Gait & Posture

Contents List

2012-04-01

Editorial Board

2012-04-01

Effects of biofeedback on secondary-task response time and postural stability in older adults

Stephanie Haggerty, Liang-Ting Jiang, Andrzej Galecki, Kathleen H. Sienko — 2012-03-14

Highlights: ► We study the effects of biofeedback on secondary task performance during standing. ► Older adults use torso-based vibrotactile feedback to minimize their body sway. ► Biofeedback improves postural metrics even while a secondary task is performed. ► Biofeedback decreases performance on secondary task.Abstract: Real-time single- and multiple-axis vibrotactile feedback of trunk motion has been shown to significantly decrease mean trunk tilt and decrease time spent outside a no vibrotactile feedback zone (dead zone) in older adults within a laboratory setting. This study aimed to determine if these improvements can translate into everyday use, during which other tasks may simultaneously demand attention. A dual-task paradigm was used in which 10 community-dwelling older adults were asked to perform standing trials in the presence of a secondary task (verbal or push-button), vibrotactile feedback, or both (dual-task). Results show that subjects significantly increased the percentage of time inside the dead zone when feedback was provided compared to when it was not during both verbal (+13.6%) and push-button (+10.1%) secondary tasks. Providing feedback also decreased RMS of trunk tilt during both secondary tasks (verbal: −0.129°; push-button: −0.138°). However, response times for secondary tasks increased (verbal: +119ms; push-button: +110ms) when feedback was provided. These results suggest that while vibrotactile feedback does increase attentional load in older adults, it can still be used effectively to improve postural metrics in high cognitive load situations.

Analysis of a kinetic multi-segment foot model. Part I: Model repeatability and kinematic validity

Dustin A. Bruening, Kevin M. Cooney, Frank L. Buczek — 2012-03-15

Highlights: ► Adding kinetics to multi-segment foot models may help diagnose some pathologies. ► We present a three segment kinetic foot model and thorough analysis of performance. ► Normative joint excursions are comparable to previously published studies. ► The hindfoot coronal plane was the least repeatable segment/orientation.Abstract: Kinematic multi-segment foot models are still evolving, but have seen increased use in clinical and research settings. The addition of kinetics may increase knowledge of foot and ankle function as well as influence multi-segment foot model evolution; however, previous kinetic models are too complex for clinical use. In this study we present a three-segment kinetic foot model and thorough evaluation of model performance during normal gait. In this first of two companion papers, model reference frames and joint centers are analyzed for repeatability, joint translations are measured, segment rigidity characterized, and sample joint angles presented. Within-tester and between-tester repeatability were first assessed using 10 healthy pediatric participants, while kinematic parameters were subsequently measured on 17 additional healthy pediatric participants. Repeatability errors were generally low for all sagittal plane measures as well as transverse plane Hindfoot and Forefoot segments (median<3°), while the least repeatable orientations were the Hindfoot coronal plane and Hallux transverse plane. Joint translations were generally less than 2mm in any one direction, while segment rigidity analysis suggested rigid body behavior for the Shank and Hindfoot, with the Forefoot violating the rigid body assumptions in terminal stance/pre-swing. Joint excursions were consistent with previously published studies.

Analysis of a kinetic multi-segment foot model part II: Kinetics and clinical implications

Dustin A. Bruening, Kevin M. Cooney, Frank L. Buczek — 2011-12-26

Highlights: ► The addition of kinetics may help diagnose some foot and ankle disorders. ► We have provided normative multi-segment foot joint moments and powers. ► Kinetics can be incorporated into other multi-segment foot models during push off. ► Power transfer occurs between the 1st metatarsophalangeal and mid-tarsal joints.Abstract: Kinematic multi-segment foot models have seen increased use in clinical and research settings, but the addition of kinetics has been limited and hampered by measurement limitations and modeling assumptions. In this second of two companion papers, we complete the presentation and analysis of a three segment kinetic foot model by incorporating kinetic parameters and calculating joint moments and powers. The model was tested on 17 pediatric subjects (ages 7–18years) during normal gait. Ground reaction forces were measured using two adjacent force platforms, requiring targeted walking and the creation of two sub-models to analyze ankle, midtarsal, and 1st metatarsophalangeal joints. Targeted walking resulted in only minimal kinematic and kinetic differences compared with walking at self selected speeds. Joint moments and powers were calculated and ensemble averages are presented as a normative database for comparison purposes. Ankle joint powers are shown to be overestimated when using a traditional single-segment foot model, as substantial angular velocities are attributed to the mid-tarsal joint. Power transfer is apparent between the 1st metatarsophalangeal and mid-tarsal joints in terminal stance/pre-swing. While the measurement approach presented here is limited to clinical populations with only minimal impairments, some elements of the model can also be incorporated into routine clinical gait analysis.

Computerized gait analysis in Legg–Calvé–Perthes disease—Analysis of the sagittal plane

B. Westhoff, F. Martiny, A. Reith, R. Willers, R. Krauspe — 2012-01-13

Highlights: ► In florid stage significantly impaired sagittal plane kinematics on involved and non-involved side. ► Significantly reduced power generation and absorption mainly at the level of involved hip. ► In final stage impaired global hip function in 46, 2% of patients.Abstract: Current follow-up- and outcome-evaluations of Legg–Calvé–Perthes disease (LCPD) are based on subjective measures of function, clinical and radiological parameters. The objective of this study was to evaluate the sagittal plane kinematics and the effect on hip joint loading on the affected hip in children with LCPD.Materials and methods: Computerized gait analysis was performed in 49 LCPD patients aged ≥5 years with unilateral hip involvement. Sagittal plane kinematics and kinetics were compared to a group of healthy children (n=30).Results: Kinematics: a significantly increased anterior tilt and range of motion (ROM) of the pelvis combined with a marked reduction of the extension of the involved hip joint compared to the control group was observed. The increased ROM of the contralateral hip results from increased maximum flexion. Power generation: overall significantly decreased on the involved side during florid stage. Global hip function: significantly reduced hip flexor index of the involved hip; 46.2% of the patients in advanced stage, although having no significant changes in kinematics – except increased anterior pelvic tilt – had a pathologic HFI.Conclusion: Sagittal plane hip function is significantly impaired in florid and advanced LCPD. The results of this study will lead to further investigations into whether this development can be prevented by conservative or operative treatment thus improving function and long-term prognosis.

