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Biomedical subjects

C L Vaughan

Publications and source records attributed to C L Vaughan.

At least 19 recordsLinked to original sources
PubMed1995

Fundamental patterns of bilateral muscle activity in human locomotion.

Human gait is characterized by smooth, regular and repeating movements but the control system is complex: there are many more actuators (i.e. muscles) than degrees of freedom in the system. Statistical pattern-recognition techniques have been applied to examine muscle activity signals, but these have all concentrated exclusively on unilateral gait. We report here the application of factor analysis to the electromyographic patterns of 16 muscles (eight bilateral pairs) in ten normal subjects. Consistent with our prior work, we have established two factors, named loading response and propulsion, which correspond with important phases in the gait cycle. In addition, we have also discovered a third factor, which we have named the coordinating factor, that maintains the phase shift between the left and right sides. These findings suggest that the central nervous system solves the problem of high dimensionality by generating a few fundamental signals which control the major muscle groups in both legs.

Adult↗
PubMed1995

Effect of foot-progression angle on hip joint moments during gait.

Loosening has emerged as the most serious long-term complication of total hip replacement and torsional loading of the femoral implant has been implicated as a possible cause. In an effort to explore a strategy for minimizing this risk, the following hypothesis was tested: the foot-progression angle has a significant effect on the resultant hip moments, and particularly the internal-external rotation moment, during level walking. Twelve normal subjects performed a total of nine trials: three in which they walked normally with the right foot pointing approximately straight ahead; three in which they were told to walk with the foot internally rotated approximately 30 degrees; and three in which the foot was externally rotated about 30 degrees. The inverse dynamics approach was used to integrate the body segment parameter, kinematic and force plate data, and to solve for the resultant moment at the right hip joint. In all three conditions--foot straight, foot in, and foot out-the subjects walked at the same average speed of 1.5 (+/- 0.3) ms-1. For the flexion-extension moment (where the maximum flexion moment of 95 Nm was in good agreement with other published data), there was no significant difference between the three foot orientation conditions. For the abduction-adduction moment, the foot straight condition exhibited the classic double peak pattern with a maximum abductor moment of 57 Nm, and there was no statistically significant difference between the three curves.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Muscle response to heavy resistance exercise in children with spastic cerebral palsy.

Fourteen ambulatory children with spastic diplegia participated in a bilateral quadriceps strengthening program in an attempt to decrease the amount of knee crouch during gait. Each child exercised three times a week for six weeks using free ankle weights at a load of 65 per cent of maximum. A normal comparison group of 25 children was also tested under identical conditions. Children with cerebral palsy were significantly weaker in the quadriceps and hamstrings muscle groups than controls. Quadriceps strength increased significantly at all three angles of knee flexion as a result of the weight-training program and did not differ statistically from normal at the end of the program. Quadriceps weakness was shown to be a factor in crouch gait; restoring strength through resistance exercise may be a useful adjunct in the treatment of cerebral palsy.

Adolescent↗
PubMed1991

Cerebral palsy and rhizotomy. A 3-year follow-up evaluation with gait analysis.

A recent increase in the popularity of selective rhizotomy for reduction of spasticity in cerebral palsy has led to a demand for more objective studies of outcome and long-term follow-up results. The authors present the results of gait analysis on 14 children with spastic cerebral palsy, who underwent selective posterior rhizotomy in 1985. Sagittal plane gait patterns were studied before surgery and at 1 and 3 years after surgery using a digital camera system. The parameters measured included the range of motion at the knee and thigh, stride length, speed of walking, and cadence. The range of motion at the knee was significantly increased at 1 year after surgery and further improved to a nearly normal range at 3 years after surgery. In contrast, postoperative measurements of thigh range exceeded normal values at 1 year, but decreased toward normal range at 3 years. While improvements in range of motion continued between Years 1 and 3, the children developed a more extended thigh and knee position, which indicated a more upright walking posture. Stride length and speed of walking also improved, while cadence remained essentially unchanged. This 3-year follow-up study, the first to examine rhizotomy using an objective approach, has provided some encouraging results regarding early functional outcome.

