PubMed Health⌕ Search

Biomedical subjects

Chris A McGibbon

Publications and source records attributed to Chris A McGibbon.

At least 19 recordsLinked to original sources
PubMed2005

Stepping stability: effects of sensory perturbation.

BACKGROUND: Few tools exist for quantifying locomotor stability in balance impaired populations. The objective of this study was to develop and evaluate a technique for quantifying stability of stepping in healthy people and people with peripheral (vestibular hypofunction, VH) and central (cerebellar pathology, CB) balance dysfunction by means a sensory (auditory) perturbation test. METHODS: Balance impaired and healthy subjects performed a repeated bench stepping task. The perturbation was applied by suddenly changing the cadence of the metronome (100 beat/min to 80 beat/min) at a predetermined time (but unpredictable by the subject) during the trial. Perturbation response was quantified by computing the Euclidian distance, expressed as a fractional error, between the anterior-posterior center of gravity attractor trajectory before and after the perturbation was applied. The error immediately after the perturbation (Emax), error after recovery (Emin) and the recovery response (Edif) were documented for each participant, and groups were compared with ANOVA. RESULTS: Both balance impaired groups exhibited significantly higher Emax (p = .019) and Emin (p = .028) fractional errors compared to the healthy (HE) subjects, but there were no significant differences between CB and VH groups. Although response recovery was slower for CB and VH groups compared to the HE group, the difference was not significant (p = .051). CONCLUSION: The findings suggest that individuals with balance impairment have reduced ability to stabilize locomotor patterns following perturbation, revealing the fragility of their impairment adaptations and compensations. These data suggest that auditory perturbations applied during a challenging stepping task may be useful for measuring rehabilitation outcomes.

Journal Article↗
PubMed2005

Tai Chi and vestibular rehabilitation improve vestibulopathic gait via different neuromuscular mechanisms: preliminary report.

BACKGROUND: Vestibular rehabilitation (VR) is a well-accepted exercise program intended to remedy balance impairment caused by damage to the peripheral vestibular system. Alternative therapies, such as Tai Chi (TC), have recently gained popularity as a treatment for balance impairment. Although VR and TC can benefit people with vestibulopathy, the degree to which gait improvements may be related to neuromuscular adaptations of the lower extremities for the two different therapies are unknown. METHODS: We examined the relationship between lower extremity neuromuscular function and trunk control in 36 older adults with vestibulopathy, randomized to 10 weeks of either VR or TC exercise. Time-distance measures (gait speed, step length, stance duration and step width), lower extremity sagittal plane mechanical energy expenditures (MEE), and trunk sagittal and frontal plane kinematics (peak and range of linear and angular velocity), were measured. RESULTS: Although gait time-distance measures were improved in both groups following treatment, no significant between-groups differences were observed for the MEE and trunk kinematic measures. Significant within groups changes, however, were observed. The TC group significantly increased ankle MEE contribution and decreased hip MEE contribution to total leg MEE, while no significant changes were found within the VR group. The TC group exhibited a positive relationship between change in leg MEE and change in trunk velocity peak and range, while the VR group exhibited a negative relationship. CONCLUSION: Gait function improved in both groups consistent with expectations of the interventions. Differences in each group's response to therapy appear to suggest that improved gait function may be due to different neuromuscular adaptations resulting from the different interventions. The TC group's improvements were associated with reorganized lower extremity neuromuscular patterns, which appear to promote a faster gait and reduced excessive hip compensation. The VR group's improvements, however, were not the result of lower extremity neuromuscular pattern changes. Lower-extremity MEE increases corresponded to attenuated forward trunk linear and angular movement in the VR group, suggesting better control of upper body motion to minimize loss of balance. These data support a growing body of evidence that Tai Chi may be a valuable complementary treatment for vestibular disorders.

Biomechanical Phenomena↗
PubMed2005

Acupuncture for upper-extremity rehabilitation in chronic stroke: a randomized sham-controlled study.

