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Biomedical subjects

B J McFadyen

Publications and source records attributed to B J McFadyen.

16 recordsLinked to original sources
PubMed2005

Instrumented staircase for kinetic analyses of upper- and lower-limb function during stair gait.

The paper describes the design, technical characteristics and first results of an adjustable staircase with commercial force plates embedded in the steps and custom force transducers as part of the handrail supports. For the railing assembly, the greatest errors (< 10% of maximum signal) and cross-talk range (0.58-6.74%) were in the medial-lateral direction and were corrected using a calibration matrix. Power spectral density analyses showed free vibration frequency responses for both the railing (15 Hz) and steps (38.6 Hz) that were relatively distinct from lower applied forces recorded during stair ascent. The creation of standardised filtering protocols was therefore possible to provide step reaction force signals identical to the literature and examples of upper-limb reaction forces that have not been shown before. Such a staircase will allow a more complete study of full body contributions to stair walking across various subject populations.

Biomechanical Phenomena↗
PubMed2003

Frontal and sagittal plane analyses of the stair climbing task in healthy adults aged over 40 years: what are the challenges compared to level walking?

OBJECTIVE: This study compared stair climbing and level walking in healthy adults aged over 40 years. DESIGN: Eleven subjects performed at their comfortable speed. BACKGROUND: The number of parameters studied during stair climbing has been limited, in particular in the frontal plane. METHODS: Time-distance parameters and three-dimensional kinematic data were obtained using foot-switches and an Optotrak system. Ground reaction forces were collected with a force platform embedded in the second step of the staircase or in the ground for level walking. Relative angles were calculated using a Cardanic rotation matrix and the net moments and the powers at the ankle, knee and hip joints were estimated with an inverse dynamic approach. RESULTS: A significant longer mean cycle duration and a shorter proportion of time in stance was obtained for stair climbing as compared to level walking. Profiles of the frontal plane joint angles, moments and powers indicated a different action of the hip abductors across tasks to control the pelvis in stance. Profiles of the sagittal plane confirmed the dominant role of the knee extensors during stair climbing but revealed also a knee-hip energy generation pattern that allows the avoidance of the intermediate step. CONCLUSIONS: Results suggest environment specific adaptations of the neuro-musculo-skeletal system that should be considered in the rehabilitation of stair climbing in patients. RELEVANCE: This study highlights the challenges of stair climbing compared to level walking in a within subject design. Key features of stair climbing that are important for the rehabilitation of step management are also reported.

Adult↗
PubMed2001

Anticipatory locomotor control for obstacle avoidance in mid-childhood aged children.

The present work explored the anticipatory locomotor adjustments during obstacle avoidance by eight children aged 7--9 years. Analyses involved kinematic, kinetic and muscle mechanical power patterns at each lower limb joint, as well as electromyographic data from five muscles. The children demonstrated adult-like limb displacements and general dynamic strategies for obstacle clearance. However, when normalized to body mass, amplitudes of certain muscle power bursts related to anticipatory locomotor adjustments were decreased from those reported in the literature for adults, and an absence of the usual antagonistic knee extensor power burst at the end of the stance phase was frequently observed. The data suggest that the expression of anticipatory locomotor adjustments is still maturing during mid-childhood.

Adult↗
PubMed2000

Magnitude effects of galvanic vestibular stimulation on the trajectory of human gait.

This study examines the contribution of the vestibular system during different magnitudes of galvanic vestibular stimulation (GVS) during human walking. Anodal threshold levels of GVS were determined for right and left sides for each subject. Seven conditions were tested (no stimulation, left and right anode stimulation) at one, two and three times threshold. GVS was delivered to the mastoid processes at first heel contact and continued for the duration of the trial. All subjects responded by deviating towards the anode while walking. In addition, the magnitude of deviation increased as the stimulus intensity increased. Our results demonstrate that the vestibular system is sensitive to GVS intensity changes and responds by altering the magnitude of the response accordingly. These data provide a strong argument in support of a significant role for vestibular information during dynamic tasks.

Adult↗
PubMed2000

Three-dimensional gait analysis in women with a total hip arthroplasty.

