• 19 Apr 2017 by John Stins

    Humans have the ability to mentally visualize all sorts of objects, events or scenes. This is known as mental imagery. For example, I can generate a vivid experience of swimming in a pool: I ‘feel’ the water flow, I ‘sense’ the temperature, and I ‘move’ my arms and legs. Research has shown that mental imagery (especially of motor acts) is accompanied by changes in bodily states, such as heart rate, muscle tension, and respiration, often in a highly specific manner. Mental imagery also affects postural control, as evidenced by analysis of the center-of-pressure (COP) trajectory as a function of mental content. We performed an experiment inspired by a study by Miles et al. (2010). They found that mental imagery of the (own) future and past induced COP changes. Thinking of the past caused backward displacement of the  COP, whereas thinking of the future caused forward displacement. The authors concluded that the direction of subjective time is represented along a spatial dimension, which in turn led to directional changes in body posture (unintentional ‘leaning’). We performed a conceptual replication and extension of this study, in order to test how general and robust the effect of ‘mental time travel’ is.

     

    Thirty-two participants stood upright and imagined various scenarios that were read aloud. Scenarios described a typical day in the past or in the future; 4 days or 4 years. In addition, some scenarios were pleasant (e.g., receiving a diploma) or unpleasant (being at a funeral). We analyzed postural displacements in the anterior-posterior direction, as a function of the mental content. An important finding was that there was no statistically significant difference between past and future imagery (see Figure). Also, no postural effects of emotion were found. This apparent null finding (all F’s < 1) received support from Bayesian statistics, which quantifies the relative predictive success of the null hypothesis relative to the alternative hypothesis. This Bayesian analysis revealed that the null hypothesis (i.e., no difference between past and future imagery) was 4.8 more likely than the alternative, which is typically considered ‘substantial’ evidence.

     

    Figure 1. Grand averaged wave forms of the COP trace (bold line), plus straight line fit (red line) for past (left panel) and future (right panel) mental imagery. There was no statistical difference between these two conditions.

     

    We have no explanation for why our results diverged from Miles et al. (2010). It could be due to subtle unidentified methodological differences. Alternatively, it could be that the effect is not robust and that posture is insensitive to abstract thought, such as mental time travel.

     

    Publication

    Stins JF, Habets L, Jongeling W, Cañal-Bruland R. (2016). Being (un)moved by mental time travel. Consciousness and Cognition; 42: 374–81. http://www.sciencedirect.com/science/article/pii/S1053810016300666

     

    The author

    Dr. Stins is assistant professor at the Department of Human Movement Sciences, VU University Amsterdam. His research focuses on the interface of experimental psychology (especially cognition and emotion) and motor control, with an emphasis on the control of posture and gait.

     

     

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  • 18 Apr 2017 by Anna Hatton

    Following anterior cruciate ligament (ACL) rupture, reconstructive surgery (ALCR) is often performed to mechanically stabilise the knee, however functional and neuromuscular deficits can persist long after surgery. Impaired single-limb balance control when standing on the ACLR limb compared to healthy individuals has been reported by other groups. Building on these findings, the current study aimed to generate new knowledge as to whether similar balance deficits exist between injured and contralateral uninjured limbs, one year post-surgery, which is typically the time when patients are permitted to return to sport. Uncovering balance deficits in patients who have undergone ACLR is clinically important information, which may help to identify a risk factor with the capacity to predict ACL re-rupture or contralateral injury, and advance rehabilitation strategies post-surgery.

    Our study investigated 100 adults who had undergone a primary hamstring-tendon ACLR in the 12 months prior to testing. Participants performed challenging tasks of static single-limb balance, with eyes closed, whilst standing on the ACLR and uninjured limb. Traditional measures of centre of pressure movement (excursion, velocity) in anterior-posterior and mediolateral directions were collected over 20 seconds, using a Nintendo Wii Balance Board (Figure 1). We were also interested in exploring possible associations between patients who presented with concomitant injury (chondral lesions) or underwent ‘additional’ surgeries (meniscectomy) at the time of ACLR, and balance ability, one year following reconstruction. We found that single-limb standing balance did not differ between the ACLR and uninjured limb for any of the centre of pressure measures of interest (all P values >0.686). Whilst 71 participants were reported to have concomitant injury/surgeries, these factors were not associated with measures of balance ability (all P values >0.213). 

    Findings reported in our article extend, and concur with, prior evidence indicating the absence of balance deficits between the injured and uninjured limbs during less challenging unilateral balance tasks, where visual information was available (i.e. quiet standing with eyes open). However, in the context of wider evidence, which demonstrates that patients who have undergone ACLR show poorer balance control relative to their healthy counterparts, our results point to the suggestion that bilateral balance deficits may exist in this clinical population. For health professionals involved in the management of patients following ACL injury and ACLR, our research implies that clinical assessments of balance, and interventions designed to enhance balance ability, should consider both the injured and uninjured limbs, within the early stages of post-ACLR rehabilitation strategies.

    Figure 1: Standing balance test procedures and Nintendo Wii output (centre of pressure movement)

     

    Publication

    Hatton AL, Crossley KM, Clark RA, Whitehead TS, Morris HG, Culvenor AG. Between-leg differences in challenging single-limb balance performance one year following anterior cruciate ligament reconstruction. Gait & Posture 2017 52:22-25. http://dx.doi.org/10.1016/j.gaitpost.2016.11.013

    The Author

    Dr Anna Hatton is a Lecturer in Physiotherapy and Co-Director of the Centre for Neurorehabilitation, Ageing and Balance Research at The University of Queensland. Her research seeks to explore the sensorimotor control of balance and gait in ageing, neurodegenerative, neuromuscular and musculoskeletal disease populations, to inform the development of novel rehabilitation techniques.

     

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  • 12 Apr 2017 by PAULA POLASTRI

    We regularly move our eyes searching for visual information, and when we do this, postural adjustments are necessary to compensate or facilitate these movements. Previous studies in young adults show that body sway is attenuated during saccadic eye movements and reveal that challenging stances affects this relationship. This suggests that in an attempt to increase visual stability to perform more spatially accurate saccades, people limit their body sway during saccadic eye movements. The eye-posture relationship appears to be affected by the aging. Older adults have slower and less accurate saccadic eye movements and exhibit more sway during postural tasks compared to young adults. These changes in gaze and postural behaviors might be associated to increase of falls in older people. We aimed to investigate the influence of saccadic eye movements on postural control in older adults by manipulating the difficulty level of visual and postural tasks.

     

    Twelve older adults were asked to maintain quiet upright standing during two stance conditions (wide or narrow stance) combined with three gaze conditions (fixation, saccades at 0.5 Hz, or saccades at 1.1 Hz). The target in the gaze conditions was a red circle on a white background, which either stayed in place or jumped horizontally to elicit saccades. We found that the mean amplitude of mediolateral head and trunk sway was higher and sway frequency was lower at narrow compared to wide stance condition. In anteroposterior direction, the mean amplitude of sway was lowest at saccades at 1.1 Hz, followed by saccades at 0.5 Hz, with highest values during the fixation condition, following a linear trend. A similar trend was observed for the frequency of head and trunk sway in mediolateral and anteroposterior direction, participants exhibited highest sway frequency at saccades 1.1 Hz, followed by saccades at 0.5 Hz, with lowest values in the fixation condition.

     

     

    Figure: (A) Summary of the effect of gaze on mean sway amplitude and frequency of the head and trunk in anteroposterior  and mediolateral  directions. (B) Summary of the effect of stance on mean sway amplitude and frequency of the head and trunk in AP and ML directions. Differently of young adults, no statistical significance was observed between wide and narrow stances in anteroposterior direction.

     

    Our results suggest that older adults attenuate their head and trunk sway during horizontal saccadic eye movements, in a similar way as young adults, during the wide stance condition. However, unlike young adults, older adults did not attenuate their sway during the more challenging narrow stance condition. This suggests a more rigid postural control strategy in older adults to maintain the postural stability during the performance of visual tasks. Further studies are required to track the way of older adults move their eyes in search of visual information during daily activities and how this affects the postural stability, particularly during challenging stance conditions.