OBJECTIVE: To compare the effects of traditional Chinese acupuncture with sham acupuncture on upper-extremity (UE) function and quality of life (QOL) in patients with chronic hemiparesis from stroke. DESIGN: A prospective, sham-controlled, randomized controlled trial (RCT). SETTING: Patients recruited through a hospital stroke rehabilitation program. PARTICIPANTS: Thirty-three subjects who incurred a stroke 0.8 to 24 years previously and had moderate to severe UE functional impairment. INTERVENTIONS: Active acupuncture tailored to traditional Chinese medicine diagnoses, including electroacupuncture, or sham acupuncture. Up to 20 treatment sessions (mean, 16.9) over a mean of 10.5 weeks. MAIN OUTCOME MEASURES: UE motor function, spasticity, grip strength, range of motion (ROM), activities of daily living, QOL, and mood. All outcomes were measured at baseline and after treatment. RESULTS: Intention-to-treat (ITT) analyses found no statistically significant differences in outcomes between active and sham acupuncture groups. Analyses of protocol-compliant subjects revealed significant improvement in wrist spasticity (P<.01) and both wrist (P<.01) and shoulder (P<.01) ROM in the active acupuncture group, and improvement trends in UE motor function (P=.09) and digit ROM (P=.06). CONCLUSIONS: Based on ITT analyses, we conclude that acupuncture does not improve UE function or QOL in patients with chronic stroke symptoms. However, gains in UE function observed in protocol-compliant subjects suggest traditional Chinese acupuncture may help patients with chronic stroke symptoms. These results must be interpreted cautiously because of small sample sizes and multiple, unadjusted, post hoc comparisons. A larger, more definitive RCT using a similar design is feasible and warranted.

Activities of Daily Living↗
PubMed2004

Knee adduction moment and development of chronic knee pain in elders.

OBJECTIVE: To determine whether the adduction moment at the knee during locomotor activity contributes to the development of future chronic knee pain. METHODS: We studied 132 community-dwelling elders who had undergone a full kinetic and kinematic motion analysis while performing 4 different activities: standing, walking, rising from a chair, and descending stairs. We contacted the participants 3-4 years after their baseline locomotion analysis and identified those who reported no knee pain at the time of motion analysis but who subsequently developed new chronic knee pain at followup. We examined whether the development of new chronic knee pain was associated with higher peak adduction moment at the knee during activities, measured at baseline. RESULTS: Of the 132 elders evaluated in 1995-1996, 118 (89%) were contacted in 1999. Of the 118 contacted, 80 (mean age 75 years; 78% women) had no lower extremity prosthetic joints at baseline, no known underlying inflammatory arthritis at baseline nor followup, and no baseline knee pain. At followup, 7 had developed new chronic knee pain defined as pain or stiffness on most days of the month and with walking 2 blocks or using stairs. Compared with those who did not develop knee pain, those who did develop new chronic knee pain had higher baseline adduction moments for all activities (P = 0.01), ranging from 8% higher during chair rise to 39% higher during stair descent. CONCLUSION: We found that greater adduction moment at the knee during activities contributes to the development of future chronic knee pain. Our results suggest that biomechanical factors may play an important role in the pathogenesis of knee pain and should be studied further.

Aged↗
PubMed2004

Instant of chair-rise lift-off can be predicted by foot-floor reaction forces.

