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Biomedical subjects

J Crosbie

Publications and source records attributed to J Crosbie.

At least 37 records · Page 2Linked to original sources
PubMed1999

A new system for the measurement of displacements of the human body with widespread applications in human movement studies.

This paper reports the development, construction and use of a new system for the measurement of linear kinematics in one, two or three dimensions. The system uses a series of rotary shaft encoders and inelastic tensioned strings to measure the linear displacement of key anatomical points in space. The system is simple, inexpensive, portable, accurate and flexible. It is therefore suitable for inclusion in a variety of motion analysis studies. Details of the construction, calibration and interfacing of the device to an IBM PC computer are given as is a full mathematical description of the appropriate measurement theory for one, two and three dimensions. Examples of the results obtained from the device during gait, running, rising to stand, sitting down and pointing with the upper limb are given. Finally it is proposed that, provided the constraints of the system are considered, this method has the potential to measure a variety of functional human movements simply and inexpensively and may therefore be a valuable addition to the methods available to the motion scientist.

Biomechanical Phenomena↗
PubMed1999

Weight bearing through flexed upper limbs in quadriplegics with paralyzed triceps brachii muscles.

STUDY DESIGN: A biomechanical analysis of lifting through flexed and extended elbows in C5 and C6 quadriplegics. OBJECTIVE: To determine the mechanisms used by C5 and C6 quadriplegics to prevent elbow collapse when bearing weight through flexed upper limbs. SETTING: A biomechanics laboratory. METHODS: Six motor complete C5 and C6 quadriplegic subjects with paralysis of their triceps brachii muscles were recruited. A three dimensional kinematic and kinetic analysis of the upper limbs was performed whilst subjects attempted to lift their body weight through their upper limbs under four different conditions. In one condition subjects lifted with their hands placed at the same height as the seat upon which they were sitting, whilst in the other three conditions subjects lifted with their hands placed on blocks of various heights. The four different conditions required subjects to bear weight through their upper limbs with their elbows initially flexed between 15 and 40 degrees. MAIN OUTCOME MEASURES: Angular displacements and corresponding moments about the shoulder, elbow and wrist joints. In addition, EMG data were collected from the upper pectoralis, anterior deltoid and biceps brachii muscles during all lifts and expressed as a percentage of maximal isometric voluntary contractions. RESULTS: As block height and initial elbow flexion increased, subjects lifted progressively less weight. However, even under the high block conditions when subjects' elbows were initially flexed up to 40 degrees, subjects lifted a mean+/-SD of 43%+/-20.4 of their seated body weight with one subject lifting 76% of his seated body weight. Subjects lifted by generating shoulder and wrist flexor moments. CONCLUSION: Quadriplegics with paralyzed triceps brachii muscles can bear moderate and sometimes substantial weight through flexed elbows. This is largely achieved by the generation of shoulder flexor moments.

Adult↗
PubMed1999

Unfractionated heparin, time for a change?

BACKGROUND: In Ireland physician transfer to utilisation of Low Molecular Weight Heparin for Venous Thromboembolism has been slow, despite evidence of efficacy and concern about the level of anticoagulation achieved with Unfractionated Heparin. OBJECTIVE: To examine the effectiveness of Unfractionated Heparin administration in a teaching hospital in Ireland. Primary outcomes measured were time to therapeutic APTT and length of hospital stay. METHODS: We identified 50 consecutive eligible patients treated with continuous intravenous unfractionated heparin for Venous Thromboembolism from the period August 1994 to December 1996 at Beaumont Hospital, Dublin, Ireland. Data analysed included length of hospital stay, costing data and anticoagulation parameters (time to therapeutic APTT, percentage of time within therapeutic range, number of diagnostic tests, heparin dosages). RESULTS: A significant number of patients (22%) never achieved therapeutic APTT levels. Of those who did achieve therapeutic APTT levels at some time during their therapy, therapeutic range APTT was maintained only 28% of the time on heparin. 57% of the time results were below therapeutic while 15% of the time results were above therapeutic. Also 26% of the patients were discharged with INR results outside the therapeutic range despite an average length of stay of 13.3 days (over twice the ideal of 6 days). Ineffective anticoagulation influenced hospital length of stay in 60% of cases in our evaluation. Average cost of treatment with Unfractionated Heparin was 5897.86 Pounds versus the projected cost of Low Molecular Weight Heparin at 2562.78 Pounds for 6 days of in-patient therapy or 60.78 Pounds for outpatient therapy (excluding physician visit costs). CONCLUSIONS: Unfractionated Heparin therapy as reviewed in our study is sub-optimal with inadequate anti coagulation and prolonged hospitalisation. Low Molecular Weight heparin, with comparable therapeutic effect documented elsewhere, overall may cost less.

