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The study objective is to test general- and sport-specific adaption during a single training on the Flexibility Trainer. The device is designed to trigger residual muscle tone decreases of the hip-joint muscles by providing (nearly) isokinetic resistance during a full range of motion strength training in adduction/abduction and flexion/extension direction. Static hip flexion and abduction as well as kinematics of double side kicks were analysed on 15 participants before and after training (or rest for controls) to assess general flexibility and sport-specific movement range. Tests were recorded by a Vicon® motion capturing system. Static hip flexion and abduction as well as leg vector spreading angles (VSA) at different nodes of the kick were selected to determine adaptions of active and passive flexibility. Normalised hip joint moments, movement velocities and VSA were calculated to evaluate the training with the device. ANOVAs with 4-repeated measures and Friedman tests were performed to identify time differences and Bonferroni post-hoc test to identify between-subject effects. Significant differences were found for both static flexibility tests (Flexion = 13.65%; Abduction = 9.94%) and the VSA at specific action phases (≤15.15%). Results indicate that short-term adaptions when training with the Flexibility Trainer are exceeding comparable literature showing improved flexibility and sport-specific performance. [ABSTRACT FROM AUTHOR]

The current badminton shuttlecock products are highly ineffective. The bird feather shuttlecocks used in official competitions have an unsustainably high change count due to rapid breakage from repeated racquet strikes. Meanwhile, the current synthetic shuttlecocks lack the structural properties of their feather counterparts to produce the desired aerodynamics as a projectile. This study discusses two material testing methods: the feather compression and hysteresis test, which can provide relevant mechanical data to be incorporated into the manufacturing process of future synthetic shuttlecocks. The compressive moduli from six feather shuttlecock products (four goose and two duck) were compared using the proposed methods at the strain rate of 1.15 mm/60 s. Subsequently, a three-cycle hysteresis test was conducted at an increasing strain rate of 1.15 mm/120 s, 1.15 mm/80 s, and 1.15 mm/60 s. The compression results were comparable to those from previous studies; however, there are currently no hysteresis data of shuttlecock feathers were available for comparison. The proposed methods have the potential to provide vital mechanical data that should be taken into account for future synthetic shuttlecock designs. [ABSTRACT FROM AUTHOR]

Medieval combat sport is a form of mixed martial art in which combatants engage in fighting using offensive and defensive equipment while dressed in full armor. The sport is considered extremely taxing, making it nearly impossible to maintain the same level of performance. However, this form of sport has not been thoroughly analyzed, and its impact on human physical response is largely unknown. To address this gap, the study reported here aimed to introduce and test a procedure for analyzing human physical responses within the framework of the sport. To accomplish this, two experienced combatants were asked to engage in a series of strikes, performed in the form of a set duel simulating a professional fight competition. The kinematic aspect of the procedure was examined using motion analysis with the help of an IMU suit, while the physiological aspect was evaluated based on blood lactate levels and heart rate measurements. Furthermore, an ergometer test conducted in a laboratory setting aimed to determine the lactate threshold. The duel results showed noticeable decreases in the kinematic aspects of the strikes, such as the velocity of impact, and a dramatic rise in physiological aspects, such as heart rate and blood lactate levels. During the duel sets, the blood lactate surpassed the threshold level, and at the end, the heart rate exceeded the maximum age-related level. Practicing medieval combat sport has been shown to impose an extreme physical load on the bodies of combatants, noticeably affecting their performance levels. [ABSTRACT FROM AUTHOR]

Creating specialized components featuring complex structures typically involves extensive time, CAD modelling and manual labor. However, with the right combination of tools and knowledge, complex components can be generated, manufactured, and utilized within hours, rather than weeks or months. By creating a portable manufacturing setup, the designer can produce components on site, significantly enhancing accessibility. An example where time and accessibility are of vital importance is in paralympic cross country skiing where training schedules are tight and snow conditions vary. The aim of this study was to generate and manufacture form-fitted, lightweight knee-supports for a Paralympic sit-ski athlete within 4 days. This was done by 3D printing components generated using Fusion 360s Generative Design (GD), based on inputs from the athlete’s geometry, material testing and force data resulting from the athlete’s weight and movement. A precise fit around the knees was achieved using a high-accuracy 3D scanner and modelling software to create an adjustable prototype to determine knee positions and key angles. Force data from the knees were gathered using a digital twin sit-ski. Based on the collected data, the maximum forces inserted into the GD model were 700N and 500N for the right and left knee, respectively. Material data was obtained through testing ABS samples manufactured under the same conditions as the knee-supports themselves. The Young’s modulus was calculated to EXY=1.945±0.061GPa and EXZ=2.123±0.108GPa and UTS was σXY=31.408±0.774MPa and σXZ=25.859±1.956MPa. The GD model generated seven models to choose from for each knee. The supports were manufactured using a 3D printer modified to increase the volumetric flow, effectively reducing manufacturing time. Manufacturing time of the final knee-supports were 6 h 33 min and 7 h 24 min and the total weight of the components including support structures were 468 g and 532 g for the right and left knee, respectively. Later optimized print settings reduced the manufacturing time to 4 h 40 min. In total, two iterations of knee-supports were produced, and the final lightweight versions were mounted onto the sit-ski within 4 days. Qualitative feedback from the athlete revealed improved fit, increased stability, surprisingly short manufacturing time and a generally pleasing result.