Adolescent↗
PubMed1990

The effect of rhizotomy on movement in patients with cerebral palsy.

Selective posterior lumbar rhizotomy has recently become an alternative method for relieving spasticity in patients with spastic cerebral palsy. This procedure involves the selective sectioning of the lumbosacral posterior nerve rootlets. Because the whole nerve root is not cut, tactile and proprioceptive sensation remain intact. The present study measured the changes that occurred in 29 patients with spastic cerebral palsy 2 days before surgery and from 4 to 14 months after surgery. Each patient was used as his or her own control. In addition to the clinical evaluation of function, gait was analyzed on appropriate patients with a simple digital camera and microcomputer. The results indicated positive gains after rhizotomy. These gains were, however, dependent on the patients' abilities before surgery. The most significant improvement occurred in thigh and knee ranges of movement. This somewhat controversial new method of treating spasticity shows promise in improving the quality of life of patients with spastic cerebral palsy and in facilitating their treatment.

Adolescent↗
PubMed1989

Cycling device powered by the electrically stimulated muscles of paraplegics.

The paper describes a device (Paracycle), that uses functional neuromuscular stimulation to exercise subjects, explore FNS technology and provide paraplegics with locomotion. The Paracycle is a four-wheeled cycling vehicle that may be used as a stationary exercise device or for locomotion. It incorporates a fully adjustable seat and an electric motor to assist or retard the cycling motion, as well as speed and direction controls. Furthermore, it has braces to fasten the feet to the pedals and to stabilise the ankle, as well as gearing to enable subjects with very small forces to move the vehicle forward. Results are presented for two cases studies. Good stability of the leg was achieved during the cycling motion and this would appear to be a major advantage of functional neuromuscular stimulation cycling over functional neuromuscular stimulation gait. Important areas for future research include a better understanding of the biomechanics of functional neuromuscular stimulation cycling and the development of Paracycle-like devices that can be used independently by paraplegics.

Bicycling↗
PubMed1988

Gait analysis of cerebral palsy children before and after rhizotomy.

Over the past decade, selective posterior rhizotomy has been used successfully to reduce spasticity in patients with cerebral palsy. Although clinical evaluation of these patients revealed functional improvement following surgery, more objective analysis of the outcome of this surgery was sought. Kinematic gait analysis of 14 patients with spastic cerebral palsy was performed before and after selective posterior rhizotomy. Measurements of stride length, thigh range of motion, knee range of motion, average speed of walking, and cadence were made. Statistically significant increases in stride length, thigh range and knee range were found. Average speed was increased and cadence was virtually unchanged. These results corroborate clinical findings of improvement in gait of spastic patients with cerebral palsy following selective posterior rhizotomy.

Adolescent↗
PubMed1984

Computer simulation of human motion in sports biomechanics.

This chapter has covered some important aspects of the computer simulation of human motion in sports biomechanics. First the definition and the advantages and limitations of computer simulation were discussed; second, research on various sporting activities were reviewed. These activities included basic movements, aquatic sports, track and field athletics, winter sports, gymnastics, and striking sports. This list was not exhaustive and certain material has, of necessity, been omitted. However, it was felt that a sufficiently broad and interesting range of activities was chosen to illustrate both the advantages and the pitfalls of simulation. It is almost a decade since Miller [53] wrote a review chapter similar to this one. One might be tempted to say that things have changed radically since then--that computer simulation is now a widely accepted and readily applied research tool in sports biomechanics. This is simply not true, however. Biomechanics researchers still tend to emphasize the descriptive type of study, often unfortunately, when a little theoretical explanation would have been more helpful [29]. What will the next decade bring? Of one thing we can be certain: The power of computers, particularly the readily accessible and portable microcomputer, will expand beyond all recognition. The memory and storage capacities will increase dramatically on the hardware side, and on the software side the trend will be toward "user-friendliness." It is likely that a number of software simulation packages designed specifically for studying human motion [31, 96] will be extensively tested and could gain wide acceptance in the biomechanics research community. Nevertheless, a familiarity with Newtonian and Lagrangian mechanics, optimization theory, and computers in general, as well as practical biomechanical insight, will still be a prerequisite for successful simulation models of human motion. Above all, the biomechanics researcher will still have to bear in mind that his or her model is merely a simplified representation of the real-world system and, as such, has certain limitations. In conclusion, it is evident that the path we have followed has been an interesting and varied one. The way ahead looks equally interesting and diverse, and we can certainly look forward with confidence to the exciting challenges and benefits that computer simulation of human motion will bring.