     

    Publication

    Aguiar SA, Polastri PF, Godoi D, Moraes R, Barela JA, Rodrigues ST. (2015). Effects of saccadic eye movements on postural control in older adults. Psychology & Neuroscience, 8:1, 19-27.

    http://psycnet.apa.org/?&fa=main.doiLanding&doi=10.1037/h0100352

     

    The author

    Paula F. Polastri – Assistant Professor of São Paulo State University (UNESP), Faculty of Science - Department of Physical Education, Bauru – Brazil. 

    Paula F. Polastri is coordinator of the Laboratory of Information, Vision and Action (LIVIA) together with Sergio T. Rodrigues. Currently, their research focuses on understanding the relationship between gaze and postural control. Their further study interests are to investigate how the changes in the eye-posture relationship affect the coupling between sensory information and body sway.

     

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  • 19 Mar 2017 by Milou Coppens

    Assessment of free-living gait is becoming increasingly popular in mobility and fall-risk research because of its ecological validity and advances in sensor technology. However, an essential step herein is detecting when someone is walking, which is not as easy as it seems. Previous studies have reported boundaries in separating gait from other activities as shuffling and standing still. Furthermore, inaccurate and instable placement of a sensor were described as difficulties for proper gait detection, even though these factors are hard to avoid when older adults wear sensors without supervision. Therefore, we set up a study to develop an algorithm for reliable gait detection from inertial sensors without the need for rigid sensor placement.

     

    Fifty-one older adults with an average age of 83 years wore the Philips Senior Mobility Monitor, containing a triaxial accelerometer and a barometer, on a lanyard around their neck. We randomly placed the device underneath or outside clothing and changed the length of the lanyard between participants to mimic real-life variations. While being filmed, participants walked in a semi-controlled environment and performed free-living activities such as climbing stairs and sit-to-stand transfers. We annotated bouts of level-ground gait (excluding shuffling) in the videos as gold standard. To differentiate gait from other activities, we developed a wavelet-based decision tree algorithm.  Data of half of the participants was used to optimize algorithm thresholds (e.g. minimal number of heel strikes), while data of the other half of the participants was kept for validation. Subsequently, the algorithm was used to detect walking episodes in the sensor data of the validation group, which strongly corresponded to those annotated in the videos with high accuracy (≥97%) and low false-positive errors (≤1.9%) (Fig. 1).

     

    To identify whether gait parameters from free-living gait were related to standardized laboratory-assessed gait parameters, we calculated the median and maximum cadence from the inertial sensor data and compared those with cadence obtained from three walks on a 10-m GaitRite walkway. We found that median and maximum cadence were strongly correlated with cadence measured on the GaitRite. Despite this strong correlation, median cadence was significantly lower in free-living gait compared to cadence measured on the GaitRite.

     

    Our novel wavelet-based method is feasible for detecting free-living gaits from a pendant-worn inertial sensor. Giving the fact that the exact location of the sensor differed between participants and could even change during the experiment, this method is promising to detect gait in the home environment. As laboratory gait parameters where related to, but more equal to someone’s ‘best’ free-living gait parameters, home assessments have the potential to provide additional information for investigating daily performance.

     

    Publication

    Brodie MAD, Coppens MJM, Lord SR, Lovell NH, Gschwind YJ, Redmond SJ, Del Rosario M, Wang K, Sturnieks DL, Persiani M, Delbaere K. (2016). Wearable pendant device monitoring using new wavelet-based methods shows daily life and laboratory gaits are different. Med Biol Eng Comput 54: 663. doi:10.1007/s11517-015-1357-9 https://link.springer.com/article/10.1007/s11517-015-1357-9

     

    The author

    Milou Coppens is a PhD Candidate at the Radboud University Medical Center in Nijmegen, The Netherlands.

     

    Milou is highly interested in using novel techniques to understand the mechanisms underpinning balance problems due to ageing and disease. Currently, she is using non-invasive brain stimulation and brain imaging techniques to investigate the neural control of postural balance and how this might be altered after brain damage.

     

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  • 13 Mar 2017 by Tanvi Bhatt

    With the evolution of bipedal posture humans are not immune to falls. Falls are a significant societal burden, being a leading cause of morbidity and mortality, especially in people aging with disabilities such as stroke. A fall after encountering a large external disturbance to the body, such as a slip or a trip, can be effectively prevented via successful protective (reactive) self-defence strategies. Such strategies include grasping and stepping, and essential re-establish the relationship between the body and the base of support, which could be displaced based on the direction of the disturbance. While earlier it was thought that such protective postural responses were primarily automatic, and initiated and controlled reflexively within the spinal cord, emerging evidence indicates that the brain has an important role to play in modulating these responses. In the healthy nervous system, this modulation can be seen in the form of rapidly and appropriately adjusting and adapting the protective response based on the perceived threat (e.g. adjusting step length based on the magnitude of the disturbance). Our study examined if age-related structural (mainly degenerative) changes in the brain would impacted this modulation, and if the magnitude of this impact would be enhanced when an additional brain injury, such as stroke, co-existed with normal aging.

     

    Young healthy adults, older healthy adults, and chronic stroke survivors were exposed to slip-like perturbations while they were standing on a motorized instrumented treadmill. The perturbations induced a balance loss much like what you would experience while standing on a bus that started to move suddenly from a standstill. Participants were tested on three levels of difficulty, which consisted of increasing acceleration levels of the treadmill belt. All subjects resorted to taking a protective step to restore their balance, even at the lowest level of belt acceleration. There were no falls in the young and the healthy older adults, but the number of falls increased with increasing acceleration level in the stroke participants. The number of steps taken to restore balance increased with increasing difficulty levels in all groups. The young subjects were able to increase control of their center of mass (COM) stability with increasing acceleration levels. This was achieved by increasing the length of their protective step (spatial parameter) along with decreasing their step velocity (temporal parameter), rather than altering the control of their trunk (upper body) movement. While older adults were able to alter their responses with an increase in stability between the lower difficulty levels, they could not scale their spatial and temporal stepping response to the highest level of acceleration. Stroke participants on the other hand could not modulate COM stability, step length, or step velocity with increasing difficulty levels, which could explain the highest number of falls in this population.

     

    An accurate sensory perception of the perturbation (in terms of displacement and velocity) is required to generate a timed and graded response to initiate and execute an appropriate body response. Our results demonstrate a partially preserved ability to efficiently respond to challenging environmental threats by modulating the reactive balance response in older adults, which breaks down as the magnitude of threat increases. Such modulatory ability is significantly impaired in people aging with stroke, which could be one of the factors explaining the 3-fold increase in fall risk in this population compared to their healthy counterparts. Results from this study suggest that reactive balance assessment measures could miss detecting community-dwelling older adults at risk of falls if these tests at conducted at lower “threat” levels. Furthermore, our results suggest that fall prevention paradigms for people aging with and without neurological disorders, such as stroke should, should include reactive balance training at progressively increasing levels of perturbation threat to entrain modulation of protective stepping responses.

    Figure A. Experimental set-up for delivering perturbations in standing position, wherein participants executed a natural response to recover balance upon receiving a sudden slip-like perturbation. B.  The perturbation outcome for each group showing the proportion of falls and recoveries (no falls) at all three perturbation levels. The older stroke survivors showed significantly higher incidence of falls on level III perturbation compared with levels I & II (p < 0.01). At the highest perturbation intensity (level III), the stroke group also had more falls compared with the young and older adults (p < 0.01). C. The percentage of multiple stepping response at each perturbation intensity. Unlike young adults, for older adults and stroke survivors the proportion of multiple stepping responses on perturbation levels II and III than at level I, * p < 0.01. Both older adults and older stroke survivors showed higher proportion of multiple steps compared with younger adults # p < 0.01. 