The sports technology industry is currently experiencing rapid growth, driven by an increasing focus on fan engagement and satisfaction in stadiums, the desire to improve player and team performance, and the widespread adoption of eSports innovations. This, in turn, predetermined the emergence of a new field of knowledge – sports engineering, which bridges the gap between sports science and engineering developments. The development of this field is supported and stimulated by sports engineers, whose professional training has become one of the tasks of educational institutions in many countries around the world. The research hypothesis is that training and talent development in the field of sports engineering requires an integrated approach that will be based on thematic concentrations of engineering, medical, information and natural sciences. The purpose of the article is to consider the development of the concept of training specialists in the field of intellectual sports engineering through the prism of interdisciplinary integration. Research methods: study of specialized literature, analysis and synthesis, generalization and grouping, modeling, abstraction, systematization. Prospects for the development of sports engineering are outlined. The interdisciplinary connections of sports engineering are formalized, covering classical engineering, sports science and medicine, and sports equipment. The features of teaching sports engineering at the Belarusian National Technical University are described. Recommendations have been developed regarding the creation of engineering sports specializations in educational institutions in Russia. Satisfying public demand for sports engineers involves the implementation of a comprehensive policy for training specialists with the active interaction of government agencies, educational institutions, sports organizations and private companies.

Physical activity analysis assessment has been a concern throughout human history. The intersection of technological growth with sports has given rise to a burgeoning field known as sports engineering. In the 19th century, the advent of chrono-photography and pioneering marked the inception of sports performance analysis. In recent years, the noticeable developments achieved in wearable low-power electronics with wireless high interconnection capability, as a part of modern technologies, have aided us in studying sports parameters such as motor behavior, biomechanics, equipment design, and materials science, playing an essential role in the understanding of sports dynamics. This study aims to review over 250 published articles since 2018, focusing on utilizing and validating these emergent technologies in sports and clinical aspects. It is predicted that one of the next steps in sports technology and engineering development will be using algorithms based on artificial intelligence to analyze the measurements obtained by multi-sensor systems (sensor fusion) to monitor biometric and physiological parameters in performance analysis and health assessments. [ABSTRACT FROM AUTHOR]

Medieval combat sport is a form of mixed martial art in which combatants engage in fighting using offensive and defensive equipment while dressed in full armor. The sport is considered extremely taxing, making it nearly impossible to maintain the same level of performance. However, this form of sport has not been thoroughly analyzed, and its impact on human physical response is largely unknown. To address this gap, the study reported here aimed to introduce and test a procedure for analyzing human physical responses within the framework of the sport. To accomplish this, two experienced combatants were asked to engage in a series of strikes, performed in the form of a set duel simulating a professional fight competition. The kinematic aspect of the procedure was examined using motion analysis with the help of an IMU suit, while the physiological aspect was evaluated based on blood lactate levels and heart rate measurements. Furthermore, an ergometer test conducted in a laboratory setting aimed to determine the lactate threshold. The duel results showed noticeable decreases in the kinematic aspects of the strikes, such as the velocity of impact, and a dramatic rise in physiological aspects, such as heart rate and blood lactate levels. During the duel sets, the blood lactate surpassed the threshold level, and at the end, the heart rate exceeded the maximum age-related level. Practicing medieval combat sport has been shown to impose an extreme physical load on the bodies of combatants, noticeably affecting their performance levels.

Physical activity analysis assessment has been a concern throughout human history. The intersection of technological growth with sports has given rise to a burgeoning field known as sports engineering. In the 19th century, the advent of chrono-photography and pioneering marked the inception of sports performance analysis. In recent years, the noticeable developments achieved in wearable low-power electronics with wireless high interconnection capability, as a part of modern technologies, have aided us in studying sports parameters such as motor behavior, biomechanics, equipment design, and materials science, playing an essential role in the understanding of sports dynamics. This study aims to review over 250 published articles since 2018, focusing on utilizing and validating these emergent technologies in sports and clinical aspects. It is predicted that one of the next steps in sports technology and engineering development will be using algorithms based on artificial intelligence to analyze the measurements obtained by multi-sensor systems (sensor fusion) to monitor biometric and physiological parameters in performance analysis and health assessments.

[Display omitted] • In all deformation systems, Zn can be stably adsorbed on the surface of HfS 2. • The shear deformation significantly affects the band structure characteristics of HfS 2. • The deformation reduces the barrier of Zn in the diffusion path to 0.16 eV. In this study, the density functional theory (DFT) based on first-principles calculations was used to conduct a comprehensive theoretical calculation of the Zn adsorption HfS 2 system (Zn-HfS 2) to develop the potential of HfS 2 as an anode material for zinc ion batteries (ZIBs). The calculation results show that the adsorption energy decreases gradually (−1.368 eV) with the increase of shear deformation. There is a significant charge transfer from Zn to HfS 2 monolayer, and the electrons of Zn atoms flow to S atoms. The intrinsic HfS 2 shows a band gap value of 2.055 eV, and Zn-HfS 2 shows a metal property with a zero band gap. The adsorption of Zn leads to an increase in energy near the Fermi level, indicating that the adsorption of Zn enhances the electronic conductivity of HfS 2. The deformation reduces the barrier of Zn in the diffusion path to 0.16 eV. The maximum specific capacity of HfS 2 to Zn is 447.445 mAh/g. The calculation results will help promote the application of zinc ion batteries in wearable devices. [ABSTRACT FROM AUTHOR]