Anticoagulants↗
PubMed1998

Variations in posteroanterior stiffness in the thoracolumbar spine: preliminary observations and proposed mechanisms.

BACKGROUND AND PURPOSE: Evaluation of posteroanterior (PA) movement in the spine is commonly used in the clinic, but little is known about the mechanisms involved. The purposes of this study were to examine variations in PA stiffness along the thoracolumbar spine and to investigate possible factors that might determine the pattern of stiffness. SUBJECTS: Twenty-one pain-free volunteers (10 male, 11 female), aged 18 to 41 years (mean age=26.6, SD=7.5), participated. METHODS: Posteroanterior stiffness was measured at 5 locations (L4, L1, T10, T7, T4), together with various subject characteristics. RESULTS: Mean PA stiffness varied among locations, with the greatest stiffness at L4 (13.3 N/mm) and the lowest stiffness at L1 (10.4 N/mm). A relatively small, but important, proportion (22% or less) of the variance in stiffness data at some vertebral levels was accounted for by the variables describing subject characteristics. CONCLUSION AND DISCUSSION: Posteroanterior stiffness varies along the spine in a manner consistent with the nature of support for the spine. The observed pattern of variation of PA stiffness along the spine appears to be influenced by some factors other than those relating to the spine.

Adolescent↗
PubMed1998

Does spasticity contribute to walking dysfunction after stroke?

OBJECTIVES: Clinically, it is assumed that spasticity of the calf muscles interferes with walking after stroke. The aim was to examine this assumption by evaluating the contribution of spasticity in the gastrocnemius muscle to walking dysfunction in an ambulant stroke population several months after stroke. METHODS: Fourteen stroke patients who were able to walk independently and 15 neurologically normal control subjects were recruited. Both resting and action stretch reflexes of the gastrocnemius muscle were investigated under conditions that simulated walking. Resting tonic stretch reflexes were measured to assess spasticity whereas action tonic stretch reflexes were measured to assess the possible contribution of spasticity to gait dysfunction. RESULTS: Two thirds of the stroke patients exhibited resting tonic stretch reflexes which indicate spasticity, whereas none of the control subjects did. However, the stroke patients exhibited action tonic stretch reflexes that were of similar magnitude to the control subjects, suggesting that their reflex activity during walking was not different from that of control subjects. Furthermore, there was no evidence that the action stretch reflex in the stroke patients contributed a higher resistance to stretch than the control subjects. CONCLUSIONS: Whereas most of the stroke patients exhibited spasticity when measured both clinically and physiologically, they did not exhibit an increase in resistance to dorsiflexion due to exaggerated action tonic stretch reflexes. It is concluded that it is unlikely that spasticity causes problems in walking after stroke in ambulant patients. Therefore, it seems inappropriate to routinely reduce or inhibit the reflex response to improve functional movement in stroke rehabilitation. Factors other than spasticity should be considered when analysing walking after stroke, so that appropriate treatment is provided to patients.

Aged↗
PubMed1997

A revised group exercise program for osteoarthritis of the knee.