OBJECTIVE: To develop a predictive model of the lift-off event during chair rise in healthy subjects, using foot-floor reaction forces. BACKGROUND: An important event during chair rise is lift-off from the seat: the transition from the inherently stable three-point contact to the unstable two-point contact. There is no consistent or generally agreed upon method for estimating the time of lift-off when an instrumented seat is unavailable. METHODS: Twenty healthy volunteers were divided into a testing set and training set. Each subject performed repeated chair rise trials at different speeds. Seat-floor and foot-floor forces, recorded with two force platforms, were used to develop a model of the lift-off event. RESULTS: The magnitude of the vertical foot-floor reaction at lift-off (F0VF) was linearly related (R2 = 0.71, P < 0.001) to the peak vertical foot-floor reaction force (FMVF). A linear model was developed for the training group, which enabled prediction of lift-off time for the testing group with an absolute average error of 6 ms (about 1 data frame at 150 Hz). The linear model derived for the entire sample was: F0VF = 28.14 + FMVF * (0.6434). CONCLUSIONS: The lift-off event for healthy subjects performing chair rise can be accurately predicted from foot-floor reaction forces, without requiring an instrumented seat.

Body Weight↗
PubMed2004

Can Tai Chi improve vestibulopathic postural control?

OBJECTIVES: To evaluate the rationale and scientific support for Tai Chi as an intervention for vestibulopathy and to offer recommendations for future studies. DATA SOURCES: A computer-aided search, including MEDLINE and Science Citation Index, to identify original Tai Chi studies published in English; relevant references cited in the retrieved articles were also included. STUDY SELECTION: A preliminary screening selected all randomized controlled trials (RCTs), non-RCTs, case-control studies, and case series that included Tai Chi as an intervention and had at least 1 outcome variable relevant to postural stability. DATA EXTRACTION: Authors critically reviewed studies and summarized study designs and outcomes in a summary table. DATA SYNTHESIS: Twenty-four Tai Chi studies met screening criteria. No studies specifically studying Tai Chi for vestibulopathy were found. Collectively, the 24 studies provide sometimes contradictory but generally supportive evidence that Tai Chi may have beneficial effects for balance and postural impairments, especially those associated with aging. Ten RCTs were found, of which 8 provide support that Tai Chi practiced alone, or in combination with other therapies, can reduce risk of falls, and/or impact factors associated with postural control, including improved balance and dynamic stability, increased musculoskeletal strength and flexibility, improved performance of activities of daily living (ADLs), reduced fear of falling, and general improvement in psychologic well-being. Studies using other designs support the results observed in RCTs. CONCLUSIONS: At present, few data exist to support the contention that Tai Chi specifically targets the impairments, functional limitations, disability, and quality of life associated with peripheral vestibulopathy. There are, however, compelling reasons to further investigate Tai Chi for vestibulopathy, in part because Tai Chi appears useful for a variety of nonvestibulopathy etiologic balance disorders, and is safe. Especially needed are studies that integrate measures of balance relevant to ADLs with other psychologic and cognitive measures; these might help identify specific mechanisms whereby Tai Chi can remedy balance disorders.

Humans↗
PubMed2004

Weight change, body image, and quality of life in HIV disease: a pilot study.

Fat distribution alterations and lipodystrophy occur as part of a broad spectrum of body alterations in human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). Recent advances in HIV therapies, including highly active antiretroviral therapy, contribute to these fat distribution alterations. The purpose of this pilot study was to investigate the relationships of weight change, body image, length of time with HIV/AIDS diagnosis, and quality of life in HIV disease. The sample consisted of 23 men with mean age of 42.2 years (SD = 8.2) and 17 women with mean age of 36.8 years (SD = 5.2). Participants reported a net increase in weight from 3 months prior (M = 2.4 lb, SD = 12.9 lb) and 12 months prior (M = 10.9 lb, SD = 19.1 lb). They also reported that their weight was greater than their ideal weight (M = 9.2 lb, SD = 22.9 lb). Body image scores (0-100 scale) were found to be significantly (F((1, 37)) = 5.41, p = .03) higher for women (73.1 +/- 17.0) compared with men (60.2 +/- 17.0). Although HIV-positive participants had slightly higher body image scores (M = 68.0, SD = 17.0) compared with participants with AIDS (M = 60.5, SD = 18.8), there was no significant difference (F((1, 37)) = 1.56, p = .22) in body image scores between those with HIV and those with AIDS. Finally, weight change was related to three scales of the Medical Outcomes Study-HIV: mental health (r = .42, p = .03), vitality (r = .53, p = .006), and quality of life (r = .45, p = .02) for men. There were no significant correlations between weight change and quality of life domains for women. Education of clinicians and individuals living with HIV/AIDS should focus on the assessment, management, and evaluation of weight change during the course of HIV disease.

