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Biomedical subjects

Richard M Smith

Publications and source records attributed to Richard M Smith.

At least 19 recordsLinked to original sources
PubMed2006

The effects of unilateral grab rail assistance on the sit-to-stand performance of older aged adults.

This study investigated the effects of unilateral grab rail assistance during the sit-to-stand transfer to develop an understanding of lower limb joint mechanics and whole body movement patterns. External reaction forces at the grab rail and floor interfaces were also investigated to understand the nature of the assistance provided by the introduction of unilateral upper body assistance. While 12 older aged adults performed the sit-to-stand, three-dimensional body segment kinematics were recorded to determine lower body joint motion and whole body centre of mass motion. Grab rail reaction forces and bilateral ground reaction forces were recorded to determine external reaction forces and lower body joint kinetics. Grab rail assisted conditions were compared with unassisted transfers. During grab rail assistance, a systematic asymmetry was introduced to lower limb joint kinetics, without noticeable alterations to peak lower body joint motion and whole body movement patterns. Ipsilateral net joint moments and powers decreased in the ankle and hip and increased in the knee, while the contralateral net joint moments and powers increased in the hip and decreased in the knee. Joint kinetic and kinematic responses suggest a motor control strategy that maintains symmetric sit-to-stand movement patterns by adjusting bilateral muscle control when a unilateral external reaction force is provided. Understanding the mechanical assistance that is generated during the sit-to-stand will facilitate optimal design of grab rails for older aged adults and may contribute to design for specific pathologies. Such design implementation will influence the ability of older aged adults to remain independent in the community.

Activities of Daily Living↗
PubMed2006

Musculo-skeletal modelling of NMES-evoked knee extension in spinal cord injury.

The objective of this study was to explore relationships among constants used in musculo-skeletal models predicting torque generated about the knee by the quadriceps muscles. A model was developed and matched to data collected from individuals with spinal cord injury performing quadriceps contractions evoked using neuromuscular electrical stimulation. After fitting tendon slack lengths to the quadriceps muscles, the model was able to accurately match experimentally measured knee extension torques using previously reported values for the moment arm-knee angle and force-velocity relationships. Fitting new constants to these relationships did not improve the match between measured and modelled knee extension torques. There was significant interaction between variables used within the model. Using a narrower active force-length relationship for the muscles required the model to have smaller moment arms about the knee to accurately match measured torque across the full range of motion. Reduced moment arms, however, lowered the model's linear velocity of muscle shortening for each angular velocity of the knee, requiring different constants within the force-velocity relationship to predict the appropriate amount of torque decline. The present study demonstrates that, when a model does not fit the observed data, it is difficult to determine exactly which components are responsible because of the interdependent nature of parameters.

Electric Stimulation↗
PubMed2006

Adjusted Rasch person-fit statistics.

Two frequently used parametric statistics of person-fit with the dichotomous Rasch model (RM) are adjusted and compared to each other and to their original counterparts in terms of power to detect aberrant response patterns in short tests (10, 20, and 30 items). Specifically, the cube root transformation of the mean square for the unweighted person-fit statistic, t, and the standardized likelihood-based person-fit statistic Z3 were adjusted by estimating the probability for correct item response through the use of symmetric functions in the dichotomous Rasch model. The results for simulated unidimensional Rasch data indicate that t and Z3 are consistently, yet not greatly, outperformed by their adjusted counterparts, denoted t* and Z3*, respectively. The four parametric statistics, t, Z3, t*, and Z3*, were also compared to a non-parametric statistic, HT, identified in recent research as outperforming numerous parametric and non-parametric person-fit statistics. The results show that HT substantially outperforms t, Z3, t*, and Z3* in detecting aberrant response patterns for 20-item and 30-item tests, but not for very short tests of 10 items. The detection power of t, Z3, t*, and Z3*, and HT at two specific levels of Type I error, .10 and .05 (i.e., up to 10% and 5% false alarm rate, respectively), is also reported.

Humans↗
PubMed2005

Survival of the fittest? Natural selection in islet transplantation.

The full potential of cadaveric islet transplantation will only be realized by avoiding both pretransplant insults programming islets for subsequent death and posttransplant triggers for apoptosis and necrosis. The immediate blood mediated inflammatory response causes significant islet loss in the immediate posttransplant period. However, if we focus on this alone we will miss many opportunities to improve transplanted islet survival. Even when single donor islet transplants become the norm, there will still be more patients who might benefit from islet transplants than grafts available. Input from "transplanters" and diabetologists is essential in order to select appropriate patients for islet transplantation.

Graft Survival↗
PubMed2005

Differences between grab rail position and orientation during the assisted sit-to-stand for able-bodied older adults.

