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1.
Gait Posture ; 29(1): 1-5, 2009 Jan.
Article in English | MEDLINE | ID: mdl-18603428

ABSTRACT

Two-dimensional magnitude squared coherence (2D-MSC) is developed to compare the two-valued time series which represent the center of pressure (COP) under each foot. A sinusoidal multiple taper spectral estimator is used to reduce bias and improve spectral resolution. The measure is applied to evaluate symmetry in the dual-plate postural steadiness time series obtained from healthy young and elderly volunteers, and patients with Huntington's Disease (HD), a group in which asymmetries in postural steadiness are anticipated. The results demonstrate that the 2D-MSC is a robust measure of inter-limb coordination that may be of value in studies of aging and neurologic disease.


Subject(s)
Huntington Disease/physiopathology , Postural Balance/physiology , Adult , Aged , Aged, 80 and over , Analysis of Variance , Female , Foot/physiology , Fourier Analysis , Humans , Male , Middle Aged , Pressure , Signal Processing, Computer-Assisted
2.
Arch Phys Med Rehabil ; 80(1): 59-65, 1999 Jan.
Article in English | MEDLINE | ID: mdl-9915373

ABSTRACT

OBJECTIVE: To evaluate patterns of successful gait strategy in Huntington disease (HD) at various stages of illness to improve fall avoidance and maintenance of independence. DESIGN: Repeated measurements of gait kinematic parameters and joint performance during gait cycles of six HD patients compared to 30 age-matched controls. SETTING: A standard gait laboratory. SUBJECTS: Six HD patients, rank-ordered for disease severity from minimal chorea to generalized dystonia, selected because they were ambulatory despite 3 to 17 years' disease duration. One patient was from a nursing home (walked with assistance) and five were living independently, either alone or with a working spouse who was the caregiver. MAIN OUTCOME MEASURES: Standardized gait evaluations (retroreflective markers on standard bony landmarks) from five video angles, fed into digitizer to computer-generate joint angles and standard gait kinematic parameters. RESULTS: Wide variability in gait kinematic parameters and joint interaction plots (phase plane and angle-angle plots) was observed between individuals and successive trials of the same limb, tending to increase with disease severity. Joint interaction plots show that random, highly variable distractions from planned trajectories are more apparent distally. CONCLUSIONS: Chorea in HD does not appreciably affect the center of gravity during ambulation, and the consistency of gait profiles at heel strike shows that the ultimate target is achieved in each step despite random and frequent variability during the gait cycle.


Subject(s)
Gait , Huntington Disease/physiopathology , Adult , Biomechanical Phenomena , Computers , Female , Humans , Male , Middle Aged , Reference Values
3.
IEEE Trans Biomed Eng ; 43(9): 956-66, 1996 Sep.
Article in English | MEDLINE | ID: mdl-9214811

ABSTRACT

Measures of postural steadiness are used to characterize the dynamics of the postural control system associated with maintaining balance during quiet standing. The objective of this study was to evaluate the relative sensitivity of center-of-pressure (COP)-based measures to changes in postural steadiness related to age. A variety of time and frequency domain measures of postural steadiness were compared between a group of twenty healthy young adults (21-35 years) and a group of twenty healthy elderly adults (66-70 years) under both eyes-open and eyes-closed conditions. The measures that identified differences between the eyes-open and eyes-closed conditions in the young adult group were different than those that identified differences between the eye conditions in the elderly adult group. Mean velocity of the COP was the only measure that identified age-related changes in both eye conditions, and differences between eye conditions in both groups. The results of this study will be useful to researchers and clinicians using COP-based measures to evaluate postural steadiness.


Subject(s)
Postural Balance/physiology , Posture/physiology , Adult , Age Factors , Aged , Analysis of Variance , Female , Fractals , Humans , Male , Models, Statistical , Reference Values , Sensitivity and Specificity
4.
Ann Biomed Eng ; 23(6): 711-9, 1995.
Article in English | MEDLINE | ID: mdl-8572421

ABSTRACT

Fractal and correlation dimensions have been computed for time series obtained from tests of balance (postural steadiness). Although these measures appear to be reliable and differentiate subject groups, it has become clear that random (noise) time series may have finite dimensions and appear to demonstrate dynamics characteristic of nonlinear systems. Consequently, it is necessary to apply a test to distinguish a time series with putative nonlinear dynamics from random noise. A simple predictor was utilized to compare center of pressure (COP) time series with surrogate data constructed to have similar time and frequency domain characteristics. It was found that the original time series was more predictable than the surrogate data, suggesting that the COP data is derived from a nonlinear system.