     

    Publication

    Patel P.J., Bhatt T. Does aging with a cortical lesion increase fall-risk: Examining effect of age versus stroke on intensity modulation of reactive balance responses from slip-like perturbations. Neuroscience 2016 Oct 1;333:252-63. http://dx.doi.org/10.1016/j.neuroscience.2016.06.044

     

    Authors

    Tanvi Bhatt, PT, PhD, Department of Physical Therapy, University of Illinois at Chicago

    Dr. Bhatt is an assistant professor in the department of physical therapy and leads the Cognitive, Motor & Balance Rehabilitation (CogMoBal) Laboratory. Her research involves investigating the neuromechanical basis of balance recovery from external perturbations such as slips and trips, and subsequently designing intervention paradigms for reducing fall-risk in healthy and pathological populations. Her research interest and focus also lays in examining effects of alternative cognitive and motor therapies for improving impairment, function, and community participation in community-dwelling people with neurological disorders.

     

    Prakruti Patel, PT, MS, PhD, Department of Physical Therapy, University of Illinois at Chicago

    Prakruti Patel is a graduate student in Dr. Bhatt’s lab. Prakruti will graduate with her doctoral degree in Rehabilitation Sciences in Spring 2017. Her dissertation focussed on examining cognitive-motor interference in for locomotor-balance tasks in people with aging and stroke.

     

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  • 02 Mar 2017 by Takahiro Higuchi

    Stroke survivors often suffer from motor paralysis on one side of the body. It can be challenging for them to walk through narrow openings, such as doorways or space created by pedestrians. This is because, while body rotation with a pivot-like turn is necessary to fit through apertures without contact, performing such a turn using the paretic limb is difficult. Therefore, we investigated how they could successfully avoid obstacles and fit through apertures in spite of their motor paralysis. 

    Participants included 10 stroke fallers, 13 stroke non-fallers, and 23 controls. A door-like aperture was created as a space between two projector screens (Fig. 1a). Participants were asked to approach and cross the aperture without contacting the screen. In some trials, the aperture was so narrow that body rotation was necessary to avoid contacting the screen. Our results showed that stroke fallers contacted the screens more frequently than any of the other participants. This suggests that the inability to safely cross an aperture is related to the risk of falling. As expected, stroke fallers contacted the screen mainly on their paretic side. Interestingly, enough, these contacts were less frequent when they tried to navigate the opening starting with their paretic side (Fig. 1b). Three-dimensional motion analyses showed that stroke participants rotated their bodies in multiple steps (rather than with pivot-like turns), possibly to deal with their motor paralysis. 

    Our results suggest that, although stroke fallers have difficulty avoiding contact with obstacles on their paretic side, adopting a strategy to fit through an opening from their paretic side can help them avoid contacts. We have two explanations as to why such a strategy helped improve their behavior; it could be that vision of the paretic side helped guiding the movement or that spatial attention was directed to the location of the paretic side of the body. We are now investigating whether such a strategy would be a helpful intervention to help stroke patients pass narrow openings safely. 

    Figure 1(a)

     

     

    Figure 1(b)

     

    Figure 1(a) Participants were asked to walk through a narrow opening created by two projector screens. Our focus was on how successfully they avoided contacts with the screen and how they approached and crossed a narrow opening while dealing with their motor paralysis. (b) Contact frequency classified according to the body side where contact occurred.

     

    Publication
    Muroi D, Hiroi Y, Koshiba T, Suzuki Y, Kawaki M, Higuchi T. (2017) Walking through apertures in individuals with stroke. PLOS ONE 12: e0170119. 

    http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170119
     

    The author
    Takahiro Higuchi (Ph.D.)
    Professor, Department of Health Promotion Science, Tokyo Metropolitan University

    Takahiro Higuchi earned a Ph.D. in Psychology from Tohoku University in Japan. He gained additional research experience during his postdoctoral fellowship with Dr. Aftab E. Patla at the University of Waterloo in Canada from 2004 to 2006. He is primarily interested in the visuomotor control of adaptive locomotor

     

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  • 07 Mar 2017 by Hiroko Tanabe

    How do we maintain balance? What is our control strategy during upright standing? These questions are not as easy as they look. Even when standing quietly, we need to activate various muscles in order to not collapse under the influence of gravity. This is made extra difficult by the frequent balance disturbances we experience in daily life, for instance due to neuromuscular noise or people bumping into us. The postural control mechanism must hence be stable, but also adaptive to internal and external disturbances (this adaptability is called postural robustness). Postural control is conventionally thought to continuously actuate the body segments based on joint state; however, this strategy cannot bring forth the bimodal distribution of ankle movements that are commonly observed during standing. Therefore, we hypothesized that balance during quiet standing is controlled intermitted, not continuous. In this study, we demonstrated the relevance of a new concept for postural control called intermittent feedback control, in which each joint is actively actuated only when the instability of the system exceeds a certain threshold.  

    We used a quadruple inverted pendulum as a model for tiptoe standing to simulate upright posture with internal disturbance accompanied by the change in posture and sensory feedback. The four segments represented the foot, shank, thigh, and head-arm-trunk segments and had human anthropometric characteristics. Each joint was actuated by an anti-gravitational joint torque generated according to three different control strategies: 1) continuous control (a continuous active and passive joint torque based on joint angle and velocity), 2) intermittent control (an intermittent active joint torque only when instability of the system increases and an continuous passive torque), and 3) passive control (only a passive torque from musculotendinous viscoelasticity). Our results show that only when the hip is controlled intermittently, we obtain joint oscillations with amplitudes and variations that are similar to those during actual human standing. Also, there were substantial differences in postural robustness among different joint control strategies.

    Figure: a visualization of our model for intermitted postural control

    Our results highlight the advantages of intermittency for the postural control system and could have far-reaching implications for training and rehabilitation. For example, based on the concept of intermittent control, we might be able to train the system to be robust to internal and external perturbations of a certain intensity. Furthermore, our findings may provide important insight into a long-lasting debate: is lower variability indeed more stable? In conclusion, our findings suggested that human upright posture could be controlled intermittently and that this intermittent feedback control may be associated with increased postural robustness.

     

    Publication

    Tanabe H, Fujii K, Suzuki Y, Kouzaki M (2016). Effect of intermittent feedback control on robustness of human-like postural control system. Scientific Reports 6, 22446. doi: 10.1038/srep22446. http://www.nature.com/articles/srep22446

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    The author

    Hiroko Tanabe, Ph.D.

    Hiroko Tanabe is an assistant professor at the Graduate School of Arts and Sciences, The University of Tokyo, Japan. Her research interests are the motor control mechanism in patients and athletes. She is currently working on neural-muscular-skeletal quantification of psychiatric patients, postural adaptation during pitching motion of baseball players, and aesthetic walking motion and its control theory of dancers.

     

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  • 19 Feb 2017 by Toby Ellmers

    During walking, we rely on visual information to identify tripping hazards and navigate safely through the environment. The way we shift our gaze and scan the environment (our visual-search behaviour) is affected by ageing and fall risk. Older adults at high-risk of falling will transfer their gaze away from a stepping target before the step has been completed (i.e., prior to heel contact); a behaviour which is causally linked to reduced stepping accuracy. Moreover, when navigating a series of stepping constraints, high-risk older adults will adopt a less-variable pattern of visual-search, whereby their gaze is fixated predominately on the initial stepping target, at the expense of upcoming obstacles or targets. We hypothesised that this maladaptive and less-variable pattern of visual-search behaviour may be caused by inefficiencies in attentional processing, with high-risk older adults possessing insufficient cognitive resources to generate and store a ‘spatial map’ of their environment. Insufficient cognitive resources for attentional processing during walking may be due to psychological factors. When anxious or following injury or accident (e.g., falls), individuals may attempt to consciously monitor and control movements, which are usually considered largely ‘automatic’. This phenomenon is frequently described as ‘reinvestment’. It is believed that cognitive resources are required to consciously attend to the process of walking, which would limit the resources available for other processes, such as proactively scanning one’s environment. Yet, little is known about how either cognitive load or reinvestment influence visual-search behaviour during walking.