The purpose of this study was to determine the effectiveness of a group exercise program for subjects with osteoarthritis of the knee referred for physiotherapy in terms of pain, physical function and gait. This study was initiated after an initial group exercise program at this centre failed to demonstrate significant changes in pain, physical function or gait. The study was based on repeated measures with a two month follow up, carried out in the outpatients department of a large public hospital. Pain levels in various functional situations were assessed on visual analogue scales, physical function with the Stanford Health Assessment Questionnaire, and quantitative gait variables at a normal and a fast self-selected speed with an electric foot switch walkway. On completion of the program (n = 40) more than 90% of the pain and physical function scores demonstrated significant improvements without increases in medication, use of walking aids or fatigue. The gait variables of velocity, cadence and stride length at both self-selected speeds demonstrated significant increases at this assessment without deterioration of gait symmetry. All improvements were maintained at the two month follow up assessments. This study suggests that a clinically realistic group exercise program supplemented with a home program can reduce pain, increase physical function and objective gait measures in subjects with osteoarthritis of the knee.

Aged↗
PubMed1997

Rest length and compliance of non-immobilised and immobilised rabbit soleus muscle and tendon.

The first aim of this study was to measure the contributions of muscle and tendon to the total compliance of resting muscle-tendon units. A second aim was to determine whether the decrease in muscle-tendon unit rest length produced by prolonged immobilisation in a shortened position is mediated primarily by adaptations of the muscle or tendon. One ankle joint from each of five rabbits was immobilised in a plantarflexed position for 14 days. The passive length-tension properties of soleus muscle fascicles and tendons from both hindlimbs were measured using a video-based tensile-testing system. In non-immobilised muscles, muscle fascicle strains exceeded tendon strains by up to four times. However, because the rest length of tendon was much greater than that of muscle fascicles, changes in tendon length accounted for nearly half of the total change in muscle-tendon unit length. The rest length of immobilised muscle-tendon units was less than that of non-immobilised muscle-tendon units from contralateral limbs. Most of this difference was attributable to a change in the rest length of the tendon; there was little change in the rest length of muscle fascicles. It is concluded that the tendon is responsible for a large part of the compliance of rabbit soleus muscle-tendon units at physiological resting tensions, and that adaptation of tendon rest length is the primary mechanism by which the rabbit soleus shortens in response to immobilisation at short lengths.

Animals↗
PubMed1997

Intersegmental dynamics of standing from sitting.

OBJECTIVE: To compare the magnitude of muscle moments acting on either end of body segments with other motion-dependent and gravitational moments during the task of standing up. DESIGN: A mathematical model which partitions moment components was developed and applied and descriptive analysis of the resultant data conducted. BACKGROUND: It has been hypothesized that segmental interactions may be exploited during the task of standing up from sitting to lessen demands for the production of large muscle forces. There has been no investigation of the relative sizes of these interactions nor of their impact on the task. METHOD: Kinematic data obtained from six healthy male subjects were used as inputs to a 'top-down' dynamic model. Each total segmental moment was partitioned into a net muscle component as well as gravitational and motion-dependent components. RESULTS: The model successfully predicted both muscle moments determined by the 'ground-up' inverse dynamics approach and also ground reaction forces measured with a force platform. Motion-dependent moments were consistently small compared with muscle and gravitational moments. CONCLUSION: Segmental motion during standing up is controlled almost entirely by gravitational moments and the direct action of muscles which span either end of the segment. Motion-dependent moments do not significantly reduce the muscle moments required to stand up. RELEVANCE: Knowledge and understanding of the mechanical demands on the body during rising from sitting to standing are important in identifying critical elements for successful performance. Such information may also provide a basis for the development or refinement of strategies to retrain the movement following injury or disease.

Journal Article↗
PubMed1997

Reliability of gait measurements in people with osteoarthritis of the knee.

BACKGROUND AND PURPOSE: The purpose of this study was to assess the intrasession and intersession reliability of measurements of quantitative gait variables at two self-selected walking speeds. SUBJECTS: Forty-one patients with osteoarthritis in one or both knees who were referred for physical therapy participated. METHODS: Three measurements were made at 1-week intervals. The quantitative gait variables of walking speed, cadence, and stride length were measured using an 8-m electronic footswitch walkway. At each measurement, subjects were asked to walk five times at a self-selected pace that they considered to be normal and five times at a self-selected pace that they considered to be fast. RESULTS: At the normal walking speed, although intraclass correlations were consistently high for all gait variables, an additive factor within and across the first two measurements was evident even when a mean of several trials was used. At the fast walking speed, the intraclass correlations were again consistently high for all gait variables, but there were no changes within or across the measurements. CONCLUSION AND DISCUSSION: The data suggest that quantitative gait analysis is a practical objective assessment tool for persons with osteoarthritis of the knee. Gait at the fast walking speed, however, will provide the more reliable stable measure on which to evaluate the effect of therapy when compared with gait at the normal walking speed. The comparative responsiveness to change between the two walking speeds still needs to be determined.