The aim of this study was to compare the effects of grab rail position, orientation, and number of hands used on the kinetics of assisted sit-to-stand transfers. Participants were 12 able-bodied older adults between the ages of 69 and 88 years. While each one performed the sit-to-stand transfer, a motion analysis system with 9 cameras recording at 60 Hz tracked the 3-D trajectories of retroreflective markers. Bilateral 37-D platform, grab rail, and seat force data were collected at 200 Hz and normalized to participant body weight. Four lateral conditions were tested: vertical, 45 degrees inclined, and horizontal with the hand placed at 150 mm and 400 mm forward of the seat front edge. Four anterior conditions were tested: vertical and horizontal orientations with the use of one hand and two hands. Posterior grab rail force increased with anterior assistance and with two-hand use compared to lateral assistance and single hand use, respectively. The selection of grab rail position and the number of hands incorporated during assistance also determined the symmetry of anteroposterior net joint forces, net joint moments, and joint powers. Grab rail orientation determined the height of the gripping hand which influenced the assistance strategy. Grab rail position, orientation, and the amount of upper body contribution influenced the assisted sit-to-stand transfer. These kinetic responses to grab rail location require careful consideration in order to optimize grab rail assistance during the sit-to-stand transfer.

Aged↗
PubMed2004

Mechanics and control of the flat versus normal foot during the stance phase of walking.

OBJECTIVE: To compare walking stance phase rearfoot and forefoot motion, ankle joint moments and extrinsic foot muscle EMG profiles between normal and pes planus feet. DESIGN: A cross-sectional comparative study. BACKGROUND: Musculoskeletal conditions are often attributed to pes planus, in which motion is assumed to be excessive and the muscle control inadequate. However, many of the speculated differences in mechanics and control between the normal and the pes planus foot have not been quantified. METHODS: Kinematic and kinetic data were obtained from video recordings of skin surface markers and a force plate, and EMG was recorded with surface electrodes. Analysis of variance was carried out to compare the group profiles. RESULTS: In the pes planus group: the forefoot was less adducted (P < .05) at toe-off, and total transverse plane range of motion, at 8 degrees versus 10 degrees, was less (P < .01); the peak plantarflexor ankle moment at push-off was greater (P < .05); the invertor moment was greater at foot flat (P < .05); for the EMG profiles, activity early in stance, relative to the mean stance phase activity was higher (P < .01) in tibialis anterior and lower (P < .05) in the peronei, soleus and medial and lateral gastrocnemius. CONCLUSIONS: Despite reaching statistical significance, the group differences were small for the task of laboratory walking at a natural pace. The main implications of the differences were for restraint of motion. The expectations of excessive motion and muscle effort in the pes planus group were therefore not substantiated. RELEVANCE: Symptomatic pes planus subjects did not reveal the expected biomechanical differences from normal subjects. The underlying causes of symptoms were not identifiable.

Adaptation, Physiological↗
PubMed2004

Role of CD4+ and CD8+ T cells in murine skin and heart allograft rejection across different antigenic desparities.

The factors that influence the relative contribution of the T cell subsets to allograft rejection remain unclear. We compared skin and heart rejection in CD4 Knockout (KO), and CD8 KO mice across full-, minor-, and class II histocompatibility antigen (HA) mismatches. Skin allografts were rejected by either CD4+ or CD8+ T cells alone at any degree of antigenic mismatch. However, either the absence of CD4+ cells or a lesser degree of HA mismatch resulted in prolongation of graft survival. In contrast, fully allogeneic heart grafts were accepted in CD4 KO recipients, and minor HA mismatched heart grafts were accepted by both CD4 KO and CD8 KO mice. Thus, the T cell subsets required for allograft rejection are determined by the immunogenicity of the tissue transplanted. In the absence of CD8+ T cells, perforin and Fas ligand (FasL) but not granzyme B mRNA were detected in rejecting grafts. Thus, granzyme B is a CD8+ cytotoxic T lymphocyte (CTL)-specific effector molecule.

Animals↗
PubMed2004

The effect of joint angle on the timing of muscle contractions elicited by neuromuscular electrical stimulation.

Neuromuscular electrical stimulation was used to evoke isometric knee extension contractions in seven individuals with spinal cord injury (SCI) and the time for knee extension torque to rise and fall was measured across a range of knee angles. The stimulated muscles took more than twice as long to develop 50% of maximum torque at an angle of 15 degrees, compared to an angle of 90 degrees. This time difference comprised both an increased delay before torque rose above resting levels (31 +/- 3 ms at 90 degrees, 67 +/- 24 ms at 15 degrees), and a prolonged duration over which torque was rising (72 +/- 14 ms at 90 degrees, 140 +/- 62 ms at 15 degrees). There was no change, however, in the time taken for torque to fall after cessation of stimulation at different knee angles (58 +/- 5-ms delay, 60 +/- 11-ms fall time). The difference in torque rise time with joint angle has implications for modeling functional activities that differ greatly in their joint angles. This study provides regression equations whereby activation times for the quadriceps muscles of individuals with SCI can be predicted for specific angles of knee flexion.