Background: Wearable technology is widely applied in performance monitoring, an integral part of sports and exercise sciences. The kick movement in soccer exemplifies a sports technique that could benefit from appropriate biomechanics assessment methodologies. However, the accuracy of wearables in quantifying soccer kick mechanics, particularly under field conditions, remains unclear., Objective: This study aims to present a protocol for a systematic review to discuss the measurement properties (validity, reliability, and/or accuracy aspects) of wearable technology systems explicitly used to measure ball-kicking features in soccer., Methods: This review protocol was preregistered in the Open Science Framework. A total of 2 authors will perform searches in major electronic databases using specific keyword combinations in PubMed, Physical Therapy and Sports Medicine, Web of Science, ProQuest, IEEE Xplore, EBSCOHost, and Scopus. Following a specific population, intervention, comparison, outcome framework (population: soccer players and/or collected human data in a football-related environment; intervention: at least 1 wearable used; comparator: criterion measures, repeated testing sessions and/or actual values; outcome: ball kicking data), studies will be screened based on predetermined inclusion and exclusion criteria. The methodological quality of the included studies will be assessed using the "consensus-based standards for the selection of health measurement instruments" checklist (in studies concerning validity or reliability) or the "quality assessment of diagnostic accuracy studies" tool (in studies concerning accuracy). Data extraction will be conducted to determine the level of evidence according to the "best evidence synthesis method," and an evidence gap map will be constructed. The Cohen κ coefficient will be used to estimate the interevaluator agreement., Results: This ongoing systematic review has completed database searches and is currently in the screening phase. Depending on the number and consistency of studies, results may be presented by meta-analysis or qualitative synthesis, with subgroup analyses considering factors such as gender, age, and playing level. The final results are expected by July 2024, with manuscript submission anticipated by November 2024., Conclusions: Our study will provide a comprehensive summary of the highest level of evidence available on the use of wearables for the assessment of soccer kick mechanics, providing practical guidance for athletes and sports sciences professionals regarding the validity and reliability aspects of using wearable technology to measure ball-kicking features in soccer., Trial Registration: OSF registries https://osf.io/zm3j6., International Registered Report Identifier (irrid): DERR1-10.2196/57433., (©Luiz H Palucci Vieira, Filipe Manuel Clemente, Felipe Armando Chang Marquez, Walter Manuel Rea Olivares, Kelly R Vargas Villafuerte, Felipe P Carpes. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 04.11.2024.)

In sprint races for runners with upper limb amputation/deficiency, it is allowed to use arm prostheses. However, there are few studies about arm prostheses for sprint running and about runners with upper limb amputation/deficiency. The objective of this study was to investigate the dynamical and musculoskeletal effects of arm swing and prosthesis on sprint running for runners with unilateral transradial deficiency. For this objective, the arm swing of runners with unilateral transradial deficiency was measured, and analyzed by using inverse dynamics calculation and musculoskeletal simulation. As the result of inverse dynamics analysis, it was found that the arm swing had the effect to increase the vertical ground reaction force, and that attaching prosthesis enlarged that effect. With respect to the anteroposterior and lateral directions, it was suggested that the arm swing contributed to maintaining balance and that the prosthesis helped to produce the force which counteracted the force produced by the intact limb. As the result of musculoskeletal analysis, it was found that the impulses of the muscle forces for the deficient limb were basically smaller than those for the intact limb. However, the ratios for the particular muscles were very large. With respect to the effect of attaching prostheses, it was found that most of the muscle force impulses increased by attaching the prostheses. In particular, the ratios of brachioradialis were significantly larger than the other muscles.

Professional horse racing is an activity known for its high risk of injuries, especially in the cranio-facial area. Nevertheless, despite the long history of horse races and the severity of the injuries sustained by professional jockeys, only very few epidemiological studies have been published to date. Cranio-maxillo-facial injuries in jockeys appear to be one of the main causes of retirement or even death. This study aimed to describe the epidemiology and distribution of cranio-facial injuries in professional jockeys through a PRISMA systematic review of the recent English literature and the description of case reports. Relevant articles were searched on PubMed, ScienceDirect, and Cochrane Library databases using the following MeSH terms: "athletic injuries" OR "athletic injuries/epidemiology" AND "Horses" on PubMed; or the following keywords "jockey, injury, epidemiology" on ScienceDirect and "jockey, injury" on Cochrane Library. Only studies with epidemiological data of cranio-facial injuries or total injuries in professional jockeys were included. In addition, recent data, supplied by the French racing authority from official reports about injuries that occurred during professional horse races in France, are analyzed. A total of 10 relevant articles were retained. The injury rate, in flat horse racing, was 0.6 to 1.8 per 1000 rides. The cranio-facial region was involved in 11.96 to 27.63% of cases. In jump horse racing, the injury rate was 5.1 to 15.8 per 1000 rides, involving the cranio-facial region in 10.6 to 26.7% of cases. Cranio-facial injuries are illustrated by impressive pictures and case reports. This systematic review highlights the high risk of cranio-facial injuries in jockeys. [ABSTRACT FROM AUTHOR]

The development of modern sports is impossible without the use of innovative scientific and technical achievements and engineering developments. The states, in which the presented approach is successfully implemented, take leading positions in international competitions. This thesis is based on the relationship between the quality indicators of athletes and the use by them of progressive tools and equipment in the training, as well as the most advanced clothing and footwear. At first glance, outfit in running sports can be considered as an insignificant factor that does not contribute to the competition results. Field-specific manufacturers use various engineering and technological resources available and contribute to the effective activities of the sports consumers. There are certain discussions in professional running about an innovative topic — “technological doping”. Professionals involved in ensuring compliance with the rules and equal opportunities for winning in running competitions need special competences in information and digital technologies. Research with the use of specialized databases within the framework of intellectual property provides an opportunity to study innovative technical solutions introduced by manufacturers of sportswear and footwear.

