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Six papers under the broad banner of biomechanics were submitted to the conference. Two of these papers deal with footwear/surface interactions, while the others deal with a unique aspect of the application of biomechanics to a sport or physical activity. All of the submitted papers address issues of practical importance to sport and exercise. What follows is a brief summary of each paper, followed by a synopsis of other activity in the field not reported at this conference. [ABSTRACT FROM AUTHOR]

The theme of Modelling Systems in sports includes a range of diverse papers presented at the ISEA Conference in Munich in July, 2006. Systems in sports are typically complex and include interactions between the athlete, equipment and sport which frequently result in unique outcomes. For this reason, it is necessary to develop models that represent a form of idealisation of the physical problem, but which nevertheless through manipulation and simulation provide greater insight into the particular questions of interest. The papers included in this theme involve interesting analytical, computational and experimental system models in a range of sports such as gymnastics, tennis, handball, alpine skiing, rowing, cricket, skydiving, figure skating, volleyball and football. The following section aims to provide an overview of the main research and development issues presented in these papers. [ABSTRACT FROM AUTHOR]

Dynamic analyses for impact of sports balls almost exclusively are based upon rigid-body dynamics. At impact speeds representative of ball games, this paper obtains effects of finite deflections and a finite contact area on the changes in velocity and angular velocity of a thin-walled, inflated ball. Momentum flux associated with the evolving contact region is shown to be non-conservative and a significant source of energy dissipation during impact of thin-walled balls against a court surface. Nevertheless, changes in both angular speed of the ball and direction of bounce are modest for coefficients of friction that are representative of sports surfaces. This paper obtains results from a large deflection theory that calculates changes of bounce that result from the finite contact area that develops during impact. These changes in rate-of-spin and rebound velocity of basketballs, soccer balls, ect are related to the structure and material properties of inflated thin-walled spherical balls. [ABSTRACT FROM AUTHOR]

This paper reviews two current and two emerging test methods for the impact assessment of sports surfaces for a variety of different sports including field hockey, soccer/rugby and sports hall floors. A good quality sports surface should enable a player to demonstrate and develop their skills, and limit the risk of injury. To ensure surfaces meet these requirements (in part) many sports governing bodies stipulate a series of (impact) tests to assess the surface shock absorption. Current industry standard impact tests have some shortcomings for either routine use and/or for research purposes. In this paper the impact performance requirements of a surface are briefly reviewed, and the four measurement methods explained. The emerging test methods are contrasted to the conventional ones, via a series of comparative data from several programmes of research. The paper concludes that there is a place for both simple `ranking΄ tests, suitable for routine use and that are comparable to the more complex sport performance tests, and for a more sophisticated engineering test that is both a suitable substitute for the industry standard methods and that better describes the behaviour of the sports surface under test. [ABSTRACT FROM AUTHOR]

At the previous ISEA conference (in Davis 2004) we reported on our work measuring a ski athlete. Each summer we add new functions to the measuring system and each winter we test the functions on the snow field. This paper is a description of the system as it was in March 2005, and is meant to provoke discussion of measurement and design issues. Developments since 2004 include Redesigned load cells for the forces between the binding plate and each skiNew strain amplifiers for all channels including automatic systems to balance the load cells and set the range˵ShapeSnakes″ – a new kind of goniometerA vertical gyroscope to assist with measurement of the absolute angle of a backpack worn by the athleteCustom acquisition of signals from foot-shaped FSA pressure sensors; andSoftware to display the acquired data in a virtual 3D world. Another paper in these proceedings, Yoneyama (2006), describes some results obtained with the new equipment Although not everything worked perfectly during our latest tests, some good results were obtained. We will also present our vision for the next generation of the equipment. [ABSTRACT FROM AUTHOR]

This paper describes the testing of a ˵simple″ and relatively inexpensive method of monitoring crew performance during on-the-water rowing. Direct oar force measurement is utilised and the results obtained are compared with alternative measurable parameters. The data derived not only allows real time comparison of the useful power being delivered by each oarsman in the boat, but also enables direct observation of blade control, synchronisation, cleanness of catch and finish etc. The purpose of this paper is not necessarily to present ˵new″ information (although where to actually find current published ˵on-the – water″ data is still a mystery), but to demonstrate that useful feedback information for coaches can easily be obtained by very simple and relatively cheap use of basic strain gauge application. [ABSTRACT FROM AUTHOR]