    Younger adults traversed a non-linear path (containing two precision stepping targets) while performing a secondary serial-subtraction task and wearing a gaze-tracker unit. Outcome measures included gaze behaviour, stepping accuracy, and time to complete the walking task. When walking while simultaneously carrying out the serial-subtraction task, participants visually fixated on task-irrelevant areas ‘outside’ the walking path more often and for longer durations, and fixated on task-relevant areas ‘inside’ the walkway for shorter durations. These changes were most pronounced in high-trait-reinvesters. The increased task-irrelevant ‘outside’ fixations were accompanied by slower walking times and greater gross stepping errors. Interestingly, these ‘outside’ fixations were temporally related to the performance of the dual-task, with participants more likely to look away from the walkway (or, ‘gaze into thin air’) in the 330ms directly preceding the verbalisation of the dual-task calculation.

    Our findings suggest that attention is important for the maintenance of effective gaze behaviours, supporting previous claims that maladaptive changes in visual-search observed in high-risk older adults may be a consequence of inefficiencies within attentional processing. As these changes were most pronounced in high-trait-reinvesters, we speculate that reinvestment-related processes placed additional cognitive demands upon working memory.

     

     

    Figure. A: An example of a task-relevant ‘inside’ fixation, whereby the participant fixates on an area within their walking path. B: An example of a task-irrelevant ‘outside’ fixation, whereby the participant fixates on an area outside of their walking path. C: Duration (as a percentage of overall fixation durations) of task-relevant ‘inside’ and task-irrelevant ‘outside’ fixations under conditions of Cognitive Load, ** p <.01. D: Number of task-irrelevant ‘outside’ fixations (per second) under conditions of Cognitive Load, * p <.05.

     

    Publication

    Ellmers TJ, Cocks AJ, Doumas M, Williams AM, Young WR (2016) Gazing into Thin Air: The Dual-Task Costs of Movement Planning and Execution during Adaptive Gait. PLoS ONE 11(11): e0166063.

    http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166063

     

    The Author

    Toby Ellmers. Ph.D. Student. Department of Life Sciences, Brunel University London.

    Toby Ellmers is a Ph.D. Student at the FP² (Falls Prediction and Prevention) Lab at Brunel University, London. His research involves the studying of the psychological mediators of elderly fall-risk and the development of intervention programs grounded in psychological and motor-learning theory.

     

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  • 17 Feb 2017 by Chris Todd

    The Prevention of Falls Network for Dissemination (ProFouND www.profound.eu.com) is a thematic network of 20 partners and 14 associate members across Europe. ProFouND organises a yearly Falls Festival to discuss pressing topics in relation to falls in older people. Falls and injurious falls represent a major public health challenge for European countries, and across the world, not in the least due to a high associated cost. Falls cost about 1-1.5% of national health care expenditure.

     

    Despite an increasing amount of evidence regarding programmes that work and programmes that do not work, there is wide disparity in fall prevention across EU and the world. Some regions are running ambitious programmes, whilst others lag behind. ProFouND, EU Falls Festival Scientific Committee, European Innovation Partnership on Active and Healthy Ageing Action Group on Falls and E-NO FALLS working groups wrote a Silver Paper[i] to address this and suggest ways of how research can help to close the implementation gap in falls prevention.

     

    There is sufficiently strong evidence of what works to create best practice models. The challenge remains how these models can be implemented coherently and comprehensively. The EC Blueprint on Digital Health and Care Innovation for Europe’s Ageing Society[ii] argues the need for models of self-organisation and citizen empowerment for social transformation facilitated by digital and technological innovation. However, in order to have successful self-management, more potential barriers need to be conquered. For example, the challenge with evidence based strength and balance programmes (for groups and for individuals at home) is that they need to be attractive to older people so that they not only start the programme but also adhere to them long term to be beneficial.

     

    Figure. Self-management of falls prevention through the use of exergames

    Technologies can help facilitate the implementation of such strategies, but they must be attractive to older people[iii]. Technologies need to be developed for the prediction, detection, assessment and prevention of falls, which provide alerts and feedback useful to the multiple stakeholders, including health and social care professionals, whilst prioritising older people and their families and taking account of older people’s needs and preferences for technologies[iv]. We are following the blog with great interest and see exciting research from the ISPGR research community coming our way, showing great promise in making this happen. Keep up the good work!

     

     

    Events: www.eufallsfest.eu

     

    Chris Todd

    Professor of Primary Care and Community Health

    School of Health Sciences

    University of Manchester, UK

    E: chris.todd@manchester.ac.uk

     

    Chris is Professor of Primary Care and Community Health in The School of Health Sciences, The University of Manchester UK. (Link for Orcid) He is a Chartered Psychologist and Associate Fellow of The British Psychological Society. He has held and/or currently holds grants from the Department of Health, NHS, various research charities, MRC, NIHR and the European Commission.  He was a member of the European Commission DG12 Expert Working Party on research into postural stability and fall prevention in the elderly population. He wrote The World Health Organisation’s policy synopsis on the prevention of falls amongst older people and was a member of the group which wrote the 2007 WHO Global Report on Falls Prevention.

     

     

     

    [iv] Helbostad J et al. Mobile health applications to promote active and healthy ageing. Sensors, 2017 Forthcoming http://www.mdpi.com/journal/sensors/special_issues/body_wbs

     

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  • 06 Feb 2017 by Jochen Klenk

    Recent advances in body-worn sensor technology make it possible to objectively measure real-world fall events. These exciting new developments in research areas of software engineering, biomechanics and big data management can improve our understanding of fall events in older people. However, there is one problem: These events are rare and hence challenging to capture. This has been the motivation behind the EU-funded FARSEEING consortium, who, together with associated partners, have started building a meta-database of real-world falls.

    Between January 2012 and December 2015, a large number of real-world fall events measured by inertial sensors have been reported to the database. A signal processing and fall verification procedure has been developed and applied to the data. Currently, more than 200 verified real-world fall events are available for analyses. The fall events have been recorded within several studies, with different methods, and in different populations. All sensor signals include at least accelerometer measurements and 58 % also include gyroscope and magnetometer measurements. The collection of data is ongoing and open to further partners contributing with fall signals.

    Figure 3 shows a real-world fall signal example (acceleration) with labeled activities and fall phases. The sensor (Samsung Galaxy S3) was attached at the lower back, sampling at 100 Hz. The faller reported a backwards fall while pushing the door opener. The person was upright at the beginning, indicated by the vertical axis (blue) showing 10 m/s2, including some walking. During the fall the vertical signal changes to 0 m/s2 and the anterior-posterior axis (red) to 10 m/s2, indicating a backward fall. After a short period of resting, the person recovered with an intermediate resting position and continued walking.

    This meta-database is currently the largest collection of real-world falls using inertial sensors. It will help to substantially improve the understanding of falls and enable new approaches in fall risk assessment, fall prevention, and fall detection. The FARSEEING consortium aims to share the falls data with other researchers. A dataset of 20 selected fall events is available on request via the project website. Researchers are also invited to collaborate with the FARSEEING consortium on specific research questions.

    More information about the project and the data sharing policy can be found on the FARSEEING website (www.farseeingresearch.eu).

     

    Publication

    Klenk J, Schwickert L, Palmerini L, Mellone S, Bourke A, Ihlen EAF, Kerse N, Hauer K, Pijnappels M, Synofzik M, Srulijes K, Maetzler W, Helbostad JL, Zijlstra W, Aminian K, Todd C, Chiari L, Becker C. The FARSEEING real-world fall repository: a large-scale collaborative database to collect and share sensor signals from real-world falls. European Review of Aging and Physical Activity. 2016;13:8.

    http://https://eurapa.biomedcentral.com/articles/10.1186/s11556-016-0168-9

     

    The author

    Jochen Klenk, Department of Clinical Gerontology, Robert Bosch Hospital Stuttgart and Institute of Epidemiology and Medical Biometry, Ulm University, Germany

    Jochen Klenk is a Senior Research Scientist at the Robert-Bosch-Hospital (RBK) and at the Institute of Epidemiology and Medical Biometry at Ulm University. He leads the working group on fall signal analysis at the RBK and is the FARSEEING database manager. Further research interests are longitudinal data analysis of large observational studies and physical activity monitoring.

