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Biomedical subjects

D A Winter

Publications and source records attributed to D A Winter.

At least 55 records · Page 3Linked to original sources
PubMed1989

Bilateral electromyographical analysis of the lower limbs during walking in normal adults.

Electromyographic (EMG) data were collected simultaneously from multiple muscles of both legs. EMG signals were normalized using the mean signal obtained by applying the same hanging weight (isometric torque) to each muscle in a muscle pair. Comparative analyses between sides were carried out for individual subjects as well as for 10 subjects grouped by dominance (all dominant side data averaged and compared with averaged non-dominant side data). We concluded the following: (1) the assumption of symmetry is not valid for individual subjects, (2) there is some evidence to suggest that the plantar-flexor EMG is related to dominance, and (3) pooled subject data conceal bilateral differences in individual subjects.

Adult↗
PubMed1989

Performance assessment of the Terry Fox jogging prosthesis for above-knee amputees.

The Terry Fox jogging (TFJ) prosthesis was developed at Chedoke-McMaster Hospital to alleviate the asymmetric jogging pattern experienced by above-knee amputees when attempting to jog with conventional walking prostheses. This prosthesis features a spring-loaded, telescoping shank designed to eliminate any vaulting action and control the trunk motion during stance. The spring is intended to attenuate the impact forces and release its stored energy at push-off to provide momentum transfer to the jogger. This prosthesis was comprehensively assessed in the gait laboratory, by evaluating the kinematics, energy and power flow patterns of an above-knee amputee jogger wearing the TFJ prosthesis. Included in the assessment is the ability of the prosthesis to satisfy a set of relevant design criteria that have been established from non-amputee jogging patterns. An increased swing phase time for the prosthetic limb and the need to have the knee hyperextended throughout the stance phase contributed to an asymmetric jogging style. The telescoping action did lower the amputee's centre of mass, thereby reducing the vaulting effect. However, the spring only imparted a lifting action to the jogger and the ground reaction forces were double those of a non-amputee jogger. These findings clearly indicate a need to redesign the TFJ prosthesis and are being incorporated in the design of a new physiological jogging prosthesis.

Adult↗
PubMed1989

A three-dimensional musculoskeletal model for gait analysis. Anatomical variability estimates.

Three-dimensional coordinates defining the origin and insertion of 40 muscle units, and bony landmarks for osteometric scaling were identified on dry bone specimens. Interspecimen coordinate differences along the anterior-posterior axis of the pelvis and the long bone axes of the pelvis, femur and leg were reduced by scaling but landmark differences along the other axes were not. The coordinates were mapped to living subjects using close-range photogrammetry to locate superficial reference markers. The error of predicting the positions of internal coordinates was assessed by comparing joint centre locations calculated from local axes defining the orientation of segments superior and inferior to a joint. A difference was attributed to: anatomical variability not accounted for by scaling; errors in identifying and placing reference landmarks; the accuracy of locating markers using photogrammetry and error introduced by marker oscillation during movement. Anatomical differences between specimens are one source of error in defining a musculoskeletal model but larger errors are introduced when such models are mapped to living subjects.

Anthropometry↗
PubMed1989

Backward walking: a simple reversal of forward walking?

The purpose of this study was to determine whether backward walking represented a simple temporal reversal of forward walking and, hence, could be controlled by a reversed cycling of the same group of neurons. Electromyographic (EMG), joint angle, joint moment, and joint muscle power patterns were compared for forward and backward walking, in 6 subjects. The joint angle patterns with the time-base of the backward walking reversed were similar, with the exception of the ankle. The moment patterns were similar except for the knee, whereas the joint muscle powers were almost reversed-polarity images of each other. This suggests that somewhat similar muscle activation patterns could be used to produce both modes of locomotion, but the temporal cycling of muscle contraction would be reversed: Concentric muscle activity in forward walking would become eccentric activity in backward walking, and visa versa. The EMG results generally supported these findings.

Journal Article↗
PubMed1989

Biomechanics of normal and pathological gait: implications for understanding human locomotor control.

The biomechanical (kinetic) analysis of human gait reveals the integrated and detailed motor patterns that are essential in pinpointing the abnormal patterns in pathological gait. In a similar manner, these motor patterns (moments, powers, and EMGs) can be used to identify synergies and to validate theories of CNS control. Based on kinetic and EMG patterns for a wide range of normal subjects and cadences, evidence is presented that both supports and negates the central pattern generator theory of locomotion. Adaptive motor patterns that are evident in peripheral gait pathologies reinforce a strong peripheral rather than a central control. Finally, a three-component subtask theory of human gait is presented and is supported by reference to the motor patterns seen in a normal gait. The identified subtasks are (a) support (against collapse during stance); (b) dynamic balance of the upper body, also during stance; and (c) feedforward control of the foot trajectory to achieve safe ground clearance and a gentle heel contact.

