Voluntary Step Research Articles

Application of the voluntary step execution test to identify elderly fallers

To assess the use of the Voluntary Step Execution Test to identify fallers. Cross-sectional retrospective. Two self-care, residential facilities. a total of 100 healthy old volunteers (mean age = 78.4 +/- 5.7). The study investigated the use of the Voluntary Step Execution Test to identify fallers under single and dual-task conditions. Berg Balance Test (BBS) and Timed Get Up and Go (TUG) were used to assess balance and gait function. There were no significant differences found between fallers and non-fallers in BBS and TUG (50.5 +/- 4.6 versus 52.5 +/- 3.4 and 9.4 +/- 3.4 versus 7.98 +/- 2.3 respectively). There were no statistically significant differences between non-fallers and fallers across all step execution parameters under the single-task condition. However, adding cognitive load to the Voluntary Step Execution Test revealed statistically significant increases in duration of the preparatory phase, swing time and the time to foot-contact (P = 0.035;P = 0.033 and P = 0.037, respectively). Based on the coefficients of the logistic regression model participants with dual-task step execution times of > or =1,100 ms had five times the risk of falling than participants with execution times of <1,100 ms. The study provides evidence that a simple, safe measure of step execution under dual-task conditions can identify elderly individuals at risk for falls.

Reliability of voluntary step execution behavior under single and dual task conditions

BackgroundThe current study investigated the repeatability (test-retest reliability) of ground reaction force parameters recorded during a voluntary step execution under single (motor task) and dual task (motor and cognitive task) conditions for healthy adults and elderly individuals as well as the number of trials required to produce repeatable results.MethodsTwenty-four healthy adults (21–63 years old) and 16 elderly adults (66–87 years) performed a voluntary rapid step execution following a tap on their heel while standing on a force platform under single and dual task conditions on three separate occasions. The first two tests were performed 30–60 minutes apart and the third test was performed a week later. Variables analyzed from the ground reaction force data included onset latency of step initiation (initiation phase), preparation and swing phases, foot-off and foot-contact times.ResultsIntraclass correlation coefficients (ICC(2,1)) were good to excellent across all parameters and test conditions for the pooled population and for elderly (0.74–0.92 and 0.62–0.88, respectively) except for the swing phase duration where lower values were seen (0.54–0.60 and 0.32–0.64 respectively). Values were similar under single and dual task conditions.ConclusionA voluntary step execution test, performed under single and dual task conditions especially foot-off and foot-contact times, is a reliable outcome measure that may be a useful tool to asses dynamic balance function for diagnostic purposes as well as clinical intervention trials.

Choice Stepping Response and Transfer Times: Effects of Age, Fall Risk, and Secondary Tasks

Deterioration with age of physiological components of balance control increases fall risk. Avoiding a fall can also require higher level cognitive processing to select correct motor and stepping responses. Here we investigate how a competing cognitive task and an obstacle to stepping affect the initiation and execution phases of choice stepping reaction times in young and older people. Three groups were studied: young persons (YOUNG: 23-40 years, n = 20), older persons with a low risk of falls (OLR: 75-86 years, n = 18), and older persons with a high risk of falls (OHR: 78-88 years, n = 22). Four conditions were examined: choice stepping, choice stepping + obstacle, choice stepping + working memory task, and choice stepping + working memory task + obstacle. Step response and transfer times were measured for each condition, in addition to hesitant stepping, contacts with the obstacle and errors made in the memory test. Older participant groups had significantly longer response and transfer times than the young group had, and the OHR group had significantly longer response and transfer times than the OLR group had. There was a significant Group x Secondary task interaction for response time (F(2,215) = 12.6, p <.001). With the memory task, response time was minimally affected in the YOUNG (7% increase, p =.11) but was slowed significantly in the OLR fallers (42% increase, p <.001) and more so in the OHR fallers (48% increase, p <.001). The obstacle had a small but significant effect on response time (9.4%) and a larger effect on transfer time (43.3%), with no differences among the groups. Errors in stepping, performing the secondary task and contacting the obstacle increased with age and fall risk. Compared with young people, older people, and more so those at risk of falling, have an impaired ability to initiate and execute quick, accurate voluntary steps, particularly in situations where attention is divided.