     

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  • 01 Feb 2017 by James Richardson

    The young woman trips on an uneven sidewalk, recovers smoothly and resumes texting. The older woman encounters the same perturbation and crashes.

    My colleagues and I have been trying to identify the key neuromuscular attributes responsible for successful response to perturbation in our clinical practice for quite some time. We have been particularly interested in older people with diabetic neuropathy since this population is advised to walk for exercise, and yet commonly falls. Traditionally, we looked at hip muscle strength generation and ankle proprioceptive precision to explain unipedal stance time and gait speed. However, against our expectations these neuromuscular attributes did not predict lateral gait variability or the few major injuries sustained by our study participants.

    Since the neuromuscular variables were unrevealing, I looked for relationships between step width variability and Simple Reaction Time and Complex Reaction Accuracy using our ReacStick device (see Figure). The ReacStick is a rigid, lightweight rod with a rectangular box at one end. To determine SRT the participant sits with an open hand around the box, and as quickly as possible catches the suspended device, which is dropped at random intervals by the examiner. When determining Complex Reaction Accuracy, the participant catches the device solely when the LED lights illuminate on the housing when dropped during 50% of the trials. If the LED lights do not illuminate then the participant is asked to let the device fall to the floor, requiring a Jedi-quick decision as the ReacStick hits the floor in about 400 msec (an interval similar to the swing phase of gait).

    Our results showed that the ratio of Complex Reaction Accuracy to Simple Reaction Time, which rewards accuracy and/or quick reaction, was strongly and inversely associated with uneven surface gait variability in participants suffering from neuropathy (R2 = .61). Further, the participants with major fall-related injuries appeared less accurate and slower than those without. The effects were less prominent in the older participants without neuropathy.

    The results suggest that people with lower limb neuromuscular impairment rely on neurocognitive speed, as determined by the ability to perceive a stimulus and quickly inhibit a motor response, to maintain postural control when navigating an uneven surface and, possibly, to prevent severe injury in the event of a fall.

    The texting young woman likely has a quicker brain… which may be clinically detectable.

    Figure A   

    A participant’s hand appropriately grasping the falling ReacStick device, which shows illuminated lights.

    Figure B

    Scatterplot demonstrating that greater (more accurate and/or faster) ReacStick performance was associated with reduce step width range on the uneven surface.

                                                             

    Publication

    Richardson JK, Eckner JT, Allet LA, Kim H, Ashton-Miller JA. Complex and simple clinical reaction times are associated with gait, balance, and major fall injury in older subjects with diabetic peripheral neuropathy. Am J Phys Med Rehabil 2017;96:8-16.

    http://journals.lww.com/ajpmr/Citation/2017/01000/Complex_and_Simple_Clinical_Reaction_Times_Are.2.aspx

     

    The Author

    Dr. Richardson is a Professor of Physical Medicine/Rehabilitation at the University of Michigan where he directs the Electrodiagnostic Laboratory and is actively engaged in patient care and teaching.His primary research interests include investigating the influence of peripheral nerve function on gait/balance, and translating insights from the biomechanics laboratory into the clinical realm. 

     

     

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  • 26 Jan 2017 by Michele Callisaya

    Falls continue to be a major cause of injury and loss of independence in older people.  Therefore, screening for fall risk is an important part of geriatric care.   We previously identified that there is a cumulative effect on fall risk if people suffer from both poorer physical and cognitive function ( https://www.ncbi.nlm.nih.gov/pubmed/23410920). The current study built further on these findings by only using clinical measures, which are quick and easy to administer (without the need of a qualified health professional) to make them feasible in a clinical setting. Therefore, we searched for a measure that incorporated both gait and cognition and was quick and easy to administer.

    We used the Motoric Cognitive Risk (MCR) syndrome - developed by Prof Joe Verghese (Albert Einstein College of Medicine, USA) – which is characterised by both slow gait and presence of a subjective cognitive complaint, and therefore ideal for our purposes.

    Our study aimed to examine if MCR increased the risk of falls and if the diagnosis of the combined MCR was a stronger risk factor for falls than its components (i.e. slow gait or cognitive complaint). Using data from five longitudinal population-based studies (n=6204), we found that 45% of participants reported a cognitive complaint, 13.8% had slow gait, 7.5% had a diagnosis of MCR, and 33.9% reported any fall (see Figure for individual study results).  MCR was associated with a 44% increase of falls in the pooled analysis of all studies.  This increased risk of falls of the combined MCR was higher than for gait speed (30%) or subjective cognitive complaints (25%) alone.

     

     

     

     

     

     

     

     

     

     

    Figure MCR status plotted against the percentage of people who reported any fall

    Reprinted from Journal of Alzheimers Disease, , 18;53(3): Callisaya ML,  Ayers E, Barzilai N et al. Motoric Cognitive Risk Syndrome and Falls A multi-center study1043-52. Copyright (2016), with permission from IOS Press”.  The publication is available at IOS Press through http://dx.doi.org/10.3233/JAD-160230

    The simplicity and low cost of MCR makes this an attractive falls-risk screening tool for the busy clinician. People with MCR should then proceed to a more thorough multifactorial falls assessment, to understand the cause of the slow gait (e.g. balance assessment) and poor cognitive function (e.g. neuropsychological assessment), and guide a tailored intervention program.

     

    Publication

    Callisaya ML, Ayers E, Barzilai N, Ferrucci L, Guralnik JM, Lipton RB, Otahal P, Srikanth VK, Verghese J.  Motoric Cognitive Risk Syndrome and Falls Risk: A Multi-Center Study.

    J Alzheimers Dis. 2016 Jun 18;53(3):1043-52. doi: 10.3233/JAD-160230.  http://dx.doi.org/10.3233/JAD-160230

     

    Dr Michele Callisaya

    Michele leads the Brain Ageing group at the University of Tasmania and is an Aged Care and Rehabilitation physiotherapist at the Royal Hobart Hospital, Australia.   She motivates herself to go trail running with thoughts of improving her strength, balance and reaction time as age inevitably creeps up. 

     

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  • 26 Jan 2017 by Yoshiyuki Kobayashi

    Recent advances in sensor technology allow for the science of gait features to be applied to new services. These services may comprise of e.g. onsite customisation of footwear or garments, sensor-based applications such as activity monitoring systems, and detailed surveillance monitoring. At the Japanese National Institute of Advanced Industrial Science and Technology, we conducted a study to describe sex- and age-differences in gait features of healthy individuals to support others developing services based on gait features.

    In this study, we analysed a large dataset of gait in healthy individuals (99 males and 92 females aged 20 to 75) measured in our laboratory. The dataset comprised of 3D positional data obtained using 55 reflective makers and a 3D motion capture system during a 10m overground walk. This dataset is now available online as part of the AIST Gait Database. The AIST Gait Database site is currently only available in Japanese but please contact "dhrc-liaison-ml@aist.go.jp" for assistance in English. We used a principal component analysis (PCA) to identify sex and age effects on walking patterns in the data. PCA can help identify waveform-features from continuous data specific to certain groups, where previous studies disregarded large amount of data and only investigated selected variables at discrete time points. In addition, the waveforms can be reconstructed from the scores of the principal component vectors (PCV), which enabled us to classify a range of different gait patterns. Using this analysis, we identified 6 PCVs which explain more than 5 % of the total variance in the data as shown in Figure 1. Of these, we found a significant interaction between sex and age on PCV 1 and a significant effect of sex on PCV 6, which indicates that these PCVs contain sex differences in the walking patterns. An animation of reconstructed gait with amplified sex differences can be seen in Figure 1 [figure 1(a): PCV1 and figure 1(b): PCV 6].

    Our findings advance the understanding of the nature of human gait. We identified clear sex differences in walking patterns, and showed that some of these patterns are affected by ageing while others are not. We believe that these finding are applicable to various health-related services. For example, we can now express gait features of an individual as a score and compare it to a reference group based on the current study’s PCVs. This information might be essential for optimising gait interventions and tracking changes over time. We are now focusing on launching new gait characteristics assessment services for healthy people based on the results of this study.
     

