Biomedical subjects

C L Richards

Publications and source records attributed to C L Richards.

At least 19 recordsLinked to original sources

PubMed2006

Has the evolution of complexity in the amphibian papilla influenced anuran speciation rates?

For anurans, increasing complexity of the inner ear has been correlated with speciation rates. The evolution of a complex amphibian papilla (AP) is thought to have facilitated speciation by extending the range of frequencies over which mating calls may diverge. Although this example has been proposed to represent a key innovation, the mechanism by which the AP is thought to promote speciation makes the questionable assumption that anurans generally use the AP for detection of their mating calls. This study uses mating calls from 852 species to test this assumption. Surprisingly, the calls of most species are not detected by the AP but by a second organ, the basilar papilla (BP). This refutes the role of AP complexity in facilitating call divergence and hence, speciation. Future research into the evolution of acoustically mediated reproductive isolation should focus instead on the BP as it may play a more critical role in anuran speciation.

Amphibians↗

PubMed2004

A task-orientated intervention enhances walking distance and speed in the first year post stroke: a randomized controlled trial.

OBJECTIVE: To evaluate the efficacy of a task-orientated intervention in enhancing competence in walking in people with stroke. DESIGN: Two-centre observer-blinded stratified block-randomized controlled trial. SETTING: General community. SUBJECTS: Between May 2000 and February 2003, 91 individuals with a residual walking deficit within one year of a first or recurrent stroke consented to participate. INTERVENTIONS: The experimental intervention comprised 10 functional tasks designed to strengthen the lower extremities and enhance walking balance, speed and distance. The control intervention involved the practice of upper extremity activities. Subjects in both groups attended sessions three times a week for six weeks. MAIN MEASURES: Six-minute walk test (SMWT), 5-m walk (comfortable and maximum pace), Berg Balance Scale, timed 'up and go'. RESULTS: At baseline, subjects in the experimental (n = 44) and control (n = 47) groups walked an average distance of 209 m (SD = 126) and 204 m (SD =131), respectively, on the SMWT. Mean improvements of 40 m (SD =72), and 5 m (SD =66) were observed following the experimental and control interventions, respectively. The between-group difference was 35 m (95% confidence interval (CI) 7, 64). Significant between-group effects of 0.21 m/s (95% CI 0.12, 0.30) and of 0.11 m/s (95% CI 0.03, 0.19) in maximum and comfortable walking speed, respectively, were observed. People with a mild, moderate or severe walking deficit at baseline improved an average of 36 (SD =96), 55 (SD = 56) and 18 m (SD = 23), respectively, in SMWT performance following the experimental intervention. CONCLUSIONS: Study findings support the efficacy of a task-orientated intervention in enhancing walking distance and speed in the first year post stroke, particularly in people with moderate walking deficits.

Adult↗

PubMed2003

Quantitative motor assessment in myotonic dystrophy.

OBJECTIVE: To establish baseline data, using a quantitative motor evaluation protocol, prior to a prospective longitudinal study of the natural history of muscular involvement in myotonic dystrophy (DM). DESIGN/METHODS: We conducted a cross-sectional study using a protocol consisting of manual muscle testing (MMT), quantitative muscle testing (QMT), and timed functional testing (TFT) on 50 definite DM patients (27 men, 23 women), aged 16 to 67 years. The relationships between MMT, QMT and TFT scores and disease duration were examined using linear regression analysis. RESULTS: The muscle weakness was symmetric and the neck flexors and the distal muscles of upper and lower extremities were weaker than proximal muscles. Using MMT scores, the average strength decline was 0.95% per year and was similar for men and women. The strength decline was significantly more rapid for distal muscles than for proximal muscles. Quantitative muscle testing scores documented a strength decline per year of disease duration of 1.2-1.6% for the hip flexors and of 2.0-3.0% for the hand grip flexors. CONCLUSIONS: We observed significant linear relationships between the scores generated by this protocol and disease duration. These data illustrate the distal to proximal progression of muscular involvement in DM, a pattern of progression well-recognized by the clinicians. The follow-up assessment of a large DM cohort in a longitudinal study will establish whether this quantitative protocol provides sensitive measures of the disease progression.