Subject(s)
Nonlinear Dynamics , Postural Balance/physiology , Posture/physiology , Signal Processing, Computer-Assisted , Adult , Algorithms , Biomechanical Phenomena , Data Interpretation, Statistical , Fourier Analysis , Humans , Reference Values , Statistics, Nonparametric , Time Factors
5.
Med Sci Sports Exerc ; 27(6): 913-9, 1995 Jun.
Article in English | MEDLINE | ID: mdl-7658955

ABSTRACT

The purpose of this study was to determine whether use of an abdominal binder would affect oxygen uptake, trunk range of motion, and duration of the stroke phase during wheelchair propulsion. The subjects were six paraplegic wheelchair athletes with T1-T6 injuries and no abdominal muscle function. Each subject performed two trials, one while wearing the binder and one without the binder. Each trial consisted of submaximal and maximal exercise tests conducted on wheelchair rollers. Oxygen uptake was determined by open circuit spirometry while heart rate was determined by telemetry. Max VO2 values averaged 2.51 l.min-1 while average maximum heart rate values were 190 b.min-1. A 3-D video-based motion analysis system was used to obtain kinematic parameters of wheelchair propulsion. In general, 30% of the cycle time was comprised of the stroke phase, while 70% was comprised of the recovery phase across speeds. There were no statistically significant effects of the abdominal binder on any of the cardiovascular or kinematic variables at submaximal or maximal levels of exercise. Under the conditions of this laboratory investigation, it appears that an abdominal binder does not alter physiological or selected biomechanical measures in highly trained athletes.


Subject(s)
Bandages , Exercise/physiology , Oxygen Consumption , Paraplegia/physiopathology , Wheelchairs , Abdomen , Adult , Biomechanical Phenomena , Female , Humans , Male , Pressure , Prospective Studies , Spinal Cord Injuries/physiopathology
6.
Neurology ; 45(5): 919-24, 1995 May.
Article in English | MEDLINE | ID: mdl-7746407

ABSTRACT

We applied functional magnetic resonance imaging (FMRI) to map the somatotopic organization of the primary motor cortex using voluntary movements of the hand, arm, and foot. Eight right-handed healthy subjects performed self-paced, repetitive, flexion/extension movements of the limbs while undergoing echo-planar imaging. Four subjects performed movements of the right fingers and toes, while the remaining subjects performed movements of the right fingers and elbow joint. There was statistically significant functional activity in the left primary motor cortex in all subjects. The pattern of functional activity followed a topographic representation: finger movements resulted in signal intensity changes over the convexity of the left motor cortex, whereas toe movements produced changes either at the interhemispheric fissure or on the dorsolateral surface adjacent to the interhemispheric fissure. Elbow movements overlapped the more medial signal intensity changes observed with finger movements. Functionally active regions were confined to the cortical ribbon and followed the gyral anatomy closely. These findings indicate that FMRI is capable of generating somatotopic maps of the primary motor cortex in individual subjects.


Subject(s)
Brain Mapping , Motor Cortex/physiology , Adult , Arm/innervation , Arm/physiology , Female , Foot/innervation , Foot/physiology , Hand/innervation , Hand/physiology , Humans , Magnetic Resonance Imaging , Male
7.
Child Dev ; 64(4): 1036-45, 1993 Aug.
Article in English | MEDLINE | ID: mdl-8404255