Biomechanical Phenomena↗
PubMed1984

Biomechanics of running gait.

With the recent world-wide upsurge in running, the preponderance of research has been of a physiological nature. This is understandable when the cardiovascular benefits are considered. However, the biomechanical component is also very important, especially when trying to establish the aetiology of various musculoskeletal injuries or the principles underlying successful technique. In this paper, therefore, we are concerned with various biomechanical aspects of sprinting, middle and long distance running, and jogging. The topics covered include: the class of running gait (sprinting, jogging, ascending/descending, load carrying, treadmill); electromyography; joints; kinematics (both linear and angular); kinetics (force place, joint forces and torques, work/energy/power, air resistance); mathematical techniques and models; orthopedic acids; various pathologies; different methods of recording motion; and sports footwear and surfaces. The material should be relevant to both the elite and recreational athlete.

Amputation, Surgical↗
PubMed1983

The helicoid knee brace: a lightweight but effective support for the damaged knee.

A lightweight helicoid knee brace is described. It allows the knee to flex and extend freely in its natural pattern of movement, while absorbing valgus/varus stresses and preventing untoward rotational motion. This brace is suitable for supporting the damaged knee joint during sporting activity. Many knees disabled by post-traumatic arthritis are enabled to resume comfortable participation in golf, bowls and gardening. Over 150 patients have used the brace with satisfying results for the following indications: (i) instability due to sports and athletic injuries 93 (+/- 60 per cent) (ii) convalescence after injury or operation 12 (+/- 10 per cent). (iii) pain in the middle-aged arthritic knee where instability is usually part of the problem 45 (+/- 30 per cent).

Braces↗
PubMed1983

Simulation of a sprinter. Part I. Development of a model.

The two horizontal forces acting on a sprinter are ground reaction driving him forward and air resistance impeding him. The driving force starts off at a maximum value but decreases with increase in velocity, whereas the resisting force varies as the square of velocity. Mathematical models of these two forces have been incorporated in Newton's Second Law to yield a second order nonlinear differential equation to describe the sprinter's motion. This equation may be numerically integrated, and validation of the model has shown there is good agreement between theory and experimental data. The model may be used to characterise a runner's performance (a so-called 'sprint profile'), to pinpoint his strengths and/or weaknesses, and to predict what his time might be for a particular distance if he were able to maintain maximum velocity.

Adult↗
PubMed1983

Simulation of a sprinter. Part II. Implementation on a programmable calculator.

Although successful models have been developed to simulate a sprinter's performance, they are often complex and sophisticated, requiring a main frame environment and expensive monitoring equipment. These disadvantages preclude the wide-spread use of the models by practitioners. This paper presents a method in which the necessary data can be easily gathered--using a tape measure, six stop watches and bollards, a starting gun, and a bathroom scale. A simple algorithm is presented for calculating the parameters of a previously defined model, and implemented on hand-held programmable calculators, the Casio FX-502P and HP41C. The model calculates the sprinter's initial horizontal acceleration, maximum horizontal velocity and can be used to predict the time for any given race distance. The model can therefore be used to evaluate the sprinter's current performance as well as indicate his potential if he were able to reach and maintain maximum velocity.

