain competitive longevity and optimise performance, athletes must employ techniques which pose minimal injury risk. A computational model was used to assess relationships between the magnitude of reaction moments at the shoulder with key propulsion characteristics, including; contact and release angles, hand speed at contact, and joint angles at contact. Subject-specific musculoskeletal models (mass, maximum isometric force) for two elite wheelchair racing athletes were derived, and driven through kinetic and kinematic data obtained using motion capture. Greater reaction moments (min 72.6 Nm, max: 1077.8 Nm) at the shoulder were correlated with hand velocity (7.2 m/s–9.3 m/s) at contact (|r| > 0.866, p < 0.013), push time (|r| > 0.866, p < 0.013), and kinematic positioning at contact (|r| > 0.784, p < 0.020). Variations between athlete reaction force at the pushrim and joint reaction moments demonstrate the importance of coupled kinematic and modelling analysis in prescribing technique adaptations. Full article

The instrumentation of wheelchair racing chairs is currently limited by the influence of the athlete-wheelchair system mass and performance. Inertial measurement units (IMUs) provide a lightweight solution, and have demonstrated accurate kinematic monitoring of wheelchair ball sports. With the aim of investigating the capability of IMUs detecting contact and release timings, a study was performed on seven national level wheelchair racing athletes (T34 and T54 classifications). Athletes performed treadmill-based propulsion at speeds ranging between 19 km/h and 32 km/h, with the population sample enabling comparison between classification, propulsion speed, gender, age, glove type and wheel type. Contact and release timing points of each athlete were verified against measures obtained using video capture (100 Hz), which is considered a gold standard measure. IMUs identified contact timings for all athletes, however could not consistently identify release points for all athletes. Propulsion speed and gender were found to have minimal influence on the capacity to determine contact. Full article

In wheelchair racing, the optimal pair of gloves, as well as knowledge of conditioning of glove-rim contact surfaces can have a significant impact on race performance. Extreme temperatures, humidity, wet or dry conditions can considerably influence not only the hand-rim friction coupling (effectiveness of the athlete’s push cycle) but also the risk of injuries, blisters or sore areas which in turn, can influence the endurance of the athlete across long distance events. This paper reports an experimental study of the effect of bio-mimicry surface textures as a supplement for heightening glove-rim coupling for dry and wet weather conditions. The paper also provides recommendations for the practical implementation of the study findings through a proposal for the design and development of a pair of bespoke gloves for a wheelchair racing athlete for initial prototyping and performance trials. Full article

The purpose of this study was to develop the new wheel-chair which had the function to drive straight by one-hand operation. To perform this purpose, the driving force transmission axis (DFTA) which had transmitted the driving force from the one side of wheel to another side of that was developed. The wheel-chair could drive straight by one-hand operation by the DFTA. The large torque, however, was generated in the DFTA, because the DFTA transmitted the driving force from the one side of wheel to another side by the axis of small diameter. Furthermore, the shear stress in the DFTA generated by this torque would lead to the DFTA break. The shear stress in the DFTA was calculated to examine the axial strength and durability. On the DETA of the wheelchair, the maximum shear stress calculated from the torque in driving was 39.53 MP and this was defined as the standard of the demand specifications as a strength and durability of the DFTA. Full article

In this study, we conducted experimental measurements and computational analysis to investigate the aerodynamics of a shuttlecock, especially the effects of the camber of the shuttle’s skirt. The static aerodynamic coefficient from the experiment showed that the camber of the skirt was able to modify the aerodynamic characteristics. A positive camber, which indicates bending the blade toward the outside, causes a slight increase in lift and a decrease in drag. On the other hand, a negative camber causes an increase in drag, and an insensitive region in the lift and a pitching coefficient of approximately 0° was observed. This result leads to instability in the flight of the shuttlecock. The pressure distribution calculated using computational fluid dynamics revealed that each blade functions as a two-dimensional airfoil. However, in most cases, the blade is in stall condition due to an initial divergence angle of the skirt. Full article

