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Biomedical subjects

D A Winter

Publications and source records attributed to D A Winter.

At least 73 records · Page 4Linked to original sources
PubMed1985

Personal styles, constructive alternativism and the provision of a therapeutic service.

A series of studies on the 'personal styles' of clients and therapists is reviewed, and their findings are drawn together within the framework of personal construct theory. It is argued that the technical eclecticism of personal construct theory reflects its central philosophical assumption of constructive alternativism; and that a treatment service organized in accordance with this assumption could accommodate therapists of different theoretical persuasions, matching clients and therapeutic conditions in terms of dimensions suggested by the 'personal styles' research.

Attitude of Health Personnel↗
PubMed1984

Biomechanics of human movement with applications to the study of human locomotion.

A review of the biomechanics of human movement is presented and covers the neural control of voluntary movement, as it manifests itself in the electromyogram, through to detailed kinetic analyses and simulation studies. The body of knowledge of muscle performance is covered in detail, from the individual motor unit characteristics, through recruitment patterns to the static and dynamic characteristics of the total muscle and its relationship to the electromyogram. A summary of research into the movement of the skeletal (segmental) system itself covers the kinematic data collection systems, the link-segment modeling with anthropometric measures, and the inverse dynamics solution of the joint kinetics. A critique of current simulation models reveals a diversity of simplifications and assumptions that seriously affect the interpretation of results. Similarly, a critical assessment of the literature pertaining to mechanical energy, work, power and efficiency exposes many varied and anomalous techniques and correspondingly confusing interpretations. At all phases of the review the author attempts to reconcile differences, criticize obvious errors, and identify important contributions.

Biomechanical Phenomena↗
PubMed1984

Electromyographic amplitude normalization methods: improving their sensitivity as diagnostic tools in gait analysis.

The effect of four amplitude normalization methods on intersubject variability of electromyographic (EMG) profiles in normal gait was examined. Bipolar silver/silver chloride surface electrodes were applied to the rectus femoris, vastus lateralis, biceps femoris, tibialis anterior, and soleus muscles of the right lower extremity, in 11 healthy subjects. The myoelectric signals were telemetered via an FM multichannel biotelemetry system, full-wave rectified and low-pass filtered, then A/D converted together with the footswitch signal. Within-subject ensemble-average patterns were generated from the linear envelope EMG of at least six strides for each subject. Each subject's ensemble average was then normalized to the following: (a) the average EMG over three 50% isometric maximum voluntary contractions (MVC), (b) the EMG per unit isometric moment of force, (c) the peak of the subject ensemble average, (d) the mean of the subject ensemble average. Intersubject variability was quantified for each of the normalization methods by the coefficient of variation (CV). The normalization to either the peak ensemble or the mean ensemble drastically reduced intersubject variability, by 12%-73%. In contrast, normalization to the average EMG during 50% MVC or to the EMG per unit moment increased intersubject variability. It was concluded that the reduction of intersubject variability by appropriate amplitude normalization is possible, thereby increasing the sensitivity of surface EMG as a diagnostic tool in gait analysis.

Adolescent↗
PubMed1984

Pathologic gait diagnosis with computer-averaged electromyographic profiles.

A computer-assisted approach is described which compares EMG profiles from each patient's gait with similar profiles from able-bodied subjects. The EMG and footswitch signals from walking trials were telemetered via a six-channel biotelemetry system; the EMGs were further processed to obtain a linear envelope before A/D conversion into a desktop computer. Simultaneously, a video camera recorded the patient's walking pattern. From 32sec of converted data, a number of strides were selected for averaging to achieve a mean ensemble pattern over the stride period, which is set to 100% for each selected stride. The ensemble average of each muscle's EMG was superimposed on a plot of the EMG patterns from able-bodied subjects. The diagnostician then correlated atypical patterns from each muscle with the stopped or slow motion television image of each patient's gait. Positive corroborative evidence yields detailed diagnostic statements about the cause of their abnormal gait. Such evidence is valuable in planning future rehabilitative procedures or in assessing the results of past efforts.

Adult↗
PubMed1983

Biomechanical motor patterns in normal walking.

Motor patterns in normal human gait are evident in several biomechanical and EMG analyses over the stride period. Some of these patterns are invariant over the stride period with changes of cadence, whole others are closely correlated with speed changes. The findings for slow, natural, and fast walking are summarized: 1. Joint angle patterns over the stride period are quite invariant, and do not change with cadence; 2. Moment of force patterns at the ankle are least variable and quite consistent at all speeds; 3. A recently defined support moment is quite consistent at all speeds. 4. Moments at the knee and hip are highly variable at all cadences but decrease their variability as cadence increases; 5. Mechanical power patterns at all joints show consistent timing over the stride period; 6. EMG profiles of 5 muscles show consistent timing over the stride, but the amplitude increases as walking speed increases. Arguments are presented to support the concept that walking speed is largely controlled by gain and that the timing of the motor patterns, which is extremely tightly synchronized with the anatomical position, is under major afferent control.