Adolescent↗

PubMed2002

Mechanisms of disturbed motor control in ankle weakness during gait after stroke.

This study investigated the role of paresis, excessive antagonist coactivation, increased muscle-tendon passive stiffness and spasticity in the reduced stance phase plantarflexor moment (Mmax) and swing phase dorsiflexion during gait (DFmax) in subjects with a recent (<6 months post-stroke) hemiparesis (patients). The gait pattern of the paretic and non-paretic sides was evaluated in 30 patients (aged 57.8+/-10.8 years), whereas only one side was evaluated in 15 healthy controls (aged 59.1+/-9.8 years) while walking at natural and very slow speeds. Peak plantarflexor moment (Mmax) and peak medial gastrocnemius (MG) activation during the stance phase, as well as peak dorsiflexion angle (Dfmax) and peak tibialis anterior (TA) activation during the swing phase, were retained for analysis. In addition, a coactivation index and a plantarflexor spasticity index were calculated for both the stance and the swing phase, and plantarflexor passive stiffness was evaluated on an isokinetic dynamometer. The results showed that Mmax on the paretic and non-paretic sides were both reduced compared with control values at natural speed. This reduction was combined to a low MG activation (paresis) on the paretic side. On the non-paretic side, the reduced plantarflexor moment was related to excessive coactivation levels. The swing phase Dfmax tended to be reduced (not significantly) on the paretic side of the patients compared with control values. This reduction was neither associated with excessive antagonist coactivation nor to plantarflexor hyperactive stretch reflexes, but rather to an increased plantarflexor passive stiffness. In some of the patients, however, an increased TA activation that overcame the plantarflexor passive stiffness allowed for normal DFmax values. The functional consequences of the disturbed mechanisms of motor control observed in both the paretic and non-paretic sides are discussed.

Adult↗

PubMed2001

Responsiveness and predictability of gait speed and other disability measures in acute stroke.

OBJECTIVES: To identify the most responsive method of measuring gait speed, to estimate the responsiveness of other outcome measures, and to determine whether gait speed predicts discharge destination in acute stroke. DESIGN: A prospective cohort study. SETTING: Five acute-care hospitals. PATIENTS: Fifty subjects with residual gait deficits after a first-time stroke. INTERVENTIONS: Five- (5mWT) and 10-meter walk tests (10mWT) at comfortable and maximum speeds, with 2 evaluations conducted an average +/- standard deviation (SD) of 8 +/- 3 and 38 +/- 5 days poststroke. MAIN OUTCOME MEASURE: Standardized response mean (SRM = mean change/SD of change) was used to estimate responsiveness for each walk test, the Berg Balance Scale, the Barthel Index, the Stroke Rehabilitation Assessment of Movement (STREAM), and the Timed Up and Go (TUG). RESULTS: The SRMs were 1.22 and 1.00 for the 5mWT, and.92 and.83 for the 10mWT performed at a comfortable and maximum pace, respectively. The SRMs for the Berg Balance Scale, the Barthel Index, the STREAM, and the TUG were 1.04,.99,.89, and.73, respectively. The probability of discharge to a rehabilitation center for persons walking at < or = 0.3m/s or > 0.6m/s at the first evaluation was.95 and.22, respectively. CONCLUSIONS: The 5mWT at a comfortable pace is recommended as the measure of choice for clinicians and researchers who need to detect longitudinal change in walking disability in the first 5 weeks poststroke.

Activities of Daily Living↗

PubMed2001

Locomotor-specific measure of spasticity of plantarflexor muscles after stroke.