A multi-segment foot model based on anatomically registered technical coordinate systems: Method repeatability in pediatric feet

Prabhav Saraswat, Bruce A. MacWilliams, Roy B. Davis — 2011-12-22

Highlights: ► We present a new pediatric foot model utilizing static anatomical registrations. ► A plaster mold was used to ensure consistent foot position. ► Three clinicians modeled at separate dates to measure intra-clinician variability. ► Two clinicians modeled same subjects to measure inter-clinician variability. ► Intra-clinician and inter-clinician joint angle variability were less than 4°.Abstract: Several multi-segment foot models to measure the motion of intrinsic joints of the foot have been reported. Use of these models in clinical decision making is limited due to lack of rigorous validation including inter-clinician, and inter-lab variability measures. A model with thoroughly quantified variability may significantly improve the confidence in the results of such foot models. This study proposes a new clinical foot model with the underlying strategy of using separate anatomic and technical marker configurations and coordinate systems. Anatomical landmark and coordinate system identification is determined during a static subject calibration. Technical markers are located at optimal sites for dynamic motion tracking. The model is comprised of the tibia and three foot segments (hindfoot, forefoot and hallux) and inter-segmental joint angles are computed in three planes. Data collection was carried out on pediatric subjects at two sites (Site 1: n=10 subjects by two clinicians and Site 2: five subjects by one clinician). A plaster mold method was used to quantify static intra-clinician and inter-clinician marker placement variability by allowing direct comparisons of marker data between sessions for each subject. Intra-clinician and inter-clinician joint angle variability were less than 4°. For dynamic walking kinematics, intra-clinician, inter-clinician and inter-laboratory variability were less than 6° for the ankle and forefoot, but slightly higher for the hallux. Inter-trial variability accounted for 2–4° of the total dynamic variability. Results indicate the proposed foot model reduces the effects of marker placement variability on computed foot kinematics during walking compared to similar measures in previous models.

Compressive tibiofemoral force during crouch gait

Katherine M. Steele, Matthew S. DeMers, Michael H. Schwartz, Scott L. Delp — 2011-12-29

Abstract: Crouch gait, a common walking pattern in individuals with cerebral palsy, is characterized by excessive flexion of the hip and knee. Many subjects with crouch gait experience knee pain, perhaps because of elevated muscle forces and joint loading. The goal of this study was to examine how muscle forces and compressive tibiofemoral force change with the increasing knee flexion associated with crouch gait. Muscle forces and tibiofemoral force were estimated for three unimpaired children and nine children with cerebral palsy who walked with varying degrees of knee flexion. We scaled a generic musculoskeletal model to each subject and used the model to estimate muscle forces and compressive tibiofemoral forces during walking. Mild crouch gait (minimum knee flexion 20–35°) produced a peak compressive tibiofemoral force similar to unimpaired walking; however, severe crouch gait (minimum knee flexion>50°) increased the peak force to greater than 6 times body-weight, more than double the load experienced during unimpaired gait. This increase in compressive tibiofemoral force was primarily due to increases in quadriceps force during crouch gait, which increased quadratically with average stance phase knee flexion (i.e., crouch severity). Increased quadriceps force contributes to larger tibiofemoral and patellofemoral loading which may contribute to knee pain in individuals with crouch gait.

Residual gait deviations in adolescents treated during infancy for unilateral developmental dysplasia of the hip using Pemberton's osteotomy

Chu-Fen Chang, Ting-Ming Wang, Jyh-Horng Wang, Shier-Chieg Huang, Tung-Wu Lu — 2012-03-19

Highlights: ► Residual gait deviations were found in adolescents treated during infancy for DDH. ► Pelvic deviations were the major contributor to the residual gait changes. ► These gait changes increased loading rates at both affected and unaffected hips.Abstract: Early reduction using Pemberton's osteotomy has been suggested for treating DDH but no data on the long-term residual gait changes in such patients are available in the literature. This study aimed to bridge the gap by performing quantitative gait analysis on eleven females (age: 10.6±1.0 years) who were treated for unilateral DDH using open reduction with Pemberton's osteotomy at 1.6±0.5 years of age, and eleven age-matched healthy controls. Walking at a normal speed, the Pemberton group displayed significantly more anterior tilt, hiking at the affected side and rotation towards the unaffected side of the pelvis, and more knee flexion and ankle dorsiflexion in the affected limb. With this asymmetrical gait, they appeared to reduce the demands on the hip flexors and abductors, and knee extensors in the affected limb, which might have been involved during the osteotomy, but increased compensatory efforts from the hip extensors, ankle plantarflexors and knee flexors in the unaffected limb.

Kinematic and kinetic characteristics of Masai Barefoot Technology footwear

Masashi Taniguchi, Hiroshige Tateuchi, Toru Takeoka, Noriaki Ichihashi — 2012-01-12

Highlights: ► We examined the immediate effects of using Masai Barefoot Technology (MBT) footwear in the lower extremity in healthy males. ► MBT shoes could assist with shock absorption and maintain the progression force. ► MBT shoes might be effective to improve shock absorption and assist ankle push-off.Abstract: The Masai Barefoot Technology (MBT) shoe was developed as a walking device to improve gait stability and reduce the joint load. Kinematic changes with MBT shoes have been reported; however, kinetic characteristics with MBT shoes have not been adequately assessed. The purpose of this study was to investigate the immediate effects of using MBT footwear on the kinetic and kinematic changes in the lower extremity in healthy males. Fourteen healthy male subjects (mean age: 25.6±5.1 years) underwent three-dimensional gait analysis. Ground reaction forces (GRF) during the shock absorption phase were significantly decreased with MBT shoes compared with stable shoes. Gait with the MBT shoes showed significantly decreased knee extension angle in the early stance phase, a decreased hip extension angle, and an increased ankle dorsiflexion angle in the late stance phase. The peak value of the ankle planter moment, ankle negative power, and vertical component of the GRF significantly decreased with MBT shoes in the late stance phase compared with stable shoes. Therefore, MBT shoes could assist with shock absorption in the early stance phase and maintain the progression force while reducing joint moment and power. The results of this study suggest that MBT shoes might be effective to improve shock absorption, increase knee extensor muscle activity, and assist ankle push-off.