     

     Figure 1: Reconstructed gait patterns related to (a) PCV1 and (b) PCV 6. (a) Since young females tend to exhibit larger scores on PCV1, PCV1 + 3 SD figures (red line) indicate extremely young female-like gait patterns, and PCV1 – 3 SD figures (green line) indicate extremely male-like gait patterns; (b) Since females tend to exhibit larger scores on PCV6, PCV6 + 3SD figures (red line) indicate extremely female-like gait patterns and PCV6 - 3SD figures (green line) indicate extremely male-like gait patterns.

     

    Publication

    Kobayashi Y, Hobara H, Heldoorn TA, Kouchi M, Mochimaru M. (2016). Age-independent and age-dependent sex differences in gait pattern determined by principal component analysis. Gait Posture. 2016 May;46:11-7.

    https://www.ncbi.nlm.nih.gov/pubmed/27131170

     

     

    The author

    ·      Yoshiyuki Kobayashi (Ph.D.)

    ·      Senior research scientist, Digital Human Research Group, Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology

    ·      Yoshiyuki Kobayashi Ph.D. is a Senior Research Scientist at Digital Human Research Group, Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology. The goal of his research is the prevention of falling during latter stage of one’s life. To achieve this goal, he is now working with various private companies in Japan to build a system to describe and feedback the gait features of users.

     

     

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  • 14 Jan 2017 by Anat Mirelman

    The prevalence of falls in older adults is huge: one out of every 3 adults aged 65 years or older will fall at least once per year. These numbers are even higher in neurodegenerative conditions such as in Parkinson’s disease and in people with cognitive impairments.  Recent studies showed that certain aspects of cognition, especially executive function, are critical for safe ambulation.  This makes sense intuitively if we imagine the cognitive skills needed just to cross a busy intersection or to negotiate obstacles. We aimed to use virtual reality to safely train the motor aspects that are important for fall risk, while also implicitly teaching participants to improve cognitive functions vital to safe ambulation.

     

    We carried out a randomized controlled trial at five clinical centers. Adults aged 60−90 years with a high risk of falls, i.e., two or more falls in the 6 months before the study, and with varied motor and cognitive deficits were randomly assigned to receive 6 weeks of treadmill training plus VR or treadmill training alone. Both groups aimed to train three times per week for 6 weeks, with each session lasting about 45 minutes. The VR system consisted of a motion-capture camera and a computer-generated simulation that includes real-life challenges such as obstacles, multiple pathways, and distracters that requires continual adjustment of the stepping pattern. The subject’s gait was measured in real-time and projected on into the VR that was displayed on a large screen. The primary outcome was the incident rate of falls during the 6 months after the end of training.

     

    Data from 282 participants (VR group n=154, and treadmill training alone group n=148) was analyzed. Before training, the falls incident rate was similar in both training arms. Six months after the end of training, the rate decreased in both groups, but it was 42% significantly lower in the treadmill training plus VR group, compared to the treadmill training alone group (figure 1).

    Figure 1:  On the left is a picture of the Virtual Reality setting. The user walks on the treadmill while engaging in tasks in the virtual scene. The figure on the right shows the reduction in incident fall rate ,6 months post intervention , in the treadmill  training plus virtual reality group compared to the active control group of treadmill training.

     

    The study has important implications for research and clinical practice. Treadmill training plus VR successfully reduced in fall rates in a diverse group of older adults at high risk for falls. Adherence and participation were very high, no serious adverse events were observed, and participants reported high satisfaction and enjoyment. This RCT demonstrates the added value of the VR component and suggests that this approach could be a viable option for improving motor-cognitive function and reducing fall risk in older adults.

     

    Publication

     

    Addition of a non-immersive virtual reality component to treadmill training to reduce fall risk in older adults (V-TIME): a randomized controlled trial.

    Mirelman A, Rochester L, Maidan I, Del Din S, Alcock L, Nieuwhof F, Rikkert MO, Bloem BR, Pelosin E, Avanzino L, Abbruzzese G, Dockx K, Bekkers E, Giladi N, Nieuwboer A, Hausdorff JM.

    Lancet. 2016 Sep 17;388(10050):1170-82. doi: 10.1016/S0140-6736(16)31325-3.

     

    http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(16)31325-3/abstract

     

    The author

    Anat Mirelman, PhD

    Laboratory for the study of Early Markers Of  Neurodegeneration (LEMON)

    Center for the study of Movement , Cognition and Mobility

    Neurological Institute, Tel Aviv Medical Center

    Sackler School of Medicine, Tel Aviv University, Israel

     

    Anat Mirelman  is the director of the Laboratory for Early Markers of Neurodegeneration at the Tel Aviv Medical Centre and a senior lecturer at Sackler school of Medicine at Tel Aviv University. Dr. Mirelman’s main research interests are in the assessment and treatment of motor-cognitive impairments in neurodegenerative conditions and in identifying early markers of disease in populations at risk.

     

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  • 07 Dec 2016 by Stephen Lord

    Motor impairment includes impairments in the control of movement which incorporates the central nervous system, muscle function and motor performance https://motorimpairment.neura.edu.au/. Motor Impairment can therefore be seen as a pathway that causes physical disability in a wide range of these diseases (Figure 1). Our research has used falls as a paradigm to investigate to which extent various motor outputs, such as reaching, standing, stepping and walking, are dysfunctional.  Within the motor impairment framework, falls can be viewed of what constitutes normal physiological performance.

    Figure 1. A conceptual model for the control of movement which emphasises that afferent feedback from muscles and motor actions arises continuously. This feedback needs to be processed with feedback from centrally generated motor signals. Deficits at any level are likely to impairments related to standing and locomotion.

    The purpose of this article was to describe a physiological profiling approach for documenting motor impairments in older people at risk of falls and clinical groups with balance disorders. In essence, this approach involves the quantitative assessment of important physiological capacities required for stable mobility and fall avoidance, and the compilation of normative data that can be used as a reference for individual and disease group-based assessments. The article collated and summarised data from several studies that have used the Physiological Profile Assessment (PPA). It presented physiological profiles across a number of seemingly ‘single’ diseases or disability groups including people with multiple sclerosis, stroke, cognitive impairment, depressed mood, macular degeneration, lower limb osteoarthritis and prior polio. It emphasized that (i) motor impairment arises via reductions in a wide range of sensorimotor abilities; (ii) the PPA approach not only gives a snapshot of the physiological capacity of an individual, but also provides insight into the deficits among groups of individuals with particular diseases; and (iii) deficits in seemingly restricted and disparate physiological domains (e.g. vision, strength, cognition) are funnelled into balance and mobility impairments.

    Figure 2. The overall PPA fall-risk scores is visualised for the clinical populations in relation to age, with the fall risk categorised from ‘very low’ to ‘very marked’. Ageing is associated with functional decline.  The clinical groups all have high scores compared to their peers of the same age.

    When used on an individual basis, the PPA can provide measurements of physiological frailty and fall risk, which can be used to guide subsequent personalised interventions to enhance mobility and reduce fall risk. Further, when viewed from the perspective of disease groups, this approach can provide insight into the physiology of tasks such as standing and walking and how these tasks are commonly affected in different diseases. With the challenges of population ageing, systematic approaches to motor impairment documentation and amelioration may assist older people and those with balance disorders to maintain functional abilities and independence.

    Publication

    Lord SR, Delbaere K, Gandevia SC. Use of a physiological profile to document motor impairment in ageing and in clinical groups. Journal of Physiology 2016;594:4513-4523. http://onlinelibrary.wiley.com/doi/10.1113/JP271108/pdf

    Affiliation

    Professor and Senior Principal Research Fellow, Neuroscience Research Australia, University of New South Wales, Sydney, Australia

    Bio

    Stephen Lord is a Senior Principal Research Scientist at Neuroscience Research Australia and chief investigator on NeuRA’s Motor Impairment Program https://motorimpairment.neura.edu.au/. He has published over 400 papers in the areas of balance, gait and falls in older people and is acknowledged as a leading international researcher in his field. His research follows two main themes: the identification of physiological risk factors for falls and the development and evaluation of fall prevention strategies.