The Hawk-Eye electronic line-calling system gives players the ability to challenge line-calling decisions. It also creates large datasets of ball and player movements during competitive play. In this paper we used a dataset taken from 5 years of the Davis and Fed Cup tournaments (comprising 71,019 points in total) to examine the effect of ball wear on aerodynamic performance. Balls were categorized as new or used depending on whether they were used in the first two games following a ball change (new) or the last two games before a ball change (used). Data falling into neither category was discarded. The coefficients of drag (Cd) of 9224 first serves from the Davis Cup were calculated by simulating their trajectories. New balls had a significantly lower average Cd of 0.579 compared to used balls’ 0.603 (p < 0.0001)—first serves made with new balls arrive 0.0074 s sooner than first serves made with used balls on average. Large sport datasets can be used to explore subtle effects despite a relative lack of precision. Full article

The effect of string pattern on the mechanical characteristics of a tennis racket were simulated numerically. A numerical simulation program to evaluate deformation of the string bed of a tennis racket was developed using the finite element method. The formulation of a numerical simulation code is described in this paper. The applicability of the developed simulation program was investigated by comparing experimental results of loading tests on string bed specimens, for which the distance between strings was 12 mm. The out-of-plane stiffness and sliding characteristics of strings of an actual racket were simulated using the developed simulation code. Full article

Tennis rackets have advanced significantly since the invention of the game in 1874, including innovations in both shape and materials. Advances in these design parameters have implications for racket performance, especially swing speed. This study tested one hundred rackets, spanning brands and eras, using simple, portable instruments in order to pilot protocols and make recommendations for streamlining testing procedures for tennis rackets. A wide range of properties were measured and documented for each racket. We suggest that since Transverse and Lateral Moment of Inertia are well correlated, measuring both is not necessary when processing a large number of rackets. In addition, it is also possible to predict the Transverse Moment of Inertia well from models that use simple dimension and mass measurements, which may be preferable in larger studies. Exploring the use of more complex modelling will allow us to better understand the impact of tennis racket design on performance in the future. Full article

This was a study of the properties of a badminton shuttle. The analysed feather was made of the brand Yonex. The properties related to the trajectory were analysed by two experiments. The first experiment provided data for the trajectory by using a camera system to capture the properties of the trajectory. Position and velocity were used to draw conclusions about the deviation to the right, as seen from the hitter. The experiment generated discrete points which made it possible to plot the data, the accuracy was estimated to ±1 cm and ±0.5 m/s. The second experiment examined the rotation of the shuttle by using a high-speed camera to capture the rotation of the shuttle. By measuring the rotation at discrete distances from the hitter, the development of the rotational speed was captured, with an accuracy of ±30 rotations per minute. The experiments described and explained a connection between sideways deviation and rotation. Full article

A novel Human Head Surrogate was obtained from available MRI scans of a 50th percentile male human head. Addictive manufacturing was used to produce the skull, the brain and the skin. All original MRI geometries were partially smoothed and adjusted to provide the best biofidelity compatible with printing and molding technology. The skull was 3D-printed in ABS and ten pressure sensors were placed into it. The brain surrogate was cast from silicon rubber in the 3D-printed plastic molds. Nine tri-axial accelerometers (placed at the tops of the lobes, at the sides of the lobes, in the cerebellum and in the center of mass) and a three-axis gyroscope (at the center of mass) were inserted into the silicon brain during casting. The cranium, after assembly with brain, was filled with silicon oil mimicking the cerebral fluid. Silicon rubber was cast in additional 3D-printed molds to form the skin surrounding the cranium. The skull base was adapted to be compatible with the Hybrid-III neck and allow the exit of brain sensors cabling. Preliminary experiments were carried out proving the functionality of the surrogate. Results showed how multiple accelerometers and pressure sensors allowed a better comprehension of the head complex motion during impacts. Full article

Studies are warranted to evaluate head injury criterion (HIC) on athletic fields to determine baseline numbers and compare those findings to current critical thresholds for impact attenuation. A two year (2016 and 2017) study was conducted on University of Tennessee athletic fields (Knoxville, TN, USA) to determine the effect of soil type (cohesive soil, United States Golf Association sand specifications) and grass species (Poa pratensis and Cynodon dactylon × C. transvaalensis) on HIC. Additionally soil moisture conditions monitored were: dry (0.06–0.16 m³/m³), acceptable (0.17–0.29 m³/m³), and wet (0.30–0.40 m³/m³). A linear relationship (r = 0.91) was identified between drop height (0.5–2.9 M) and HIC value (35-1423 HIC) on granular root zones of both grass types. However, HIC on cohesive soil is a function of soil water content in addition to drop height. These results demonstrate to aid in head injury prevention on cohesive soil athletic fields the HIC can be lowered by managing soil water content. Full article