Adult↗
PubMed2004

Tai Chi and vestibular rehabilitation effects on gaze and whole-body stability.

Tai Chi (TC) is a comparatively new intervention for peripheral vestibular hypofunction, which is often treated with vestibular rehabilitation (VR). We compared gaze stability (GZS), whole-body stability (WBS) and footfall stability (FFS) during locomotion among 26 people with vestibulopathy (VSP), randomized into two treatment arms (13 TC and 13 VR). Each intervention program was offered for 10 weeks. GZS improved more for VR than for TC, but WBS (and FFS) improved more for TC than for VR. There was a significant relationship between changes in GZS and WBS for the VR subjects (r=0.60, p=0.01), but not for TC subjects. There was a significant relationship between changes in WBS and FFS for both VR (r=0.65, p <0.01) and TC (r=0.58, p=0.02) groups; the relationship disappeared in the VR but not the TC group when controlling for GZS. These findings suggest that VR and TC both benefit patients with VSP but via differing mechanisms. Moreover, these data are the first to test the assumption that improving gaze control among patients with VSP perforce improves postural stability: it does not. We conclude that GZS is most improved in those who receive VR, but that TC improves WBS and FFS without improving GZS, suggesting patients with VSP can rely on non-gaze related mechanisms to improve postural control.

Female↗
PubMed2003

Discriminating age and disability effects in locomotion: neuromuscular adaptations in musculoskeletal pathology.

We identified biomechanical variables indicative of lower extremity dysfunction, distinct from age-related gait adaptations, and examined interrelationships among these variables to better understand the neuromuscular adaptations in gait. Sagittal plane ankle, knee, and hip peak angles, moments, and powers and spatiotemporal parameters were acquired during preferred-speed gait in 120 subjects: 45 healthy young, 37 healthy elders, and 38 elders with functional limitations due to lower extremity musculoskeletal pathology, primarily arthritis. Multiple analysis of covariance with discriminate analysis, adjusted for gait speed, was used to identify the variables discriminating groups. Correlation analysis was used to explore interrelationships among these variables within each group. Healthy elders were discriminated (sensitivity 76%, specificity 82%) from young adults via decreased late-stance ankle plantar flexion angle, increased late-stance knee power absorption, and early-stance hip extensor power generation. Disabled elders were discriminated (sensitivity 74%, specificity 73%) from healthy elders via decreased late-stance ankle plantar flexor moment and power generation, increased early-stance ankle dorsiflexor moment, and late-stance hip flexor moment and power absorption. Relationships among variables showed a higher degree of coupling for the disabled elders compared with the healthy groups, suggesting a reduced ability to alter motor strategies. Our data suggest that, beyond age-related changes, elders with lower extremity dysfunction rely excessively on passive action of hip flexors to provide propulsion in late stance and contralateral ankle dorsiflexors to enhance stability. These findings support a growing body of evidence that gait changes with age and disablement have a neuromuscular basis, which may be informative in a motor control framework for physical therapy interventions.

Adaptation, Physiological↗
PubMed2003

Accuracy of cartilage and subchondral bone spatial thickness distribution from MRI.