     

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  • 01 Dec 2016 by Matija Milosevic

         Individuals with cervical spinal cord injury (SCI) usually sustain impairments of the trunk as well as the lower and upper limb muscles, resulting in compromised sitting balance. They are often unable to maintain unsupported sitting balance and rely on their feet and arms for support. However, foot support forces have often been ignored during sitting balance assessments. Therefore, the objectives of this study were to: 1) present an experimental setup for measuring postural control during sitting balance that includes contributions of the foot support forces; and 2) compare postural control of individuals with cervical SCI to able-bodied individuals during sitting balance.

         Ten able-bodied individuals and six individuals with cervical SCI were recruited and asked to maintain upright quiet sitting posture on an instrumented chair during two 60 second trials. The forces on the seat and the foot support surfaces were measured separately using two force plates (Figure 1A). The global center of pressure sway (COPG) was obtained from the measurements on the two force plates according to Equation 1, and the sway on the seat (COPS) and foot support (COPF) force plates was calculated individually. The results illustrated in Figure 1B showed that global and seat support sway of individuals with cervical SCI was twice as large compared to able-bodied individuals, while foot support sway was not significantly different between the two groups. Comparison between global and seat sways showed that anterior-posterior velocity of global sway was larger compared to the seat sway in both groups.

         Our study presented the experimental setup for measuring postural control during sitting balance of individuals with SCI that includes contributions of the foot support forces. The results suggest that postural control of individuals with cervical SCI was worse than that of able-bodied individuals. The trunk swayed more in individuals with SCI, while the stabilization effect of the feet did not differ between the groups. Foot support affected anterior-posterior fluctuations in both groups equally. Thus, trunk control is the dominant mechanism contributing to sitting balance in both able-bodied and SCI individuals, whereas foot support forces provide passive support, which is important for sitting stability. Overall, these results suggest that rehabilitation should focus on recovering trunk function as well as on optimizing foot placement to provide additional support.

     

    Figure 1: A) Experimental setup for sitting balance, where COPS represents trunk sway on the seat surface, COPF represents foot support sway on the ground, and COPG represents the global sway. Vertical forces on the seat surface (FzS and FzS), shear forces on the foot support surface (FxF and FyF) and the height between the seat and foot support force places (h) are also shown in Equation 1. B) Example of the sway for COPG, COPS, and COPF sway for one able-bodied individual (AB) and one individual with spinal cord injury (SCI), where AP is anterior-posterior and ML is medial-lateral sway.

     

    Publication
    Milosevic M, Masani K, Kuipers MJ, Rahouni H, Verrier MC, McConville KM, Popovic MR (2015). Trunk control impairment is responsible for postural instability during quiet sitting in individuals with cervical spinal cord injury. Clin Biomech (Bristol, Avon). 2015 Jun;30(5):507-12. doi: 10.1016/j.clinbiomech.2015.03.002.
    Link: https://www.ncbi.nlm.nih.gov/pubmed/25812727
     

    The author
    Matija Milosevic, Ph.D.
    University of Tokyo
    Department of Life Sciences, Graduate School of Arts and Sciences

    Matija Milosevic received the Ph.D. degree in biomedical engineering from the University of Toronto, Canada, in 2015. He is currently an NSERC Post-Doctoral Fellow at the University of Tokyo, Japan. His research interests include postural control, biomechanics, neurophysiology, neural systems, functional electrical stimulation, spinal cord injury and rehabilitation engineering.
     

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  • 16 Nov 2016 by Masahiro Fujimoto

    People at increased risk of falls may be less able to control their balance. The ability to control balance is loosely defined as the ability to maintain the body’s center of mass (COM) within the base of support (BOS) formed by the feet. During dynamic activities such as walking, this definition does not hold as the COM frequently travels out of the BOS without leading to falls. Dynamic balance control during walking has therefore been quantified based on the position and velocity of the COM with respect to the BOS, where an inability to regulate the COM velocity or momentum could be a cause for gait imbalance. Given that acceleration induces changes in velocity, COM acceleration could enhance our understanding of how momentum is controlled during gait, which would allow us to better understand and identify individuals with balance control difficulties. In this study, we compared dynamic momentum control among healthy young adults, elderly non-fallers and elderly fallers during walking.

     

    The control of the COM in forward-backward direction was examined during walking in 15 healthy young adults, 15 elderly non-fallers and 15 elderly fallers. Using a single-link-plus-foot inverted pendulum model, we determined the boundaries of the region of stability in two ways. One used conventional method based on the COM position at toe-off and its instantaneous velocity. The other used our novel method based on the peak acceleration of the COM prior to toe-off. Although there was no significant difference in the peak forward COM velocity between healthy young adults and elderly non-fallers, the peak forward COM acceleration differed significantly, suggesting age-related differences in momentum control during walking (Fig.1a). Elderly fallers demonstrated significantly lower forward COM velocities and accelerations and placed their COM significantly more forward at toe-off than the other groups, which resulted in their COM position-velocity or COM position-acceleration combination to stay within or close to the forward boundaries of the region of stability (Fig.1b, c). This suggests that elderly fallers adopted a more conservative gait balance strategy compared to healthy subjects, demonstrating larger stability margins. Importantly, our novel method was capable of distinguishing elderly non-fallers from the young group.

     

    Healthy young adults and elderly non-fallers utilized similar momentum to propel the body forward, but controlled this momentum differently. Our elderly participants demonstrated significantly smaller COM acceleration, which could be indicative of their poor momentum control perhaps due to reduced muscular functions and a protective strategy for potential falls. Since a fall could be induced by a sudden change in momentum, such as trips or slips, inability to properly control COM momentum would result in imbalance in response to such external perturbations, predisposing them to a greater risk of falls. Examining the COM acceleration in addition to its velocity would provide a better understanding of a person’s momentum control. This would facilitate early identification of older individuals at a high risk of falls and implementation of fall prevention interventions.

    Figure 1: (a) Peak forward COM velocity and acceleration during walking in healthy young participants (Young), elderly non-fallers (Elderly) and elderly fallers (Fallers). (b) Region of stability (ROS) calculated based on the conventional method using COM velocity and position. The black and gray solid lines indicate the forward and backward boundaries of the ROS, respectively. (c) ROS calculated based on our method using peak COM acceleration and position. Solid and dashed curves indicate the forward boundaries of the ROS averaged for each subject group. *†‡p<0.05.

     

    Publication

    Fujimoto M, Chou LS. (2016). Sagittal plane momentum control during walking in elderly fallers. Gait Posture. 2016 Mar;45:121-6. doi: 10.1016/j.gaitpost.2016.01.009.
    http://www.ncbi.nlm.nih.gov/pubmed/26979893

     

    The author

    Masahiro Fujimoto, Ph.D.
    Assistant Professor
    College of Sport and Health Science, Ritsumeikan University, Japan

    Masahiro Fujimoto received his Ph.D. in Biomechanics at the University of Oregon and worked as a Postdoctoral Fellow in the University of Maryland School of Medicine. His research interests include fall risk assessment and fall prevention in older adults through a better understanding of the biomechanics and motor control of human balance and movement.

     

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  • 11 Nov 2016 by Soichiro Fujiki

    The ability to adapt our walking pattern to the environment is essential for everyday locomotion. This adaptive locomotion is achieved through highly coordinated movements within (intra) and between (inter) our limbs. However, it is not clear what mechanisms exist behind this coordination. Adaptation strategies during walking have previously been examined using split-belt treadmills. In these experiments, the treadmill has two independently controlled belts that force the legs to move at different speeds. In such split-belt treadmill walking, two types of adaptations have been observed: early and late adaptations. Early adaptations appear as rapid changes in inter-limb (e.g. relative phase between the legs) and intra-limb (e.g. stance duration per gait cycle) coordination. By contrast, late adaptations occur gradually after the early adaptations and only involve inter-limb coordination. Furthermore, inter-limb coordination shows after-effects when the belt speeds are equalized. It has been suggested that these adaptations are governed primarily by the spinal cord and cerebellum, but the underlying mechanism remains unclear. To understand the mechanism of these adaptations, we developed a control model based on the physiological findings, and investigated its adaptive behavior via split-belt treadmill walking experiments using both computer simulations and an experimental bipedal robot (Fig. A).