Headform impact testing is commonly used in the evaluation of helmets and head gear, head impact sensors and in sports related accident reconstruction. While linear acceleration of the headform center of mass can be measured using three linear accelerometers, the preferred method for measuring rotational acceleration of the headform requires six or more additional accelerometers. Some measurement systems use gyroscopes to directly measure headform angular velocity and obtain angular acceleration through differentiation. This approach simplifies instrumentation of the headform and reduces costs, but at the expense of accuracy. Error introduced through differentiation of angular velocity data can be prohibitively large for some sports applications, particularly in the consideration of un-helmeted headform impacts. This work considers the application of a new, optimization-based differentiation technique to improve the fidelity of headform angular acceleration estimates based on gyroscope measures of headform angular velocity. A Hybrid III headform instrumented with three gyroscopes and nine linear accelerometers was subject to drop impacts, as well as being impacted with soccer balls and softballs projected over a range of velocities. Measures of resulting headform angular acceleration were obtained from the gyroscope data using five-point stencil differentiation and the new optimization based algorithm. These results were compared to the nine accelerometer array measurements of angular acceleration across impact scenarios. Full article

This paper reports the outcomes of a series of two Concussion Research Workshops held in Lowell, MA, USA. The workshop examined the state-of-the-art in concussion research, research challenges and the future directions of research within the following three core topic areas: (A) Concussion Prevention Techniques & Technology, (B) Concussion Diagnosis, and (C) Treatment of Concussions. Concussions are a form of traumatic brain injury caused by an impact and are a growing concern among athletes and those who are involved with sports. Recent years have led to increasing awareness and research related to concussions with limited definitive understanding of the specific mechanism and pathology. Technology is beginning to take on an important role in the prevention, diagnosis and treatment of concussions. Currently, sensors provide data about the impact and the athlete. However, sensors and better protective equipment can enable an effective monitoring and thus protection of athletes. Only when a more definitive understanding of the injury mechanism is achieved, can sensors and protective equipment design contribute to effective monitoring and protection of athletes. Full article

A participant wearing the Pedar-X performed 6 activities on level ground: Slow, medium and fast walk, medium and fast run, and limping. Static BW was measured prior each activity. The dynamic and static BWs were calculated from the mean of the sum of forces of both feet over time and compared to the force measured from the force-plate. As the base pressure during the swing phase was not zero, it was treated in 3 ways: including the base pressure; subtracting the mean base pressure from the swing phase; subtraction of the base pressure from the entire signal. The calculated BWs were normalised to the actual BW of the participant. From the results, the BWs calculated had 10% error when static and 6% error when walking. To zero or subtract the baseline pressures improved the BW measurement by 1.75% and 4% respectively. Running data could not be analysed at a sampling rate of 50 Hz. Full article

Support interference in wind tunnel testing is an unavoidable effect. It is difficult to measure the aerodynamic force acting on a model such as a ball owing to this effect [1]. A magnetic suspension and balance system (MSBS) suspends the model without any mechanical supports by using magnetic force, and at the same time, can measure the aerodynamic force acting on the model. The 1-m MSBS, located at the Institute of Fluid Science, Tohoku University, is the world’s largest MSBS. It has a 1-m-wide octagonal cross section. A sphere is taken as the experimental object, and the results of the aerodynamic force acting on it are presented. The diameter of the sphere is 150 mm, and its blockage ratio is 2.1%. The experiment was conducted at Reynolds numbers ranging from 0.5 × 10⁵ to 4.7 × 10⁵. It clearly shows the drag crisis at approximately Re = 3.7 × 10⁵, and the fluctuation of the sphere abruptly increase around this region. Full article