OBJECTIVES: To study the stretch reflex excitability (spasticity) of the plantarflexor muscles during gait in patients with hemiparesis and to study the relationships of spasticity during gait with spasticity at rest and gait speed. DESIGN: Cross-sectional, descriptive. SETTING: Rehabilitation center. PARTICIPANTS: Convenience sample of 30 patients (58 +/- 11yr) with hemiparesis (<6mo poststroke) and 15 healthy controls (59 +/- 8yr). INTERVENTIONS: Patients walked at natural speed, healthy subjects at very slow speed for 10 gait cycles. Electromyographic activation of the medial gastrocremius was recorded by using surface electrodes. A 2-dimensional video camera system with reflective markers was used to acquire kinematics of the lower limbs. MAIN OUTCOME MEASURES: Electromyography-lengthening velocity slopes, calculated from measures obtained during the lengthening periods of the medial gastrocnemius muscle during the stance and the swing phases. Measured spatisticity (Modified Ashworth Scale [MAS]), static strength (ankle clonus), and motor control (Fugl-Meyer test). RESULTS: Velocity-sensitive electromyographic responses, indicative of hyperactive stretch reflexes, were found on the paretic side during the stance phase of gait (in 66% of the patients), but not on the nonparetic side or in controls. In many patients, velocity-sensitive responses coexisted with low plantarflexor activation levels during the stance phase. No clear patterns of response were measured during the swing phase in either group. Spasticity during gait in the patients was found to be positively related (r = .47, p < .01; r = .57, p < .001) to spasticity at rest (MAS; ankle clonus), whereas it was found to be negatively related to gait speed (r = -.47 to -.53, p < .01). CONCLUSIONS: The validity of the present method is supported by the fact that it is locomotor-specific and that it allowed for a good discrimination between spastic and nonspastic limbs, as well as between stance and swing phases of the gait cycle. The results also support plantarflexor spasticity as a factor contributing to the poor locomotor performance after stroke.

Adult↗

PubMed2001

Walking speed over 10 metres overestimates locomotor capacity after stroke.

OBJECTIVE: To examine 10-m comfortable walking speed and 6-minute distance in healthy individuals and individuals after stroke and to assess the level of disability associated with poor walking endurance after stroke. DESIGN: Descriptive study in which comfortable walking speed over 10 m and distance covered in 6 minutes (6-minute walk test) were compared between healthy subjects and subjects after stroke. SUBJECTS: Twelve healthy subjects and 14 subjects after stroke. MAIN OUTCOME MEASURES: Walking speed and 6-minute distances were compared between groups. In addition, for each group, actual distance walked in 6 minutes was compared with the distance predicted by the 10-m walking speed test and the distance predicted by normative reference equations. RESULTS: Subjects after stroke had significant reductions in 10-m speed and 6-minute distance compared with healthy subjects (p < 0.05). Subjects after stroke were not able to maintain their comfortable walking speed for 6 minutes, whereas healthy subjects walked in excess of their comfortable speed for 6 minutes. The average distance walked in 6 minutes by individuals after stroke was only 49.8+/-23.9% of the distance predicted for healthy individuals with similar physical characteristics. CONCLUSION: In our subjects after stroke, walking speed over a short distance overestimated the distance walked in 6 minutes. Both walking speed and endurance need to be measured and trained during rehabilitation.

Adult↗

PubMed2000

Contribution of passive stiffness to ankle plantarflexor moment during gait after stroke.

OBJECTIVE: To measure the contribution of passive stiffness to the ankle plantarflexor moment during gait in subjects with hemiparesis early after stroke. The relationship of passive stiffness with gait speed was also examined. DESIGN: Cross-sectional, descriptive. PATIENTS AND OTHER PARTICIPANTS: A sample of convenience of 14 patients (54.7+/-10.9 yrs) with a hemiparesis for less than 5 months and 11 healthy controls (50.6+/-11.6 yrs). MAIN OUTCOME MEASURES: The contribution of passive stiffness to the plantarflexor moment during gait was obtained using moment-angle slope (stiffness) values. Total plantarflexor stiffness was measured during gait, and passive stiffness was measured during passive dorsiflexion imposed by an isokinetic dynamometer at velocities and ranges of movement matched with values recorded during the plantarflexor lengthening period of the stance phase. The contribution of passive stiffness was obtained by dividing the passive stiffness (dynamometer) by the total plantarflexor stiffness (gait). RESULTS: On the paretic side, passive stiffness contributed more (16.8%; range 2.9% to 49.6%) to total plantarflexor stiffness during gait compared (p<.01) with both the nonparetic side (7.3%) and control values (5.9%). This increased contribution on the paretic side resulted from a large muscle-tendon passive stiffness, a decreased active muscle contribution, or both. Although in some patients the increased passive component led to the development of a total plantarflexor stiffness that was within normal values, it did not in others either because the active component was very small or because limited dorsiflexion during the stance phase prevented the passive component tension to develop. The contribution of passive stiffness was not significantly (p>.05) related to gait speed in both the patients and the controls. CONCLUSIONS: The increased contribution of passive stiffness to total plantarflexor moment during gait likely acts as an adaptation for a defective muscle active component, helping ankle push-off at the end of the stance phase. Although this mechanism is effective in most of the patients, it cannot come into action if the dorsiflexion movement during the stance phase is prevented, for instance, by enhanced stretch reflexes.

