• 24 Oct 2017 by Mario Inacio

    As people get older, neuromuscular changes often result in an impaired ability to produce rapid force. Such a reduction in muscular power can then lead to functional mobility impairments, poor balance and an increased risk for falls. However, the mechanistic understanding of how reduced muscular power affects function and balance recovery, and how we can counteract it, is still lacking. This review selected studies that would provide further insight about the mechanisms that lead to the reported age-related loss of muscular power and functional impairments, as well as the benefits of power training compared to the traditional strength training approach for muscular performance, function and balance.

     

    Our narrative review demonstrated that age-related reductions in nerve conduction velocity, discharge rate, number of functional motor units and available motorneurons are well-established.  Furthermore, muscle architecture and composition, muscle contractility and selective denervation of type II skeletal muscle fibers (high force and fast contraction fibers) are also affected by old age. These age-related changes lead to reduced neural drive, rate of neuromuscular activation and reduced muscle mass, classically known as sarcopenia. Ultimately, these changes have an impact on muscular performance and the rate of force development, which are both a crucial for generating muscle power. This could explain why impaired muscle power is such a potent predictor of functional independence, functional impairments and falls.

     

    It seems quite clear from the literature that these age-related changes in our muscles are inevitable. So should we just give up and accept our fate? Or can we actually defeat the laws of nature and reduce (or even reverse!) the rate of age-related decline through exercise training. There is evidence that strength resistance training can prevent neuronal denervation and increase neural drive resulting in a greater neuromuscular performance. However, this type of resistance training has limited effects on power production because it does not focus on velocity of execution. A potentially viable alternative is power training. This alternative focuses on fast, explosive movements to have a stronger effect on muscle power.

     

    Our literature review revealed a large variability in the paradigms used for traditional strength and power training, which makes it difficult to draw firm conclusions. Nonetheless, there seems to be some evidence suggesting that muscle power training might be beneficial in older individuals for improving muscular performance and functional mobility. Future research could look at whether power training could also prevent falls and investigate the optimal dose to have a maximal effect on functional mobility.

     

     

    Figure. Conceptual model for age-related changes that lead to functional impairments and how strength and power training can affect these changes.

     

    Copyright

    The ISPGR blog applies Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license to figure and text of the article.

    https://creativecommons.org/licenses/by-sa/4.0/

    Publication

    Inacio, M. (2016). The Loss of Power and Need for Power Training in Older Adults. Current Geriatrics Reports, 5(3), 141-149. doi: 10.1007/s13670-016-0176-7.

    https://link.springer.com/article/10.1007/s13670-016-0176-7

    The author

    • Mario Inacio, MS, PhD

                   Physical Therapy and Rehabilitation Science Department, University of Maryland, Baltimore.

    • I am a postdoctoral fellow at the Physical Therapy and Rehabilitation Science Department in the University of Maryland, Baltimore. My research interests are in understanding the neuromuscular mechanisms of balance control and fall prevention, with emphasis in muscular performance and power production.

     

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  • 15 Oct 2017 by Katrijn Smulders

    Every neurologist who treats people with Parkinson’s disease knows that his patient has difficulty walking and is at risk for falls. Also, they know that the pharmacological treatment that they will prescribe, levodopa, can only partly improve these symptoms. The neurologist will assess their patient on their ability to walk, their postural instability and will also ask whether they have had any recent falls. In addition to these subjective assessments, more objective measures of gait and balance in PD have been collected in the lab. This wealth of data inspired my colleagues and I to review these more objective studies. Our aim was to evaluate the effect of drugs prescribed to alleviate gait impairment and fall risk in PD.

    We started this project taking on two positions: First, walking ability in daily life goes beyond gait patterns during straight ahead walking, and should include starting to walk, turning, and avoiding obstacles. Second, people with PD often take medication for other reasons than for PD, as comorbidities are common. Thus, we also wondered what beneficial or detrimental effects these drugs can have on gait in people with PD.

    The literature reports quite consistently that levodopa and other dopaminergic medication improve spatial parameters of gait, but not temporal parameters. Other drugs used in PD treatment aim to modulate activity of acetylcholine, glutamate and norepinephrine. Of these drugs, cholinergic agents are the most promising to improve postural instability. Glutamate and norepinephrine drugs are much less studied and show inconsistent findings.