PURPOSE: To assess three-dimensional measurement accuracy of articular cartilage (AC) and subchondral bone (SB) thickness from MRI. MATERIALS AND METHODS: A computer program was used to calculate AC and SB thickness from MRI (three-dimensional spoiled gradient echo (SPGR),.31-mm resolution, 1-mm slice thickness) of six adult femoral heads. Specimens were imaged in five anatomical planes ranging between +30 degrees to -30 degrees from neutral and cut into 2-mm thick sections along the five anatomical planes. Faxitron x-ray was used to produce microradiographic (.05-mm resolution) images of the sections. RESULTS: In-plane measurement accuracy was.165 +/-.108 mm for AC thickness and.387 +/-.174 mm for SB thickness. Taking into account chemical-shift misregistration in SB thickness, accuracy of measurements improved to.213 +/- 128 mm. Out-of-plane (three-dimensional) thickness accuracy of the model, assessed by numerical simulation, was.015 mm. However, three-dimensional thickness errors in specimens were.319 +/-.256 mm for AC and.253 +/-.183 mm for SB thickness. CONCLUSION: Errors in three-dimensional AC thickness were attributed to volume-averaging effects caused by oblique intersection of the image plane with the joint surface. Errors in three-dimensional SB thickness were attributed to chemical-shift artifact. We conclude that accuracy of AC thickness is within clinically acceptable standards but that more sophisticated pulse sequences are needed to improve the measurement of SB thickness.

Adult↗
PubMed2003

Subchondral bone and cartilage thickness from MRI: effects of chemical-shift artifact.

Magnetic resonance imaging (MRI) is the modality of choice for visualizing and quantifying articular cartilage thickness. However, difficulties persist in MRI of subchondral bone using spoiled gradient-echo (SPGR) and other gradient-echo sequences, primarily due to the effects of chemical-shift artifact. Fat suppression techniques are often used to reduce these artifacts, but they prevent measurement of bone thickness. In this report, we assess the magnitude of chemical-shift effects (phase-cancellation and misregistration artifacts) on subchondral bone and cartilage thickness measurements in human femoral heads using a variety of pulse sequence parameters. Phase-cancellation effects were quantified by comparing measurements from in-phase images (TE=13.5 ms) to out-of-phase images (TE=15.8 ms). We also tested the assumption of the optimal in-phase TE by comparing thickness measures at small variations on TE (13.0, 13.5 and 14.0 ms). Misregistration effects were quantified by comparing measurements from water+fat images (water-only+fat-only images) to the measurements from in-phase (TE=13.5) images. A correction algorithm was developed and applied to the in-phase measurements and then compared to measurements from water+fat images. We also compared thickness measurements at different image resolutions. Results showed that both phase-cancellation artifact and misregistration artifact were significant for bone thickness measurement, but not for cartilage thickness measurement. Using an in-phase TE and correction algorithm for misregistration artifact, the errors in bone thickness relative to water+fat images were non-significant. This information may be useful for developing pulse sequences for optimal imaging of both cartilage and subchondral bone.

Adipose Tissue↗
PubMed2003

Inter-rater and intra-rater reliability of subchondral bone and cartilage thickness measurement from MRI.

MRI is often used to visualize and quantify the articular cartilage layer of load bearing joints affected by degenerative diseases, such as osteoarthritis (OA). Although the role played by the subchondral bone in the etiology and/or progression of OA may be important, the ability to visualize and quantify subchondral bone with MRI has received little attention. In this report we examined the inter-rater and intra-rater reliability of subchondral bone and cartilage thickness measurements from MR images of cadaver femoral head specimens. A 3D-SPGR pulse sequence tuned to eliminate chemical shift artifact through phase cancellation was used to image the specimens. Three raters manually segmented four specimens on two different occasions. Subchondral bone and cartilage thickness measurements were calculated from the segmented images. Inter-rater and intra-rater reliabilities were very high (>.98) for both cartilage and subchondral bone thickness measurements. We conclude that subchondral bone thickness can be measured as reliably as cartilage thickness from MR images.

Cadaver↗
PubMed2003

Kinetic analysis of planned gait termination in healthy subjects and patients with balance disorders.