Adult↗

PubMed2000

Preparatory adjustments during gait initiation in 4-6-year-old children.

The preparatory adjustments related to gait initiation in a group of six children (4-6 years old) were studied in comparison to a group of six adults (50-61 years old). Muscle activity, ground reaction forces and body kinematics were recorded during the initiation of gait in subjects standing with one foot on each of two forceplates. Like adults, children had consistent anticipatory activations of the tibialis anterior (TA) muscle accompanied by center of pressure (COP) displacements, but the relative magnitude of both the backward COP displacement and concomitant initial TA activation burst were lower (P<0.03 and P<0.001 respectively) in children. The latter findings were associated with a lower rate of forward progression in children (P=0.01), and a lack of significant covariance between the backward shift and forthcoming velocity. In contrast, the preparatory adjustments in the medio-lateral (M/L) direction were prominent in children. Larger M/L peak force rates in children (P=0. 01) were associated with an earlier (P=0.007) weight transfer to the stance limb; moreover, children initiated gait from a wider (P=0.04) base of support and had a trajectory of the total COP that was lateral rather than posterior like in adults. The consistent preparatory adjustment responses indicate that the motor program for initiating gait is functional at this age. The prominence of the preparatory adjustments in the M/L direction together with a reduced magnitude of the responses in the antero-posterior direction suggest that the anticipatory behavior for initiating gait develops first in the frontal plane and that more walking experience and better postural stability are required to fully achieve the adult-like control of the gait initiation process.

Aging↗

PubMed2000

Coactivation during gait as an adaptive behavior after stroke.

The aims of the present study were to quantify the impairment in ankle coactivation on the paretic and non-paretic sides of subjects with hemiparesis and to examine the relationship of ankle coactivation with postural instability, motor deficit of the paretic lower extremity and locomotor performance. Electromyography of the medial gastrocnemius (MG) and tibialis anterior (TA) muscles were recorded bilaterally during gait in 30 subjects (62.1+/-9.9 years) who had suffered a recent stroke (<6 months) as well as on one side of 17 healthy controls (59.3+/-9.1 years) walking at very slow speed. Ankle muscle coactivation was calculated by dividing the time of overlap between MG and TA signals (threshold of 20 microV) by the duration of the gait phases of interest: stance, swing, first and second double support sub-phases and single support sub-phase. The time spent in single support and the peak plantarflexor moment of force on the paretic side were used to measure, respectively, postural stability and dynamic strength of the paretic plantarflexors. The subjects with hemiparesis demonstrated less coactivation on the paretic side during the single support sub-phase (p<0.01) and more coactivation during first and second double support sub-phases on the non-paretic side (p<0.001) compared to control values. The patients with coactivation patterns that differed the most from controls were the patients with the more severe impairments and disabilities. While the reduced coactivation on the paretic side may contribute to poor postural stability and poor locomotor performance, the presence of excessive coactivation on the non-paretic side when both limbs were in ground contact may be an adaptation to help maintain postural stability during gait.

Adaptation, Physiological↗

PubMed2000

Task-related circuit training improves performance of locomotor tasks in chronic stroke: a randomized, controlled pilot trial.