OBJECTIVES: The purposes of this study were: (1) to identify the primary (hip) and secondary (neighboring joints) impairments during gait in subjects with a total hip arthroplasty total hip arthroplasty, (2) to determine which impairments persist when controlling for gait speed and (3) to study the relationships between primary and secondary impairments in order to describe the locomotor strategies used by these patients.DESIGN. This cross-sectional study compared the gait patterns of women with a total hip arthroplasty to those of healthy women.BACKGROUND. Several studies have reported residual hip impairments in the sagittal plane during gait after a total hip arthroplasty. There is, however, a substantial lack of knowledge in regard to the changes at the neighboring joints and in the other planes of movement.METHODS. Subjects have been examined during a gait laboratory testing session including the simultaneous recording of three-dimensional kinematics and ground reaction forces on one side, and bilateral activation of six lower limb muscles.RESULTS. A significant decrease of 20% in the hip extensor moment of force during the early stance phase was correlated (R(2)=43%) with a significant decrease of 14% in gait speed. Moreover, a significant decrease of 59% in the range of hip extension at the end of the stance phase was observed together with secondary impairments such as a significant increase in the anterior pelvic rotation, in knee flexion and in ankle dorsiflexion. Lastly, a significant increase in ipsilateral bending of the trunk during the single limb support on the operated limb was concomitant with a significant decrease in the hip abductor moment of force.CONCLUSIONS. The decrease in gait speed and the persistence of abnormal gait patterns one year after the total hip arthroplasty were associated respectively with a decrease in the hip extensor moment of force and with a decrease in the range of hip extension (sagittal plane) or in the hip abductor moment of force (frontal plane). RelevanceThe data provided in this paper may serve as guidelines to establish rehabilitation programs designed to restore optimal locomotor function.

Adaptation, Physiological↗
PubMed2000

A method of measuring three-dimensional scapular attitudes using the optotrak probing system.

OBJECTIVE: To develop a method to obtain accurate three-dimensional scapular attitudes and to assess their concurrent validity and reliability. STUDY DESIGN: In this methodological study, the three-dimensional scapular attitudes were calculated in degrees, using a rotation matrix (cyclic Cardanic sequence), from spatial coordinates obtained with the probing of three non colinear landmarks first on an anatomical model and second on a healthy subject. BACKGROUND: Although abnormal movement of the scapula is related to shoulder impingement syndrome, it is not clearly understood whether or not scapular motion impairment is a predisposing factor. Characterization of three-dimensional scapular attitudes in planes and at joint angles for which sub-acromial impingement is more likely to occur is not known. METHODS: The Optotrak probing system was used. An anatomical model of the scapula was built and allowed us to impose scapular attitudes of known direction and magnitude. A local coordinate reference system was defined with three non colinear anatomical landmarks to assess accuracy and concurrent validity of the probing method with fixed markers. Axial rotation angles were calculated from a rotation matrix using a cyclic Cardanic sequence of rotations. The same three non colinear body landmarks were digitized on one healthy subject and the three dimensional scapular attitudes obtained were compared between sessions in order to assess the reliability. RESULTS AND CONCLUSIONS: The measure of three dimensional scapular attitudes calculated from data using the Optotrak probing system was accurate with means of the differences between imposed and calculated rotation angles ranging from 1.5 degrees to 4.2 degrees. Greatest variations were observed around the third axis of the Cardanic sequence associated with posterior-anterior transverse rotations. The mean difference between the Optotrak probing system method and fixed markers was 1.73 degrees showing a good concurrent validity. Differences between the two methods were generally very low for one and two direction displacements and the largest discrepancies were observed for imposed displacements combining movement about the three axes. The between sessions variation of three dimensional scapular attitudes was less than 10% for most of the arm positions adopted by a healthy subject suggesting a good reliability. The Optotrak probing system used with a standardized protocol lead to accurate, valid and reliable measures of scapular attitudes. RELEVANCE: Although abnormal range of motion of the scapula is often related to shoulder pathologies, reliable outcome measures to quantify three-dimensional scapular motion on subjects are not available. It is important to establish a standardized protocol to characterize three-dimensional scapular motion on subjects using a method for which the accuracy and validity are known. The method used in the present study has provided such a protocol and will now allow to verify to what extent, scapular motion impairment is linked to the development of specific shoulder pathologies.

Biomechanical Phenomena↗
PubMed1999

Kinetic and energetic patterns for hindlimb obstacle avoidance during cat locomotion.