Body-worn motion sensors detect balance and gait deficits in people with multiple sclerosis who have normal walking speed

2012-01-25

Highlights: ► Stopwatch-timed mobility tests are insensitive to mild multiple sclerosis (MS). ► We compared timed mobility tests with instrumented body-worn sensors in the clinic. ► Stopwatch timed measures did not distinguish mild MS from control subjects. ► The sensors found significant differences in balance and gait parameters in MS. ► Body-worn sensors may prove a useful and practical MS mobility outcome measure.Abstract: While balance and gait limitations are hallmarks of multiple sclerosis (MS), standard stopwatch-timed measures practical for use in the clinic are insensitive in minimally affected patients. This prevents early detection and intervention for mobility problems. The study sought to determine if body-worn sensors could detect differences in balance and gait between people with MS with normal walking speeds and healthy controls. Thirty-one MS and twenty-eight age- and sex-matched control subjects were tested using body-worn sensors both during quiet stance and gait (Timed Up and Go test, TUG). Results were compared to stopwatch-timed measures. Stopwatch durations of the TUG and Timed 25 Foot Walk tests were not significantly different between groups. However, during quiet stance with eyes closed, people with MS had significantly greater sway acceleration amplitude than controls (p=0.02). During gait, people with MS had greater trunk angular range of motion in roll (medio-lateral flexion, p=0.017) and yaw (axial rotation, p=0.026) planes. Turning duration through 180° was also longer in MS (p=0.031). Thus, body-worn motion sensors detected mobility differences between MS and healthy controls when traditional timed tests could not. This portable technology provides objective and quantitative mobility data previously not obtainable in the clinic, and may prove a useful outcome measure for early mobility changes in MS.

Quantifying individual muscle contribution to three-dimensional reaching tasks

2012-03-14

Highlights: ► We analyze the muscle contributions to control of the individual DOFs during 3D reaching. ► The contributions agree with the responses elicited during electrostimulation. ► The task specific kinematics determine the individual muscle contributions. ► Muscle action effects on un-spanned joints are confirmed.Abstract: We investigated the individual muscle contribution to arm motion to better understand the complex muscular coordination underlying three-dimensional (3D) reaching tasks of the upper limb (UL). The individual contributions of biceps, triceps, deltoid anterior, medius, posterior and pectoralis major to the control of specific degrees of freedom (DOFs) were examined: using a scaled musculoskeletal model, the muscle excitations that reproduce the kinematics were calculated using computed muscle control and a forward simulation was generated. During consequent perturbation analyses, the muscle excitation of selected muscles was instantaneously increased and the resulting effect on the specific DOF was studied to quantify the muscle contribution. The calculated muscle contributions were compared to the responses elicited during electrical stimulation experiments. Innovative in our findings is that muscle action during reaching clearly depended on the reaching trajectory in 3D space. For the majority of the muscles, the magnitude of muscle action changed and even reversed when reaching to different heights and widths. Furthermore, muscle effects on non spanned joints were reported. Using a musculoskeletal model and forward simulation techniques, we demonstrate individual position-dependent muscle contributions to 3D joint kinematics of the UL.

Vision and agility training in community dwelling older adults: Incorporating visual training into programs for fall prevention

Rebecca J. Reed-Jones, Sandor Dorgo, Maija K. Hitchings, Julia O. Bader — 2011-12-29

Highlights: ► We examined the effects of visual training on mobility of older adults. ► A 12 week exercise intervention with visual training was used. ► The Nintendo Wii® was used as the tool for visual training. ► Visual training group significantly reduced collisions with obstacles. ► Visual training may be an important aspect for fall prevention programs.Abstract: This study aimed to examine the effect of visual training on obstacle course performance of independent community dwelling older adults. Agility is the ability to rapidly alter ongoing motor patterns, an important aspect of mobility which is required in obstacle avoidance. However, visual information is also a critical factor in successful obstacle avoidance. We compared obstacle course performance of a group that trained in visually driven body movements and agility drills, to a group that trained only in agility drills. We also included a control group that followed the American College of Sports Medicine exercise recommendations for older adults. Significant gains in fitness, mobility and power were observed across all training groups. Obstacle course performance results revealed that visual training had the greatest improvement on obstacle course performance (22%) following a 12 week training program. These results suggest that visual training may be an important consideration for fall prevention programs.

Gait symmetry and velocity differ in their relationship to age

Kara K. Patterson, Neelesh K. Nadkarni, Sandra E. Black, William E. McIlroy — 2012-02-02

Highlights: ► Gait velocity declines with age. ► Measures of swing time, stance time and step length symmetry are not significantly associated with age in healthy adults or stroke survivors. ► Therefore, gait symmetry ratios can inform about effects of disease on the control of gait without the confound of age.Abstract: Measurement of gait is essential for identifying underlying deficits contributing to gait dysfunction, guiding clinical decisions and measuring rehabilitation outcomes. Velocity is commonly used to measure gait, however, its interpretation in patient populations is complicated by the confound of age. Gait symmetry may be an additional and valuable measure since it may not feature the same age-related changes as velocity. The purpose of this study was to determine if gait symmetry is related to age.Methods: Spatiotemporal gait parameters were recorded for 172 individuals with stroke and 81 healthy adults walking across a pressure sensitive mat at their preferred speed. Swing time, stance time and step length symmetry ratios were calculated. The relationship of age to velocity and symmetry was examined using Pearson correlations.Results: There was a significant negative association between velocity and age in the healthy group (r=−0.57, p<0.01). There were no significant relationships between age and any of the three symmetry ratios for either the stroke or healthy groups.Conclusions: The main finding of the current study is that gait symmetry ratios are not significantly associated with age in either a healthy or a post-stroke group. Gait symmetry ratios may therefore, allow the clinician and the researcher to make judgments about the effects of disease (such as stroke) on the control of an individual's gait without the confound of age.

