Biomedical subjects

Rod Barrett

Publications and source records attributed to Rod Barrett.

6 recordsLinked to original sources

PubMed2006

The role of the neck and trunk in facilitating head stability during walking.

An apparent goal of the human postural system is to maintain head stability during walking. Although much is known about sensory-motor stabilising mechanisms associated with the head and neck, less is known about how the postural system attenuates motion between the trunk and neck segments in order to regulate head motion. Therefore the purpose of this study was to determine the role that the neck and the trunk play in stabilising the head at a range of walking speeds. Eight healthy male subjects (age: 23+/-4 years) performed self-selected slow, preferred, and fast walking speed trials along a 30 m walkway. Four custom-designed wireless triaxial accelerometers were attached to the head, upper trunk, lower trunk, and shank of each subject to measure vertical (VT), anterior-posterior (AP), and mediolateral (ML) accelerations. Acceleration data were examined in each direction using RMS, power spectral, harmonic, and regularity measures. Signal regularity was increased from the lower to upper trunk for all walking speeds and directions with the exception of the slow speed in the AP direction. Evidence from analysis of power spectral and amplitude characteristics of acceleration signals was suggestive that accelerations are also attenuated from the lower to upper trunk by dynamics of the intervening trunk segment. Differences in selected power spectral and amplitude characteristics between the accelerations of the upper trunk and head due to the intervening neck segment were only detected in the AP direction at preferred and fast walking speeds. Overall the findings of the present study suggest that the trunk segment plays a critical role in regulating gait-related oscillations in all directions. Only accelerations in the direction of travel at preferred and fast speeds required additional control from the neck segment in order to enhance head stability during walking.

Acceleration↗

PubMed2006

Change in impairments in the first two treatments predicts outcome in impairments, but not in activity limitations, in subacute neck pain: an observational study.

QUESTION: Does change in impairments within and between the first two manual therapy treatments predict change in activity limitations by the end of treatment in patients with subacute neck symptoms? DESIGN: Longitudinal, observational study. PARTICIPANTS: 29 people with neck pain for more than two weeks who subsequently received >or= three treatments. OUTCOME MEASURES: Impairments measured were active neck ROM in six directions (total ROM), most limited direction of ROM (limited ROM), pain intensity, and pain location. Activity limitations were measured using the Neck Disability Index and the Patient Specific Functional Scale. Patients' perceptions of change were measured using the Global Perceived Effect Scale. Impairments and patients' perceptions were measured before and after the first two treatments and before the final treatment whereas activity limitations were measured only before the first and last treatments. RESULTS: All measures improved by the end of treatment.Between-treatment change in limited ROM predicted change in limited ROM (rs2 = 0.53 and 0.57) and total ROM (rs2 = 0.26) by the end of treatment. Within- and between-treatment change in pain location predicted change in pain location (rs2 = 0.24, 0.27,0.28, and 0.57) by the end of treatment. No significant relationships were found between change in any impairments in the first two treatments and change in activity limitations by the end of treatment. CONCLUSIONS: Change in impairments predicts change in the same impairment by the end of treatment, but not in other impairments or activity limitations. It is recommended that there assessments used to guide and refine treatment be individualised and related to the specific goals for that patient.

Activities of Daily Living↗

PubMed2006

Differences in multiple segment tremor dynamics between young and elderly persons.

BACKGROUND: Physiological tremor is an intrinsic and highly variable motor output that is sensitive to alteration in both neuromuscular function and/or changing task demands. Given that any tremor increase can severely influence fine motor performance, there is a requirement to clarify what factors lead to increased tremor. Identification of those factors that alter tremor may be particularly pertinent for elderly persons, who often exhibit a decline in postural control and amplified tremor. The aim of this study was to examine the effect of whole body posture (seated vs standing) on multiple segment tremor and forearm electromyogram (EMG) activity of younger and older individuals. METHODS: Fourteen older and 12 young participants performed a bilateral pointing task. Tremor data were collected using accelerometers attached to the forearm, hand, and finger segments of each arm. Surface EMG data were also collected from the extensor digitorum muscle of each arm. RESULTS: Although the pattern of tremor was similar between age groups, older participants exhibited increased hand and finger tremor amplitude and increased EMG activity across all postural conditions. For older individuals, tremor increases were greatest when the participant performed the task in a standing position. All age-related increases in hand and/or finger tremor were confined to increases in peak power between 8 Hz and 12 Hz. CONCLUSIONS: From a clinical perspective, these findings illustrate that using multiple segment tremor analyses can provide additional insight into potential age-related tremor differences. Additionally, the fact that postural position had a pronounced effect on tremor in older individuals suggests that body posture should be considered as a potential confounding factor when assessing tremor differences between population groups.

