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Foot clearance is an important variable for understanding safe stair negotiation, but few studies have provided detailed measures of it. This paper presents a new method to calculate minimal shoe clearance during stair descent and compares it to previous literature. Seventeen healthy young subjects descended a five step staircase with step treads of 300 mm and step heights of 188 mm. Kinematic data were collected with an Optotrak system (model 3020) and three non-colinear infrared markers on the feet. Ninety points were digitized on the foot sole prior to data collection using a 6 marker probe and related to the triad of markers on the foot. The foot sole was reconstructed using the Matlab (version 7.0) "meshgrid" function and minimal distance to each step edge was calculated for the heel, toe and foot sole. Results showed significant differences in minimum clearance between sole, heel and toe, with the shoe sole being the closest and the toe the furthest. While the hind foot sole was closest for 69% of the time, the actual minimum clearance point on the sole did vary across subjects and staircase steps. This new method, and the findings on healthy young subjects, can be applied to future studies of other populations and staircase dimensions. [ABSTRACT FROM AUTHOR]

The present study examined upper and lower limb coordination during lower limb asymmetry in a split-belt walking paradigm. Eleven healthy individuals walked on a split-belt treadmill with 4 different speed ratios (2:2, 2:4, 2:6 and 2:8 km/h) and the left belt fixed at 2 km/h. Spatial (upper and lower limb movement amplitudes) and temporal (correlations between trajectories) aspects of limb movement were analyzed. Results showed that while amplitudes of the right lower limb increased and left lower limb decreased with increasing asymmetry, both upper limb amplitudes increased. Correlations between diagonal upper/lower limb trajectories increased as right belt speed became faster, suggesting increasing cross-body matching regardless of side. As the treadmill asymmetry increased, ipsilateral lower/upper limbs became more out of phase suggesting a more precise gait pattern to regulate timing between limbs. The upper limbs reached maximum horizontal displacement before the lower limbs except between the right upper limb/left lower limb for asymmetrical belt speeds. From these results, it appears the faster moving lower limb drives the motion of both upper limbs. These changes are most likely due to neural mechanisms in which upper and lower limb CPGs regulate full body movement and maintain the rhythmic locomotor pattern., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Virtual reality (VR) technology offers a new and safe way to increase practice time and provide the varied environments and constraints needed to optimize locomotor training. Our specific objectives are (1) to create a virtual environment (VE) coupled with a self-paced treadmill for locomotor training; (2) to compare temporal and distance measurements of gait during treadmill walking while looking at different scenarios of VE; and (3) to develop a protocol optimized for the training of locomotor disorders after stroke. A motorized treadmill was mounted on a six-degree-of-freedom motion platform. VEs were created using commercial software (SoftImage) and projected on a large screen, while system control was administered through the CAREN software (Motek BV). The instantaneous treadmill speed and scene progression were servo-controlled. Preliminary results show that healthy subjects are able to have full control of their own walking speed both on the treadmill and within the virtual scene, while experiencing a strong sense of presence. A street crossing training protocol has been developed for locomotor training. It is expected that locomotor training with increasingly complex VEs will allow persons with stroke to increase progressively their locomotor capacity, as required and entrained by the VE.

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.

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.

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.

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.

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.

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.