Evaluation of robot-assisted gait training using integrated biofeedback in neurologic disorders

Oliver Stoller, Marco Waser, Lukas Stammler, Corina Schuster — 2012-01-03

Highlights: ► This biofeedback approach cannot detect progress during robot-assisted gait training (RAGT). ► Hip flexion activity decreased following 8 RAGT sessions. ► Knee extension activity increased following 8 RAGT sessions. ► Consider these findings when refining existing or developing new biofeedback strategies for RAGT.Abstract: Background: Neurological disorders lead to walking disabilities, which are often treated using robot-assisted gait training (RAGT) devices such as the driven gait-orthosis Lokomat. A novel integrated biofeedback system was developed to facilitate therapeutically desirable activities during walking. The aim of this study was to evaluate the feasibility to detect changes during RAGT by using this novel biofeedback approach in a clinical setting for patients with central neurological disorders.Methods: 84 subjects (50 men and 34 women, mean age of 58±13years) were followed over 8 RAGT sessions. Outcome measures were biofeedback values as weighted averages of torques measured in the joint drives and independent parameters such as guidance force, walking speed, patient coefficient, session duration, time between sessions and total treatment time.Results: Joint segmented analysis showed significant trends for decreasing hip flexion activity (p≤.003) and increasing knee extension activity (p≤.001) during RAGT sessions with an intercorrelation of r=−.43 (p≤.001). Further associations among independent variables were not statistically significant.Conclusion: This is the first study that evaluates the Lokomat integrated biofeedback system in different neurological disorders in a clinical setting. Results suggest that this novel biofeedback approach used in this study is not able to detect progress during RAGT. These findings should be taken into account when refining existing or developing new biofeedback strategies in RAGT relating to appropriate systems to evaluate progress and support therapist feedback in clinical settings.

Motor learning benefits of self-controlled practice in persons with Parkinson's disease

Suzete Chiviacowsky, Gabriele Wulf, Rebecca Lewthwaite, Tiago Campos — 2012-01-03

Highlights: ► Persons with Parkinson's disease practice a balance task (stabilometer). ► We compare learning in groups with and without self-controlled use of a balance pole. ► Self-controlled use of the pole enhances learning compared with no self-control. ► Self-controlled practice increases motivation and reduces nervousness. ► Satisfying people's need for autonomy promotes learning.Abstract: The present study examined the effectiveness of a training method to enhance balance in people with PD, which could potentially reduce their risk for falls. Specifically, we investigated whether the benefits of the self-controlled use of a physical assistance device for the learning of a balance task, found previously in healthy adults, would generalize to adults with PD. Twenty-eight individuals with PD were randomly assigned to one of two groups, a self-control and a yoked (control) group. The task required participants to stand on a balance platform (stabilometer), trying to keep the platform as close to horizontal as possible during each 30-s trial. In the self-control group, participants had a choice, on each of 10 practice trials, to use or not to use a balance pole. Participants in the yoked group received the same balance pole on the schedule used by their counterparts in the self-control group, but did not have a choice. Learning was assessed one day later by a retention test. The self-control group demonstrated more effective learning of the task than the yoked group. Questionnaire results indicated that self-control participants were more motivated to learn the task, were less nervous, and less concerned about their body movements relative to yoked participants. Possible reasons for the learning benefits of self-controlled practice, including a basic psychological need for autonomy, are discussed.

A linear soft tissue artefact model for human movement analysis: Proof of concept using in vivo data

2012-01-09

Highlights: ► We linearly modelled soft tissue artefact (STA) for walking, cutting and hopping. ► The linear model parameters were computed from bone pin data using PCA. ► Modelling errors were reduced from cm to mm scale compared to a rigid-body model. ► 95% of the STA variance are captured with a five degrees-of-freedom linear model. ► STA is dominated by rigid-body motions rather than deformations.Abstract: We investigated the accuracy of a linear soft tissue artefact (STA) model in human movement analysis. Simultaneously recorded bone-mounted pin and skin marker data for the thigh and shank during walking, cutting and hopping were used to measure and model the motion of the skin marker clusters within anatomical reference frames (ARFs). This linear model allows skin marker movements relative to the underlying bone contrary to a rigid-body assumption. The linear model parameters were computed through a principal component analysis, which revealed that 95% of the variance of the STA motion for the thigh was contained in the first four principal components for all three tasks and all subjects. For the shank, 95% of the variance was contained in the first four principal components during walking and cutting and first five during hopping. For the thigh, the maximum residual artefact was reduced from 27.0mm to 5.1mm (walking), 22.7mm to 3.0mm (cutting) and 16.2mm to 3.5mm (hopping) compared to a rigid-body assumption. Similar reductions were observed for the shank: 24.2mm to 1.9mm (walking), 20.3mm to 1.9mm (cutting) and 14.7mm to 1.8mm (hopping). A geometric analysis of the first four principal components revealed that, within the ARFs, marker cluster STA is governed by rigid-body translations and rotations rather than deformations. The challenge remains, however, in finding the linear model parameters without bone pin data, but this investigation shows that relatively few parameters in a linear model are required to model the vast majority of the STA movements.

The minimal clinically important difference for the Gait Profile Score

2012-01-09

Highlights: ► A minimally clinically important difference is derived for the Gait Profile Score. ► Based on variability of typically developing children. ► Based on difference between Functional Assessment Questionnaire levels. ► MCID is 1.6°.Abstract: The minimally clinically important difference (MCID) is an important concept for interpreting the results of clinical research. This paper proposes a rationale for defining an MCID for the Gait Profile Score (GPS) based on an analysis of the difference in median GPS for children classified at different levels of the Functional Assessment Questionnaire. A strong linear correlation between median score and FAQ level was found. An MCID of 1.6° is therefore suggested, reflecting the mean difference between adjacent FAQ levels. Comparison of this value with (i) the standard deviation of GPS from typically developing children (1.4°) and (ii) the percentage of the difference between the median GPS for each FAQ level and that for typically developing children offers further support to suggest that 1.6° is an appropriate figure.

Online control of anticipated postural adjustments in step initiation: Evidence from behavioral and computational approaches

L. Mouchnino, G. Robert, H. Ruget, J. Blouin, M. Simoneau — 2012-01-13

Highlights: ► Online control of the anticipatory postural adjustments (APAs) during gait initiation was investigated. ► APAs were modified online when a body perturbation occurred during their execution. ► Changes in the APAs were triggered when a mismatch between passively originated forces and those actively specified by the central command was detected.Abstract: Anticipatory postural adjustments (APAs) prior to step execution are thought to be immutable once released. Here we challenge this assumption by testing whether APAs can be modified online if a body perturbation occurs during execution. Two directions of perturbation (resisting and assisting) relative to the body weight transfer were used during the execution of APAs. We found that APAs are modified online (increase in both ground pressure and muscle activity) to compensate for resisting perturbations. The outcomes of a biomechanical model confirmed that the early changes in the APAs resulted from an active control of the APAs and were not merely mechanical consequences of the perturbation. However, no modification of the initial feedforward command was observed for assisting perturbations. The motor command changes for the resisting perturbation may originate from the mismatch between passively originated forces and those actively specified by the central command when acting in the opposite direction. The absence of a mismatch in the assisting perturbation might explain why the central nervous system was not prompted to modify the APAs in this condition.