Adolescent↗
PubMed1982

Smoothing and differentiation of displacement-time data: an application of splines and digital filtering.

The advent of the digital computer has allowed workers in the field of biomechanics to perform data smoothing and time differentiation numerically. The methods which are most commonly used are spline functions and digital filtering. This paper provides raw displacement-time data for an object falling in the earth's gravitational field and demonstrates the results obtained using splines and digital filtering to calculate acceleration. It is recommended that the quintic spline is a good method to use provided one has sufficient core available, and the digital filter, with some form of augmentation and/or velocity smoothing, can yield satisfactory results for the user who has a mini- or micro-computer. Listings of the digital filter and finite difference subroutines are provided.

Biomechanical Phenomena↗
PubMed1982

Closed loop problems in biomechanics. Part I--a classification system.

Biomechanics researchers have relied heavily on the inverse dynamics approach for calculating the forces and torques at human joints. However, implicit in this approach is the assumption that there are sufficient independent equations of motion to uniquely determine these unknown kinetics. There exists a class of problems, commonly referred to as closed loop problems, when there are insufficient equations and indeterminacy arises. The purposes of the present paper are (1) to develop a general classification system of closed loop problems for whole body movements; and (2) to identify the minimum number of force transducing devices necessary to uniquely determine joint kinetics for these problems. The classification system is based on the human subject's interaction with his environment and with himself. Two criteria are considered: first, the number of the subject's extremities in contact with fixed external reference systems, and second, the number of closed loops formed by those extremities not in contact with fixed external systems. Different combinations of these two criteria are examined and grouped into five cases according to the degree to which the equations of motion are over-determined, determined, or under-determined. Examples are given to illustrate the concepts. It is felt that the use of this system should aid in the understanding of joint force and torque calculations, especially with regard to the under-determined cases.

Biomechanical Phenomena↗
PubMed1982

Closed loop problems in biomechanics. Part II--an optimization approach.

A closed loop problem in biomechanics may be defined as a problem in which there are one or more closed loops formed by the human body in contact with itself or with an external system. Under certain conditions the problem is indeterminate--the unknown forces and torques outnumber the equations. Force transducing devices, which would help solve this problem, have serious drawbacks, and existing methods are inaccurate and non-general. The purposes of the present paper are (1) to develop a general procedure for solving closed loop problems; (2) to illustrate the application of the procedure; and (3) to examine the validity of the procedure. A mathematical optimization approach is applied to the solution of three different closed loop problems--walking up stairs, vertical jumping and cartwheeling. The following conclusions are drawn: (1) the method described is reasonably successful for predicting horizontal and vertical reaction forces at the distal segments although problems exist for predicting the points of application of these forces; (2) the results provide some support for the notion that the human neuromuscular mechanism attempts to minimize the joint torques and thus, to a certain degree, the amount of muscular effort; (3) in the validation procedure it is desirable to have a force device for each of the distal segments in contact with a fixed external system; and (4) the method is sufficiently general to be applied to all classes of closed loop problems.

Biomechanical Phenomena↗
PubMed1982

Selection of body segment parameters by optimization methods.

The selection of body segment parameters (BSPs) is a difficult yet essential task in many biomechanical studies. The methods used to date-cadaver, reaction board, mathematical modeling, gamma scanning, and kinematics-all have a number of drawbacks. The purpose of the present paper is to present an alternative method, based on kinematic data and optimization theory, for selecting BSPs. The design variables are the BSPs and the objective function to be minimized is based on the difference between calculated and measured distal extremity kinetics, while the equality constraints are based on Newtonian principles as well as bilateral symmetry of the BSPs. Three different activities are used to generate "optimal" sets of BSPs and these values are different, but not markedly so, from cadaver values. Further detailed investigation appears warranted.

Anthropometry↗