Acute effects of a lateral postural assist on voluntary step initiation in patients with Parkinson's disease

Anticipatory postural adjustments (APAs) for lateral weight transfer and stability precede and accompany voluntary stepping. Patients with Parkinson's disease (PD) show delays in step initiation with altered APA characteristics that may reflect impaired interactions between posture and locomotion. The purpose of this study was to examine the influence of a lateral postural assist on step initiation in patients with early stage PD while off medication and healthy controls. Subjects performed self-paced rapid forward steps. In one condition (ASSIST), the APA was assisted at onset with a lateral pull applied to the pelvis by a motor-driven robotic system. Ground reaction forces and whole body kinematics were recorded to characterize the APA and step characteristics. Overall, PD subjects had a longer APA duration (P < 0.01) and longer first step duration (P < 0.027) than Control subjects. With the ASSIST, the APA duration for both groups was shorter (P < 0.001), the step onset time was earlier (P < 0.001), and the speed of the first step became faster for PD subjects. Postural assistance affecting the interaction between posture and locomotion may have therapeutic potential for improving movement function in patients with PD.

The challenge of the change management in an information and management systems unit: what strategy to manage the human resources?

Our research took place within the Data-processing Management and Network (DMN) of a state-owned health establishment. We presented the change and resistances to the change by making much of the concept of intentional action of change. The members of the organisation intending to introduce change should hold account of this latter in the development of their project. But how to integrate the probable resistance at the beginning of the creation of voluntary change step's design? How to overcome these obstacles and how to succeed in applying the proposed change? This study confirmed the difficulties of the intentional actions of change.

External postural perturbations induce multiple anticipatory postural adjustments when subjects cannot pre-select their stepping foot

Previous research on human balance recovery suggests that, prior to an externally triggered postural perturbation, healthy subjects can pre-select their postural response based on the environmental context, but it is unclear whether this pre-selection includes the selection of a stepping leg when performing compensatory steps. We sought to determine how pre-selecting a stepping limb affects the compensatory steps and stability of young, healthy subjects when responding to postural perturbations. Nine healthy subjects (24-37 years of age) stepped in response to backward translations of a platform under their feet when, prior to the perturbations, the subjects either knew whether they were to step with their left or right leg to a visual target (the Predictable condition) or did not know whether to step with their left or right leg until one of two targets appeared at perturbation onset (the Unpredictable condition). The Unpredictable condition also included randomly inserted trials of toes-up rotations and backward translations without targets (catch trials). The results showed that, in the Predictable condition, the subjects consistently exhibited one anticipatory postural adjustment (APA; a lateral weight shift toward the stance limb) before stepping accurately to the target with the correct leg. In the Unpredictable condition, the subjects either (1) exhibited multiple APAs, late step onsets, and forward center-of-mass (CoM) displacements that were farther beyond their base of support, or (2) exhibited an early step with only one APA and kept their CoM closer to the base of support, but also stepped more often with the incorrect leg. Thus, when the subjects had to select a stepping leg at perturbation onset, they either became more unstable and used multiple APAs to delay stepping in order to provide enough time to select the correct stepping leg, or they stepped earlier to remain stable but often stepped with the incorrect leg. In addition, responses to catch trials in the Unpredictable condition included distorted step placements that resembled steps to anticipated targets, despite allowing the subjects to step with a leg of their choice and to a location of their choice. Lastly, the subjects' voluntary stepping latencies to visual targets presented without perturbations were twice as long as their stepping latencies to the backward platform translations. Therefore, healthy subjects appear to pre-select their stepping limb, even when the perturbation characteristics are unpredictable, because relying on visual input provided at perturbation onset requires a delayed response that leads to greater instability.

Voluntary step initiation in response to a visual stimulus: effects of movement direction and age

Voluntary step initiation in response to a visual stimulus: effects of movement direction and age

7.18 Reorganisation of postural adjustments associated with rapid voluntary stepping initiation during the synchronization with an upper limb pointing task

There are various methods to quantify the flexion-relaxation phenomenon (FRP); however, there is little standardization. This study aimed to evaluate the performance of various quantification methods in terms of their ability to identify lumbar erector spinae flexion-relaxation during standing forward trunk flexion.The study was a cross-sectional design in a laboratory setting. Lumbar erector spinae activation levels were measured in 12 male participants performing full trunk flexion movements. Electromyographical signals were assessed using 16 criteria within 4 quantification methods (visual, statistical, threshold, ratio), and the sensitivity of each was assessed relative to the benchmark criterion (visual inspection of raw electromyography data).Visual inspection and most of the threshold and ratio criteria displayed the highest sensitivity. On average (SD) across the 16 criteria, FRP was positively identified 21.6 (6.2) times of 24 data sets (12 participants, 2 muscles). The visual inspection criteria positively identified FRP in all 24 trials, whereas the statistical method did not identify FRP at all (P = .44 and P = .46 for the left and right sides, respectively). The threshold and ratio criteria positively identified FRP 23.2 (1.5) and 22.5 (3.7) times, on average, respectively. Results from criteria based on differences between upright and fully flexed muscle activation tended to be conservative in FRP identification. The methods were classified as reliable or nonreliable, based on their sensitivity when specific characteristics were evident in the electromyography signals.Although many of the criteria identified FRP with 100% sensitivity, others produced unrealistic results. The latter may be suitable for other experimental designs or may require reevaluation regarding their ability to identify FRP. Although visual inspection, threshold, or ratio methods performed well and may be appropriate for either biomechanical or clinical research, the threshold method provided the optimal trade-off between performance, consistency, and feasibility for these data.