This paper attempts to guide readers through the development of equipment and related testing procedures at the RMIT University Industrial Wind Tunnel facility designed to replicate and assess flow mechanics relevant to motorcycles. The paper particularly addresses design and development of the preliminary test rig to support both motorcycle and rider. A Cobra probe, the University΄s own 13-hole probe and various surface pressure measuring devices are used to analyse near wake and other basic flows pertinent to stakeholders associated with the development of supersports class motorcycles. The test matrix addresses not only various rider configurations but seeks to assess the effect of appendices such as mirrors. [ABSTRACT FROM AUTHOR]

Vibration levels are of major concern in tennis racquet design. If the racquet structure is to be dynamically tuned so that negative consequences of racquet vibration are alleviated, the parameters defining the degree to which vibration is transferred to the athlete must first be quantified and fully understood. This paper investigates some of the main parameters contributing to vibration transfer in tennis racquets via the hand grip. The work presented here allows for a correlation to be established between grip characteristics and vibration response of the racquet. In-order gain more insight into the mechanics of vibration transfer to the athlete the tennis grip is quantified here in terms of pressure distribution and its relationship with amplitude of vibration in frequency and time domain. The pressure distribution in the grip is determined using hydrocell pressure sensors. Grip anticipation times have been measured and assessed giving a comprehensive understanding of the tennis grip dynamics. The gripping characteristics during ball impact are related to the dynamic response of the tennis racquet. [ABSTRACT FROM AUTHOR]

The satellite navigation system GPS has gradually gained a usability that was never expected during its design 30 years ago. Similar statements can also be made for other central elements of modern navigation technology like gyroscopes and accelerometers as well as microprocessors for synchronizing and processing sensor signals. GPS receivers and other navigation sensors are in principle devices that detect single motion components. To obtain a more complete and plainer description of the motion considered, a suitable tight combination of several sensors of different kind should be employed. This leads to integrated navigation or motion measurement which can simultaneously provide a good long-term accuracy and a high resolution with respect to time. In ship, aireraft, and spacecraft navigation the use of such integrated systems is well established. The technological progress as mentioned above suggests now also the utilization for sports science: Indeed, interesting approaches do already exist (at least partially) and show a promising potential for biomechanical analyses, for documentation of training units, and for competition diagnosis. Together with theoretical basics for integrated motion measurement. the paper gives a survey of some realized systems. [ABSTRACT FROM AUTHOR]

˵La Pilota Valenciana″ is a traditional sport native from the Region of Valencia (Spain). In a modality of it, two teams hit a ball with the hand to pass it above a net. The balls are made by highly skilled craftsmen and there are neither technical criteria for quality control nor design criteria for developing new products. At present, the decision about the suitability of a ball for the game is made on the base of manufacturers and players subjective opinion. This paper presents the research done to establish which mechanical properties of balls correlate with players΄ perception to generate design and evaluation criteria. The results showed several significant correlations between some mechanical properties as the Coefficient of restitution and users opinion. For example, hardness correlated positively with the perception of injury risk. The results of this study establish the necessary knowledge and methodology to advance in the quality control and design of balls for the ˵pilota valenciana″, which is very necessary to ensure the future of this traditional game. [ABSTRACT FROM AUTHOR]

The consideration of energy expenditure rates of limb movement sequences is important when designing new exercise machines or developing novel exercise modes. Given a design that focuses on maximizing energy expenditure for a given exercise intensity, the ability to determine energy expenditure rates is essential. A novel exercise test machine has been developed that enables the performance of exercise sequences in multiple directions and planes. This paper presents a methodology to evaluate the energy expenditure rate associated with different limb movement sequences during continuous upper body cyclic exercise. Eight male subjects completed maximal and submaximal trials (RPE-11, RPE-13, RPE-15) for 4 different movement sequences. Although significant differences in energy expenditure rates were observed between exercise intensities, differences between movement sequences were less pronounced. The oxygen uptakes observed during experimentation correlate with values observed in past studies for single arm cranking. These findings indicate the methodology established in this study is a viable means of measuring energy expenditure for a wide variety of upper extremity cyclic movements. [ABSTRACT FROM AUTHOR]

This paper describes the design and development of an instrumented force shoe which allows measurement of three orthogonal components of ground reaction force during locomotion in horses, and presents preliminary GRF data for consecutive strides at walk and trot. The authors discuss the design constraints and technical difficulties imposed by a solid frame shoe design and as an alternative propose a novel sandwich design which avoids cross coupling between vertical (compression) and horizontal (shear) forces. The authors present GRF data for a horse moving between walk and trot. They believe this is the first time that three orthogonal components of GRF have been presented for successive strides for any terrestial animal during acceleration or deceleration. [ABSTRACT FROM AUTHOR]

