No abstract

No abstract

Assessment of sports equipment 'performance' is generally derived from physical and technical parameters, such as power, speed, distance and accuracy. However, from a psychological perspective, players need to feel comfortable with their equipment and confident in its properties. These factors can only be measured via the subjective assessment of individual perceptions. Using a study of a group of elite golfers as an example, this paper presents a formalised approach for eliciting and structuring player's descriptions of their perception of sports equipment. Qualitative methods of inquiry are employed to generate perceptions from a group of professional golfers (n=15) during play testing. The equipment characteristics of significance to the golfers emerged from an inductive analysis of their responses. However, whilst this method of representation of the results was invaluable in identifying the key components or dimensions of a player's subjective perception, it was insufficient to describe the potential relationships between the dimensions. With this in mind, a new technique, entitled structured relationship modelling, was developed to illustrate these associations. Ten general dimensions emerged from the analysis, of which three are presented in this paper along with a section of the relationship model. These results demonstrate the effectiveness of qualitative techniques for eliciting human perceptions and of structured relationship models for representation of the associations found.

No abstract

a b s t r a c tA torque-driven, 3D computer simulation model of an arm-racquet system was used to investigate the effects of ball impact location and grip tightness on the arm, racquet and ball during one-handed tennis backhand groundstrokes. The stringbed was represented by nine point masses connected to each other and the racquet frame with elastic springs and three torsional spring-dampers between the hand and the racquet were used to represent grip tightness. For each perturbation of nine impact locations and grip tightness, simulations were run for a 50 ms period starting with ball-racquet impact. Simulations showed that during off-centre impacts below the longitudinal axis of the racquet, the wrist was forced to flex up to 161 more with up to six times more wrist extension torque when compared to a centre impact simulation. Perturbing grip tightness had no substantial effect on centre impact simulations. However, for off-centre impacts (below the longitudinal axis of the racquet) a tight grip condition resulted in a substantial decrease in racquet rotation within the hand (less than 21) and an increase of 61 in wrist flexion angle when compared to the equivalent simulation with a normal grip. In addition there was approximately 20% more wrist extension torque when compared with equivalent off-centre impact simulation with a normal grip. Consequently off-centre impacts below the longitudinal axis of the racquet may be a substantial contributing factor for tennis elbow injuries with a tight grip aggravating the effect due to high eccentric wrist extension torques and forced wrist flexion.

BackgroundIn contact sports (eg, American football or rugby), injuries resulting from impacts are widespread. There have been several attempts to identify and collate, within a conceptual framework, factors influencing the likelihood of an injury. To effectively define an injury event it is necessary to systematically consider all potential causal factors but none of the previous approaches are complete in this respect.AimsFirst, to develop a superior deterministic contextual sequential (DCS) model to promote a complete and logical description of interrelated injury event factors. Second, to demonstrate systematic use of the model to construct enhanced perspectives for impact-injury research.MethodPrevious models were examined and elements of best practice synthesised into a new DCS framework description categorising the types of causal factors influencing injury. The approach's internal robustness is demonstrated by consideration of its completeness, lack of redundancy and logical consistency.ResultsThe model's external validity and worth are demonstrated through its use to generate superior descriptive injury models, experimental protocols and intervention opportunities. Comprehensive research perspectives have been developed using a common rugby impact-injury scenario as an example; this includes: a detailed description of the injury event, an experimental protocol for a human-on-surrogate reconstruction, and a series of practical interventions in the sport of rugby aimed at mitigating the risk of injury.ConclusionsOur improved characterisation tool presents a structured approach to identify pertinent factors relating to an injury.

An initial study of racket motion in the power serve executed by six tennis players was performed using several rackets with different inertia properties. Both two‐dimensional high‐speed video and three‐dimensional active marker measurement techniques were employed at 4500 and 400 Hz sampling rates, respectively. The results indicate that a decrease in racket inertia, within realistic limits, can significantly increase the head speed achieved by skilled players. The racket’s instantaneous centre of rotation position at impact, with respect to a locally defined frame of reference, was also found to be remarkably consistent for most subjects and all rackets tested. A larger scale study is necessary to confirm or deny these observations, but the initial findings encourage the view that realistic racket service performance comparison tests must take account of the variations in head speed likely to be achieved in play.

A forward dynamics computer simulation for replicating tennis racket/ball impacts is described consisting of two rigid segments coupled with two degrees of rotational freedom for the racket frame, nine equally spaced point masses connected by 24 visco-elastic springs for the string-bed and a point mass visco-elastic ball model. The first and second modal responses both in and perpendicular to the racket string-bed plane have been reproduced for two contrasting racket frames, each strung at a high and a low tension. Ball/string-bed normal impact simulations of real impacts at nine locations on each string-bed and six different initial ball velocities resulted in <3% RMS error in rebound velocity (over the 16-27 m/s range observed). The RMS difference between simulated and measured oblique impact rebound angles across nine impact locations was 1°. Thus careful measurement of ball and racket characteristics to configure the model parameters enables researchers to accurately introduce ball impact at different locations and subsequent modal response of the tennis racket to rigid body simulations of tennis strokes without punitive computational cost.