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Factor analysis of bilateral EMG in human gait
Abstracts-International Society of Biomechanics XIV Congress 1993
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FACTOR ANALYSIS OF BILATERAL EMG IN HUMAN GAIT Kenneth S. Olree’ and Christopher L. Vaughan”’ Departments of Biomedical Engineering* and Orthopaedics+ University of Virginia, Charlottesville, Virginia, USA We hypothesize that the central nervous system solves the problem of high dimensionality by generating a few fundamental signals which control all the muscles in both legs. Electromyographic data from eight bilateral muscles were gathered on ten normal adults (five male, five female, ages 21 to 40) using bipolar surface electrodes. Muscles studied were: erector spinae, gluteus maximus, gluteus medius, rectus femoris, hamstrings, adductor magnus, tibialis anterior. and gastrocnemius. Each subject was instructed to “walk briskly” along a walkway for three trials, and the EMG and footswitch data were telemetered to the host computer which sampled at 1 kHz for four seconds. The EMG data were full wave rectified and low pass filtered with a cutoff frequency of 3 Hz. For each trial we extracted two to three cycles (heelstrike to heelstrike) which allowed us to normalize the data in magnitude and in time (0 to 100% in 2% intervals). The three trials thus provided six to nine cycles of data which were ensemble averaged for each muscle of each subject, and finally an ensemble average was generated for all 10 subjects. The data were then factor analyzed using a commercially available statistics package (StatView). This analysis produced five factors which accounted for 97.7% of the variance in the data. We conclude that the fifth factor is the result of the bilateral study. We interpret this factor to be a coordinating factor which maintains the 180”phase shift between the left and right sides. Furthermore, factors 1 and 2 appear to be almost identical except for a 180”phase shift. These factors can be interpreted as loading responsefactors for each side. Factors 3 and 4 also appear to be nearly identical except for a 180”phase shift and can be interpreted as propulsion factors for the left and right side. We believe that our data, which show that 16 muscle patterns can be representedby just 3 fundamental patterns, provide support for our original hypothesis.
OUTCOMES ASSOCIATED WITH BALANCE FUNCTION DURING TRANSITIONS FROM BH’EDAL TO SINGLE LIMB STANCE IN HEMIPARETIC ADULTS Yi-Chung Pai, Mark W. Rogers, Lois Deming Hedman and Timothy A. Hanke, Programs in Physical Therapy, Northwestern University Medical School, Chicago, IL 60611, U.S.A. The purpose of this study was to examine the position and trajecto in the frontal plane of the body center of mass (CM) with respect to the base of support during single leg ‘Kexion movementsamong fourteen volunteers with right-side hemiparcsis. Subjectsperformed single leg flexion movementswith the paretic and non-paretic limbs while standing on two separateforce platforms. Motion analysis and force platform data were used to determine the outcome of the CM displacement. Successfulperformance occur& for 48% (to non-paretic stanceside) and 20% (to paretic stanceside) of all trials. Lack of successwas due to insufficient displacementof the CM (26% of all trials to non-paretic stanceside and 17% to paretic stanceside) or a failure to maintain single limb stance(26% of all trials to non-paretic stanceside and 63% to paretic stance side). Overall, the final position of the CM was outside the single support region for insufficient transfers, and differed from that for successand failure to hold outcomes. Incomplete transfers could have been caused by an insufficient initial propulsive impulse generatedbeneaththe upcoming flexing limb, and/or inadequate reduction of the initially passive braking impulse beneaththe stancelimb which prematurely terminated the weight transfer. In contrast, failure to hold the final position of the CM during single limb stancemay have been attributable to inadequateand/or inappropriate fine adjustmentsin ground reaction forces possibly due to alteredjoint torques at the hip and/or ankle. Failure to maintain quasi-static single limb stancemight also have been a consequenceof inadequateanti-gravity support against collapse with respect to the vertical direction.