Gait and menstrual cycle: Ovulating women use sexier gaits and walk slowly ahead of men

Nicolas Guéguen — 2012-01-16

Highlights: ► Gait and women’ walking were examined according to their menstrual cycle. ► The amount of time that women spent walking ahead a male was measured. ► The sexiness of their gaits recorded with the help of a spy-camera was evaluated by males. ► Ovulation phase was measured with an LH salivary test. ► Near ovulation, women walked slower and their gait was subjectively rated as sexier.Abstract: Previous research has demonstrated that women's physical appearance or sexual interest is different across the menstrual cycle. However, the nonverbal behavior of women toward men according to their menstrual cycle has not been previously explored. In this study, the gait of women walking ahead a male confederate was recorded with the help of a spy-camera. The amount of time that women spent walking was the first dependent variable whereas the extent to which the women were perceived to be sexually attractive by two judges was the second dependent variable. Comparisons were performed according to the women's ovulation phase measured with an LH salivary test. Near ovulation, it was found that women walked slower and their gait was subjectively rated as sexier. Such behaviors were interpreted as unconscious desires of women near ovulation to reinforce their attractiveness in order to attract more men and to increase their choice of a partner.

Direction specific preserved limits of stability in early progressive supranuclear palsy: A dynamic posturographic study

Mohan Ganesan, Shaik Afsar Pasha, Pramod Kumar Pal, Ravi Yadav, Anupam Gupta — 2012-01-09

Highlights: ► Patients with PSP had impaired dynamic balance indices compared to controls. ► The overall limits of stability (LOS) was decreased in PSP compared to controls. ► In early PSP, the LOS was preserved in the left and forward-left directions. ► Evidence of lateralization for balance and postural control in normal subjects.Abstract: Objectives: To quantitatively detect the nature of balance impairment in patients with progressive supranuclear palsy (PSP) using dynamic posturography.Methods: Twenty clinically diagnosed PSP patients (8 women, 12 men; age: 62.1±7.7 years; duration: 2.6±1.3 years) and 20 healthy controls were studied. All subjects were right side dominant. They were evaluated by dynamic posturography (Biodex, USA). The measurements included (i) balance indices: ability to control balance in all directions (overall balance index, OBI), front to back (anterior–posterior index, API) and side-to-side (medio-lateral index, MLI), and (ii) the limits of stability (LOS) in 8 directions: forward (FW), backward (BW), right (RT), left (LT), forward-right (FW-RT), forward-left (FW-LT), backward-right (BW-RT) and backward-left (BW-LT).Results: Compared to controls, patients showed significantly higher OBI (p<0.001), API (p=0.003) and MLI (p<0.001), implying impaired balance. The total LOS score was significantly lower (implying poor stability) in PSP than in controls (18.3±7.3 vs. 28.4±8.5, p<0.001). Patients took significantly longer time to complete LOS test (262.7±33.0s vs. 135.4±20.6s, p<0.001). Direction-wise analysis showed that PSP patients had significantly lower LOS scores in FW, BW, RT, FW-RT, BW-RT and BW-LT directions compared to controls. However the scores in LT and FW-LT did not differ significantly.Conclusions: PSP patients showed impaired balance indices and decreased overall LOS compared to controls. Though LOS is affected in PSP, the scores in the left (non-dominant side) and forward-left (non-dominant forward diagonal) directions were preserved.

Enhanced somatosensory information decreases postural sway in older people

2012-01-16

Highlights: ► We examined the effects of textured insole surfaces on changing postural sway of young and older people during standing. ► We tested people under conditions of vision, no vision, firm and foam surfaces. ► The textured insole surface decreased postural sway in older people especially while standing on a foam surface with no vision. ► Changes in postural sway were attributed due to the enhancement of the somatosensory information received from the feet.Abstract: The somatosensory system plays an important role in balance control and age-related declines in somatosensory function have been implicated in falls incidence. Different types of insole devices have been developed to enhance somatosensory information and improve postural stability. However, they are often too complex and expensive to integrate into daily life and textured insole surfaces may provide an inexpensive and accessible means to enhance somatosensory input. This study investigated the effects of textured insole surfaces on postural sway in ten younger and seven older participants performing standing balance tests on a force plate under three insole surface conditions: (1) barefoot; (2) with hard; and (3), soft textured insole surfaces. With each insole surface, participants were tested under two vision conditions (eyes open, closed) on two standing surfaces (firm, foam). Four 30s trials were collected for different combinations of insole surface, standing surface and vision. Centre of pressure measurements included the range and standard deviation of anterior–posterior and medial–lateral displacement, path length and the 90% confidence elliptical area. Results revealed a significant Group*Surface*Insole interaction for five of the dependent variables. Compared to younger individuals, postural sway was greater in older people on both standing surfaces in the barefoot condition. However, both textured insole surfaces reduced postural sway for the older group especially in the eyes closed condition on a foam surface. These findings suggest that textured insole surfaces can reduce postural sway in older people, particularly during more challenging balance tasks. Textured insole surfaces may afford a low-cost means of decreasing postural sway, providing an important intervention in falls prevention.

Ambulatory measurement of the scapulohumeral rhythm: Intra- and inter-operator agreement of a protocol based on inertial and magnetic sensors

I. Parel, A.G. Cutti, G. Fiumana, G. Porcellini, G. Verni, A.P. Accardo — 2012-02-02

Highlights: ► We developed a motion analysis protocol named ISEO for the ambulatory measure of the scapulohumeral rhythm. ► We assessed ISEO intra and inter-operator agreement involving 2 operators and 40 subjects. ► We quantified the similarity of scapulohumeral patterns and the smallest detectable difference in scapula range of motion. ► The similarity was acceptable for most of the scapula rotations. ► The smallest detectable difference ranged from 4.4° to 8.6°.Abstract: To measure the scapulohumeral rhythm (SHR) in outpatient settings, the motion analysis protocol named ISEO (INAIL Shoulder and Elbow Outpatient protocol) was developed, based on inertial and magnetic sensors. To complete the sensor-to-segment calibration, ISEO requires the involvement of an operator for sensor placement and for positioning the patient's arm in a predefined posture. Since this can affect the measure, this study aimed at quantifying ISEO intra- and inter-operator agreement. Forty subjects were considered, together with two operators, A and B. Three measurement sessions were completed for each subject: two by A and one by B. In each session, the humerus and scapula rotations were measured during sagittal and scapular plane elevation movements. ISEO intra- and inter-operator agreement were assessed by computing, between sessions, the: (1) similarity of the scapulohumeral patterns through the Coefficient of Multiple Correlation (CMC2), both considering and excluding the difference of the initial value of the scapula rotations between two sessions (inter-session offset); (2) 95% Smallest Detectable Difference (SDD95) in scapula range of motion.Results for CMC2 showed that the intra- and inter-operator agreement is acceptable (median≥0.85, lower-whisker ≥0.75) for most of the scapula rotations, independently from the movement and the inter-session offset. The only exception is the agreement for scapula protraction–retraction and for scapula medio-lateral rotation during abduction (inter-operator), which is acceptable only if the inter-session offset is removed. SDD95 values ranged from 4.4° to 8.6° for the inter-operator and between 4.9° and 8.5° for the intra-operator agreement.In conclusion, ISEO presents a high intra- and inter-operator agreement, particularly with the scapula inter-session offset removed.