We examined the stability and strategies used by balance impaired (vestibular hypofunction, VH: n=25; cerebellar damage, CB: n=20) patients and healthy (HE: n=52) controls during planned gait termination. Upper body strategies (during final stride and final step) were investigated using peak positive kinetic power (KP((+)): kinetic energy increasing), and peak negative kinetic power (KP((-)): kinetic energy decreasing) of the head-arms-trunk segment. Compared to HE controls (P<0.05): CB patients' medio-lateral KP((+)) and KP((-)) and were 53 and 71% higher during final stride, respectively; VH patients medio-lateral KP((+)) and KP((-)) was 78 and 57% higher during final step, respectively, and; during the final, standing stage VH patients were 32% less stable (from phase plane analysis) in the frontal plane. The excessive energy transfers in final stride for CB patients was likely due to poor eccentric muscle control when preparing for the stop. VH patients had difficulty controlling lateral stability during final step and once they had stopped walking, probably due to the lack of vestibular feedback regarding forward velocity changes. A better understanding of these abnormal movement patterns or compensatory strategies may assist in rehabilitation of patients with balance dysfunction.

Adult↗
PubMed2003

Measurement accuracy of focal cartilage defects from MRI and correlation of MRI graded lesions with histology: a preliminary study.

OBJECTIVES: Although accurate spatial measurement of cartilage thickness from MRI is possible, no studies have assessed the accuracy of measuring cartilage defect dimensions from MRI. In addition, current MR grading scales for assessing cartilage lesions have limited categories, and little is known about how well these scales correlate with histological assessment of the lesion. The objective of this preliminary study is to address both these issues. METHODS: We performed two experiments on four cadaver knee joints from elderly donors: Experiment 1 assessed the accuracy of measuring controlled defects in cartilage, and Experiment 2 compared MRI grading (Noyes scale) of natural cartilage lesions to histological grading (Mankin scale) of the sectioned cartilage tissue. MRI was performed on 1.5 T clinical scanner (fat-suppressed 3D-SPGR at TR/TE/alpha=55/13.5/45 and 256 x 256 matrix). RESULTS: The mean difference between defect diameters measured and introduced was less than 0.1mm, which was statistically insignificant (P=0.754). Defect depth was less accurate at >0.4mm, significantly under predicting actual defect depth (P=0.004). Correlation between Noyes grading scores and Mankin grading scores of natural lesions was moderately high (r=0.7) and statistically significant (P=0.001). CONCLUSIONS: Three-dimensional mapping of cartilage thickness shows great promise for the accurate measurement of focal cartilage defects, though improvement is needed. The Noyes grading scale is consistent with histological Mankin grading of cartilage lesions, though enhancement of MR grading scales is needed, and warranted, based on the signal intensity information available from clinical MRI. Integration of these two analyses-focal defect measurement and signal intensity analysis-could potentially result in a valuable clinical tool for early osteoarthritis diagnosis and longitudinal tracking.

Aged↗
PubMed2003

Toward a better understanding of gait changes with age and disablement: neuromuscular adaptation.

Gait changes in the elderly, such as reduced step length and walking speed, are well documented but not well understood. This review explores the hypothesis that neuromuscular adaptations are a response to age-related impairments and play a key role in causing gait changes in the elderly, and that different neuromuscular adaptations may exist depending on the impairment and presence of comorbidities, such as knee arthritis.

Adaptation, Physiological↗
PubMed2003

A behavioral-medicine program in HIV. Implications for quality of life.

The purpose of this descriptive study is to examine quality of life issues in participants in a behavioral-medicine group (N = 24). Of the sample, 60% indicated current use of complementary therapies. Sexual functioning, a subscale of the quality-of-life measure, was positively correlated with length of time with HIV. CD4+ lymphocyte counts were not significantly correlated with quality of life (QOL). Viral load (VL) was positively correlated with the social-support subscale of the QOL scale. Use of body therapies (massage, acupuncture) was associated with social functioning and use of nutritional therapies was associated with mental health. Results of the study indicate that clinical interventions, including behavioral-medicine interventions and complementary therapies for persons with HIV/AIDS, can result in greater QOL.

Adult↗