Journal Article↗
PubMed1988

Biomechanics of below-knee amputee gait.

Sagittal plane biomechanical and EMG analyses from eight below knee (B/K) amputee trials demonstrate considerably modified motor patterns from the residual muscles at the hip and knee. Five SACH fittings, two Uniaxial and one Gressinger prostheses were analysed. Moments of force and mechanical power were analysed on all eight trials and EMG profiles are reported for three of the amputees fitted with SACH prostheses. The findings can be summarized as follows: 1. All eight trials had similar internal moment of force patterns at the ankle. A dorsiflexor moment commenced at heel contact and continued for the first third of stance. The prostheses generated a plantarflexor moment for the balance of stance which increased in late stance to about 2/3 that seen in normals. 2. The two Uniaxial prostheses showed a 20% recovery of stored energy which was returned at push-off. The recovery by the Gressinger fitting was 30%. 3. For all but the Gressinger prosthesis the knee moment of force was negligible during early stance (when normals have an extensor moment), below normal in late stance and fairly normal during swing. The amputee wearing the Gressinger prosthesis had a normal but slightly reduced pattern of moments of force over the entire stride. 4. All eight trials had hyperactive hip extensors during early and mid-stance which resulted in above-normal energy generation by these concentrically contracting muscles. This compensation makes up for the loss of the major energy generation by the plantarflexors at push-off. 5. The moment of force and power patterns at the hip for all eight trials during late stance and swing were fairly normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Amputation Stumps↗
PubMed1988

An integrated biomechanical analysis of normal stair ascent and descent.

Three normal males of similar height and weight ascended and descended a five step staircase with a riser height of 22 cm and a tread of 28 cm. EMG, force plate and cine data were collected for the stride over the second to fourth step during each mode. Kinematic and kinetic analyses were integrated with EMG to yield an interpretation of the mechanics of normal stair walking. Movement from one step to the next involved simultaneous lifting and horizontal translation of the body, and each stride showed specific phases for progression. The extensor muscles about the knee played a dominant role in progression from one step to the next in both modes coupled with the ankle plantar flexors. The total lower limb extensor pattern, called the support moment, was highly correlated between subjects and to level walking. Intra- and inter-subject variability of the motor patterns were also determined. The greatest variability was seen at the hip, while stereotypic kinetic patterns emerged at the ankle and knee for all subjects across the 24 trials of each mode.

Ankle Joint↗
PubMed1987

EMG profiles during normal human walking: stride-to-stride and inter-subject variability.

The EMG patterns for 16 muscles involved in human walking are reported along with stride-to-stride and inter-subject variability measures. These profiles and measures were developed for basic researchers and clinical investigators as a baseline reference of motor patterns and for use in the diagnosis of gait pathologies. Evident from a comparison of these patterns were some fundamental aspects of the neuromuscular control and the mechanical demands of walking. These comparisons can be summarized as follows: (1) The distal support muscles (soleus, tibialis anterior, gastrocnemii) are the most active muscles, the more proximal muscles are least active. (2) The least variable EMG patterns, as quantified by the normalized inter-subject variability measures, are seen in the most distal single joint muscles, the most variable are the more proximal muscles. The EMGs of the biarticulate muscles, both proximal and distal, exhibit higher variability than the EMGs of the single joint muscles. (3) The detailed patterns and levels of EMG activity demonstrate the different mechanical tasks of each muscle over the gait cycle.

Adult↗
PubMed1987

Explorations of a crisis intervention service.

Descriptive studies of a crisis intervention service replicated previous findings of relationships between staff members' attitudes towards treatment and their 'personal styles'. The attitudes and personal styles of crisis team members and non-members differed, largely because of differences in the professions making up these groups. While all staff groups shared the same concept of crisis, they differed in their discrimination of crisis cases from 'furores'. Initial crisis intervention interviews exhibited more confrontation and less exploration by therapists than did initial psychiatric out-patient clinic interviews. Patients referred to the crisis team differed from significant other people in their lives, and from control patients referred to the ordinary out-patient clinic, in aspects of their perception of problems.