This paper describes the development of a new six component dynamometer for measuring ground reaction forces in alpine skiing. Unique of this new dynamometer is its ability to be used with any kind of skiing equipment, its easy adjustability to different boot size and its wireless data transmission. The mechanical construction consists of three parts: the fixation to the boot, the fixation to the binding and the load cell. To measure the loads a mechanically uncoupled assembling of shear beams attached with gauges are mounted in the load cell. Power supply and Bluetooth⠪ module are integrated into the system, data is acquired and stored on an external PDA. [ABSTRACT FROM AUTHOR]

In aiming it is important that an archer΄s draw-length is quite constant and that the clicker position is only a few millimeters behind the tip of the arrow. At the end of the aiming phase the archer pulls back the arrow a little bit before he releases the shot. This is called the final pull. (1993) measured the alteration of the draw-length indirectly using an electromechanical device that was fixed to the grip and to the lower limb of the bow, but it is very time-consuming and complex to affix this electromechanical device to a bow. The aim of this paper was to describe a system developed to measure the draw-length in the final pull that is easy to handle and to research the final pull in highly skilled archers. The alteration of the draw-length was measured by acquiring the bending of the clicker using a strain gage that is fixed to the clicker: The clicker position during aiming is only a few millimeters behind the tip of the arrowhead. Therefore each alteration of the draw-length leads to an alteration of the bending line of the clicker because of the shape of the arrowhead. Seven archers (two male, five fe-male), all participants at the Junior World Championships and German National Championships performed 66 shots at 30m indoors. Each archer shot with his own personal bow, and the alterations of the draw-length in the final pull were acquired. The results suggest that irregularities in the final pull, especially the so-called ˵shrinking″, have a negative influence on the archers΄ score. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate, using finite element analysis, a possible cause of fatigue failure due to the pick of an ice axe impacting a semi-rigid surface This simulates the pick striking a thin layer of ice covering rock. The technical ice axes used by climbers for ice wall climbing are subjected to a number of different loading situations in use. These can result in high stresses being generated. The geometry of the ice axe pick consists of a series of teeth along the bottom surface, which bite into the ice to give the mountaineer purchase when climbing. The tooth profile is such that, at the root, they would act as points of high stress concentrations in the presence of tensile stresses. However the stresses at the root of the tooth are generally compressive for most load cases. However, there have been recorded instances where an ice axe pick has failed in use due to fatigue with the crack being initiated at the root of a tooth. The requirement for a fatigue failure is a cyclic load which has at some point a tensile stress present. As part of an initial study a transient dynamic finite element analysis was carried out on the geometry of an ice axe pick striking a semi-rigid surface. The pick was assumed to strike at velocity of 9m/s at an angle to the tip of 20°. It was assumed that the pick was manufactured from steel and both elastic and plastic properties modelled. The impact surface was given the physical properties of granite and was considered to be flat. A two-dimensional analysis was carried out. Only the pick of the axe was modelled, the adze and handle ignored. It was assumed that the pick was rigidly held at the junction with the ice axe handle. To model the impact the surface was given an initial velocity and a mass of 0.7kg, which was the total mass of the ice axe. The analysis revealed that a compressive failure occurred at the tip of the ice axe pick causing the characteristic rounding of the pick tip (blunting). The stress at the root of the teeth nearest to the tip of the pick yielded in compression, which resulted in a tensile residual stress in the unloaded pick. Each successive impact would therefore result in a tensile-compressive stress cycle which is conducive to fatigue failure. [ABSTRACT FROM AUTHOR]

Professional team-sport training involves demanding work. In this discussion paper we explore the possibilities and challenges involved in adapting an existing analysis approach from the domain of Distributed Tactical Operations to the domain of professional team sports. In particular, we outline how advanced computer-supported data collection and data presentation could contribute to a general football training system. [ABSTRACT FROM AUTHOR]

An approach is proposed for automatically modifying a shape and shoe center (design valuables) of a ski. The proposed approach needs the inverse analysis method (sensitivity analysis) and two indices of the ski turn (˵Locus of ski turn″ and ˵Rotational angle of ski″) as the objective functions. Firstly, to obtain the two indices of the ski turn, the outline of the numerical approach for a ski turn is introduced. Subsequently, the sensitivity analysis is shown to estimate the change quantities for the modification of the ski. Finally, referring two indices of the ski turn, a prototype ski is modified into an objective ski by tuning the width and shoe center of the ski. From the above-mentioned numerical calculations, it follows that one can efficiently modify the prototype ski by using the proposed approach. [ABSTRACT FROM AUTHOR]