The safe control of walking over different terrains requires appropriate adaptations in the dynamic and kinematic limb patterns. To date, the study of locomotor dynamics in the cat has been confined to level, unobstructed walking. The present study extends the work of Lavoie et al. by applying linked segment analyses to estimate muscle contributions to torque and mechanical power at the hindlimb joints of two female cats during both unobstructed walking and obstacle avoidance. Data during obstacle avoidance were analyzed both when the hindlimb led in clearance and was farthest from the obstacle, and when it trailed in clearance and was closest or near to the obstacle. It was found that, in both the Far and Near obstructed conditions, the cats cleared the obstacles primarily by increasing the knee flexor torque already used during unobstructed gait. Contributions from the hip and ankle muscle groups were more variable. There was more emphasis on the hip extensors in mid to late stance, and the hip flexors generated a small amount of energy at paw-lift in the Far condition. In the Near condition, the hip extensors were employed to control hip flexion. We suggest that hip flexor generation power in mid-swing contributes to the clearance of the upcoming obstacle in the Far condition while, in the Near condition, hip flexion advances the already extended limb ahead of the obstacle. The ankle was actively dorsiflexed in the Near condition but was maintained in extension in the Far condition. The emphasis on active knee flexor control by the cat to avoid obstacles, as well as the dependence of ankle control on obstacle proximity, is similar to strategies seen for humans. However, the knee flexor strategy is innate to the cat's normal level walking control, whereas in humans active knee flexion at toe-off requires a reorganization from level, non-obstructed gait.

Adaptation, Physiological↗
PubMed1997

Anticipatory locomotor adjustments for accommodating versus avoiding level changes in humans.

The control of locomotion has been studied from various perspectives related to the tasks of pattern generation, equilibrium control or adaptation to the environment. The last of these locomotor components has received comparably less attention, specifically pertaining to anticipatory adjustments. Continuing the work which has been conducted on both humans and cats, the present paper explores the nature of the differences in anticipatory locomotor adjustments for obstacle avoidance versus the accommodation to level changes. Six subjects walked in six different environments including no obstructions, a simple obstacle, two different level changes (a platform and stairs), and a combination of an obstacle with each respective level change. Full dynamic analyses allowed comparison of muscle torques as well as muscle power generated and absorbed at the lower limb joints across conditions. It was found that the previously shown robust lower limb reorganization characterized by a knee flexor generation strategy was upheld in all conditions when the obstacle was present. Pure level changes involved an augmentation of the ongoing hip strategy inherent in normal level walking. In the compound environment of obstructed level changes, subjects chose to combine an augmentation of hip flexor power with a reorganization to active knee flexion. The results are discussed from the point of view of general principles of mechanical coordination and the exploitation of intersegmental dynamics for foot transport.

Accommodation, Ocular↗
PubMed1996

Visuomotor control when reaching toward and grasping moving targets.

Two experiments were conducted to examine the influence of target motion on the control and coordination of reaching and grasping movements. In Experiment 1 all the measures which reflected the transport or reaching phase of prehension (movement time, peak velocity, time to peak velocity, and transport tau margin) were sensitive to the velocity of the target, with subjects moving even slower than during the stationary trials, when the target was moving very slowly. Measures which reflected grasp formation such as the size of maximum aperture and the grasping tau margin were not influenced by target speed. To further investigate this dissociation between grasp and transport, different object sizes and even slower object speeds were introduced in Experiment 2. Transport results similar to those found in the first study were observed. However, in Experiment 2, both size of peak aperture and the grasping tau margin were sensitive to target movement. The results of these two studies are discussed in terms of the limitations of optic variables in the visual regulation of movement, and the independence of control of the reach and grasp phase of prehension.

Acceleration↗
PubMed1995

A preliminary analysis of the coordination of reaching, grasping, and walking.

The purpose of this investigation was to describe the strategies used by individuals when motor systems controlling locomotion and prehension must be used simultaneously to perform a task. Subjects were required to perform five tasks: walk normally, walk and pick up a small object, walk and pick up a large object, pick up a small object from a stationary standing position, and pick up a large object while standing. The grasping and walking movements were videotaped and the frequencies of various behaviors were observed (type of grasp, location of contact with the object, support leg during contact with the object, timing of gaze toward object). Characteristics of the grasp were influenced by object size, not by whether the subject was walking. Gaze was shifted to the object before initiation of reach and this pattern was not influenced by size of the object or movement of the subject. Finally, subjects preferred using an ipsilateral support leg while generating the reach, which is a deviation from normal gait patterns. Findings indicate that the motor control system may be hierarchically organized in such a way that stability of the lower limbs supersedes the control of the movement patterns of an upper limb.

Adult↗
PubMed1994

Simulated control of unilateral, anticipatory locomotor adjustments during obstructed gait.

