PC User 1998 October/Image.iso/educat/kairos/_SETUP.1/MedLine.cgi

Text File | 1998-06-30 | 9.2 KB | 196 lines

1

AU  - Wootten ME

AU  - Kadaba MP

AU  - Cochran GV

TI  - Dynamic electromyography. I. Numerical representation using

      principal component analysis.

AB  - A complete description of human gait requires consideration

      of linear and temporal gait parameters such as velocity,

      cadence, and stride length, as well as graphic waveforms

      such as limb rotations, forces, and moments at the joints

      and phasic activity of muscles. This results in a large

      number of interactive parameters, making interpretation

      of gait data extremely difficult. Statistical pattern recognition

      techniques can simplify this problem. For this approach

      to be successful, first it is necessary to reduce the number

      of interactive parameters to a manageable set. In this

      study, we present an application of principal component

      analysis as a means for representing graphic waveforms

      in a parsimonious manner. In particular, we concentrate

      on representing the phasic muscle activity recorded using

      surface electrodes from ten major muscles of the lower

      extremity of 35 normal subjects during level walking. A

      32 point vector is created in which each point of the vector

      represents the normalized area under the curve of a portion

      of rectified and smoothed electromyographic signal, expressed

      as a function of gait cycle. Principal components are computed

      and the first few weighting coefficients are retained as

      features to represent the original EMG data. We show that

      the corresponding basis vectors span parts of the gait

      cycle where the most variability between individual subjects

      exists. We also show that the basis vectors can be used

      to represent the EMG data of subjects not originally used

      to generate the basis vectors.

MH  - Electromyography|*MT

AD  - Orthopaedic Engineering and Research Center

AD  - Helen Hayes Hospital

AD  - West Haverstraw

AD  - NY 10993.

SO  - J Orthop Res 1990 Mar; 8(2):247-58

DP  - 1990 Mar

TA  - J Orthop Res

PG  - 247-58

IP  - 2

VI  - 8

UI  - 90155633



2

AU  - Herzog W

AU  - Nigg BM

AU  - Read LJ

AU  - Olsson E

TI  - Asymmetries in ground reaction force patterns in normal

      human gait [see comments]

AB  - The purpose of this study was to propose a measure of symmetry/

      asymmetry for normal human gait and to quantify symmetries/

      asymmetries of normal human gait for selected gait variables

      using a force platform. Sixty-two subjects performed ten

      gait trials each, stepping on the force platform five times

      with each leg. From these gait trials a symmetry index

      was calculated for 34 gait variables. The upper and lower

      limits of normal gait were calculated such that 95% of

      all symmetry indices obtained from this subject population

      fell within these limits. Upper and lower limits were found

      to vary from +/- 4% to over +/- 13,000%. Extremely high

      percentages were found for variables which had absolute

      magnitudes close to zero and/or variables which occurred

      at distinctly different instants during the gait cycle.

      The results of these variables need to be interpreted with

      caution.

MH  - Gait|*

AD  - Biomechanics Laboratory

AD  - Faculty of Physical Education

AD  - University of Calgary

AD  - Canada.

SO  - Med Sci Sports Exerc 1989 Feb; 21(1):110-4

DP  - 1989 Feb

TA  - Med Sci Sports Exerc

PG  - 110-4

IP  - 1

VI  - 21

UI  - 89180901



3

AU  - Finch L

AU  - Barbeau H

AU  - Arsenault B

TI  - Influence of body weight support on normal human gait:

      development of a gait retraining strategy.

AB  - The recovery of locomotion, following interactive training

      with graded weight support, in the adult spinal cat has

      led to the proposal that removal of body weight may be

      a therapeutic tool in human gait retraining. There would

      be benefits, however, in knowing normal responses of humans

      to partial weight bearing before applying this strategy

      to patients. In this study, 10 nondisabled male subjects

      walked on a treadmill while 0%, 30%, 50%, and 70% of their

      body weight was supported by a modified climbing harness.

      To dissociate the changes attributable to walking speed

      from those attributable to body weight, each subject walked

      at the specified body-weight-support (BWS) levels and at

      full weight bearing (FWB) at the same speed. Simultaneously,

      electromyographic data from the right leg muscles, footswitch

      signals, and video recording of joint motion were collected.