Modelling has become an important tool for answering open questions in skiing. Three major applications can be seen for modelling and simulation: first to work on the theory of the ski turn, second to systematically design skis with definite characteristics and third overcome ethical or measurement problems when it comes to biomechanics of ski injuries. Models and even more their validation are highly dependent on accurate experimental data. Great efforts are necessary due to the inherent difficulties with measurements on the ski slope and due to the fact that data collection should not interfere with the athlete. A total of seven contributions express the achieved high level of research and development in these two fields. [ABSTRACT FROM AUTHOR]

The three different words defining this theme ˵testing″, ˵prototyping″ and ˵bench-marking″ represent in fact only one large engineering field. For designing the best product, it is necessary to benchmark prototypes (future products) with all existing products and/or to optimize these prototypes due to testing methods. [ABSTRACT FROM AUTHOR]

The aim of the present study was to validate a full-body computer simulation of a golfer΄s swing for driving clubs. An elite male golfer performed 24 shots in a laboratory, comprised of 8 trials using each of three drivers of different shaft length (46", 48", & 50"). A 5-camera MACTM system operating at 240 Hz collected kinematic data which was subsequently used to drive the model utilising ADAMS/LifeMOD software. Additional skin markers were used for model validation. A large-scale musculoskeletal human model was constructed, with a parametric model of a driver. Inverse and forward dynamics calculations were performed with the imported experimental motion data in order to generate model movement. A commercially available launch monitor recorded experimental eclubhead and launch conditions. There was a very high level of agreement (r=0.995) between experimental kinematic data and the predicted trjectory splines of the model. There was also a high level of correlation (r=0.989) between the model predicted mean values for clubhead speed and the experimental values for each of the club lengths, both demonstrating increased clubhead velocity as club length increased. Muscle contraction force output by the model showed a significant difference (p≤0.001) between driver simulations, demonstrating its capability to illustrate the link between gross muscle force production and club length, as evidenced by the increased force output for the longest shafted club. [ABSTRACT FROM AUTHOR]

˵Pelota Vasca″ is a traditional sport coming from the País Vasco with a long history and different modalities. In one of them the ball is hit with the hand against a wall placed in front of the players. A high incidence of hand injuries is found in this sport which has been related to high impact loads and to not adequate protection. Nevertheless, there is not knowledge about biomechanical parameters as impact forces in the hand, hand pressure distribution and others that would be required for an adequate protection design. The purpose of this study was to measure the hand impacts magnitude and distribution when playing ˵Pelota Vasca″. Nine high level players took part in the study. A pneumatic canon was used to throw the ball at 80 km/h speed, that was controlled by two photocell gates. The ball rebounded first against the wall and then on the floor before to be hit by the player. The players hand was equipped with an instrumented glove especially developed for this study. It included 8 piezoelectric sensors distributed according to hand functional anatomy and considering the hitting areas of the hand. Specific software was developed to compute peak pressure at each sensor which was stored for further statistical analysis. The maximum recorded pressure ranged between 4020 kPa and 4378 kPa, at the 2nd and 3rd metacarpal heads respectively. Those values are very high, similar to plantar pressures recorder for speed athletes during maximal speed running, what suggest that the current protection should be improved to reduce pressures. [ABSTRACT FROM AUTHOR]

Twenty golfers of varying ability took ten shots each with a standard golf club fitted with thin-film force sensors at the grip. Force was monitored at 84 locations, with the moment of impact determined for each shot. Evaluation of the sensor outputs has shown that each player has a grip force signature, i.e. total grip force throughout each shot is very repeatable for a given player, but varies considerably between players. [ABSTRACT FROM AUTHOR]

As the performance of athletes and their equipment is pushed to new limits, the importance of understanding the behaviour of sports balls is becoming increasingly apparent. Athletes and equipment manufacturers may try to maximise the distance travelled by a ball (e.g. golf, rugby) or unexpectedly swerve a ball to deceive the opposition (e.g. soccer, cricket, baseball). It is known that the surface geometry, spin and Reynolds number of a ball greatly affect its flight through the air, and this work focuses on understanding the effects of surface geometry. Computational Fluid Dynamics (CFD) has been used to help with the design and development of sports balls, firstly by understanding the details of the flow close to the surface, and secondly by attempting to characterise the surface geometry. CFD studies have been conducted on a smooth sphere and four different soccer balls, including a 1/3 scale model soccer ball and a real ball. The results have been compared to previous wind tunnel results of these balls, and the drag coefficients show consistent trends. It was found that the seam width and sharpness have a large effect on the ball΄s aerodynamic behaviour. Various other balls have been scanned and will be modelled in the future. These results will be combined with trajectory methods in order to accurately simulate the flight of any given sports ball through the air, with any given input condition. [ABSTRACT FROM AUTHOR]