Effects of explicit prioritization on dual task walking in patients with Parkinson's disease

2012-02-20

Highlights: ► We examined the effects of explicit prioritization on dual tasking during walking. ► Patients with Parkinson's disease (PD) and healthy older adult controls were tested. ► Task prioritization abilities did not differ in the patients and controls. ► Patients without cognitive problems and controls used cognitive resources similarly. ► By default, both groups naturally apply some form of the posture second strategy.Abstract: Patients with Parkinson's disease (PD) have difficulties performing a dual task (DT) while walking and may use the “posture second” strategy. It is not clear if this is a result of motor or cognitive impairments. We examined the effects of explicit prioritization of walking or the cognitive task on gait speed (GS) and variability in 20 patients (Hoehn & Yahr stage: 2.3±0.5) and 20 healthy older adults during usual-walking and under three DT (verbal-fluency) conditions: (1) no instruction for prioritization, (2) specific attention to the walking pattern (gait prioritization), and (3) specific attention to the cognitive task (prioritization of verbal-fluency). The Montreal Cognitive Assessment, the Frontal Assessment Battery, and the Trail Making Tests assessed cognitive status. The two groups did not differ on these cognitive tests. Compared to usual-walking, all subjects reduced their GS in the un-instructed DT condition. Compared to the un-instructed DT condition, both groups significantly (p<0.001) increased GS when prioritizing walking and maintained about the same GS when prioritizing the cognitive task (p>0.155). All three DT conditions increased gait variability in both groups (p<0.001 usual-walking compared to uninstructed DT). Verbal-fluency tended (p=0.073) to be influenced by prioritization in both groups. Task prioritization abilities were similar in the patients and controls, even though the patients generally walked more slowly. PD patients without cognitive impairment apparently utilize their cognitive resources in the same manner as healthy older adults. Both groups, however, use some form of the posture second strategy and naturally focus on the cognitive task.

Planar covariation of elevation angles in prosthetic gait

F. Leurs, A. Bengoetxea, A.M. Cebolla, C. De Saedeleer, B. Dan, G. Cheron — 2012-01-18

Highlights: ► Kinematic strategies in transfemoral amputees were analyzed by planar covariation. ► The typical elliptic loop was preserved in prosthetic walking in both limbs. ► The orientation of the loop for the prosthetic limb did not change with speed. ► The relation to speed was even stronger for the sound limb than for control subjects. ► These results reveal a centrally commanded compensation strategy.Abstract: In order to achieve efficacious walking, transfemoral amputees must adapt coordination within both the artificial and the sound lower limb. We analyzed kinematic strategies in amputees using the planar covariation of lower limb segments approach. When the elevation angles of the thigh, shank and foot are plotted one versus the others, they describe a regular loop which lies close to a plane in normal adults’ gait. Orientation of this plane changes with increased speed, in relation to mechanical energetic saving. We used an opto-electronic device to record the elevation angles of both limbs’ segments of novice and expert transfemoral amputees and compared them to those of control subjects. The statistical structure underlying the distribution of these angles was described by principal component analysis and Fourier transform. The typical elliptic loop was preserved in prosthetic walking, in both limbs in both novice and expert transfemoral amputees. This reflects a specific control over the thigh elevation angle taking into account knowledge of the other elevation angles throughout the gait cycle. The best-fitting plane of faster trials rotates around the long axis of the gait loop with respect to the plane of slower trials for control subjects, and even more for the sound limb of expert amputees. In contrast, plane rotation is very weak or absent for the prosthetic limb. We suggest that these results reveal a centrally commanded compensation strategy.

Time-of-day influences postural balance in older adults

2012-03-05

Highlights: ► Postural balance in older adults appear to be affected by time-of-day. ► Time-of-day should be controlled when assessing postural balance in research and clinical settings. ► Postural balance is inferior in the afternoon relative to the morning and noon.Abstract: Background: Postural balance assessments are performed in both clinical and basic research settings on a daily basis. During a 24-h time span our physiology and physical performance undergo radical changes as we are influenced by the circadian rhythm. The time-of-day interaction on postural balance is unknown in older adults. The aim of this study was to investigate the time-of-day effect on postural balance in older adults.Methods: Center of pressure (CoP) excursion was measured (100Hz) by force plate analysis in 34 older adults during 30s of narrow quiet bilateral stance. Measurements were performed around 9a.m., 12.30p.m. and 4p.m. on the same day. Postural balance was quantified by velocity-moment, confidence ellipse area, total sway area and total sway length.Results: An overall significant time-of-day (between 9a.m. and 4p.m.) effect was observed for velocity-moment (mm2/s) 57±27–65±29 (p=0.001), confidence ellipse area (mm2) 36±16–44±19 (p<0.001), total sway area (mm2) 548±263–627±285 (p=0.001) and total sway length (mm) 373±120–379±113 (p=0.037). The variation of postural balance was mostly pronounced from midday (12.30p.m.) toward the afternoon (4p.m.) in all sway parameters. Specifically between 12.30p.m. and 4p.m. confidence ellipse area increased by 18.5%, total sway area by 17.1%, velocity-moment by 15.8% and total sway length by 4.6%. No differences were observed between 9a.m. and 12.30p.m. in any of the sway parameters.Conclusions: This study demonstrates that time-of-day influences postural balance in older adults. These findings have important scientific and clinical relevance, as they imply that time-of-day should be a controlled factor when assessing postural balance in older adults.