Smart Search and Analysis of ASCO Abstracts: The 2003 ASCO Pilot Breast Cancer Information Exchange (BCIE) project

6066 Background: ASCO abstracts are a leading source of cancer research information. The ASCO Breast Cancer Information Exchange (BCIE) project was developed to better organize and access abstracts in breast cancer for a faster, more precise, and targeted search. Methods: Traditional web search engines allow simple keyword-based queries. Improvements in precision and ease of use require software that “knows” the domain. We developed XML/Java models of breast cancer clinical studies, from molecular diagnostics to disease stages. From these models, we developed a study characterization form, included as a voluntary author step in the 2003 Annual Meeting abstract submission process, to capture the study clinical parameters. We also developed a corresponding user search form, publicly available onhttp://webapp.asco.org/bcie. Results: Almost 95% of breast cancer abstract first authors (352) participated, completing the web-based form to characterize their studies from a uniform descriptive variable set. Since ...

Cerebellar damage produces context-dependent deficits in control of leg dynamics during obstacle avoidance

It has been suggested that the cerebellum is an important contributor to CNS prediction and control of intersegmental dynamics during voluntary multijoint reaching movements. Leg movements subserve different behavioral goals, e.g., locomotion versus voluntary stepping, which may or may not be under similar dynamic control. The objective was to determine whether cerebellar leg hypermetria (excessive foot elevation) during obstacle avoidance in locomotion and voluntary stepping could be attributed to a particular deficit in appropriately controlling intersegmental dynamics. We compared the performance of eight individuals with cerebellar damage to eight healthy controls as they walked or voluntarily stepped in place over a small obstacle. Joint kinematics and dynamics were calculated during swing phase for both movement contexts. The kinematic analysis showed that hypermetria occurred during both walking and stepping and was associated with excessive knee flexion. When present, the amplitude of hypermetria was greater during stepping compared to walking. During stepping, subjects with cerebellar damage produced excessive knee flexor muscle torques and consequently overcompensated for interaction and gravitational torques normally used to decelerate the limb. During walking, the torque pattern was very similar to that of control subjects walking over a taller obstacle, and therefore might be a voluntary compensatory strategy to avoid tripping. Our results show that the extent of kinematic and dynamic abnormalities associated with cerebellar leg hypermetria is context-specific, with more fundamental abnormalities of leg dynamics being apparent during stepping as opposed to walking.

Effects of age, step direction, and reaction condition on the ability to step quickly.

The ability to take a step quickly is important for balance maintenance during activities of daily living. The purpose of this study was to investigate the effects of age, reaction condition, and step direction on the ability to take a volitional step as fast as possible. The performance of a voluntary step task was measured in young adult (mean age 20, SD 0.9 years), young-old adult (mean age 67, SD 3.7 years), and old adult (mean age 78, SD 2.3 years) healthy female participants. Each participant stepped as fast as possible in eight directions in response to a visual cue in a simple or choice reaction time condition. The effects of age, reaction condition, and step direction and their interactions on the primary outcome variables of response time, step liftoff, and step landing time were examined. The normal aging process progressively increased the response, liftoff, and landing times. The choice reaction time condition, compared to the simple, had significantly increased response, liftoff, and landing times. Step direction significantly affected the liftoff and landing times, with lateral, diagonal, and anterior and posterioir (A-P) times increasing, respectively. We found substantial declines in the ability to step rapidly in healthy adults as age increased. When a decision was required regarding the step direction, the step performance also declined. Step direction also significantly affected step performance. The assessment of voluntary step performance, which may be an indicator of balance ability, should include dimensions of both direction and the choice condition.