Wheelchair sports have an important role as a tool of rehabilitation for people with physical disabilities in lower limbs, and have been a driving force for innovation in wheelchair technology and practice as well. In wheelchair tennis, it is important to evaluate the pushing motion by players as well as the performance of the wheelchair when pushing. The objective of this study was to construct a comprehensive simulation model which was capable of evaluating the design parameters of a wheelchair as well as the pushing motion by a player in wheelchair tennis, and to investigate the effect of seat height of a wheelchair on the joint torques of the player as an example of analysis. The pushing motion during short distance dash was focused in the present study. The simulation model was constructed based on a multibody dynamics analysis software. Pushing motions by a player were acquired in the experiment by using a motion capture system and a specially developed wheelchair ergometer. Simulations reproducing the experimental conditions were conducted using the acquired pushing motions. The simulation model was validated since it could predict the propulsion torque and angular velocity overall within 10% error, although there was a room for improvement especially for the instantaneous characteristics around the timing of initial contact between the hand and hand rim. A parameter study changing the seat height of the wheelchair was conducted using the constructed simulation model. It was found that the joint torques of the thorax and shoulder decreased according to the decrease in the seat height, while joint torque of the elbow increased. It suggests that there is a trade-off relationship between the joint torques of the thorax and shoulder and that of the elbow with respect to the seat height.

In skateboarding as a sports event, the riders compete in difficulty and completeness of acrobatic motions called “tricks”. As a basic trick, Ollie is performed popularly. However, the basic mechanical principle of the Ollie has not been discussed to date, especially for the Ollie jump (the jumping phase of Ollie). The objective of this study was to elucidate the mechanism of Ollie jump in skateboarding. A simulation model was firstly constructed on a multibody dynamics analysis platform. Next, an experiment using an actual rider was conducted to acquire the motion of the feet during the Ollie jump. By inputting the acquired motion of the feet into the model, a simulation of Ollie jump was carried out. In addition, a parameter study with respect to the geometry of the skateboard and the motion of the rider’s feet was conducted. It was found that the simulated Ollie jump was successful since the skateboard reached a sufficient height and became sufficiently horizontal at the peak height. It was also found that the Ollie jump can be divided into five stages from the mechanical point of view. From the parameter study, it was found that large kick angle of the deck or large distance between two trucks of the deck might cause difficulty in the contact of the tail and the ground, while small kick angle or small distance between two trucks might result in excessive rotating angle of the deck. In addition, three important points for a successful Ollie jump were found to be, to produce sufficiently fast rotational movement of the skateboard around the rear wheels, to separate both feet from the deck before the tail of the deck hits the ground, and to separate the rear foot from the deck at the final stage.

We develop an output simulator for a baseball-type acceleration sensor in which one three-axis sensor for low acceleration and three sensors for high acceleration are installed. The acceleration vector at any position inside this ball-type sensor in rotational motion is formulated on the basis of the assumption that all the sensors are in rigid configuration. Since this simulator can estimate kinematically the acceleration under the change in time of rotation axis on the sensor coordinate system, we investigate the behavior of the rotation axis suggested in the previous flight experiment. In order to confirm the accuracy of the sensor outputs, preliminary experiment is performed, in which acceleration outputs are measured by rolling the ball-type sensor along a slope. The comparison of obtained acceleration outputs with theoretical values shows sufficient agreement. At the same time, the moment of inertia of the ball-type sensor is measured. Sensor outputs are simulated under two different conditions, in one of which the rotation axis is changing in time and the axis is fixed in the other. As the result, the acceleration output in the former condition varies linearly while the output keeps almost constant in the latter. The measured outputs of the flight experiment successfully reappear in the results under the former condition. The error between the simulated and measured outputs is calculated to 18 trial data of straight and curve balls, and the errors in the former condition become smaller than those in the latter. The present result therefore concludes that the rotation axis of the ball-type sensor in flight changes with time.

This study was conducted to clarify relationship between putter head motions of golf and ball hitting direction, distance with use of statistical techniques. Measurement was carried out by measuring systems for golf putting which composed of 3D gyro sensor and infrared sensors. From the measurement data, 27 parameters related to putting were selected. From the 27 parameters, 10 parameters related to hitting distance and direction were selected by analysis of variance. 10 parameters were applied principal component analysis to eliminate data redundancy. Using the first to forth principal components obtained by principal component analysis, the hitting distance and direction were learned and identified by the neural network. In addition, it was shown from the principal component analysis, angle around y axis, z axis at impact, angle about z axis, maximum of angular velocity, angular velocity around z axis at impact,the maximum and minimum angles around the y axis are important parameter for expressing the ball hitting result. Moreover it was shown that the parameter that most influence the estimation of the hit ballistic result are the angle around the y axis at the time of impact, and the angular velocity around the z axis at the time of impact.

In this study, as part of efforts to assist beginners in sports such as tennis and badminton in selecting the most suitable equipment, an index for objectively evaluating such equipment is proposed. To accomplish this, standard swing trajectory variations are used to create an index from the viewpoint of human motion control. We begin by noting that human body data gained via motion capture are large in number because of the wide variety of equipment types used and due to the significant diversity of human body characteristics. Hence, even though motion capture devices are often used to capture swing motions, the most suitable human body segments for use in equipment evaluations have not yet been clarified. To facilitate this, it is necessary to reduce the overall number of body segments under consideration. In this paper, the method of deriving the feature points in sports motion was examined. More specifically, in order to obtain fundamental findings, tennis stroke and badminton smash motions are used as representative movements, and experiments using a motion capture device are performed. In the motion analysis that follows, we then investigate which markers can most clearly express the relationship between the racket and the human body in order to capture stroke motion characteristics. Then, an index of contribution is adapted to tennis swing and badminton smash motions, the motion feature points in the stroke and smash motion are derived, and the significant markers for motion analysis are identified and discussed.

