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Christopher L Vaughan

Publications and source records attributed to Christopher L Vaughan.

9 recordsLinked to original sources
PubMed2006

Automatic detection of gait events using kinematic data.

The timing of heel strike (HS) and toe off (TO), the events that mark the transitions between stance and swing phase of gait, is essential when analysing gait. Force plate recordings are routinely used to identify these events. Additional instrumentation, such as force sensitive resistors, can also been used. These approaches, however, include restrictions on the number of steps that can be analyzed and further encumbrance of the subject. We developed an algorithm which automatically determines these times from kinematic data recorded by a motion capture system, which is routinely used in gait analysis laboratories. The foot velocity algorithm (FVA) uses data from the heel and toe markers and identifies features in the vertical velocity of the foot which correspond to the gait events. We verified the performance of the FVA using a large data set of 54 normal children that contained both force plate recordings and kinematic data and found errors of (mean+/-standard deviation) 16+/-15 ms for HS and 9+/-15 ms for TO. The algorithm also worked well when tested on a small number of children with spastic diplegia. We compared the performance of the FVA with another kinematic method previously described. Our foot velocity algorithm offered more accurate results and was easier to implement than the previously described one, and should be applicable in a variety of gait analysis settings.

Adolescent↗
PubMed2006

A brain-behaviour initiative for South Africa: the time is right.

BACKGROUND: Many have advocated for science and health research in developing world settings. However, there has been less focus on the value of basic and clinical neuroscience research in this context. The current paper focuses on the relevance of a brain-behaviour research initiative in South Africa. METHODS: Workshops sponsored by the University of Cape Town Research Office and by the National Research Foundation have recently focused on the state of South African basic and clinical neuroscience, and on how to strengthen research in these areas. The context of the discussion included national science and health priorities, as well as local research opportunities. RESULTS: Neuropsychiatric disorders account for the second largest proportion of the burden of disease in South Africa, but receive relatively little research funding. There is a critical need for research, and there are unique research opportunities, in areas such as trauma and resilience, impulsive behaviour (eg violence, sexual risk taking, and substance abuse), and neuroAIDS. Basic, clinical, and systems research can all make important contributions. CONCLUSION: There is a need to apprise policy-makers in developing world countries such as South Africa of the need for increased expenditure on basic and clinical neuroscience research. Local and international collaboration may be useful in increasing research capacity in South Africa, and ultimately in improving mental health services.

Mental Health↗
PubMed2006

Differences in lower limb transverse plane joint moments during gait when expressed in two alternative reference frames.

When comparing previous studies that have measured the three-dimensional moments acting about the lower limb joints (either external moments or opposing internal joint moments) during able-bodied adult gait, significant variation is apparent in the profiles of the reported transverse plane moments. This variation cannot be explained on the basis of adopted convention (i.e. external versus internal joint moment) or inherent variability in gait strategies. The aim of the current study was to determine whether in fact the frame in which moments are expressed has a dominant effect upon transverse plane moments and thus provides a valid explanation for the observed inconsistency in the literature. Kinematic and ground reaction force data were acquired from nine able-bodied adult subjects walking at a self-selected speed. Three-dimensional hip, knee and ankle joint moments during gait were calculated using a standard inverse dynamics approach. In addition to calculating internal joint moments, the components of the external moment occurring in the transverse plane at each of the lower limb joints were calculated to determine their independent effects. All moments were expressed in both the laboratory frame (LF) as well as the anatomical frame (AF) of the distal segment. With the exception of the ankle rotation moment in the foot AF, lower limb transverse plane joint moments during gait were found to display characteristic profiles that were consistent across subjects. Furthermore, lower limb transverse plane joint moments during gait differed when expressed in the distal segment AF compared to the LF. At the hip, the two alternative reference frames produced near reciprocal joint moment profiles. The components of the external moment revealed that the external ground reaction force moment was primarily responsible for this result. Lower limb transverse plane joint moments during gait were therefore found to be highly sensitive to a change in reference frame. These findings indicate that the different transverse plane joint moment profiles during able-bodied adult gait reported in the literature are likely to be explained on this basis.

Adolescent↗
PubMed2005

Froude and the contribution of naval architecture to our understanding of bipedal locomotion.