In the Olympic competitions the so-called recurve bows are used in archery. Typical characteristics of a good bow riser are little weight and high stiffness. Hence a trend in the design of risers is to reduce weight without loosing other properties. The aim of this study was to design a riser with a considerably reduced weight at a quite similar stiffness compared to the lightest riser (1114g) that is used by archers of the German National Archery Team. A parametric CAD model of the riser was designed and optimized using evolutionary computing. Best model was selected out of 1650, and a riser was manufactured with a forged aluminum alloy (AS 28) using a CNC milling machine. A test of the riser in practice by archers of the German National Archery Team succeeded: the riser is not only very stiff and light (871g) but also damps the vibrations after the shot very well. [ABSTRACT FROM AUTHOR]

Carved turns with Alpine Skis were investigated using a computer simulation model. Varied input data to the model were the bending stiffness of the skis, the edging angle, and the velocity. Results include the turn radius and the force distribution along the running surface of the skis. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate whether an additional dynamic eccentric-concentric strength training of the finger flexors may improve the performance of rock climbers. A device was developed and constructed to train the finger flexors in a dynamic eccentric and concentric fashion and was distributed along with a specific exercise plan to rock climbers. Forty five male and I female rock climbers participated in the retrospective study and answered a questionnaire concerning their training time, climbing performance (grade) and subjective strength increase. The duration of the training averaged 19 months (SD 16, range 1–60) with 40 minutes per week (SD 38, range 5–210) and constituted 15% of the whole training (range 5–100). The difficulty of climbing redpoint style (known route) improved significantly on average from 12.1 to 14.4 (numeric scale of increasing difficulty 1–24, in relation to the French scale grade 3–9a), on sight style (unknown route) from 9.5 to 11.4 and boulder (short routes) from 8.7 to 11.8. In comparison, improvement of climbing performance during the 12 months before the start of the dynamic training was significantly less averaging redpoint 11.6 to 12.1, on sight 9.3 to 9.5 and boulder 7.9 to 8.7. Increase of maximal strength was subjectively rated to be 21%, increase of endurance strength 20% and improvement of over all climbing performance 15%. Dynamic eccentric – concentric strength training of the finger flexors in rock climbers may improve strength, endurance and climbing performance (grade of difficulty) and may be of value in addition to the static strength training. [ABSTRACT FROM AUTHOR]

It is the common experience of many sports engineers that the culmination of their research often involves the building, testing and measuring of a final product. After theoretical calculations have been completed, simplified experiments undertaken, and new designs proposed, often the final, and some would say, most important part of a project involves a comparison of the theoretical predictions with what actually happens – the so-called ˵proof of the pudding″. To this end, the ability to measure changing parameters and to record data accurately and with absolute confidence is essential if any real assessment of a product in use is to be obtained. Modern developments in sports engineering require greater and greater precision in measuring techniques, plus the increasing requirement for new, or improved, methods using state of the art technologies. What wasn΄t possible only a few years ago, is now often possible today; and what isn΄t possible today may well be possible tomorrow. In terms of obtaining data, the technology of data acquisition and storage moves on at a pace that becomes bewildering to those attempting to keep up. The advances that are being made virtually everyday in terms of speed, accuracy and resolution are effectively taken for granted and go hand in hand with the development of cheap off-the-shelf components which, with a little ingenuity, can often be used by aspiring researchers to produce sophisticated and cost effective solutions to both acquire and output data within their own skill areas. [ABSTRACT FROM AUTHOR]

Competitive and recreational athletes are continually increasing the demands on the performance of their equipment. The days of athletes tweaking their equipment for the extra few percentage points of improvement, if not completely in the past, is nearly so. Sports engineers, applying the latest and most powerful modelling and analysis tools to each and every piece of sports equipment, are replacing the age-old tinkering process. In some cases the goals are to optimize the design and performance of the equipment, in other cases, it is simply to understand the physics of existing sports equipment as a starting point to future development. [ABSTRACT FROM AUTHOR]