Footwear-based wearable applications are relevant to numerous fields and have great commercial and clinical potential. However, scientifically validated, reliable data on these devices is largely missing. Centre of pressure (COP) is an important and common factor for measuring balance and gait and hence the validity of such devices is essential for reading accurate data. This study aims to investigate COP accuracy of an existing system, Pedar (PE), and a newly designed Smart Insole (SI) using a force plate (FP). This was done by means of COP data noise (R²), and gradient of the fit function (k). For the SI, the maximum COPx and COPy data achieved R² values of 0.7837 and 0.9368 and k values of 0.8867 and 0.8538 respectively when compared with the FP. Conversely, the Pedar achieved R² values of 0.8409 and 0.9401 and k values of 1.0492 and 1.08 when compared with the FP respectively. Full article

One of the primary causes of discomfort to both irregular and elite cyclists is heat entrapment by a helmet resulting in overheating and excessive sweating of the head. To accurately assess the cooling effectiveness of bicycle helmets, a heated plastic thermal headform has been developed. The construction consists of a 3D-printed headform of low thermal conductivity with an internal layer of high thermal mass that is heated to a constant uniform temperature by an electrical heating element. Testing is conducted in a wind tunnel where the heater power remains constant and the resulting surface temperature distribution is directly measured by 36 K-type thermocouples embedded within the surface of the head in conjunction with a thermal imaging camera. Using this new test system, four bicycle helmets were studied in order to measure their cooling abilities and to identify ‘hot spots’ where cooling performance is poor. Full article

Excessive heat at the foot-shoe sole interface negatively affects a human’s thermal comfort. An understanding of the thermal behavior at this interface is important for alleviating this discomfort. During gait motion, a human’s body weight cyclically compresses a shoe sole (commonly constructed of viscoelastic materials), generating heat during loading. To evaluate the thermal effects of this internal heat generation on foot comfort, we developed and empirically validated a thermal analysis model during gait motion. A simple, one-dimensional prediction model for heat conduction with heat generation during compressive loading was used. Heat generation was estimated as a function of the shoe sole’s material properties (e.g., elastic modulus) and various gait parameters. When compared with experimental results, the proposed model proved effective in predicting thermal behavior at the foot-shoe sole interface under various conditions and shows potential for improving a human’s thermal comfort during gait motion through informed footwear design. Full article

There is great benefit for small medium enterprises (SMEs) and startups to utilize lead users in product development. By utilizing lead users companies can make products that are more commercially attractive and better accepted in the market. However, identifying lead users has traditionally been a difficult and expensive task. In the past, lead users have been found through time consuming personal networking, telephone interviews, mail questionnaires and data mining of often large user bases. This paper proposes that identification can be made more efficient by adapting some of these techniques, through taking a digital approach using existing social media communities such as those on Facebook. It is proposed that using social media application programming interfaces (APIs) could allow what used to be reserved for large multinationals, could be made accessible to SMEs and startup companies without extensive resources. Full article

Understanding the action of the metatarsophalangeal joint (MTP) is fundamental to improving the design process of a new outdoor shoe. Coming from the stated consideration, the aim of this research is to study the influence of shoe sole stiffness and terrain slope on the MTP joint angle of subjects walking in different conditions. To pursue this intent, different data collection sessions have been carried out in-vitro and in-vivo, indoor and outdoor. Two different approaches have been used to collect gait kinematics: an IMU (Inertial Measurement Unit) based system for the first campaign of tests, and a 2D video analysis for the second. Major findings showed a linear correlation between shoe sole stiffness and peak MTP joint angle during gait, as well as consistency in the value of the slope of the linear regression curves corresponding to the different conditions examined. Full article

The purpose of this study is to propose a two-dimensional (2-D) mathematical model of sports surfaces for evaluating the shock attenuation and deformation properties in both the vertical and horizontal direction, especially in competitive track and field materials. We develop a 2-D impact test device that can control the initial impact angle and intensity with parallelogram linkage. Using this device, various intensity impacts with angles ranging from 5–25 degrees were performed on test specimen. A 2-D mathematical model for sports surfaces and parameter identification method is also proposed for evaluating such surfaces, especially for polyurethane competitive track and field materials. The model is constructed from vertical and horizontal elements, and the parameters for each element are identified separately. Finally, vertical and horizontal forces with various angles and intensities can be estimated with an identified parameter set. Full article