OBJECTIVE: To evaluate the immediate and retention effects of a 4-week training program on the performance of locomotor-related tasks in chronic stroke. DESIGN: Randomized, controlled pilot study with 2-month follow-up. SETTING: Rehabilitation center. SUBJECTS: A convenience sample consisting of 12 chronic stroke subjects was used. Subjects were randomly assigned to the experimental or the control group. Three subjects withdrew from the study. INTERVENTION: Both experimental and control groups participated in exercise classes three times a week for 4 weeks. The exercise class for the experimental group focused on strengthening the affected lower limb and practicing functional tasks involving the lower limbs, while the control group practiced upper-limb tasks. MAIN OUTCOME MEASURES: Lower-limb function was evaluated by measuring walking speed and endurance, peak vertical ground reaction force through the affected foot during sit-to-stand, and the step test. RESULTS: The experimental group demonstrated significant immediate and retained (2-month follow-up) improvement (p < or = .05) compared with the control group in walking speed and endurance, force production through the affected leg during sit-to-stand, and the number of repetitions of the step test. CONCLUSION: The pilot study provides evidence for the efficacy of a task-related circuit class at improving locomotor function in chronic stroke.

Aged↗

PubMed1999

A ventricular assist device powered by conditioned skeletal muscle.

BACKGROUND: We are developing and testing a new ventricular assist device (VAD) to be powered by conditioned skeletal muscle. METHODS: To evaluate the VAD hardware and to develop a muscle training regimen, 8 calves have been used in studies in which the right latissimus dorsi muscle was employed. The experiments were carried out to an approximately 4-month duration. RESULTS: There was significant conversion of type II (fast twitch) to type I (slow twitch) muscle fibers. This did not correlate well, however, with device performance. The device stroke volumes ranged from approximately 17 to 90 cc. This variability of outcome occurred despite the fact that identical hardware, surgical procedures, and training regimens were employed. CONCLUSIONS: The results from the first eight studies lead us to speculate that perfusion may be important even when the muscle is working at pressures much lower than systemic blood pressure levels. In an attempt to augment tissue perfusion, we plan to investigate thermally induced angiogenesis as a possible mechanism for increasing blood flow to the tissue.

Animals↗

PubMed1999

Lessons from recent nosocomial epidemics.

This review describes important examples of recent nosocomial infection epidemics. Current trends suggest that emerging problems in nosocomial infections include increased nosocomial epidemics in out-of-hospital settings, contamination of medical devices and products, and antimicrobial resistance. Increased attention should be focused on outbreak investigations in these areas.

Journal Article↗

PubMed1999

Gait in stroke: assessment and rehabilitation.

This article discusses the assessment and treatment of gait disorders after stroke. After consideration of the effects (of the disturbed motor control resulting from stroke) on the gait movements and the expected rate of recovery of walking capacity, different methods of assessment are considered. Emphasis is placed on selecting the appropriate measurement tool according to the individual's level of function. Also, the need to measure walking performance under different environmental constraints and the importance of instrument responsiveness to change over the range of walking disabilities are discussed. Task-related training with the opportunity for large amounts of practice is recommended to improve walking performance after stroke.

Environment↗

PubMed1998

Effects of the type of meniscal lesion on knee function.

