Subject-specific computer simulation model for determining elbow loading in one-handed tennis backhand groundstrokes.

A subject-specific angle-driven computer model of a tennis player, combined with a forward dynamics, equipment-specific computer model of tennis ball–racket impacts, was developed to determine the effect of ball–racket impacts on loading at the elbow for one-handed backhand groundstrokes. Matching subject-specific computer simulations of a typical topspin/slice one-handed backhand groundstroke performed by an elite tennis player were done with root mean square differences between performance and matching simulations of < 0.5°over a 50 ms period starting from ball impact. Simulation results suggest that for similar ball–racket impact conditions, the difference in elbow loading for a topspin and slice one-handed backhand groundstroke is relatively small. In this study, the relatively small differences in elbow loading may be due to comparable angle–time histories at the wrist and elbow joints with the major kinematic differences occurring at the shoulder. Using a subject-specific angle-driven computer model combined with a forward dynamics, equipment-specific computer model of tennis ball–racket impacts allows peak internal loading, net impulse, and shock due to ball–racket impact to be calculated which would not otherwise be possible without impractical invasive techniques. This study provides a basis for further investigation of the factors that may increase elbow loading during tennis strokes

A subject-specific computer simulation model of the one-handed backhand groundstroke in tennis

A subject-specific computer model of a tennis player, combined with an equipmentspecific computer model of tennis ball/racket impacts was used to determine the effect of ball/racket impacts on loading at the elbow for one-handed backhand groundstrokes. A matching subject-specific computer simulation of a typical topspin one-handed backhand groundstroke performed by an elite tennis player was determined with a root mean square difference between performance and matching simulation of less than 1º over a 50 ms period starting from ball impact. Using a subject-specific angle-driven computer model combined with a forward dynamics, equipment-specific computer model of tennis ball/racket impacts allows peak internal loading, net impulse and shock due to ball/racket impact to be calculated which would not otherwise be possible without impractical invasive techniques. This investigation provides a basis for further studies into the factors that may increase elbow loading during tennis strokes

A computer simulation model of tennis racket/ball impacts

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

A comparison of wrist angular kinematics and forearm EMG data for an elite, intermediate and novice standard tennis player performing a one-handed backhand groundstroke

Wrist angular kinematics (flexion/extension) and electromyography (EMG) data of a one-handed tennis backhand groundstroke were compared for an elite, intermediate and novice standard tennis player. For this purpose, synchronisation of the data with respect to ball impact time was achieved by a system of wireless and wired triggers and receivers. All three players maintained wrist extension for the 0.6 second period centred on ball impact. The elite and intermediate player struck the ball with the wrist extended by an average of 10o from neutral alignment whilst moving towards flexion. After ball impact the wrist moved back towards and further into extension. The novice player was characterised by fluctuations in the wrist flexion/extension angle prior to ball impact with the wrist extended on average by 30o from neutral alignment at impact. The wrist of the novice palyer moved back towards and further into extension after ball impact, although less than for intermediate and elite players. For the elite player, peak EMG levels for the wrist flexors and extensors were reached consistently 0.05-0.1 seconds prior to ball impact. Wrist flexor EMG levels for the intermediate and novice players peaked on average 0.02 seconds after ball impact and extensor EMG levels peaked at ball impact. For the novice player, both flexor and extensor EMG data exhibited fluctuations consistent with the wrist kinematics data. Previously cited conditions that predispose a novice player to injury were not observed in this study. Given current injury mechanism theories, the data from this study suggests that the susceptibility of a player to tennis elbow injury cannot be established by generic skill level alone. Tennis players need to analysed as individuals