ABSTRACT

The stretch reflex is a spinal cord pathway between a muscle's stretch receptors and its own motor units. This reflex is thought to play an important role in normal motor function, because it is unique as a monosynaptic pathway, and because its hyperactivity is a hallmark of many motor disorders. We previously reported a difference in the stretch reflexes in healthy newborn infants and nonambulatory individuals with cerebral palsy (CP): these reflexes are characterized by responses from the stretched muscle and from the reciprocal or antagonist muscle. We proposed the existence of a functional spinal cord pathway that connects both agonist and antagonist muscles at a single joint. We hypothesized that this "reciprocal excitation" is a functional pathway of all newborn infants, which during the normal course of development of motor skills in infants is eliminated. If the CNS is damaged at birth, as in CP, the pathway of reciprocal excitation endures and is reinforced. In the current study of newborns, we recorded stretch reflex responses from all major muscle groups of the lower limb. This "irradiation of reflexes" is a normal phenomenon of the newborn CNS. This pathway becomes suppressed during normal maturation and control of coordinated limb movements.


Subject(s)
Infant, Newborn/physiology , Joints/innervation , Muscles/innervation , Reflex, Stretch/physiology , Spinal Cord/physiology , Achilles Tendon/innervation , Electromyography , Humans , Male , Motor Neurons/physiology , Muscle Contraction/physiology , Reaction Time/physiology , Reference Values
8.
Am J Phys Med Rehabil ; 71(6): 333-42, 1992 Dec.
Article in English | MEDLINE | ID: mdl-1466871

ABSTRACT

The purpose of this study was to determine whether a moderate to high intensity strengthening and aerobic exercise program can improve the strength, exercise capacity, gait and balance of deconditioned male nursing home residents. Ambulatory subjects who scored 30 or less on the modified Tinetti gait and balance assessment scale, who demonstrated less than 80% of age-matched lower extremity strength on isokinetic muscle testing and who gave informed consent were enrolled. Subjects were randomized to either an exercise (n = 8) or a control (n = 6) group. All participants underwent an exercise test to determine maximal oxygen uptake (VO2max) and received quantitative gait and balance measurements. The subjects assigned to the exercise group than completed a 12-wk program of weight training for the lower extremities and stationary cycling. Both the exercise and control groups were then retested. Ten outcome variables were assessed: Tinetti mobility scores, VO2max, isokinetic-tested lower extremity strength and endurance, stride length, gait velocity, stance time, gait duration, cadence and balance. The exercise group, after completion of the program, demonstrated significant improvements in Tinetti mobility scores (P < 0.05), combined right and left quadricep muscle strength (P < 0.01), right and left lower extremity muscular endurance (P < 0.01), left stride length and gait velocity (P < 0.05), although other outcome variables changed insignificantly. The control group revealed no changes of significance with the exception of improvement of the combined right and left hamstring muscle strength (P < 0.05). Nevertheless, for those outcome variables that had improved significantly in the exercise group, the changes amounted to only a 5 to 10% increase over the baseline measurements. These findings showed that an appropriately designed high intensity exercise program can result in significant although limited improvements for clinical mobility scores, strength, muscular endurance and certain gait parameters.


Subject(s)
Exercise , Gait/physiology , Aged , Aged, 80 and over , Humans , Inpatients , Male , Middle Aged , Patient Compliance , Physical Endurance , Postural Balance/physiology , Posture/physiology
9.
Arch Phys Med Rehabil ; 73(7): 609-17, 1992 Jul.
Article in English | MEDLINE | ID: mdl-1622314

ABSTRACT

The sit-to-stand motion of ten healthy subjects, 65 to 76 years old, was evaluated using kinematic, force plate, and electromyographic data to characterize the sit-to-stand motion. Kinematic data collected by video, muscle activity monitored by surface electromyography, and ground reaction forces analyzed by a piezoelectric force plate were used for analysis. Using these synchronized data, three phases of the sit-to-stand motion were identified--phase 1, weight shift; phase 2, transition; and phase 3, lift. A consistent pattern of trunk and lower extremity motion was observed, and two distinct upper extremity movement strategies were identified. The onset of muscle activity occurred in the following order: erector spinae, rectus femoris, and vastus medialis (phase 1); biceps femoris, gluteus maximus, and rectus abdominus (phase 2). This characterization of the sit-to-stand motion for a small population of healthy elderly subjects serves as a basis for identifying problems in elderly patients who demonstrate difficulty getting up from a chair.