Abstract Baseball has been enjoyed by many generations and there are many people who play the game. Swing speed increases are generally required to develop ideal batting skill; nevertheless, no study has proposed a system to swing speed and develop an idea swing performance kinetic chain using auditory biofeedback, which is often used for motor modification. Thus, the purpose of our study was to devise a system that allows users to develop their kinetic chains and increase swing speeds using auditory cues, and to verify the proposed system’s effect in the bat swing performance of novices. We developed a system that output auditory cues (i.e., sound) linked with body motion. First, we conducted an experiment to confirm whether our proposed method could detect the difference between skilled players and beginners. Second, we applied the system to a tee-batting task in 22 novice baseball players. Using our proposed system, participants could increase swing speed and acquire a better kinetic chain in upper body motion but not in trunk motion. We expect this system is, in part, applicable to developing swing performance that requires sequential motion. This auditory biofeedback system warrants further investigation.

In rowing, rowers need outdoor and indoor training to develop a proficient technique. Although numerous indoor rowing machines have been proposed, none of the devices can realistically render the haptic, visual, and auditory characteristics of an actual rowing scenario. In our laboratory, we developed a simulator to support rowing training indoors. However, rendered forces with the initial rowing model, which was based on a simplified fluid dynamic model that approximated the drag/lift forces, were not perceived realistic enough for indoor training by expert rowers. Therefore, we implemented a new model for the blade–water interaction forces, which incorporates the three-dimensional rotation of the oar and continuously adjusts drag/lift coefficients. Ten expert rowers were asked to evaluate both models for various rowing aspects. In addition, the effect of individualization of model parameters on the perceived realism of rowing forces was elaborated. Based on the answers of the experts, we concluded that the new model rendered realistically resistive forces and ensured a smooth transition of forces within a rowing cycle. Additionally, we found that individualization of parameters significantly improved the perceived realism of the simulator. Equipped with a configurable rowing model, our simulator provides a realistic indoor training platform for rowers. [ABSTRACT FROM AUTHOR]

The present study focused on freestyle swimming by swimmers with unilateral transradial deficiency. It has not been clarified yet whether the deficient limb should move so as to match the tempo of the intact upper limb, or if it should move as fast as possible to produce thrust by itself. The objective of this study was to solve the theoretically ideal deficient limb’s strokes in freestyle for a swimmer with unilateral transradial deficiency by using the optimizing simulation. The method of the optimizing simulation of arm strokes considering muscle strength characteristics was developed in a previous study. This method was utilized to solve the deficient limbs’ strokes in the present study. Actual swimming by a participant was reproduced by simulation first. Since the resultant swimming speed of the simulation was in the range of the experimental speed, the validity of the simulation was confirmed. Next, optimizing simulations were conducted for the case of maximum shoulder joint torque multiplied by 1.0, 0.85 and 0.72. From these results, a significant increase in the swimming speed was found for the optimized cases. It was also suggested that the contribution by the deficient limb to propulsion can be increased by up to 15% of the intact limb. The optimized stroke was found to have a later timing and faster motion than the original stroke. This motion was realized by the principle that more joint torque can be exhibited in adduction than in flexion when the joint angular velocity was high.

The frame stiffness in a racing bicycle might influence not only toughness as the frame structure but also performance of an athlete. The purpose of this study is to clarify biodynamic relations between the frame stiffness in a racing bicycle and the physical loads of an athlete by using a forward dynamics simulation model. The human body structure was represented by the 13-rigid-links and 23-degrees-of-freedom model. Based on the theory of multibody dynamics, the frame structure was expressed by combination of 12 rigid pipes, and the frame stiffness was modeled by rotational springs at the connecting joint between the rigid pipes. Spring coefficients were changed according to the thickness of the frame pipes. The pedaling load from the crank was computed by the angular velocity and angular acceleration of the crank. Moreover, the driving force in the bicycle was additionally defined to consider the influence of the frame weight on the human joint load. The human body model was driven by the joint toques to minimize the cost function consisting of the joint loads in the human body and the driving force in the bicycle, and also to keep desired angular velocity of the crank. Validity of the simulation was evaluated by comparing the joint angles and torques with the measured ones. As for the result, the larger stiffness of the frame resulted in smaller the joint loads in the human body, and optimal stiffness would be determined by the balance between the joint loads in the human body and the driving force in the bicycle.

In rubber baseball games, when the rubber ball is hit by a baseball bat, the rubber ball is deformed greatly comparing to an official baseball ball, and the batted ball speed decreases due to the energy loss during the deformation. Since the new rubber ball has been applied in games from 2018, the material properties and the restitution characteristics of the new rubber ball attract plenty of attention among scholars. In this study, the difference of the material properties and the restitution characteristics between the new and old rubber balls is investigated deeply by the static compression and collision tests. According to the static compression test, we find that the new rubber ball is harder and more difficult to generate deformation than the old one. In the collision test, the rebound ball speeds of both of the new and the old balls become faster when using a smaller diameter of steel cylinder instead of baseball bat, and the rebound ball speed of the new ball is slower than that of the old one under the same experimental conditions. Furthermore, to develop high performance baseball bats adapting to the new rubber baseball, the diameter of the baseball bat is studied by the impact simulation based on the finite element analysis. In the simulation, the batted ball speed under the analytical conditions of different offset heights and different barrel diameters of the bat are evaluated considering the initial spin. As a result, the batted ball speed generated by the bat with diameter φ55 mm is faster than generated by the bat with diameter φ70 mm when the offset height range is smaller than 14.6 mm, so that the bat diameter φ55 mm is recommended according to the present work.