Aged↗
PubMed1996

Towards a theory of lumbar mobilisation - the relationship between applied manual force and movements of the spine.

Optimal use of lumbar mobilisation requires a theoretical knowledge of the mechanical effects that occur. When a mobilisation force is applied the target vertebra will move with accompanying intervertebral displacements at many intervertebral joints. In addition, displacements and deformations of other tissues will contribute to the movement of the skin surface under the therapist's hands. The responses can be quantified in terms of the movements of the skin surface (described by the force-displacement relation), the absolute movement of the target vertebra, or the relative intervertebral movements. There are at least seven variables related to the manner of application of the mobilisation force that can be controlled by the therapist to alter the nature of the response. The patient's response is also determined by a number of variables related to the mechanical properties of the tissues of the spine, extra-spinal structures and the interaction between the patient and the treatment couch. Currently there is a moderate amount of information available about the effects of technique variations but there is very little data to directly link variations in the properties of specific anatomical structures with variations in either absolute or relative spinal movements or tissue loads.

Journal Article↗
PubMed1994

Effects of imposed postfeedback delays in programmed instruction.

Imposed postfeedback delays promote discrimination training; the present experiments determined whether they also improve performance in programmed instruction. In two experiments, college students completed 45 sets of Holland and Skinner's (1961) programmed text on behavior analysis in a computerized format in a three-component multiple schedule. In Experiment 1, the conditions were (a) no delay between questions, (b) a 10-s delay after each question (noncontingent delay), and (c) a 10-s delay after each question answered incorrectly (contingent delay). Noncontingent delay produced better performance than no delay and contingent delay. To determine whether performance increased in the noncontingent delay condition because subjects studied the material during delay periods, Experiment 2 tested three conditions: (a) no delay between questions, (b) a 10-s delay after each question (noncontingent delay), and (c) a 10-s delay after each question with the screen blank during the delay period. Noncontingent delay produced better performance than no delay, but there was no difference in performance between no delay and noncontingent delay with blank screen. Hence, noncontingent delay improved performance because students used delay periods to study. Furthermore, subjects preferred noncontingent delay to the other conditions, and session time increased only slightly.

Journal Article↗
PubMed1994

Comparative kinematics of two walking frame gaits.

Walking frames are commonly used as part of the gait rehabilitation process for a variety of clinical conditions. There has been little investigation of the characteristics of gait with such frames or of the advantages of one gait style compared with others. The kinematics of two simulated gait patterns with walking frames were investigated using conventional video analysis techniques. The purpose of the study was to compare the two gaits with respect to patterns of joint motion and temporospatial parameters. It was found that simultaneous motion of the protected limb and the frame during stepping (gait S) permitted a faster walking speed than a gait in which the frame and the protected limb were moved separately (gait D). Although the patterns of hip motion in both aided gaits differed markedly from that found in free gait, gait S encouraged more hip extension on the protected side than gait D. Since this is seen as a desirable feature in gait retraining, patients using walking frames, particularly after hip trauma, should be assessed carefully and encouraged to use gait pattern S when possible.

Adult↗
PubMed1993

Human G gamma and A gamma globin gene constructs containing the 3' A gamma enhancer show persistent fetal expression in transgenic mice.