Adult↗
PubMed2004

Equating rehabilitation outcome scales: developing common metrics.

Transparency with regard to measuring devices is one of the fundamental requirements for progress in science. The ability to derive comparable measures from different measuring devices is the cornerstone of transparency. To this end, progress in measuring and understanding rehabilitation outcomes requires that there is a method of measuring outcomes that is independent of the particular collection of items that is used to assess the outcomes. The purpose of this study is to develop a equivalence between the PECS Motor Skills and Cognition and Communication LifeScales with the FIM Motor Skills and Cognitive items. However, only the results of the Motor Skills Scale are reported here in the interest of brevity. This equating is based on approximately 500 simultaneous evaluations using bout the PECS and FIM scales on admission and discharge. The patients in this study were consecutive admissions to a free-standing rehabilitation hospital in early 1998. Patients from five diagnostic groups were included in this study, Brain Injury, Spinal Cord Injury, Stroke, Neuromuscular, and Musculoskeletal. The results indicate that it is possible to construct a common equal interval translation between the PECS and FIM for the two scales. Measures on the common metric can be based to either scale and are independent of the number of items completed. This use of these anchored scales will allow institutions using either the PECS and FIM to make direct comparisons of clinical outcomes with other institutions, independent of the particular outcome tool used to evaluate patients.

Activities of Daily Living↗
PubMed2004

Detecting item bias with the Rasch model.

The purpose of this article is to introduce the concept of item bias, highlighting the differences between the definition of the term as it is used within Rasch measurement and the definition of the term as it is used in the true-score model, non-model based approaches, or multi-item parameter latent trait models. The discussion continues with a description of alternative methods of assessing item bias within the Rasch measurement framework and discusses the power of these methods to detect the presence of item bias. The discussion concludes with several examples drawn from a number of different mathematics tests. This includes a comparison of the Rasch separate calibration t-test and the Mantel-Haenszel approaches.

Aptitude Tests↗
PubMed2003

Measurement precision of the clinician administered PTSD scale (CAPS): a RASCH model analysis.

The Clinician Administered PTSD Scale (CAPS), originally developed as a diagnostic tool, is frequently used to evaluate treatment responses. Defining a case and measuring symptom changes are different processes that require different attributes for the instrument. Measuring symptom changes requires precision in measurement. Using the Rasch rating scale model, we evaluated this instrument for construct validity in a veteran sample. The distribution of the veteran measures did not align with the distribution of the item measures in the CAPS instrument. Separate analysis of the CAPS Frequency subscale and Intensity subscale were conducted. The Frequency subscale produced measures that encompassed the level of severity found in the veteran sample. Items from this instrument can be used to develop an equal interval scale to provide precise measurements for treatment evaluations and to identify clinical cut points for diagnostic purposes.

Calibration↗
PubMed2003

Rasch fit statistics as a test of the invariance of item parameter estimates.

The invariance of the estimated parameters across variation in the incidental parameters of a sample is one of the most important properties of Rasch measurement models. This is the property that allows the equating of test forms and the use of computer adaptive testing. It necessarily follows that in Rasch models if the data fit the model, than the estimation of the parameter of interest must be invariant across sub-samples of the items or persons. This study investigates the degree to which the INFIT and OUTFIT item fit statistics in WINSTEPS detect violations of the invariance property of Rasch measurement models. The test in this study is a 80 item multiple-choice test used to assess mathematics competency. The WINSTEPS analysis of the dichotomous results, based on a sample of 2000 from a very large number of students who took the exam, indicated that only 7 of the 80 items misfit using the 1.3 mean square criteria advocated by Linacre and Wright. Subsequent calibration of separate samples of 1,000 students from the upper and lower third of the person raw score distribution, followed by a t-test comparison of the item calibrations, indicated that the item difficulties for 60 of the 80 items were more than 2 standard errors apart. The separate calibration t-values ranged from +21.00 to -7.00 with the t-test value of 41 of the 80 comparisons either larger than +5 or smaller than -5. Clearly these data do not exhibit the invariance of the item parameters expected if the data fit the model. Yet the INFIT and OUTFIT mean squares are completely insensitive to the lack of invariance in the item parameters. If the OUTFIT ZSTD from WINSTEPS was used with a critical value of | t | > 2.0, then 56 of the 60 items identified by the separate calibration t-test would be identified as misfitting. A fourth measure of misfit, the between ability-group item fit statistic identified 69 items as misfitting when a critical value of t > 2.0 was used. Clearly relying solely on the INFIT and OUTFIT mean squares in WINSETPS to assess the fit of the data to the model would cause one to miss one of the most important threats to the usefulness of the measurement model.