We attempt to measure the rotational characteristics of a ball in flight by using a baseball-like ball with a built-in acceleration sensor unit which consists of one three-axis sensor for low G and three sensors for High G. Two approaches for obtaining the rotational speed and its axis of the ball from outputs of the sensors are formulated; one is based on rotational component in the acceleration outputs and the other is based on translational one. We employ in the present approaches the assumption that the time variation of rotation axis can be neglected because it is sufficiently slow. In flight experiments, we obtain nine time series data of acceleration for straight and curve ball trajectories, respectively. By using these experimental data, we estimate the rotational speed and rotation axis with the present two algorithms. As the results, it is shown that the rotation axis keeps almost constant during the flight in each algorithm’s result and this means the validity of our assumption on rotation axis. The difference in the rotation axis obtained by the two algorithms ranges from 3.5 to 10.6 degrees in the straight ball data while it does from 3.9 to 18.8 degrees in the data of curve ball. Also, the averaged rotational speed in the nine trials is 12.56 rps in the straight data, and the difference between the algorithms indicates 0.10 rps (after pitching) and 0.17 rps (before catching). In the curve ball data, the averaged value and the difference between the algorithms are 19.22 rps, 0.10 rps (after pitching) and 0.14 rps (before catching), respectively. The present result shows the decrease of the rotational speed along flight trajectories, and it is probably the effect of aerodynamic torque.

The objective of this study was to simulate the swimming motion with bi-fins and investigate the effect of ankle joint motion by simulation. A model of a swimmer was constructed by utilizing the swimming human simulation model SWUM. The bi-fin was modeled as a series of five rigid plates. One rigid plate was connected to another by virtual springs and dampers. In order to determine the spring constants of the springs and damping coefficients of the dampers, static and dynamic bending tests were conducted. In order to determine the fluid force coefficients for the fin, an experiment in which the fin was located vertically in a pool and was moved horizontally by an air cylinder was conducted. In order to acquire the motion of swimming with fins, two swimmers were asked to perform maximal front crawl swimming with/without fins in an indoor swimming pool. The swimming motion was filmed by three cameras underwater and one camera on land. Using all of the input data, simulations reproducing the experimental trials were carried out. By the simulation, the developed simulation method was validated since the simulated swimming speeds were consistent with the experimental values in errors less than 6% of accuracy. By analyses with the validated simulation method, it was found that the smaller ankle joint movements resulted in a faster swimming speed. It was also found that the fixed angle of ankle joints affected the body pitch angle and that there is an optimum fixed angle for a swimmer to maximize swimming speed.

Biomechanical tools capable of detecting external forces in swimming starts and turns have been developed since 1970. This study described the development and validation of a three-dimensional (six-degrees of freedom) instrumented block for swimming starts and turns. Seven force plates, a starting block, an underwater structure, one pair of handgrips and feet supports for starts were firstly designed, numerically simulated, manufactured and validated according to the Fédération Internationale de Natation rules. Static and dynamic force plate simulations revealed deformations between 290 to 376 µε and 279 to 545 µε in the anterior-posterior and vertical axis and 182 to 328.6 Hz resonance frequencies. Force plates were instrumented with 24 strain gauges each connected to full Wheatstone bridge circuits. Static and dynamic calibration revealed linearity ( R 2 between 0.97 and 0.99) and non-meaningful cross-talk between orthogonal (1%) axes. Laboratory and ecological validation revealed the similarity between force curve profiles. The need for discriminating each upper and lower limb force responses has implied a final nine-force plates solution with seven above and two underwater platforms. The instrumented block has given an unprecedented contribution to accurate external force measurements in swimming starts and turns. [ABSTRACT FROM AUTHOR]

At present, there are only a few developed pitching machines that can throw a ball with gyro spin. In this study, we aimed to develop a new baseball pitching machine using four rollers, where the rotational speed of each of the four rollers and the crossing angle of the opposite gyro rollers can be controlled optionally to generate an objective gyro spin more efficiently. We also elucidate the throwing mechanism of the developed baseball pitching machine and confirm its performance by finite element analysis. The newly developed pitching machine can throw a baseball with a wide range of speeds from 22.2 m/s (80 km/h) to 44.4 m/s (160 km/h) with all pitch types (fastball, curveball, gyroball, etc.), and the spin axis can be controlled in any designated direction. Moreover, this machine is capable of throwing a baseball with higher accuracy compared to commercially available pitching machines.

There is a shortage of young people studying physics and engineering and these professions could benefit from greater diversity. Sports engineering is often used as a tool to change the public perceptions of engineering and sporting examples can be used in physics and engineering classes to engage people. Video analysis is widely used by sports engineers, and this publication showcases how the video analysis of sporting scenarios can be used to teach mechanics. Examples illustrate how the movement of an athlete and equipment can be analysed and linked to basic physics, for sports ranging from sumo to soccer. The examples presented can be used for teaching and outreach, with a view to enthuse students about physics and engineering.

Steel, being the most commonly used bicycle frame material, has a major role to play in future developments within the bicycle industry, and there is scope to enhance the role of engineering in the development of steel bicycles. This paper introduces The Steel Bicycle Project (TSBP), an open-ended project which aims to raise awareness of engineering principles that relate to steel bicycle frames and aims to support frame builders in designing and fabricating better and safer products. In this paper, we give details of the main project themes (Design and simulation, Materials and fabrication, Testing and measurements, Knowledge and education) and outcomes. We also present some initial activities from the early stages of the project and will discuss general models to bring together key partners under the umbrella of the sports engineering community.

