Asst TechnoI1998;10:151-1 52© 1998 RESNA

1998 RESNA/Whitaker Student Scientific PaperCompetition

Estimating Postural Disturbances Caused by Vol­untary Arm Movements. Kristin N. Werner, B.Sc.,Ronald J . Triolo, Ph.D., Robert F. Kirsch, Ph.D.,and Weifeng Zhao, Ph.D., Departments ofBiomed­ical Engineering and Orthopaedics, Case WesternReserve University, Cleveland, Ohio.

The purpose of this study is to develop and val­idate a three-dimensional, inverse dynamic modelof the upper extremity for estimating the types ofreaction forces and moments that are generated atthe shoulder during volitional arm movements.Experiments were conducted to validate the modelunder a variety of real-world conditions. The mod­el's predictions appear to be consistent and accu­rate. These methods may be useful in a variety ofrehabilitat ion applications, including the develop­ment of control strategies for maintaining balancewhile standing in patients requiring functionalelectrical stimulation.

A Relationship Between Pushrim Kinetics and Me­dian Nerve Dysfunction. Mark. A. Baldwin. l-' Mi­chael L. Beninger,':" Sean Shimada. l-" Rory A.Cooper ,':" and Tom O'Connor.s> 'Department ofRehabilitative Science and Technology, Universityof Pittsburgh, Pittsburgh, Pennsylvania; 2HumanEngineering Research Lab, Veterans Affairs Med­ical Center, Pittsburgh, Pennsylvania; and 3Divi­sion of PM&R, University of Pittsburgh MedicalCenter, Pittsburgh, Pennsylvania

The purpose of this study was to compare kineticparameters of wheelchair propulsion between ex­perienced wheelchair users with and without evi­dence of median mononeuropathy, an indicator ofcarpal tunnel syndrome.

Bilateral kinetic data was collected withSMARTWheels on 31 subjects who propelled theirown wheelchairs at two speeds while secured to adynamometer. Nerve conduction studies of eachsubject were used to place them in either the groupwith or without evidence of median mononeuro-

pathy. The peak radial, axial, tangential and re­sultant forces, efficiency, and propulsion frequencywere compared between the two groups.

Significantly higher peak radial and resultantforces along with stroke frequency were found inthe group with evidence of median mononeuropa­thies. Reducing these forces and stroke frequencycould lead to a reduction of carpal tunnel syndromein manual wheelchair users.

Signal-to-Noise-Ratio-Based Sorting of VoluntaryEvent Related Potential Averages for AssistiveTechnology Applications. M. M. Rohde , S. L.BeMent, S. P. Levine , J . E. Huggins, and R. K.Kushwaha. Biomedical Engineering Department,University of Michigan, Ann Arbor , Michigan

A method of sorting constituents of an averagesignal based on a running signal-to-noise measureis proposed. Its performance is examined with sim­ulated data that includes four different types of ex­perimental data corruption. The proposed methodis able to reject bad constituents ofthe average forthe simulated data.

The Effect of Stimulated Hip Extensor Movementon the Loads Imposed on the Arms During Stand­ing With FES. Michael A. Wibowo,' Ronald J . Tri­010,2 James P. Uhlir,' and Rudi Kobetic .v-Depart­ment of Biomedical Engineering and 20 rthopedics,Case Western Reserve University, Cleveland,Ohio; and 3Motion Study Laboratory, ClevelandVA Medical Center, Cleveland, Ohio

The overall goal of this study is to understandhow the hip extension moment produced by func­tional electrical stimulation affects the loads im­posed on the arms during upright posture. A bio­mechanical model of quiet standing was used topredict the effects of hip angle and stimulated hipextension moment on the arm support required tomaintain balance. Two individuals with completethoracic spinal cord injuries stood with continuous

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stimulation to the knee and trunk extensors; hipextension activation varied. The vertical loadsplaced on a set of parallel bars by the arms and ona force plate by the feet dring standing were mea­sured. Results suggest that the loads imposed onthe arms during quiet standing are highly depen­dent upon the extension moments at the hip andthe hip flexion angle . These findings imply that thestimulation of hip extensors that produces thelargest moment should result in the least weightplaced on an assistive device by the arms.

Delaying the Onset of Functional NeuromuscularStimulation-Induced Muscle Fatigue: A Study ofMuscle, Fiber Recruitment During IntramuscularStimulation. Kan Singh, Anne C. Dupont, and Fr­ances J. R. Richmond, Department of Physiology,Queen 's University, Kingston, Ontario, Canada

Functional neuromuscular stimulation, the useof electrical stimulation to activate paralyzed or

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paretic muscle, has the potential to provide stroke­and spinal cord-injured persons with a significantimprovement in their quality of life. However , thecurrent application methods result in the rapid on­set of muscle fatigue. This paper compares electri­cal stimulation using an intramuscular (IM) elec­trode with a nerve cuff (NC) electrode to determinedifferences in muscle fiber recruitment and loss offorce due to fatigue. The electrodes were implantedacutely in feline medial gastrocnemius. Physiolog­ical tests of force development and histologicalevaluation of glycogen depletion provided infor­mation about muscle performance and recruit­ment of different fiber types. Force decrement dueto fatigue was reduced with the 1Melectrode com­pared with the NC electrode. Predominantly fastglycolytic fatiguable fibers were recruited by theNC electrode, whereas a more representative mixof three fiber types was recruited following 1Mstimulation.

ASSISTIVE TECHNOLOGY, VOL. 10, NO. 2