DOPAMINBRGICEPPBCTSON INlTIATION AND EXECUTION OF GOAL DIRECTED VOLUNTARY POSTURAL MOIN PARKINSON’SDISEASE VictoriaPanzer-Decillsalldclu?ry1Manley NearoComIntemtioaat, Clackamas,OR 97015USA TllCpUpOlXOfthiSstudyWStOd~~theresponsivene ss of initiation and executioncomponentsof~oshmil mrvementto&pamincrep&cementtherapyinParkimo~sdisease(PD). TenPDpatientsand13normalcontmlsubjeRP~ ~~onaforceplatformasiheyperformed~~~weiglltshiftingmwements to targetsdisplayedon a video monitor. Tt&~~in~ardcr,~anadysignalfotto\redbyarandom~inccrvrdand~~to~ mwleinoneofeightpossible.directions. Patkntsweretestedafteruvmnightwith&awalofall&pmninergic~~~~ ~onebourafterbeginninganIVlransfwpionoftheirpreviouslydetermiiLedoptimaldoseofLQI#I. Fiwwntrolsnbjacts repetedthetcstingprotowiforcomparisonwiththesecondpatientsession. Basedoadirectionofdisp~maxi~ dishace-d-velocityofthecoGdatafromtarget~untilfirst movementtoule~the le.edontilnc(R~wasdaivtd Movementtime~wascalarlaadirthesllbjectachievedthetargetwitbintheti~alottcd (z~~.~,~~~to~~totaltimrequired,minusRT. Thetotddistancetravelledinmovingtothetarget~~ bythatomltimewasllwagemwement velocity(Mv). Amlysisofvariaaw methodswereusedto-astical signeaw. F+aticmwcrealmparcdonmldoffmedicationmldolltyMvsignificanttyimpmvcd Patielltsoaandoff mf&cationwefetbenqemtelycoqxuedtoamtrols. RTwasabnorma@prolongedin~&ntson,butnotoffme&cation. PatientMvwassi~sllrlowerthmlaolm4bothonaadoffmedication consistentresultswerefoundforMv;patienta ~~mdicstioqbOtWneSi@icilntIyabnormalbothonandoffmedieation. Asexumicmof movement(decreased ~impovtEwith~~itapppearstobcthedi&cultyininitiationofpostural -thStiSthebasiSOfthe uwspomkposhualde&itinPD.
731
FACTOR ANALYSIS OF BILATERAL EMG IN HUMAN GAIT Kenneth S. Olree’ and Christopher L. Vaughan”’ Departments of Biomedical Engineering* and Orthopaedics+ University of Virginia, Charlottesville, Virginia, USA We hypothesize that the central nervous system solves the problem of high dimensionality by generating a few fundamental signals which control all the muscles in both legs. Electromyographic data from eight bilateral muscles were gathered on ten normal adults (five male, five female, ages 21 to 40) using bipolar surface electrodes. Muscles studied were: erector spinae, gluteus maximus, gluteus medius, rectus femoris, hamstrings, adductor magnus, tibialis anterior. and gastrocnemius. Each subject was instructed to “walk briskly” along a walkway for three trials, and the EMG and footswitch data were telemetered to the host computer which sampled at 1 kHz for four seconds. The EMG data were full wave rectified and low pass filtered with a cutoff frequency of 3 Hz. For each trial we extracted two to three cycles (heelstrike to heelstrike) which allowed us to normalize the data in magnitude and in time (0 to 100% in 2% intervals). The three trials thus provided six to nine cycles of data which were ensemble averaged for each muscle of each subject, and finally an ensemble average was generated for all 10 subjects. The data were then factor analyzed using a commercially available statistics package (StatView). This analysis produced five factors which accounted for 97.7% of the variance in the data. We conclude that the fifth factor is the result of the bilateral study. We interpret this factor to be a coordinating factor which maintains the 180”phase shift between the left and right sides. Furthermore, factors 1 and 2 appear to be almost identical except for a 180”phase shift. These factors can be interpreted as loading responsefactors for each side. Factors 3 and 4 also appear to be nearly identical except for a 180”phase shift and can be interpreted as propulsion factors for the left and right side. We believe that our data, which show that 16 muscle patterns can be representedby just 3 fundamental patterns, provide support for our original hypothesis.