In rowing, rowers need outdoor and indoor training to develop a proficient technique. Although numerous indoor rowing machines have been proposed, none of the devices can realistically render the haptic, visual, and auditory characteristics of an actual rowing scenario. In our laboratory, we developed a simulator to support rowing training indoors. However, rendered forces with the initial rowing model, which was based on a simplified fluid dynamic model that approximated the drag/lift forces, were not perceived realistic enough for indoor training by expert rowers. Therefore, we implemented a new model for the blade−water interaction forces, which incorporates the three-dimensional rotation of the oar and continuously adjusts drag/lift coefficients. Ten expert rowers were asked to evaluate both models for various rowing aspects. In addition, the effect of individualization of model parameters on the perceived realism of rowing forces was elaborated. Based on the answers of the experts, we concluded that the new model rendered realistically resistive forces and ensured a smooth transition of forces within a rowing cycle. Additionally, we found that individualization of parameters significantly improved the perceived realism of the simulator. Equipped with a configurable rowing model, our simulator provides a realistic indoor training platform for rowers.

The principles of slipstreaming or drafting are very well known in muscle-powered sports, but unknown in gravity-powered sports. Typical examples of gravity-powered sports, where several athletes are racing against each other, are ski-cross and snowboard-cross. The aim of this research is to investigate the effectiveness and practical applicability of slipstreaming in ski-cross. A glide model consisting of leading and trailing skiers was developed and used with existing aerodynamic drag and lift data sets from wind tunnel tests. Different scenarios were tested as to their effect on slipstreaming, such as variation of speed, skiers' mass, slope angle, air density, and racing posture (high/low tucked position). The higher the trailing skier's inertial force and acceleration is compared to the leading one, the quicker the trailing skier can catch up. Making more ground up on the racing track is related to higher speed, less body mass (of both skiers), flatter slope angle, denser air, and higher racing posture (high tucked position of both skiers). The glide model presented in this research can be used in the future for testing of slope track design, provided that precise dimensions of terrain features are available.

For the crawl stroke in swimming, it is important that the stroke made by the upper limbs and the flutter kick made by the lower limbs are well coordinated in order to enhance swimming performance. However, the training method to acquire the appropriate flutter kick timing has not been sufficiently established. In the present study, a biofeedback training system for swimmers to acquire appropriate kick timing was proposed. In this system, the most difficult and important part is the estimation of the appropriate kick timing. Therefore, the objective of this study was to develop a kick timing estimation algorithm in the crawl stroke for biofeedback training system using neural oscillators. First, a CPG network which outputs the kick estimation timing according to the input was constructed. In order to synchronize the roll angle in the CPG network with the actual one measured by a sensor, a special algorithm to change the cycle of the oscillation for the CPG network was introduced. Validation for the output of sinusoidal input accompanying sudden change in cycle was examined. It was found that the output signal for the roll tracked the input signal well, despite the sudden change in cycle. Validation for the actual input obtained in the experiment was next examined. It was found that the output from the CPG network was sufficiently consistent with the experimental values, suggesting sufficient performance of the proposed estimation algorithm.

In this paper we present the design, prototyping and validation of a novel adjustable foot stretcher for indoor rowing training. The overall process is user-centered, in the sense that the athletes are directly involved in all the phases of the product development, from conceptual design to evaluation and validation. The conceptual design starts from well-known rowers needs. Accordingly, two design factors are selected to parametrize the prototype, namely the inter-axle spacing feet and the foot angle. The experimental evaluation and validation involve two phases, one based on a quantitative analysis of the performance, one based on subjective questionnaires submitted to the athletes. The performance-based analysis comprises the derivation of three pressure indices and one power transmission index. Indeed, the subjective analysis regards the users comfort and power transmission feelings. The results of both evaluations testify that an improvement in performance and comfort of the indoor rowing training session can be achieved. [ABSTRACT FROM AUTHOR]

The principles of slipstreaming or drafting are very well known in muscle-powered sports, but unknown in gravity-powered sports. Typical examples of gravity-powered sports, where several athletes are racing against each other, are ski-cross and snowboard-cross. The aim of this research is to investigate the effectiveness and practical applicability of slipstreaming in ski-cross. A glide model consisting of leading and trailing skiers was developed and used with existing aerodynamic drag and lift data sets from wind tunnel tests. Different scenarios were tested as to their effect on slipstreaming, such as variation of speed, skiers' mass, slope angle, air density, and racing posture (high/low tucked position). The higher the trailing skier's inertial force and acceleration is compared to the leading one, the quicker the trailing skier can catch up. Making more ground up on the racing track is related to higher speed, less body mass (of both skiers), flatter slope angle, denser air, and higher racing posture (high tucked position of both skiers). The glide model presented in this research can be used in the future for testing of slope track design, provided that precise dimensions of terrain features are available. [ABSTRACT FROM AUTHOR]

The objective of this study was to solve the theoretically ideal arm stroke for a swimmer with hemiplegia by using the optimizing simulation. The method of optimizing simulation for non-disabled swimmers was extended to a swimmer with hemiplegia. In order to evaluate the arm strokes in the optimizing calculation, the swimming human simulation model SWUM was employed. As the design variables, the joint angles in the three time frames, in which the arm was performing underwater strokes, were used. The objective function was the swimming speed. Three constraint conditions including the maximum joint torque characteristics were imposed on the optimizing calculation. The swimming motion of an actual swimmer with hemiplegia was measured and put into the simulation as the original motion. In the simulation, significant increase in the swimming speed was obtained in the case of the optimized stroke with the actual swimmer's wrist motion at the slower stroke cycle. From the comparison between the optimized stroke and the actual swimmer's stroke, several differences were found as follows. First, at the entry phase in the fastest optimized stroke, the left elbow was more extended than the actual swimmer's stroke. Second, at the catch phase in the fastest optimized stroke, the forearm in the side view was more tilted with respect to the vertical line, while that in the actual swimmer was almost vertical. Third, at the pull and finish phases in the optimized stroke, the hand pushed the water sufficiently to the end, while that in the actual swimmer went out from the water earlier. Overall, it was found that the optimized stroke effectively utilized the joint torque at the shoulder and elbow to the maximum extent, by selecting the more natural positions and the slower stroke cycle.