Transgenic mice were produced from two 13 kb constructs containing the fetal (gamma) globin genes. Each construct consisted of a G gamma globin gene linked to one of two alternative A gamma genes. The first construct contained a normal G gamma gene plus an A gamma gene with the -198 T-->C hereditary persistence of fetal haemoglobin (HPFH) mutation. In the second, a normal G gamma gene was linked to a A gamma gene with a -222 to -225 four base pair deletion in the promoter. This latter mutation has been associated with low A gamma expression in humans. Both A gamma genes in these constructs also contained the 3' flanking enhancer. The two different constructs showed expression throughout gestation from day 11 yolk sac, through the fetal period and for a variable time during the first three postnatal weeks. Thereafter, no expression of any of the gamma-globin genes was seen in adult erythroid tissues. Transcription from the normal G gamma and HPFH A gamma genes in the first construct paralleled each other in developmental timing, with a proportionate excess of A gamma more evident in later gestation. G gamma and A gamma mRNA transcripts from the normal G gamma + 4 bp deletional A gamma construct were unable to be distinguished because of a 3' G gamma-like conversion in the deletional A gamma gene. Combined gamma-globin expression from the two genes in this second construct was detectable until just after birth, as seen with the individual genes in the first construct.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Interrupted time-series analysis with brief single-subject data.

Assessing change with short time-series data is difficult because visual inference is unreliable with such data, and current statistical procedures cannot control Type I error because they underestimate positive autocorrelation. This article describes these problems and shows how they can be solved with a new interrupted time-series analysis procedure (ITSACORR) that uses a more accurate estimate of autocorrelation. Monte Carlo analyses show that, with short series, ITSACORR provides better control of Type I error than all previous procedures and has acceptable power. Clinical examples also show that ITSACORR is easy to use and functions well with real data.

Adolescent↗
PubMed1993

The effects of response cost and response restriction on a multiple-response repertoire with humans.

In two experiments a multiple-response repertoire of four free-operant responses was developed with university students as subjects using monetary gain as reinforcement. Following baseline, one of the responses was reduced either by making monetary loss contingent upon it (response cost) or by removing it from the repertoire (response restriction). In Experiment 1 a multielement baseline design was employed in which baseline and restriction or response-cost contingencies alternated semirandomly every 3 minutes. In Experiment 2 a reversal design was employed (i.e., baseline, restriction or response cost, then baseline), and each response required a different amount of effort. Both experiments had the following results: (a) The target response decreased substantially; (b) most nontarget responses increased, and the rest remained near their baseline levels; and (c) no support was found for Dunham's hierarchical, most frequent follower, or greatest temporal similarity rules. For several subjects, the least probable responses during baseline increased most, and the most probable responses increased least. Furthermore, in Experiment 2, responses with the lowest frequency of reinforcement increased most (for all 7 subjects), and those with the greatest frequency of reinforcement increased least (for 5 subjects).

Journal Article↗
PubMed1992

Immunoglobulin M and D antigen receptors are both capable of mediating B lymphocyte activation, deletion, or anergy after interaction with specific antigen.

A series of immunoglobulin (Ig)-transgenic mice were generated to study the functional capabilities of the IgM and IgD classes of B lymphocyte antigen receptor in regulating both cellular development and responses to specific antigen. B cells from Ig-transgenic mice expressing either hen-egg lysozyme (HEL)-specific IgM or IgD alone were compared with B cells from mice that coexpressed IgM and IgD of the same anti-HEL specificity. In all three types of Ig-transgenic mice, conventional B cells specific for HEL exhibited exclusion of endogenous Ig expression and matured to populate the usual microenvironments in peripheral lymphoid tissues. These peripheral B cells could be stimulated by HEL through either IgM or IgD antigen receptors to generate T cell dependent antibody production in vivo or to enhance T cell independent proliferative responses to lipopolysaccharide in vitro. Conversely, when HEL was encountered in vivo as a self-antigen, B cells expressing HEL-specific IgM or IgD alone were both rendered tolerant. In each case this occurred by clonal anergy in response to soluble autologous HEL, and clonal deletion when HEL was recognized as a membrane-bound self-antigen. Taken together, these findings indicate that IgM and IgD antigen receptors expressed alone on conventional B cells can support normal differentiation, antigen-dependent activation, and induction of self-tolerance, the only overt difference lying in a greater degree of receptor downregulation for IgM relative to IgD after induction of clonal anergy by soluble HEL.

Animals↗