Adult↗

PubMed2005

Reliability of segmental accelerations measured using a new wireless gait analysis system.

The purpose of this study was to determine the inter- and intra-examiner reliability, and stride-to-stride reliability, of an accelerometer-based gait analysis system which measured 3D accelerations of the upper and lower body during self-selected slow, preferred and fast walking speeds. Eight subjects attended two testing sessions in which accelerometers were attached to the head, neck, lower trunk, and right shank. In the initial testing session, two different examiners attached the accelerometers and performed the same testing procedures. A single examiner repeated the procedure in a subsequent testing session. All data were collected using a new wireless gait analysis system, which features near real-time data transmission via a Bluetooth network. Reliability for each testing condition (4 locations, 3 directions, 3 speeds) was quantified using a waveform similarity statistic known as the coefficient of multiple determination (CMD). CMD's ranged from 0.60 to 0.98 across all test conditions and were not significantly different for inter-examiner (0.86), intra-examiner (0.87), and stride-to-stride reliability (0.86). The highest repeatability for the effect of location, direction and walking speed were for the shank segment (0.94), the vertical direction (0.91) and the fast walking speed (0.91), respectively. Overall, these results indicate that a high degree of waveform repeatability was obtained using a new gait system under test-retest conditions involving single and dual examiners. Furthermore, differences in acceleration waveform repeatability associated with the reapplication of accelerometers were small in relation to normal motor variability.

Acceleration↗

PubMed2002

Stability and skill in driving.

Two experiments addressed the relation between postural stability, perceptual sensitivity, and stability of driving performance. A vehicle was fitted with differential GPS for measuring position and speed, position sensors for measuring brake and accelerator depression, force transducers for measuring door, console and footrest bracing forces, and an accelerometer for measuring the 3D accelerations of the vehicle. In Experiment 1, we investigated whether the initiation of deceleration and the control of braking might be due to sensitivity to the perceptual variable tau, which specifies time-to-contact (TTC), and in particular, whether its first derivative, tau-dot, is used to maintain a constant deceleration profile. Using both untrained experienced drivers (EDs) and trained driving instructors from the Holden Performance Driving Centre (HPDC), results confirmed that, regardless of skill level, tau-dot was maintained at a value close to 0.5 and, as predicted by Lee [Perception 5 (1976) 437], braking was initiated when TTC approximately 5 s. In Experiment 2, we wished to quantify the purported differences in driving behaviour between EDs and HPDC instructors during a variety of everyday manoeuvres. Results indicated that instructors utilised a different cornering trajectory, a different emergency braking strategy, and were able to perform a high-speed swerve and recovery task more effectively than the EDs. In general, the instructors applied greater bracing forces using the door and console compared with EDs. The instructors also applied greater footrest forces during emergency braking than did the EDs. The greater use of bracing by instructor drivers to resist g-forces represents a strategy of active stabilisation that enhances both postural stability, as well as overall stability and consistency of driving performance. Results are discussed with regard to the dynamics of perceptual-motor coordination, and how increased stability might improve sensitivity to relevant perceptual information. We conclude that driver-training programmes that focus on increasing driver stability (as a pre-requisite for increased control) show great promise as a means to improving one's attention during driving, and hence have the potential to dramatically improve road safety in general.

Adult↗

PubMed2002

A computer-graphics model of muscle activation and contraction dynamics.

An interactive computer-graphics model of the mechanical interaction between the structural components of a Hill-type muscle model is presented. The model allows the length, velocity, and force in the contractile component, parallel elastic component, and series elastic of a generic (normalised) muscle-tendon complex to be computed from input defining instantaneous muscle stimulation and muscle-tendon length. By altering model inputs and model parameter values the user can observe corresponding model behaviour in schematic and graphical form. In this paper a general description of the model is provided together with examples of how the model can be used to simulate different contractile conditions. It is intended that the model will serve as a useful tool for demonstrating the behaviour of Hill-type muscle models.

Computer Graphics↗