Journal Article↗
PubMed1983

Knee flexion during stance as a determinant of inefficient walking.

A biomechanical analysis of normal walking assessed the mechanical work cost in joules per unit mass and distance walked. For 21 walking trials--seven subjects at slow, natural, and fast cadences--these work costs (min = .73 J/kg.m, max = 1.65 J/kg.m) were correlated with maximum knee flexion during stance (min=6 degrees, max=33 degrees). The results were contrary to the predictions of previous researchers who claimed that the energy cost would increase as the knee became more rigid during stance. This study showed a significant positive correlation between work cost and maximum knee flexion. The implications of these findings and the predicted increase of bone-on-bone forces as knee flexion increases are discussed relative to the gait training of certain patient populations.

Adult↗
PubMed1983

Electromyography reliability in maximal and submaximal isometric contractions.

The purpose of this study was to determine the reliability of average surface electromyography (EMG) within and between days. Nine subjects were tested on three different days. Five maximum and 10 submaximum (five at each of two different levels) isometric contractions were performed each day. The submaximum levels were determined by the 30% and 50% maximum voluntary contraction (MVC) on day one and kept constant over days two and three. The myoelectric signal from the triceps was full wave rectified and low-pass filtered at 1 Hz to yield a relatively noise-free average EMG that corresponded in time to the force signal. The scores were normalized to the force level. The reliability was estimated with intraclass correlations coefficients (R). The magnitude of score variation was also expressed as a ratio, coefficient of variation, CV = standard deviation/mean X 100%. R values were significantly greater for the submaximal levels than the 100% MVC; no significant difference existed between the two submaximal levels. The within-day CV values were similar for all three levels, ranging from 8% to 10%. The between-days variability was higher than that within days, ranging from 12% to 16%. The results suggest that submaximal isometric contractions are more reliable. Measurement error is substantial in this technique and should be included in statistical designs.

Arm↗
PubMed1983

Energy generation and absorption at the ankle and knee during fast, natural, and slow cadences.

In 15 normal adults an advanced biomechanical analysis of walking patterns at slow, natural, and fast cadences showed that the ankle had two mechanical power phases: a negative work phase during weight acceptance, followed by a dominant burst of positive work at push-off. The knee had four power phases: a negative work phase at weight acceptance, a small positive work phase during mid-stance, a major negative work burst at push-off and early swing, and a final energy-absorbing phase at the end of swing. The power phases at the hip are quite irregular and somewhat lower than those at the knee and ankle. The dominant positive work burst by the plantarflexors drops as speed decreases, but less rapidly than the positive work by the knee muscles during midstance. The energy absorption by the quadriceps during weight acceptance decreases rapidly as speed decreases and at late stance decreases moderately. The energy absorption by the ankle plantarflexors during weight acceptance remains fairly constant at all walking speeds, and the absorption by the knee flexors at end of swing drops only slightly as cadence decreases.

Adult↗
PubMed1982

Construct relationships, psychological disorder and therapeutic change.

The problem of interpretation of construct relationships of abnormal content is considered in the context of the use of the repertory grid to assess therapeutic outcome in neurotics. With a view to providing a rationale for such interpretation, examples are presented of construct relationships indicative of psychopathology, and of predicted changes in them during therapy. Implications for the planning and evaluation of therapy are discussed, and the importance of exploring the personal meaning of the patient's complaints is emphasized.

Adult↗
PubMed1981

Errors in the use of isokinetic dynamometers.

The use of constant velocity dynamometers in functional testing and in exercise and therapy programs has been increasing in the past few years. For movements in the horizontal plane there are no gravitational errors. However, in vertical movements the limbs are not only working against the dynamometer but also are either aided or opposed by gravity. Far too often these gravitational forces have not been taken into account, and the error involved can be quite large. 1. A study on four subjects using knee extension (against gravity) and flexion (with gravity) showed the error in mechanical work to vary from 26-43% in extension and from 55-510% in flexion. 2. A relatively simple solution is offered to overcome the problem by compensating for the gravitational errors over the full range of movement. The time course of the error is such as to cause erroneous magnitudes of recorded moments which are a maximum at low level contractions and minimum at high level contractions. 3. The effect of gravitational and other acceleration errors are such as to cause false early peaks in the muscle moment curves resulting in erroneous conclusions about muscle function.

Biomechanical Phenomena↗