Anticipatory adjustments of our locomotor patterns are necessary in order to negotiate our uneven daily environments. Recent work (McFadyen and Winter 1991) has shown the re-organization of lower limb mechanics for obstacle avoidance during level walking. The present work describes a model which sets the ground work for predicting how such re-organized motor patterns might be generated from stereotypic unobstructed patterns. Pattern-generating algorithms use an estimation of future contacts with obstacles to create weighting functions that modify joint angle trajectories towards new patterns capable of clearing the obstacle. Feedforward/feedback control is then used to generate the necessary joint torques. The results show that model parameters can be found to generate not only kinematic but also energetic patterns for obstacle clearance that mimic experimental results. The validity of the model with respect to human locomotor control is discussed.

Anthropometry↗
PubMed1994

A geometric analysis of muscle mechanical power with applications to human gait.

The interpretation and assessment of the biomechanical behaviour underlying complex movements such as human walking often requires that different time-series representations of the data be mentally combined. Geometrically based data presentation techniques (e.g. phase diagrams) which have been used in the past can sometimes reveal such information more easily through the link of mechanical behaviour to single plot geometries. Yet, examples such as phase or angle-angle diagrams are limited to movement description only (i.e. kinematics). In the present work, a method is introduced which graphs the factors of the muscle mechanical power equation (i.e. net muscle moment of force and relative joint angular velocity). The resulting planar space is called the "power plane" and it offers direct and simultaneous access to the relationship between specific variables associated with both movement and movement cause about a joint from the very plot geometry. In particular, the shape of the power portrait can reveal information about external influences and multiarticular interaction. The power plane diagram extends the phase diagram and is shown to reveal common patterning at the knee joint across various types of human gait which is not evident from the very different time-series plots.

Adult↗
PubMed1993

Comparison of gait between young adults fitted with the space foot and nondisabled persons.

Prosthetic feet having new keel configurations were specially designed to store deformation energy during early and midstance and release it at push-off. These prosthetic components display longitudinal symmetry favoring good energy storage/release capability in the sagittal plane. The need for inverters/everters either as independent components or within the foot structure has long been recognized. This article documents the walking and slow jogging performances of six young adults wearing below-knee prostheses fitted with the Space Foot, a flexible foot prosthesis that provides medio-lateral control at heel-strike and lateral and forward propulsion at push-off. Results indicate that the Space Foot behaves as a flexible keel foot prosthesis. Its gait performances are also good for fast walking; however, the Space Foot's actual design should be modified if used in sporting activities involving running.

Adult↗
PubMed1992

Running gait impulse asymmetries in below-knee amputees.

In running, large gait asymmetry is expected due to the inability of the foot prosthesis to comply with the kinematic demands and produce a powerful plantarflexion moment. In this work, interlimb asymmetry in below-knee (BK) amputee running gait was assessed for one rigid and three flexible keel prostheses, using vertical and anteroposterior ground reaction forces and respective impulses. Nine BK amputees and 6 controls participated in this study. The running speed was monitored by two light sensitive detectors while the ground reaction forces were measured with a Kistler force plate. Between the prosthetic side and the sound limb the impulse indicator showed greater asymmetry than the force. Interlimb asymmetry was very much present in all types of prosthesis tested but is less pronounced in the flexible keel prostheses. In the latter, the asymmetry may be associated with the force-time history modulation rather than its magnitude alone. Generally, the impulses better describe interlimb asymmetry and the forces allow a greater discrimination between prosthetic foot types.

Adolescent↗
PubMed1988

An integrated biomechanical analysis of normal stair ascent and descent.

Three normal males of similar height and weight ascended and descended a five step staircase with a riser height of 22 cm and a tread of 28 cm. EMG, force plate and cine data were collected for the stride over the second to fourth step during each mode. Kinematic and kinetic analyses were integrated with EMG to yield an interpretation of the mechanics of normal stair walking. Movement from one step to the next involved simultaneous lifting and horizontal translation of the body, and each stride showed specific phases for progression. The extensor muscles about the knee played a dominant role in progression from one step to the next in both modes coupled with the ankle plantar flexors. The total lower limb extensor pattern, called the support moment, was highly correlated between subjects and to level walking. Intra- and inter-subject variability of the motor patterns were also determined. The greatest variability was seen at the hip, while stereotypic kinetic patterns emerged at the ankle and knee for all subjects across the 24 trials of each mode.

Ankle Joint↗