Gait intiation in bilateral vestibular loss

Objective: Gait initiation is a transient procedure between orthostatic posture and steady-state locomotion and includes anticipatory anteroposterior (AP) and lateral movements. Commands for this task are located in some levels of brain stem, which modulates activity of central pattern generator in the spinal cord. The purpose of this work was to explore the role of the vestibular system in this voluntary stepping. Methods: Six patients with chronic bilateral vestibular loss (BVL) were measured by means of a large force plate (70 cm×120 cm ) and the displacement of the center of pressure (COP) during gait initiation was calculated. Measurement parameters comprised maximum distance (MD), velocity (MV) in the AP and lateral direction as well as for pre-, first- and second-step stages, and the angle of the COP trajectory. Results: For all stages, BVL patients registered lower values for both MD and MV in the AP direction than did normal subjects. In the lateral direction, however, neither MD nor MV in BVL patients showed any difference from those of normals. The step angle of the COP trajectory was obviously reduced. Conclusion: These results suggest that in the AP direction, the vestibulospinal pathway can influence the locomotor related neural circuits, including the central pattern generator and supraspinal levels, by means of modifying the velocity and step length in order to stabilize the trunk. On the other hand, the control mechanism in the lateral direction may be different from that in the AP direction.

Assessments of axial motor control during deep brain stimulation in parkinsonian patients.

We tested the hypothesis that bilateral deep brain stimulation (DBS) in the globus pallidus internus or the subthalamic nucleus improves various components of postural and oromotor function and that some of the components correlate with changes in the Unified Parkinson's Disease Rating Scale (UPDRS) in patients with Parkinson's disease. Six patients with Parkinson's disease were evaluated for four postural and two orofacial UPDRS items, and quantitative tests of posture adjustments and oromotor control were performed while the patients were on and off DBS. Measurements of postural adjustments included reactive force and latency before a voluntary step. The oromotor assessments involved velocity and amplitude changes during voluntary jaw movement. DBS significantly improved the total UPDRS motor score by an average of 44%, which included improvement of 18 to 54% in the postural and orofacial items. DBS also decreased foot lift-off latency significantly, but it produced a variable response to the preparatory postural force in the swing limb. DBS significantly improved jaw-opening velocity by 14 to 50% and jaw opening amplitude by 5 to 41%. Significant correlations for the percentage change from off and on DBS occurred among a few UPDRS items and foot lift-off latency and jaw-opening velocities. DBS in either the globus pallidus internus or the subthalamic nucleus induces improvements in bradykinesia of specific components of postural and oromotor control, which also can be measured by the postural and orofacial UPDRS items. In some Parkinson's disease patients, DBS results in improvements in force or amplitude control, although these changes are not reflected in changes in UPDRS postural and orofacial items. A battery of quantitative and clinical tests must be used to evaluate the effects of DBS on axial motor control adequately.

Effects of fatigue on activation profiles and relative torque contribution of elbow flexor synergists.

The purpose of this study was to examine changes in elbow flexion synergies as a result of fatigue. Subjects performed a series of five isometric contractions at 10% maximum voluntary contraction step intervals. Pre- and post-fatigue surface electromyograms for the muscles were rectified, integrated, normalized, a representative equation determined using the least-squares method, and the equations numerically differentiated. The differentiated curves represent the change of excitation (and therefore, change of isometric torque) with respect to the change in resultant torque (dIEMG/dT). Pre-fatigue synergy, as indicated by the dIEMG/dT, was characterized by both co-activation and trade-off patterns. The nature of the synergy was changed as a result of fatigue. This technique, focusing upon synergistic patterns, quantifies differences in excitation profiles in a manner not previously described.

Visual stimulation affects the perception of voluntary leg movements during walking.

When a limb is used for locomotion, patterns of afferent and efferent activity related to its own motion are present as well as visual, vestibular, and other proprioceptive information about motion of the whole body. A study is reported in which it was asked whether visual stimulation present during whole-body motion can influence the perception of the leg movements propelling the body. Subjects were tested in conditions in which the stepping movements they made were identical but the amount of body displacement relative to inertial space and to the visual surround varied. These test conditions were created by getting the subjects to walk on a rotatable platform centered inside a large, independently rotatable, optokinetic drum. In each test condition, subjects, without looking at their legs, compared, against a standard condition in which the floor and drum were both stationary, their speed of body motion, their stride length and stepping rate, the direction of their steps, and the perceived force they exerted during stepping. When visual surround motion was incompatible with the motion normally associated with the stepping movements being made, changes in apparent body motion and in the awareness of the frequency, extent, and direction of the voluntary stepping movements resulted.

Coordination of head and eye movements to fixate continuous and intermittent targets

To compare head-eye co-ordination with and without a target which was visible during the movement, subjects fixated in the direction of target lamps which: (i) flashed for 40 msec followed by 1 sec darkness; (ii) were continuously illuminated for 3 sec. Ballistic head movements were produced which made up 85 and 75 per cent respectively of the gaze displacement in conditions (i) and (ii). Eye movements were a combination of voluntary step, vestibulo-ocular reflex, position correcting steps and slow movements. Saccades produced by passive head rotation were modified during similar fixation movements. Accuracy of responses to flash was high although response components showed wide variability.