Effects of age and pathology on stance modifications in response to increased postural threat

James A. Shaw, Leslie E. Stefanyk, James S. Frank, Mandar S. Jog, Allan L. Adkin — 2012-01-27

Highlights: ► Potential of a physical threat to stability elevated postural anxiety. ► Trunk sway changes in response to elevated anxiety depended on age. ► Anxiety increased sway in young adults but decreased sway in older adults. ► Trunk sway did not change in response to elevated anxiety in individuals with PD. ► This lack of adaptation should be considered when training balance and gait in PD.Abstract: This study investigated modifications to standing posture in response to elevated postural anxiety evoked by a potential physical threat to stability. Sixteen young adults, 16 older adults and 16 patients diagnosed with Parkinson's disease (PD) stood with or without the expectation of a threat to their posture (i.e., external trunk perturbation). This method allowed for the assessment of the effects of anticipatory anxiety on standing posture associated with an ecologically valid and direct threat to stability. Our manipulation was successful as all participants, independent of age and disease, reported significant increases in postural anxiety when anticipating a threat to their posture. The trunk sway modifications observed in response to elevated postural anxiety were dependent on age and disease. Young adults showed increased trunk sway in both pitch and roll directions while older adults demonstrated decreased trunk sway but only in the roll direction when standing and expecting a threat to posture compared to standing without this threat. Individuals with PD showed no significant changes in trunk pitch or roll sway when anticipating a threat to posture compared to standing without this threat. Our findings suggest that the effects of postural anxiety on postural control are dependent on the context associated with the postural threat, and age and disease status.

Relation between risk of falling and postural sway complexity in diabetes

S. Morrison, S.R. Colberg, H.K. Parson, A.I. Vinik — 2012-01-24

Highlights: ► Older individuals with type 2 diabetes are at a high risk of falling than healthy people of a similar age. ► Persons at high risk of falling exhibited changes in postural motion compared to low-risk, healthy adults. ► Balance training resulted in a decline in falls risk for all older persons. ► With training, the postural motion of the older person with type 2 diabetes became more similar to the healthy adult.Abstract: For older individuals with diabetes, any decline in balance control can be especially problematic since it is often a precursor to an increased risk of falling. This study was designed to evaluate differences in postural motion dynamics and falls risk for older individuals with type 2 diabetes (T2DM) classified as fallers/non-fallers and, to assess what impact exercise has on balance and falls risk. The results demonstrated that the risk of falling is greater for those older individuals with multiple risk factors including diabetes and a previous falls history. The postural motion features of the high-risk individuals (T2DM-fallers) were also different, being characterized by increased variability and complexity, increased AP-ML coupling, less overall COP motion and increased velocity. One suggestion is that these individuals evoked a stiffening strategy during the more challenging postural tasks. Following training, a decline in falls risk was observed for all groups, with this effect being most pronounced for the T2DM-fallers. Interestingly, the COP motion of this group became more similar to controls, exhibiting decreased complexity and variability, and decreased velocity. The reciprocal changes in COP complexity support the broader view that age/disease-related changes in physiological complexity are bi-directional. Overall, these results show that, even for older T2DM individuals at greater risk of falling, targeted interventions can positively enhance their postural dynamics. Further, the finding that the pattern of postural motion variability and complexity was altered highlights that a decline in physiological complexity may not always be negatively associated with aging and/or disease

Progressive resistance training improves gait initiation in individuals with Parkinson's disease

Chris J. Hass, Thomas A. Buckley, Chris Pitsikoulis, Ernest J. Barthelemy — 2012-01-24

Highlights: ► Strength training (ST) may improve postural control in Parkinson's disease patients. ► Studied a 10-week ST program and biomechanical analysis of gait initiation (GI). ► ST subjects improved GI anticipatory postural adjustments and stride performance. ► ST subjects increased strength and safely completed the 10 week program.Abstract: An impaired ability to initiate walking is a common feature of postural instability and gait impairment in Parkinson's disease. While progressive resistance training (PRT) has been proposed to be an effective modality to improve balance and gait function in people with Parkinson's disease, there are a limited number of randomized trials and no studies have evaluated gait initiation performance. Thus, the purpose of this study was to examine the potential benefits PRT on GI performance in people with Parkinson's disease. Eighteen individuals with idiopathic PD were randomly assigned to either a twice weekly PRT program or a non-contact control group for 10 weeks. Biomechanical analysis of GI was performed pre- and post-intervention. Dependent variables of interest included the displacement of the center-of-pressure (COP) during the anticipatory postural phase of GI as well as the initial stride length and velocity. The PRT group demonstrated improvements in the posterior displacement of the COP and the initial stride length and velocity. There were no improvements in any variables for the control subjects. These results suggest that PRT may be an effective non-pharmacological and nonsurgical treatment to improve GI performance in PWP.

Validation of an ear-worn sensor for gait monitoring using a force-plate instrumented treadmill

2011-12-14

Abstract: A force-plate instrumented treadmill (Hp Cosmos Gaitway) was used to validate the use of a miniaturised lightweight ear-worn sensor (7.4g) for gait monitoring. Thirty-four healthy subjects were asked to progress up to their maximum walking speed on the treadmill (starting at 5km/h, with 0.5km increments). The sensor houses a 3D accelerometer which measures medio-lateral (ML), vertical (VT) and anterior–posterior (AP) acceleration. Maximum signal ranges and zero crossings were derived from accelerometer signals per axis, having corrected for head motion and signal noise. The maximal force, measured by the instrumented treadmill correlated best with a combination of VT and AP acceleration (R-squared=0.36, p=0), and combined VT, ML, and AP acceleration (R-squared=0.36, p=0). Weight-acceptance peak force and impulse values also correlated well with VT and AP acceleration (Weight acceptance: R-squared=0.35, p=0, Impulse: 0.26, p=0), and combined VT, ML, and AP acceleration (Weight acceptance: R-squared=0.35, p=0, Impulse: 0.26, p=0). Zero crossing features on the ML axis provided an accurate prediction of the gait-cycle, with a mean difference of 0.03s (−0.01, 0.05 confidence intervals).