Subject(s)
Aging/physiology , Muscles/physiology , Adult , Aged , Biomechanical Phenomena , Electromyography , Female , Humans , Kinetics , Male
10.
Phys Ther ; 70(3): 188-203, 1990 Mar.
Article in English | MEDLINE | ID: mdl-2304976

ABSTRACT

Although the mechanism of the phasic myotatic (or "stretch") reflex is well-known, the role of this reflex in adult gait remains speculative. The acquisition and development of locomotor skills with respect to the development of the myotatic reflex require further study in both healthy and neurologically impaired children. In this article, the well-documented properties of the healthy adult's myotatic reflex are compared with recent findings of the myotatic reflex in healthy infants and children and contrasted with reflex properties in patients with cerebral palsy. These data allow us to begin to characterize the emerging features of the stretch reflex in normal and pathological early development. From these data, we can begin to speculate about the relationship between changes in stretch reflexes and the acquisition of skillful movement and gait in early childhood.


Subject(s)
Gait/physiology , Motor Skills/physiology , Reflex, Stretch/physiology , Adult , Cerebral Palsy/physiopathology , Child , Child, Preschool , Electromyography , H-Reflex/physiology , Humans , Infant , Infant, Newborn , Locomotion/physiology , Muscle Contraction , Neural Pathways/physiology
12.
Brain ; 109 ( Pt 5): 1043-58, 1986 Oct.
Article in English | MEDLINE | ID: mdl-3779370

ABSTRACT

Spastic patients were instructed to make accurate, rapid ankle dorsiflexion and plantarflexion movements over different distances to a target. Ankle position and surface electromyograms (EMGs) from tibialis anterior (TA) and soleus (SOL) muscles were recorded. In 3 of 8 spastic patients tested, dorsiflexion evoked velocity-dependent activation of the antagonist (SOL) muscle which impeded the movement to the extent that the limb unintentionally reversed movement direction. We propose that this activation is reflex in origin since it is tightly synchronized, has a large peak amplitude, occurs about 50 ms after the initiation of the movement, and is velocity dependent. One of the 3 patients who had reflex-induced antagonist activation in dorsiflexion also demonstrated sustained clonus during plantarflexion. This usually occurred only if the target had been overshot so that the return of the limb stretched the soleus muscle and triggered clonus. We conclude that in some patients, hyperactive stretch reflexes cause movement deficits.


Subject(s)
Movement , Muscle Spasticity/physiopathology , Reflex, Stretch , Adult , Child , Electromyography , Female , Humans , Male , Middle Aged , Muscles/physiopathology , Reflex, Abnormal/physiopathology
13.
Dev Med Child Neurol ; 28(4): 440-9, 1986 Aug.
Article in English | MEDLINE | ID: mdl-2944785

ABSTRACT

Tendon-jerk reflexes were tested in normal, fullterm infants aged one to four days. EMGs were recorded from gastrocnemius-soleus and tibialis anterior muscles. Reflex-like EMGs were evoked when tapping sites which should not excite the muscles from which that activity is recorded--this included the simultaneous activation of antagonistic muscles by a tendon tap. The possible mechanisms which could produce these results are discussed, as are the possible relationships between the proposed pathways and the reciprocally excitatory paths in cerebral palsy.


Subject(s)
Infant, Newborn , Reflex, Stretch , Electromyography , Humans , Motor Neurons/physiology , Muscle Spindles/physiology , Muscles/innervation , Neural Inhibition , Neural Pathways/physiology , Vibration
14.
Neurology ; 35(5): 699-704, 1985 May.
Article in English | MEDLINE | ID: mdl-3887212

ABSTRACT

Electrical stimulation of the spinal cord (SCS) to reduce spasticity was evaluated in seven patients who, along with their physicians, perceived significant and prompt benefit from stimulation. In two 24-hour test periods, on or off stimulation, we used two independent methods of evaluation: quantitative measures of joint compliance and stretch reflexes, and a standardized neurologic examination. Neither method did better than chance in determining whether SCS was actually being received. Problems with the experimental protocol are discussed, but the results cannot be interpreted as supporting the efficacy of SCS as a treatment for spasticity.