Attitude of Health Personnel↗
PubMed1986

A new projective test: the Caine-Marteau-Dympna Test (CMD).

The Caine-Marteau-Dympna (CMD) Test, a new thematic apperception projective test, has acceptable inter-rater reliability. Validity was demonstrated by its ability to differentiate psychiatric in-patients from out-patients and non-patients, and by the relationships found between ratings derived from the test protocols and various questionnaires. These latter provide measures associated with either an inner or outer orientation towards the world. This has implications for many different areas of life, including occupational preference and adjustment, psychiatric symptom formation, psychological treatment expectancies and therapeutic outcome. Thus, the inner oriented individual, who is likely to be responsive to interpretative psychotherapy, tends to produce CMD responses displaying individualistic, abstract themes; a concern with intrapsychic conflict, deficiencies in social interaction and lack of structure; and internal control.

Adult↗
PubMed1986

How many strides are required for the analysis of electromyographic data in gait?

This study was conducted to obtain information on the number of strides of EMG data needed per subject in a gait study. Ten strides of EMG data were cumulated on eight subjects for each of the soleus, rectus femoris, biceps femoris, vastus medialis and tibialis anterior muscles. The linear envelope of the EMG, normalized in time and amplitude, demonstrated a very high level of stability for a given subject, relative to the variability that was found across subjects. It was concluded that three strides of EMG data per subject provides information as reliable as that obtained from twelve strides.

Adult↗
PubMed1986

Bilateralism of EMG profiles in human locomotion.

In gait studies, minor importance has been generally given to the aspect of symmetry. Consequently, an unstated assumption has been that the right and left legs present symmetrical outcomes. The purpose of the present study was to verify this assumption throughout the use of electromyographic (EMG) profiles of activity from the two legs during gait. Eight subjects participated in the study. Two muscles, the soleus and rectus femoris, were recorded from both legs using surface electrodes. Foot switches placed under each heel served to indicate the gait cycles (N = 10) that were recorded per subject. The EMG signal was transformed into a linear envelope through full-wave rectification and filtering using second order low-pass filters (6 Hz). These envelopes were transformed in amplitude in percent of a maximum voluntary contraction (% MVC). These were digitized (50 Hz) and the sample points used to perform regression analyses contrasting left and right (homologus) muscles. Coefficients of correlation between the EMG linear envelopes of the homologous muscles showed high correlations and thus nearly identical shape. However important differences in EMG amplitude between the legs were found. Implications of these findings for future research in gait are discussed.

Adult↗
PubMed1985

Surface EMG profiles during different walking cadences in humans.

The ensemble electromyogram (EMG) patterns associated with different walking cadences were examined in 11 normal subjects. Five muscle groups were studied: the rectus femoris, vastus lateralis, lateral hamstring, tibialis anterior and soleus muscles of the right lower extremity. The myoelectric signals were telemetered, full-wave rectified and smoothed. Subjects walked at cadences of 115, 95 and 75 steps/min. Footswitches indicated the different phases of the stride. Six or more strides per subject were averaged for each cadence. Cadence-related changes in (1) mean EMG amplitude during stance, and during swing, and (2) the shape of the EMG patterns, were analyzed. One-way repeated-measures analyses of variance on the mean EMG amplitude in stance and in swing revealed significant changes with cadence (P less than 0.05) in all muscles examined. The magnitude of these changes could be related to the mechanical function of the muscles involved. The shape of the EMG patterns generally remained similar at the different cadences. The timing of EMG activity was closely related to the normalized stride time and remained invariant at different cadences.

Adolescent↗
PubMed1985

Predictions of knee and ankle moments of force in walking from EMG and kinematic data.

A deterministic model was developed and validated to calculate instantaneous ankle and knee moments during walking using processed EMG from representative muscles, instantaneous joint angle as a correlate of muscle length and angular velocity as a correlate of muscle velocity, and having available total instantaneous joint moments for derivation of certain model parameters. A linear regression of the moment on specifically processed EMG, recorded while each subject performed cycled isometric calibration contractions, yielded the constants for a basic moment-EMG relationship. Using the resultant moment for optimization, the predicted moment was proportionally augmented for longer muscle lengths and reduced for shorter lengths. Similarly, the predicted moment was reduced for shortening velocities and increased if the muscle was lengthening. The plots of moments predicted using the full model and those calculated from link segment mechanics followed each other quite closely. The range of root mean square errors were: 3.2-9.5 Nm for the ankle and 4.7-13.0 Nm for the knee.

Ankle Joint↗