The influence of heel height on lower extremity kinematics and leg muscle activity during gait in young and middle-aged women

Anna Mika, Łukasz Oleksy, Piotr Mika, Anna Marchewka, Brian C. Clark — 2012-02-02

Highlights: ► In young and middle-aged women muscle activity and lower limbs kinematics were assessed during gait in heeled shoes. ► Footwear of the stiletto type increases the leg muscle activity and changes knee and ankle kinematics during gait. ► Permanent wearing of heeled footwear could contribute to muscle overuse and repetitive strain injuries. ► Age-related changes alter in certain body segments the biomechanical adjustments associated with wearing heeled shoes.Abstract: The aim of this study was to evaluate the changes in electromyographic (EMG) activity of the lower limb muscles, and hip, knee and ankle kinematics during gait while wearing low- (4-cm) and high-heeled (10-cm) shoes in 31 young and 15 middle-aged adult women.We observed an increase in knee flexion and decrease in ankle eversion associated with elevated heel heights suggesting that compensatory mechanisms attenuating ground reaction forces may be compromised during gait with higher-heeled shoes. Additionally, we observed increased muscle activity during high-heeled gait that may exacerbate muscle fatigue. Collectively, these findings suggest that permanent wearing of heeled footwear could contribute to muscle overuse and repetitive strain injuries.

Compensatory balance reactions during forward and backward walking on a treadmill

D.A.E. Bolton, J.E. Misiaszek — 2012-01-09

Highlights: ► Balance perturbations that oppose the direction of walking are expected to yield larger amplitude corrective reactions. ► We compared corrective balance reactions during forward and backward treadmill walking. ► Backwards perturbations resulted in the largest amplitude reactions, regardless of walking direction.Abstract: Previous work suggests that balance perturbations to the body opposing the direction of progression during walking lead to larger amplitude corrective reactions than perturbations concurrent with walking direction. To test this hypothesis, subjects received forward and backward perturbations applied to the pelvis through a padded harness, while walking forwards or backwards on a treadmill. Contrary to our hypothesis, the greatest responses were associated with backward perturbations regardless of the direction of walking.

Comparison of plantar pressure distribution in adolescent runners at low vs. high running velocity

2011-12-28

Highlights: ► The impact of running velocity on foot plantar patterns distribution has not been explored in adolescent distance runners. ► Relative loads under the medial and central forefoot regions are higher while jogging compared to running. ► Relative loads under the lesser toes are higher while running compared to jogging. ► In order to prevent overloading of the metatarsals in young runners, excessive mileage at jogging pace should be avoided. ► Strengthening exercises of the foot musculature are recommended for protecting the first three metatarsals from overload.Abstract: This study aimed to compare foot plantar pressure distribution while jogging and running in highly trained adolescent runners. Eleven participants performed two constant-velocity running trials either at jogging (11.2±0.9km/h) or running (17.8±1.4km/h) pace on a treadmill. Contact area (CA in cm2), maximum force (Fmax in N), peak pressure (PP in kPa), contact time (CT in ms), and relative load (force time integral in each individual region divided by the force time integral for the total plantar foot surface, in %) were measured in nine regions of the right foot using an in-shoe plantar pressure device. Under the whole foot, CA, Fmax and PP were lower in jogging than in running (−1.2% [p<0.05], −12.3% [p<0.001] and −15.1% [p<0.01] respectively) whereas CT was higher (+20.1%; p<0.001). Interestingly, we found an increase in relative load under the medial and central forefoot regions while jogging (+6.7% and +3.7%, respectively; [p<0.05]), while the relative load under the lesser toes (−8.4%; p<0.05) was reduced. In order to prevent overloading of the metatarsals in adolescent runners, excessive mileage at jogging pace should be avoided.

Cell phones change the way we walk

Eric M. Lamberg, Lisa M. Muratori — 2012-01-09

Highlights: ► While walking and using a cell phone is common, effects on gait are unclear. ► We investigated if walking errors occur when talking or texting on a cell phone. ► Gait velocity is reduced when using a cell phone while talking or texting. ► Navigational errors occur when texting while walking. ► Texting while walking produces greater interference than talking on a cell phone.Abstract: Cell phone use among pedestrians leads to increased cognitive distraction, reduced situation awareness and increases in unsafe behavior. Performing a dual-task, such as talking or texting with a cell phone while walking, may interfere with working memory and result in walking errors. At baseline, thirty-three participants visually located a target 8m ahead; then vision was occluded and they were instructed to walk to the remembered target. One week later participants were assigned to either walk, walk while talking on a cell phone, or walk while texting on a cell phone toward the target with vision occluded. Duration and final location of the heel were noted. Linear distance traveled, lateral angular deviation from the start line, and gait velocity were derived. Changes from baseline to testing were analyzed with paired t-tests. Participants engaged in cell phone use presented with significant reductions in gait velocity (texting: 33% reduction, p=0.01; talking: 16% reduction, p=0.02). Moreover, participants who were texting while walking demonstrated a 61% increase in lateral deviation (p=0.04) and 13% increase in linear distance traveled (p=0.03). These results suggest that the dual-task of walking while using a cell phone impacts executive function and working memory and influences gait to such a degree that it may compromise safety. Importantly, comparison of the two cell phone conditions demonstrates texting creates a significantly greater interference effect on walking than talking on a cell phone.

The effects of word length, articulation, oral-motor movement, and lexicality on gait: A pilot study

2012-01-09

Highlights: ► It is possible to deconstruct a verbal task to examine motoric, articulatory, and lexical demands. ► Gait seems to be most affected by the motoric demands of speaking. ► Articulatory and lexical demands may not produce incremental changes in gait over the motoric demands of speaking.Abstract: Previous research has suggested that articulatory demands are important predictors of the impact of dual-task interference on spatial-temporal parameters of gait. In this study, we evaluated the effects of word length, oral-motor movement, articulation, and lexicality, within a verbal task, on a continuous gait task. Fifteen healthy young women participated in a study in which two word lengths (monosyllabic and bisyllabic) were crossed with four levels of secondary task complexity (no dual-task, non-speech movement, spoken non-word, and spoken word). Spatial and temporal parameters of gait were measured using a 23′ instrumented carpet. Results indicated a significant multivariate main effect for task type, F(15, 120)=3.07, that explained 71.1% of the demonstrated variability in gait. Univariate analyses of this main effect revealed statistically significant effects for velocity, step time, swing time, and stance time, but no statistically significant effect for step length. Post hoc analyses suggested that dual-task interference produced significant changes in the parameters of gait, but that this interference was not significantly greater with non-words as compared to the non-speech movement condition, nor was it significantly greater with words as compared to non-words. The results of this systematic deconstruction of a simple verbal task suggest that the motor component of a secondary speech task may produce the largest amount of interference within a dual-task interference paradigm.

SIAMOC Sociey Announcement

2012-04-01