It is fascinating to think that the ideas of two 19th century naval architects could offer useful insights for 21st century scientists contemplating the exploration of our planetary system or monitoring the long-term effects of a neurosurgical procedure on gait. The Froude number, defined as Fr = v2/gL, where v is velocity, g is gravitational acceleration and L is a characteristic linear dimension (such as leg length), has found widespread application in the biomechanics of bipedal locomotion. This review of two parameters, Fr and dimensionless velocity beta = (Fr)1/2, that have served as the criterion for dynamic similarity, has been arranged in two parts: (I) historical development, including the contributions by William Froude and his son Edmund, two ship designers who lived more than 130 years ago, the classic insights of D'Arcy Wentworth Thompson who, in his magnum opus On Growth and Form, espoused the connection between mathematics and biology, and the pioneering efforts of Robert McNeill Alexander, who popularised the application of Fr to animal locomotion; and (II) selected applications, including a comparison of walking for people of different heights, exploring the effects of different gravitational fields on human locomotion, establishing the impact of pathology and the benefits of treatment, and understanding the walking patterns of bipedal robots. Although not all applications of Fr to locomotion have been covered, the review offers an important historical context for all researchers of bipedal gait, and extends the idea of dimensionless scaling of gait parameters.

History, 19th Century↗
PubMed2005

A gait nomogram used with fuzzy clustering to monitor functional status of children and young adults with cerebral palsy.

We have developed a gait nomogram based on dynamic similarity to characterize and compare neuromuscular function. We used temporal-distance data based on 669 normal participants (age range 5 to 98 years), and 78 children and young adults with spastic diplegia (43 males, 35 females; mean age 10 y 8 mo, standard deviation 3 y 11 mo, range 5 to 20 y), all of whom were independent ambulators. A new statistical algorithm known as fuzzy clustering was implemented and five cluster centres were identified, each representing distinct walking strategies adopted by children with cerebral palsy. Using just three easily obtained parameters--leg length in metres, stride length in metres, and cadence in steps per minute--our program calculates a child's dimensionless step length and step frequency, generates the individual's membership values for each of the five clusters, and plots the gait nomogram. The clinical utility of our approach has been demonstrated for two test participants with spastic diplegia, using pre- and postoperative data (one neurosurgical and one orthopaedic), where changes in membership of the five clusters provide objective measures of improvement in their neuromuscular function.

Adolescent↗
PubMed2003

Neuromaturation of human locomotion revealed by non-dimensional scaling.

When two fundamental gait parameters--step length and step frequency--are scaled non-dimensionally, thereby accounting for increases in a child's physical size, ontogenetic changes in the locomotor control strategy are revealed. We believe dimensionless velocity beta, the product of dimensionless step length and frequency, serves as a measure of neural development. It increases from the age of 18 months and reaches a plateau between 50 and 90 months, attaining the adult value of 0.45. Based on a study of 200 children, our findings lend support to a theory that posits a neuromaturation growth curve with the form: beta (t)=0.45 (1-e(-0.05t)) where t is the age in months and 0.05 is the growth coefficient.

Adolescent↗
PubMed2003

Theories of bipedal walking: an odyssey.

In this paper six theories of bipedal walking, and the evidence in support of the theories, are reviewed. They include: evolution, minimising energy consumption, maturation in children, central pattern generators, linking control and effect, and robots on two legs. Specifically, the six theories posit that: (1) bipedalism is the fundamental evolutionary adaptation that sets hominids--and therefore humans--apart from other primates; (2) locomotion is the translation of the centre of gravity along a pathway requiring the least expenditure of energy; (3) when a young child takes its first few halting steps, his or her biomechanical strategy is to minimise the risk of falling; (4) a dedicated network of interneurons in the spinal cord generates the rhythm and cyclic pattern of electromyographic signals that give rise to bipedal gait; (5) bipedal locomotion is generated through global entrainment of the neural system on the one hand, and the musculoskeletal system plus environment on the other; and (6) powered dynamic gait in a bipedal robot can be realised only through a strategy which is based on stability and real-time feedback control. The published record suggests that each of the theories has some measure of support. However, it is important to note that there are other important theories of locomotion which have not been covered in this review. Despite such omissions, this odyssey has explored the wide spectrum of bipedal walking, from its origins through to the integration of the nervous, muscular and skeletal systems.

Adult↗
PubMedDate not supplied

Role of depth in eye distance measurements: comparison of single and stereo-photogrammetry.

Photogrammetry has been used as an alternative to direct measurements to obtain facial distances for a variety of anthropometric applications. Taking measurements from photographs is less intrusive to subjects and reduces screening time, but measurements from single frontal photographs neglect depth information and may be inadequate for screening purposes. This study examined the role of depth in measurements of palpebral fissure length, interpupillary distance, inner canthal distance, and outer canthal distance using single- and stereo-photogrammetry; an operator selected landmarks on single and stereo digital photographs displayed on a computer monitor. Depth was not found to make a significant contribution to eye distances in an idealized system where the real-world coordinates of points on the eye were known from three-dimensional calibration of stereo photographs. However, the differences found between measurements taken from single frontal photographs and those from stereo-photogrammetry indicated that measurements from single photographs are prone to errors due to misalignment of the camera, the face, and the calibration instrument during image acquisition; if single photographs are to be used, the placement of these components should be carefully monitored.

Anthropometry↗