Subject(s)
Electric Stimulation Therapy/methods , Muscle Spasticity/therapy , Spinal Cord/physiology , Cerebral Palsy/physiopathology , Cerebral Palsy/therapy , Clinical Trials as Topic , Electric Stimulation Therapy/instrumentation , Electrodes, Implanted , Electromyography , Evaluation Studies as Topic , Humans , Joints/physiopathology , Muscle Spasticity/physiopathology , Muscles/physiopathology , Neurologic Examination , Research Design
15.
J Neurosurg ; 62(4): 558-62, 1985 Apr.
Article in English | MEDLINE | ID: mdl-3871847

ABSTRACT

Six patients with intractable spasms after spinal cord injury underwent implantation of an epidural spinal cord stimulation system. All the patients experienced good relief postoperatively. In three patients spinal cord stimulation consistently produced immediate inhibition of the spasms. This was evident within less than 1 minute of stimulation. Conversely, the spasms reappeared within less than 1 minute after cessation of the stimulation. The clinical observations were confirmed by polygraphic electromyographic recordings.


Subject(s)
Electric Stimulation Therapy , Spasm/therapy , Spinal Cord Diseases/therapy , Spinal Cord Injuries/therapy , Adult , Aged , Humans , Male , Prostheses and Implants , Spasm/etiology , Spinal Cord Diseases/etiology , Spinal Cord Injuries/complications
16.
Neurosci Lett ; 48(2): 223-30, 1984 Jul 27.
Article in English | MEDLINE | ID: mdl-6333004

ABSTRACT

Hoffmann and tendon jerk reflexes were tested in human subjects at various orientations between vertical, prone and supine. The data suggest that artifacts due to movement of soft tissue may explain the current disagreement in the literature on otolithic influences on these reflexes.


Subject(s)
Muscles/physiology , Otolithic Membrane/physiology , Posture , Reflex, Monosynaptic , Reflex, Stretch , Saccule and Utricle/physiology , Electromyography , Gravitation , Humans , Recruitment, Neurophysiological , Spinal Cord/physiology , Vestibule, Labyrinth/physiology
17.
Ann Neurol ; 12(4): 367-74, 1982 Oct.
Article in English | MEDLINE | ID: mdl-7149662

ABSTRACT

The electromyographic activity evoked by forced ankle rotation in spastic patients with cerebral palsy differs markedly from that found in normal subjects or in patients with adult-onset injuries to the central nervous system. Rapid dorsiflexion can produce a strong myotatic reflex electromyogram at 30 to 50 msec in the normal adult's stretched soleus muscle, while the antagonist tibialis anterior muscle quiet. The same is true of spastic patients whose injury has an adult onset. In patients with cerebral palsy this early response is found in both muscle groups. The pattern of "reciprocal excitation" is in marked contrast to the reciprocal inhibition normally seen. This reflex behavior suggests a fundamental developmental error in neuronal interconnections of the spinal cord in cerebral palsy.


Subject(s)
Muscle Spasticity/physiopathology , Muscles/physiopathology , Adolescent , Adult , Brain Injuries/physiopathology , Cerebral Palsy/physiopathology , Cerebrovascular Disorders/physiopathology , Child , Electromyography , Humans , Middle Aged , Physical Stimulation , Reaction Time , Reflex, Stretch , Spinal Cord Injuries/physiopathology
19.
J Neurosurg ; 53(2): 160-5, 1980 Aug.
Article in English | MEDLINE | ID: mdl-6968819

ABSTRACT

The effects of chronic electrical stimulation of the cerebellum in patients with cerebral palsy have been studied using objective tests of joint compliance, and standardized assessments of developmental reflexes and motor skills. Of 14 patients studied prospectively for 1 to 44 months, 11 showed improvement in motor function. A double-blind test of 10 patients off and on stimulation for an average 8-week period showed no significant changes. Thus, we have no proof that the functional improvements seen with long-term stimulation are the result of cerebellar stimulation.


Subject(s)
Cerebral Palsy/therapy , Adolescent , Adult , Cerebellum , Child , Double-Blind Method , Electric Stimulation Therapy/methods , Humans , Prospective Studies
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