High surface temperatures are often recorded on or close to the surface of an artificial turf pitch (ATP). Many literature sources from different countries have reported surface temperatures on artificial pitches rising up to 90–95 °C on hot days, which has raised numerous concerns about health risks for adult and child users. This study has investigated the thermal behavior of an instrumented 3rd generation ATP at Loughborough University in the UK, and related data also collected from several similar ATPs and a natural turf field. The data show the ATP is warming up and cooling down very quickly, up to 2.5–3.0 °C per minute. Solar radiation is the main factor driving the surface temperature fluctuations. A numerical model was developed to predict the surface temperatures and showed good approximation to the observed data. The model was used to show peak surface temperatures could be significantly reduced by increasing the albedo of the surface. Full article

The synthetic clay tennis court’s properties need to be examined and modified to converge towards the playing characteristics of the natural clay tennis court. The aim of this study was to investigate the responses of three distinct carpet-material combinations and evaluate how the materials’ alteration affected the results. The specimens were compressed uniaxially up to 2 kN at 400 N/s loading rate at varying number of cycles. Energy transformation, strain accumulation, step of strain accumulation and moduli of each surface combination were calculated. Results indicated that the measurements were affected by the loading history and that the carpet modification influenced mainly the energy transformation and the strain accumulation, while the material change affected additionally the moduli of the system. Conduction of the experiments enhanced understanding of the clay court’s response and could attribute to the initial modelling of the synthetic clay surface. Full article

Third generation (3G) artificial turf systems use in sporting applications is increasingly prolific. These multi-component systems are comprised of a range of polymeric and elastomeric materials that exhibit non-linear and strain rate dependent behaviours under the complex loads applied from players and equipment. To further study and better understand the behaviours of these systems, the development of a numerical model to accurately predict individual layers’ behaviour as well as the overall system response under different loading conditions is necessary. The purpose of this study was to characterise and model the mechanical behaviour of a rubber shockpad found in 3G artificial surfaces for vertical shock absorption using finite element analysis. A series of uniaxial compression tests were performed to characterise the mechanical behaviour of the shockpad. Compression loading was performed at 0.9 Hz to match human walking speeds. A Microfoam material model was selected from the PolyUMod library and optimised using MCalibration software before being imported into ABAQUS for analysis. A finite element model was created for the shockpad using ABAQUS and a compressive load applied to match that of the experimental data. Friction coefficients were altered to view the effect on the loading response. The accuracy of the model was compared using a series of comparative measures including the energy loss and root mean square error. Full article

The planning for major international sporting events such as the Olympic Games and Commonwealth Games require the use of a range of Field of Play facilities. Often these are required to be temporary overlay installations due to the cost of constructing new standalone facilities. The planning for the 2018 Gold Coast Commonwealth Games included the construction of several permanent new build facilities that would be retained as legacies for the Gold Coast and Brisbane regions. The games will also include several temporary overlay Field of Play facilities; these are the competition and warm-up athletics track and field and the beach volleyball facilities. The design of such temporary overlay sites need to ensure the construction adheres with the governing sport body as well as providing quick and economical construction methodology. This paper provides an overview of the design for the temporary Field of Play facilities. Full article

The purpose of this study was to compare the active drag values estimated by the MRT-method and the MAD-system. Six male competitive swimmers participated in this study and performed front crawl with arms only condition. The drag was compared at six-staged velocities ranged from 0.9 to 1.4 m/s between MRT-method and MAD-system. The drag estimated by MRT-method showed larger values than that obtained using MAD-system at each velocity (MRT-method/MAD-system: 119% at 1.0 m/s; 133% at 1.2 m/s; 147% at 1.4 m/s). In addition, the stroke length in MRT-method condition decreased with swimming velocity being increased, while that in MAD-system condition was constant. Therefore, swimmers had to increase their stroke frequency in MRT-method condition in order to achieve the same swimming velocities as MAD-system condition, especially at high velocities. It was concluded that the difference in the way of exerting propulsion between MAD-system and MRT-method influenced the active drag which were estimated in two methods. Full article