OUTCOMES ASSOCIATED WITH BALANCE FUNCTION DURING TRANSITIONS FROM BH’EDAL TO SINGLE LIMB STANCE IN HEMIPARETIC ADULTS Yi-Chung Pai, Mark W. Rogers, Lois Deming Hedman and Timothy A. Hanke, Programs in Physical Therapy, Northwestern University Medical School, Chicago, IL 60611, U.S.A. The purpose of this study was to examine the position and trajecto in the frontal plane of the body center of mass (CM) with respect to the base of support during single leg ‘Kexion movementsamong fourteen volunteers with right-side hemiparcsis. Subjectsperformed single leg flexion movementswith the paretic and non-paretic limbs while standing on two separateforce platforms. Motion analysis and force platform data were used to determine the outcome of the CM displacement. Successfulperformance occur& for 48% (to non-paretic stanceside) and 20% (to paretic stanceside) of all trials. Lack of successwas due to insufficient displacementof the CM (26% of all trials to non-paretic stanceside and 17% to paretic stanceside) or a failure to maintain single limb stance(26% of all trials to non-paretic stanceside and 63% to paretic stance side). Overall, the final position of the CM was outside the single support region for insufficient transfers, and differed from that for successand failure to hold outcomes. Incomplete transfers could have been caused by an insufficient initial propulsive impulse generatedbeneaththe upcoming flexing limb, and/or inadequate reduction of the initially passive braking impulse beneaththe stancelimb which prematurely terminated the weight transfer. In contrast, failure to hold the final position of the CM during single limb stancemay have been attributable to inadequateand/or inappropriate fine adjustmentsin ground reaction forces possibly due to alteredjoint torques at the hip and/or ankle. Failure to maintain quasi-static single limb stancemight also have been a consequenceof inadequateanti-gravity support against collapse with respect to the vertical direction.
DOPAMINBRGICEPPBCTSON INlTIATION AND EXECUTION OF GOAL DIRECTED VOLUNTARY POSTURAL MOIN PARKINSON’SDISEASE VictoriaPanzer-Decillsalldclu?ry1Manley NearoComIntemtioaat, Clackamas,OR 97015USA TllCpUpOlXOfthiSstudyWStOd~~theresponsivene ss of initiation and executioncomponentsof~oshmil mrvementto&pamincrep&cementtherapyinParkimo~sdisease(PD). TenPDpatientsand13normalcontmlsubjeRP~ ~~onaforceplatformasiheyperformed~~~weiglltshiftingmwements to targetsdisplayedon a video monitor. Tt&~~in~ardcr,~anadysignalfotto\redbyarandom~inccrvrdand~~to~ mwleinoneofeightpossible.directions. Patkntsweretestedafteruvmnightwith&awalofall&pmninergic~~~~ ~onebourafterbeginninganIVlransfwpionoftheirpreviouslydetermiiLedoptimaldoseofLQI#I. Fiwwntrolsnbjacts repetedthetcstingprotowiforcomparisonwiththesecondpatientsession. Basedoadirectionofdisp~maxi~ dishace-d-velocityofthecoGdatafromtarget~untilfirst movementtoule~the le.edontilnc(R~wasdaivtd Movementtime~wascalarlaadirthesllbjectachievedthetargetwitbintheti~alottcd (z~~.~,~~~to~~totaltimrequired,minusRT. Thetotddistancetravelledinmovingtothetarget~~ bythatomltimewasllwagemwement velocity(Mv). Amlysisofvariaaw methodswereusedto-astical signeaw. F+aticmwcrealmparcdonmldoffmedicationmldolltyMvsignificanttyimpmvcd Patielltsoaandoff mf&cationwefetbenqemtelycoqxuedtoamtrols. RTwasabnorma@prolongedin~&ntson,butnotoffme&cation. PatientMvwassi~sllrlowerthmlaolm4bothonaadoffmedication consistentresultswerefoundforMv;patienta ~~mdicstioqbOtWneSi@icilntIyabnormalbothonandoffmedieation. Asexumicmof movement(decreased ~impovtEwith~~itapppearstobcthedi&cultyininitiationofpostural -thStiSthebasiSOfthe uwspomkposhualde&itinPD.