      The FWB and BWS gaits appeared similar, except at the highest

      level of BWS studied (ie, 70% of BWS). Significant differences

      among other BWS and FWB trials at comparable speeds included

      decreases in percentage of stance, percentage of total

      double-limb support time, and maximum hip and knee flexor

      swing angle. Other adaptations to BWS were a reduction

      in the mean burst amplitude of the muscles that are active

      during stance and an increase in the mean burst amplitude

      of the tibialis anterior muscle. The possible implications

      of this new gait retraining strategy for patients with

      neurological impairment are discussed. [Finch L, Barbeau

      H, Arsenault B. Influence of body weight support on normal

      human gait: development of a gait retraining strategy.

MH  - Body Weight|*PH

MH  - Gait|*PH

MH  - Physical Therapy|*

AD  - Department of Physiotherapy

AD  - Montreal Neurological Institute

AD  - Quebec

AD  - Canada.

SO  - Phys Ther 1991 Nov; 71(11):842-55; discussion 855-6

DP  - 1991 Nov

TA  - Phys Ther

PG  - 842-55; discussion 855-6

IP  - 11

VI  - 71

UI  - 92052534



4

AU  - Schubert M

AU  - Curt A

AU  - Jensen L

AU  - Dietz V

TI  - Corticospinal input in human gait: modulation of magnetically

      evoked motor responses.

AB  - Transcranial magnetic stimulation (TMS) of the motor cortex

      was applied during locomotion to investigate the significance

      of corticospinal input upon the gait pattern. Evoked motor

      responses (EMR) were studied in the electromyogram (EMG)

      of tibialis anterior (TA), gastrocnemius (GM) and, for

      reference, abductor digiti minimi (AD) muscles by applying

      below-threshold magnetic stimuli during treadmill walking

      in healthy adults. Averages of 15 stimuli introduced randomly

      at each of 16 phases of the stride cycle were analysed.

      Phase-dependent amplitude modulation of EMR was present

      in TA and GM which did not always parallel the gait-associated

      modulation of the EMG activity. No variation of onset latency

      of the EMR was observed. The net modulatory response was

      calculated by comparing EMR amplitudes during gait with

      EMR amplitudes obtained (at corresponding background EMG

      activities) during tonic voluntary muscle contraction.

      Large net responses in both muscles occurred prior to or

      during phasic changes of EMG activity in the locomotor

      pattern. This facilitation of EMR was significantly higher

      in leg flexor than extensor muscles, with maxima in TA

      prior to and during late swing phase. A comparison of this

      facilitation of TA EMR prior to swing phase and prior to

      a phasic voluntary foot dorsiflexion revealed a similar

      onset but an increased amount of early facilitation in

      the gait condition. The modulated facilitation of EMR during

      locomotion could in part be explained by spinal effects

      which are different under dynamic and static motor conditions.

      However, we suggest that changes in corticospinal excitability

      during gait are also reflected in this facilitation. This

      suggestion is based on: (1) the similar onset yet dissimilar

      size of facilitatory effects in TA EMR prior to the swing

      phase of the stride cycle and during a voluntary dynamic

      activation, (2) the inverse variation of EMR and EMG amplitudes

      during this phase, and (3) the occurrence of this inversion

      at stimulation strengths below motor threshold (motor threshold

      was determined during weak tonic contraction and EMR were

      facilitated during gait). It is hypothesized that the facilitation

      is phase linked to ensure postural stability and is most

      effective during the phases prior to and during rhythmical

      activation of the leg muscles resulting in anticipatory

      adjustment of the locomotor pattern.

MH  - Electromagnetic Fields|*

MH  - Gait|*PH

MH  - Motor Cortex|*PH

MH  - Movement|*PH

MH  - Spinal Cord|*PH

AD  - Department of Clinical Neurology and Neurophysiology

AD  - University of Freiburg

AD  - Germany. [e-mail]

SO  - Exp Brain Res 1997 Jun; 115(2):234-46

DP  - 1997 Jun

TA  - Exp Brain Res

PG  - 234-46

IP  - 2

VI  - 115

UI  - 97368085