Ball shooting machine (pitching machine) is used for practicing ball sports, and it is widely prevalent. However, there are few pitching machines that can throw a ball with a gyro spin, such as a football or rifle bullet, in which the axis of the ball spins in the same direction as the ball travels. In this study, a new ball shooting machine, which can throw in the ball in a wide range of speeds and all pitch types (no, top, down, side and gyro spin balls) was invented by introducing a launch mechanism using four rollers (two launch and two gyro rollers). The shooting machine is able to arbitrarily change the rotational speed of the four rollers and the crossing angle of both gyro rollers. Shooting tests were conducted using the prototype shooting machine to confirm the ability of its performance. From the experiment results, the prototype machine had a maximum ball speed of 42.5 m/s, a spin rate of exceeding 5000 rpm, and a ball of any pitch type could also be shot. In addition, the position accuracy (shot accuracy) at the targeted fall position in the opponent's court was high because the gyro spin and other pitch types (no, top and side spins) were less than 140 mm and 40 mm (the diameter of one table tennis ball), respectively. The prototype machine had the necessary launching performance for table tennis practice of a college student level.

We aim to clarify dynamics of the wrist turn of the golf swing and the effect of the parameters on dynamic behavior at the wrist turn using the double pendulum model and the modal analysis method. Eigenvalue analysis was carried out and natural frequency and mode were calculated by using linearized equation of motion assuming the exterior angle of the cock angle is small. We found out that the first mode is a rigid mode and the second one is a vibration mode of the double pendulum, and the mode shapes are constant during the wrist turn even though natural frequency changes. By applying the modal analysis method we obtained equations of motion for the rigid mode and the vibration mode separately. Furthermore, using the theory of linear superposition, the equation of motion for the vibration mode was separated again into 3 equations which can help to understand the mechanism of the wrist turn. After accuracy of the proposed method for small exterior angle of the cock angle was confirmed by comparing with the exact solution using numerical integration, the proposed method was applied to the general case with large exterior angle of the cock angle which has nonlinearity, and the mechanism of the wrist turn and the effect of the parameters of the arm and wrist torque on the dynamic behavior at the wrist turn were clarified qualitatively. Finally parameter survey using the numerical integration for the original nonlinear equation of motion was carried out to show the validity of the proposed method.

The objective of this study was to propose a CPG network which can generate the swimming motion of the crawl stroke. First, the CPG network for legs performing a flutter kick was constructed by connecting the neural oscillators for the leg joints. The flutter kick motion was successfully generated by the proposed CPG network. The propulsion by the generated flutter kick motion was confirmed by the simulation of the swimming movement. Next, the CPG network for both the arms and legs were constructed, in which the neural oscillator for the arms initiated the trigger signal to start the prescribed stroke motion. By changing the intrinsic cycle of the neural oscillators for the legs, both six- and two-beat crawls could be realized. It was also found that a stable region with respect to the relationship between the intrinsic cycles of the neural oscillators for the arms and legs certainly existed for the six-beat crawl, although the intrinsic cycles of the arms were three times longer than those of the legs in this case. The propulsion by the generated swimming motion was confirmed by the simulation of the swimming movement both for the six- and two-beat crawls. Finally, the roll angle of the swimmer was fed back into the CPG network in order to restore the balance in the roll direction. Restoring the balance in the roll direction was successfully realized by the proposed feedback algorithm. The resultant motion showed a complicated behavior, such as skipping strokes.

Biomechanical tools capable of detecting external forces in swimming starts and turns have been developed since 1970. This study described the development and validation of a three-dimensional (six-degrees of freedom) instrumented block for swimming starts and turns. Seven force plates, a starting block, an underwater structure, one pair of handgrips and feet supports for starts were firstly designed, numerically simulated, manufactured and validated according to the Fédération Internationale de Natation rules. Static and dynamic force plate simulations revealed deformations between 290 to 376 µε and 279 to 545 µε in the anterior-posterior and vertical axis and 182 to 328.6 Hz resonance frequencies. Force plates were instrumented with 24 strain gauges each connected to full Wheatstone bridge circuits. Static and dynamic calibration revealed linearity ( R 2 between 0.97 and 0.99) and non-meaningful cross-talk between orthogonal (1%) axes. Laboratory and ecological validation revealed the similarity between force curve profiles. The need for discriminating each upper and lower limb force responses has implied a final nine-force plates solution with seven above and two underwater platforms. The instrumented block has given an unprecedented contribution to accurate external force measurements in swimming starts and turns.

Individual athletes, coaches and sports teams seek continuously for ways to improve performance and accomplishment in elite competition. New techniques of performance analysis are a crucial part of the drive for athletic perfection. This paper discusses the ethical importance of one aspect of the future potential of performance analysis in sport, combining the field of biomedicine, sports engineering and nanotechnology in the form of 'Nanobiosensors'. This innovative technology has the potential to revolutionise sport, enabling real time biological data to be collected from athletes that can be electronically distributed. Enabling precise real time performance analysis is not without ethical problems. Arguments concerning (1) data ownership and privacy; (2) data confidentiality; and (3) athlete welfare are presented alongside a discussion of the use of the Precautionary Principle in making ethical evaluations. We conclude, that although the future potential use of Nanobiosensors in sports analysis offers many potential benefits, there is also a fear that it could be abused at a sporting system level. Hence, it is essential for sporting bodies to consider the development of a robust ethically informed governance framework in advance of their proliferated use. [ABSTRACT FROM AUTHOR]