2010 Asics Conference of Science and Medicine in Sport / Journal of Science and Medicine in Sport 13S (2010) e1–e107 e33

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Using wearable inertial sensors for skill assessment of thetennis serve

A. Ahmadi 1,2,∗, D. Rowlands 1, D. James 1,2

1 Griffith University, Centre for Wireless Monitoring Appli-cations, Australia2 Queensland Academy of Sport, Centre of Excellence forApplied Sports Science Research, Australia

The use of MEMS inertial gyroscopes to assess andimprove the skill of tennis players during the first serve wasinvestigated. A marker based virtual gyroscope was devel-oped to measure the upper arm internal rotation and othervector based methods were developed to measure the wristflexion and shoulder rotation of a player during the first serve.Athletes from amateur to elite participated in this study. Threegyroscope sensors were attached on the hand, chest and upperarm of the subjects. Subjects were asked to perform the firstserve and 30 successful serves were utilized for the exper-iment. Results showed that the output of the gyroscopesattached to the athlete’s body and the marker based meth-ods were in close agreement. The peak values of the angularvelocities for upper arm internal rotation, wrist flexion andshoulder rotation were calculated for athletes of different skilllevels. These values were plotted and compared with racquethead speed. Clear banding and well separated clustering wasshown for the different skill levels. Higher level athletes pro-duced greater upper arm internal rotation, wrist flexion andshoulder rotation and hence produced greater racquet headspeed. A line of best fit through the clusters of all the athletes(as a function of upper arm internal rotation, wrist flexion andshoulder rotation) indicated a possible path of improvementfrom amateur to elite. The line was considered a possible aidfor feedback to athletes aiming for skill improvement by sug-gesting which variables could be adjusted. It was concludedthat gyroscope sensors can be used for skill assessment andskill improvement for a first tennis serve.

doi:10.1016/j.jsams.2010.10.530

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Multidisciplinary Grand Rounds Clinical session:Lumbo, pelvic, hip and lower limb

T. Wisbey-Roth

Bounce Back Active Rehabilitation Systems, Australia

For the first time at the National SMA conference a highlyexperienced and interactive discussion panels have been com-plied to discuss clinical cases. A Multidisciplinary expertPanel consisting of Sports Physicians, Hip and groin Sur-geon, Radiology, Specialist Physiotherapists, and Podiatristswill discuss interesting clinical cases. True clinical cases willbe presented with history, signs and symptoms outlined. The

aim of this interactive session is to encourage lively discus-sion between the expert panel and the audience on processesof Differential diagnosis, required investigations and plannedtreatment approach.

doi:10.1016/j.jsams.2010.10.531

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Functional improvements and electromyographic (EMG)changes in multidirectional instability of the shoulderafter conservative rehabilitation

N. Johnson 1,∗, T. Pizzari 1,2, L. Watson 1,2,3, J. Wickham 4,S. Balster 3

1 School of Physiotherapy, Faculty of Health Sciences, LaTrobe University, Australia2 Musculoskeletal Research Centre, Faculty of Health Sci-ences, La Trobe University, Australia3 LifeCare Prahran Sports Medicine, Australia4 School of Biomedical Science, Faculty of Science, CharlesSturt University, Australia

Objective: Using a pre-post intervention study design, toevaluate functional changes and EMG characteristics fol-lowing a conservative rehabilitation program for a cohortdiagnosed with glenohumeral multidirectional instability(MDI). Methods: The Melbourne Instability Shoulder Scale(MISS) questionnaire and the Western Ontario ShoulderIndex (WOSI) were used to examine functional changes and.EMG analysis was used to determine temporal (onset, peakand termination) and intensity characteristics of 14 shouldermuscle segments before and after an 8–12 week individ-ualised rehabilitation program. Previously compiled EMGdata for a cohort of asymptomatic shoulders (n = 24) werealso used for comparative analysis. Results: Eleven subjects(5 male, 6 female) with a mean age of 22.4 years (range17–32) were included in the MDI group and participatedin the rehabilitation program. Post rehabilitation, significantfunctional improvement was demonstrated on both the MISS(p = 0.00) and the WOSI (p = 0.00) questionnaires whencompared with the pre-rehabilitation scores. EMG analysisshowed that upper trapezius (p = 0.01), upper (p = 0.02) andlower subscapularis (p = 0.02) were activating significantlyearlier compared with asymptomatic controls followingrehabilitation. The early onsets displayed between the pre-rehabilitation MDI data and the controls for supraspinatus,infraspinatus, middle trapezius, middle deltoid and lowersubscapularis were no longer significant after rehabilitation.The significantly lower intensities noted in supraspinatuspre-rehabilitation (p = 0.01) also normalised following theprogram. Potentially the most important EMG finding in thepost rehabilitation phase was the development of marked vari-ability for most muscles, across all the temporal and intensityEMG characteristics. Prior to rehabilitation all the EMG char-acteristics demonstrated considerably narrower variability