The relationship between the type of meniscal lesion (bucket-handle, flap or degenerative tears) and preoperative knee function (5.1 +/- 6.2 days before arthroscopic meniscectomy) was studied in 35 patients. Patients with bucket-handle tears (group B, n = 12) had large knee extension work deficits during maximal voluntary contractions at 30 degrees and 180 degrees/s (Kin-Com dynamometer). These work deficits were accompanied by proportional decreases in the prime mover or agonist-EMG levels (VM: vastus medialis and/or VL: vastus lateralis). These patients had smaller deficits during flexion movements at 30 degrees/s. Moreover, a larger number of negative clinical signs and symptoms (pain at rest and during tests, locking, thigh atrophy, extension and flexion movement deficits larger than 10 degrees) were found with an equal or a higher prevalence in group B than in the other groups. Patients with flap tears (group F, n = 15) had deficits in work and agonist-EMG activity (VM and VL) only during the extension tests. In contrast, patients with degenerative tears (group D, n = 8) had a work deficit and a concomitant decrease in the EMG level of the medial gastrocnemius (MG), only during the flexion test at 30 degrees/s. Comparable mean knee function scores, as measured by the Lysholm and Gillquist questionnaire [35], were obtained for the three groups of patients, suggesting that this measure was not sensitive enough to discern functional differences related to types of meniscal tears. The results of this study have demonstrated a link between the type of meniscal lesion and the consequent preoperative knee joint disability profile as defined by comparison with the sound leg. These results emphasize the need to consider meniscal lesion type and an individual's preoperative strength deficit when group comparisons of patients are made or the effects of therapy (arthroscopic surgery and rehabilitation) are evaluated.

Adult↗

PubMed1998

Evaluation of reflex- and nonreflex-induced muscle resistance to stretch in adults with spinal cord injury using hand-held and isokinetic dynamometry.

BACKGROUND AND PURPOSE: In this study, we compared the intertrial reliability of resistive torque measurements obtained with hand-held and isokinetic dynamometers and examined the validity of the hand-held dynamometers for the assessment of spastic hypertonia, defined as reflex- and nonreflex-induced resistance to stretch. SUBJECTS: Nine subjects (mean age = 40.6 years) with a chronic (1-5 years) spinal cord injury participated. METHODS: The plantar flexors were stretched at 5 degrees /s (low velocity [LV]) and 180 degrees /s (high velocity [HV]) with an isokinetic dynamometer while the evaluator attempted to match these velocities with a hand-held dynamometer. Electromyographic activity of the soleus and tibialis anterior muscles as well as ankle displacements were recorded. Resistive torque and velocity, measured at -5 degrees of dorsiflexion, were averaged (n = 4). RESULTS: High intraclass correlation coefficients (ICCs) were found at LV and HV for both the hand-held (ICC = .93 and .84) and isokinetic (ICC = .99 and .93) dynamometers. With the hand-held dynamometer, lower resistive torques were found at LV (0.8 N.m) and HV (1.2 N.m), whereas higher velocities were attained at HV. CONCLUSION AND DISCUSSION: The results indicate that the reproducibility of resistive torques obtained with hand-held dynamometry compares with that obtained with isokinetic dynamometry and allows testing of velocities that can be adjusted to the specific level of resistance to stretch. Electromyography confirmed the validity of hand-held dynamometry for assessing reflex and nonreflex components of SH. [Lamontagne A, Malouin F, Richards CL, Dumas F. Evaluation of reflex- and nonreflex-induced muscle resistance to stretch in adults with spinal cord injury using hand-held and isokinetic dynamometry.

Adult↗

PubMed1998

Lessons learned: the managed care experiences of family planning providers.

This article examines key opportunities and obstacles facing community-based family planning agencies seeking to be "players" in the provision of contraceptive and related services in the managed care context. Based on telephone interviews with people working in or closely with a range of family planning provider agencies in five states, it identifies a range of innovative strategies that family planning providers have developed in pursuing arrangements with managed care organizations. It further identifies five difficult issues that have arisen repeatedly in the course of negotiating or implementing those arrangements.

Continuity of Patient Care↗

PubMed1998

Bringing down the barriers to mammography: a review of current research and interventions.

Although mammography screening is effective in reducing breast cancer mortality, major challenges still remain in increasing rates of initial mammography and in improving subsequent adherence to mammography screening. Behavioral science theories offer insights into the potential for individual, organizational, community, and population-level interventions to address these challenges. In this review, we draw on social ecological approaches to health promotion to suggest a conceptual framework for such interventions. After discussing theories of who is and is not screened regularly, and why, we consider selected barriers to mammography and corresponding interventions to overcome them. We conclude with an illustration of the North Carolina Breast Cancer Screening Program (NC-BCSP), a series of interventions informed by the social ecological perspective.

Journal Article↗