Calibration↗
PubMed2002

Effector mechanisms in murine allograft rejection: comparison of skin and heart grafts in fully allogeneic and minor histocompatibility antigen-mismatched strain combinations.

Cytotoxic T lymphocytes (CTLs) and macrophage-mediated delayed-type hypersensitivity (DTH) responses may both mediate allograft rejection. Furthermore, although allograft rejection is classically considered a type [22, 23, 38, 50, 52] 1 cellular immune response, type-2 cytokines can support rejection. This study examines whether the immunogenicity of the transplanted tissue, as determined by type of tissue (skin versus heart) and degree of antigenic mismatch, influences recruitment of these effector mechanisms. Graft survival, histological appearance and intragraft gene expression (IL-2, IFN-gamma, IL-12 p40, IL-4, IL-10, perforin, Fas ligand (Fas L), iNOS and TNF-alpha) were compared for fully allogeneic, minor histocompatibility (mHC) antigen-mismatched and syngeneic skin and heart grafts. We found mRNA characteristic of CTLs and DTH responses in fully allogeneic and mHC antigen-mismatched skin and heart grafts. Concomitant type-1 and type-2 cytokine gene transcription was seen. These findings demonstrate that the tissue grafted and degree of antigenic disparity between donor and recipient do not restrict the repertoire of cellular immune responses involved in graft rejection. This finding has implications in the design of new immunosuppressive strategies for clinical transplantation.

Animals↗
PubMed2002

Biomechanics feedback for rowing.

Factors that affect boat speed are important determinants of rowing performance and should form the basis of feedback to rowers and their coaches. Biomechanical analysis of rowing has led to variables that are causally linked to boat speed. With modern technology, these variables can be measured and feedback can be presented instantaneously on-water, or be presented simultaneously with video after the event. This paper demonstrates the links between the criterion of success in rowing, the time for completing 2000 m and the forces acting on the boat, and describes an instrumentation system for providing feedback of these variables to rowers and coaches. These feedback techniques have been used with rowers from national to Olympic competition standard. Aspects of technique have been linked to the determinants of boat speed and several examples are presented here. The motor learning literature supports the effectiveness of kinetic information feedback for the improvement of motor skill and provides a relevant conceptual framework for the improvement of rowing performance. However, although rowers and their coaches value this feedback, further research must be undertaken to establish a sound basis for comparing the effectiveness of such feedback compared with traditional styles, such as verbal feedback of performance.

Biofeedback, Psychology↗
PubMed2002

Tuberculosis of the pancreas: report of two cases and review of the literature.

Tuberculosis of the pancreas is a clinical entity rarely described in the literature. The pancreas is biologically protected from infection by Mycobacterium tuberculosis, probably because of the presence of pancreatic enzymes that interfere with the seeding of M. tuberculosis. However, when pathogens are able to overcome the resistance, they can have diverse presentations, such as pancreatic masses that can mimic carcinoma, obstructive jaundice, pancreatitis, and gastrointestinal bleeding. Herein we describe 2 cases of pancreatic tuberculosis that presented as multicystic masses, and we review the literature to describe the diverse clinical manifestations of this condition.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Hyperpnea training attenuates peripheral chemosensitivity and improves cycling endurance.

Well-trained endurance athletes frequently have a lower peripheral chemoreceptor (pR(c)) sensitivity and a lower minute ventilation (E) during exercise compared to untrained individuals. We speculated that the decreased pR(c) response may be specifically associated with repeated exposure to the high rates of ventilation occurring during exercise training. We therefore examined the effect of respiratory muscle training (RMT; 20x 30 min sessions of voluntary normocapnic hyperpnea) on the pR(c) sensitivity during exercise and on cycling performance. RMT was chosen to achieve a high E, similar to that of heavy exercise, while avoiding the other accompanying effects of whole body exercise. 20 trained male cyclists were randomized into RMT (N=10) or control (N=10) groups. Subjects' pR(c) response was assessed by a modified Dejours O(2) test (10-12 breaths of 100% O(2), repeated 4-6 times) during cycling exercise at 40% of the maximal work capacity ((max)). Cycling performance was measured during a cycling test to exhaustion (85% (max)). The RMT group exhibited a significantly reduced pR(c) sensitivity (mean +/- S.D.) compared to the control group (-5.8+/-6.0% versus 0.1+/-4.6%, P<0.5). Cycling endurance improved significantly after RMT in comparison to the control group (+3.26+/-4.98 versus -1.46+/-3.67 min, P<0.05). However, these changes in pR(c) response were not significantly correlated with exercise ventilation or cycling endurance time. We conclude that the high levels of ventilation achieved during exercise, as simulated by RMT in this study, appear to be accompanied by a reduction in pR(c) sensitivity; however, the role of the pR(c) in the control of ventilation during exercise seems to be minor.

Adult↗