    We assumed that the foot contact timing plays a crucial role for these adaptations because previous studies have showed that the vertical ground reaction forces and ankle stiffness remarkably change at foot contact due to changes in the belt speed condition. We developed a two-layered control model composed of spinal and cerebellar models (Fig. B). The spinal model generates rhythmic motor commands using an oscillator network based on a central pattern generator (CPG). It modulates the command timings formulated in immediate response to foot contact, while the cerebellar model modifies motor commands (only affecting the temporal pattern) through learning based on error information related to differences between the predicted and actual foot contact timings of each leg.

    Our results showed that the robot exhibited rapid changes in inter-limb and intra-limb coordination that were similar to the early adaptations observed in humans. In addition, despite the lack of direct inter-limb coordination control, gradual changes and after-effects in the inter-limb coordination appeared in a manner that was similar to the late adaptations and after-effects observed in humans (Fig. C). Our results suggest that the modulation of the foot contact timing of each limb could induce the appropriate modulation of the whole body motion (i.e. achieving inter-limb coordination). The model studies are expected to be a useful tool to investigate hypotheses, such as ours, which are difficult to examine from the human measurement experiments.

     

    Publication

    Fujiki S, Aoi S, Funato T, Tomita N, Senda K, Tsuchiya K (2015). Adaptation mechanism of interlimb coordination in human split-belt treadmill walking through learning of foot contact timing: a robotics study. J. R. Soc. Interface. 2015 Jul 12:20150542. doi:10.1098/rsif.2015.0542.

    http://dx.doi.org/10.1098/rsif.2015.0542

     

    The author

    Soichiro Fujiki is an assistant professor at the University of Tokyo. He obtained a PhD in Engineering at the Kyoto University, Japan. The goal of his research is to elucidate the mechanism behind motor control during locomotion.  To investigate the control mechanism in humans and animals, he measures the motions of humans and animals and conducts numerical simulations and the robot experiments.

     

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  • 10 Nov 2016 by Brad Manor

    When standing or walking, we often perform additional cognitive tasks such as talking, reading or listening to a friend.  This “dual tasking” is critical to the completion of activities of daily living.  Dual-tasking often results in reduced performance in one or both tasks, especially in older adults. The observation that dual tasking comes at a “cost” to performance means that the involved tasks use shared brain networks. Strategies designed to increase brain network excitability and/or efficiency thus hold great promise to improve dual task capacity across the lifespan. Transcranial direct current stimulation (tDCS) is one safe and non-invasive method that uses low-level electrical currents to temporarily change brain excitability. The purpose of this experiment was to determine the immediate effects of tDCS on dual task balance performance in older adults.

     

    Thirty-seven adults aged 60-85 years completed two laboratory visits separated by one week.  They received 20-minutes of tDCS during each visit. On one visit, they received tDCS designed to increase the excitability of the left dorsolateral prefrontal cortex—a region closely linked to cognition and motor control.  On the other visit, they received “sham,” (i.e. placebo) stimulation.  Participants and study personnel were blinded to tDCS condition.  Before and after each tDCS session, participants completed a dual task paradigm comprising trials of standing and walking both with and without performance of a mental arithmetic task.  The Figure below illustrates the effects of tDCS on single- and dual-task standing postural sway in a selected participant.  Results indicated that real tDCS reduced the dual task cost to both standing postural sway area and walking speed compared to sham stimulation. It also effectively mitigated the cost of walking on performance within the serial subtraction task. Intriguingly, tDCS did not alter standing, walking, or serial-subtraction performance within single task conditions. The reduction in dual task costs was instead spurred by significantly improved performance in each outcome specifically within dual task conditions.

     

    This study demonstrated for the first time that dual tasking performance can be enhanced by modulating prefrontal brain excitability using non-invasive electrical brain stimulation. These results suggest that following just 20 minutes of stimulation, older adults may be able to more safely stand and walk while completing additional, unrelated cognitive tasks.  These results also suggest that the cost of dual tasking is not a fixed, obligatory consequence of aging, and identify tDCS as a novel approach to preserving dual tasking and balance into old age.

     

    Publication

    Manor B, Zhou J, Jor’dan A, Zhang J, Fang J, Pascual-Leone A. (2016). Reduction of dual-task costs by noninvasive modulation of prefrontal activity in healthy elders. Journal of Cognitive Neuroscience. Doi: 10.1162/jocn_a_00897.
    https://www.ncbi.nlm.nih.gov/pubmed/26488591

     

    The author

    Brad Manor, PhD
    Assistant Scientist II, Institute for Aging Research, Hebrew SeniorLife
    Assistant Professor of Medicine, Harvard Medical School

    Brad Manor is the Director of the Mobility and Brain Function Research Program at Hebrew SeniorLife’s Institute for Aging Research and Harvard Medical School.  His research combines brain imaging, non-invasive brain stimulation, and advanced signal processing techniques to understand and enhance the neural control of balance in aging and disease.  

     

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  • 07 Nov 2016 by Masahiro Shinya

    Reflex is the first line of defense for preventing falls when you are perturbed. The reflex system, especially medium-latency or long-latency reflex system, is very flexible and it has been known that the central nervous system takes advantage of prior knowledge about potential upcoming perturbations for modulating postural reflexes. In other words, if you know that may be perturbed, you can prepare for the perturbation. There are two distinct aspects of prior knowledge: spatial and temporal. This study investigated how each of spatial and temporal prior knowledge contributes to the shortening of muscle response latency.

     

    Eleven participants walked on a split-belt treadmill. They were perturbed by sudden and unexpected acceleration or deceleration of the right belt at right foot contact. Spatial prior knowledge was given by verbal instruction of possible direction (only acceleration, only deceleration, or both might occur) of upcoming perturbation at the beginning of an experimental session. Temporal prior knowledge was given to participants by warning tones at foot contact during three consecutive strides before the perturbation. In response to acceleration perturbation, reflexive muscle activity was observed in soleus and gastrocnemius muscles. Onset latency of the gastrocnemius response was shorter (72 ms vs. 58 ms) when participants knew the timing of the upcoming perturbation, whereas the latency was independent no matter whether the participants knew the direction of the perturbation. Soleus latency (44 ms) was not influenced by directional or temporal prior knowledge.

     

    The results suggest that excitability in the supra-spinal neural circuit, which mediates the long-latency reflex, might be enhanced by knowing the timing of the upcoming perturbation. On the other hand, excitability in the spinal neural circuit, which mediates the short-latency reflex, was not influenced by the prior knowledge. Future research should investigate whether it is possible for older people to anticipate both predictable and unpredictable perturbations and find a way to train the Central Nervous Systems to prepare for the postural responses by guessing about potential perturbation.

     

    Figure. Knowing the timing of upcoming perturbation shortens reflex latency.

     

    Publication

    Shinya M, Kawashima N, Nakazawa K (2016). Temporal, but not Directional, Prior Knowledge Shortens Muscle Reflex Latency in Response to Sudden Transition of Support Surface During Walking. Front Hum Neurosci. 2016 Feb 8;10:29. doi: 10.3389/fnhum.2016.00029.

    https://www.ncbi.nlm.nih.gov/pubmed/26903838

     

    The author

    Masahiro SHINYA, assistant professor at Sports Science Laboratory, Department of Life Sciences, the University of Tokyo, works on human motor control during walking and standing. He got his PhD in Human and Environmental Studies at the Kyoto University, Japan. Before he got this position, he worked as a postdoc fellow with Prof. Pearson at University of Alberta where he studied spatial working memory during animal and human locomotion.

     

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