    The effect of drugs with sedative or anticholinergic properties – frequently prescribed for bladder problems, pain, or mental health problems - have been widely studied in populations other than PD. These drugs can worsen gait and put people at risk for falls. It is not unreasonable to suspect that these effects would also occur in patients with PD, but this hypothesis remains to be tested.

    Unfortunately, there are very few studies that evaluate gait initiation, turning and obstacle avoidance or any walking that is not just straight walking. This is remarkable considering that people with PD are particularly limited in more complex gait tasks than straight ahead walking. Therefore, our review was not able to draw any conclusions on walking ability during more realistic scenarios.

    We found serious gaps in the literature. First, walking ability other than straight ahead walking is highly understudied. Secondly, trial designs are largely suboptimal. Studies are either placebo-controlled RCT’s using subjective gait scores, or use objective gait measures but are poorly controlled. It seems feasible to use the best of both ‘worlds’ to improve trial design and further enhance our insights into pharmacological effects on gait and fall risk in PD.

     

     

     

     

    Copyright

    The ISPGR blog applies Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license to figure and text of the article.

    https://creativecommons.org/licenses/by-sa/4.0/

    Publication

    Katrijn Smulders, Marian L. Dale, Patricia Carlson-Kuhta, John G. Nutt, Fay B. Horak. Pharmacological treatment in Parkinson's disease: effects on gait. Parkinsonism Rel Disorders 2016 vol 31:3-13. https://www-ncbi-nlm-nih-gov.liboff.ohsu.edu/pmc/articles/PMC3923955/   

    The author

    Katrijn Smulders is Senior researcher at the Research department of the Sint Maartenkliniek, Nijmegen (The Netherlands).

    Katrijn’s research in PD has focused predominantly on higher-order control of gait and balance. She completed her PhD at the Parkinson Center at the Radboudumc in Nijmegen (Netherlands) with Bas Bloem and was a post-doc in Fay Horak’s Balance Disorders Lab at OHSU (Portland, OR). At the Sint Maartenskliniek, she studies gait and balance control in orthopedic patients, with a specific interest in the evaluation of orthopedic surgery using objective performance measures. 

     

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  • 28 Sep 2017 by Marie-Laure Welter

    In humans, gait initiation is particularly challenging for motor and postural control. While standing on only two legs, we have to move our whole body forward and pass from a (relatively) stable (double leg stance) to an (very!) unstable position (single leg stance). This process is associated with anticipatory postural adjustments (APAs). The neural substrates for generating these APAs and initiating a step are not fully known. By applying repetitive transcranial magnetic stimulation (rTMS), we can manipulate APAs. Previous research showed that rTMS applied above the supplementary motor area provokes a shortening of the APA duration of the first step with no change in APA amplitude and rTMS applied over the cerebellum affects spatial characteristics of walking during locomotor adaptation. This study extends this research further by looking at the effects of supplementary motor area and cerebellar stimulation on the generation of APAs and gait initiation.

     

    We selectively disrupted the supplementary motor area and cerebellum with continuous theta burst rTMS (cTBS, 600 stimuli, three-pulse bursts at 50 Hz, repeated every 200 ms continuously for 40 s-5 Hz) and evaluated the effects of the stimulation on the APAs and execution phases of gait initiation. We recorded biomechanical parameters of gait initiation and EMG activity of the lower leg muscles in 22 healthy volunteers. Our volunteers were instructed to walk at their usual self-paced speed for 10 trials before and after rTMS. They performed separate sessions in a randomised order for rTMS over the supplementary motor area, cerebellum and sham stimulation (to either supplementary motor area or cerebellum), the sessions being separated at least 7 days. We found that functional inhibition of the supplementary motor area led to a shortened APA phase duration with advanced and increased muscle activity. During execution, it also advanced muscle co-activation and decreased the duration of stance soleus activity. Functional inhibition of the cerebellum on the other hand did not influence the APA phase duration and amplitude. During execution, it did increase muscle co-activation and decreased execution duration with increased swing soleus muscle duration and activity. Neither SMA nor cerebellar functional inhibition provoked significant changes in the step length and velocity or postural control during gait execution (i.e. double stance duration and braking index).

    The results support distinct roles for the supplementary motor area and the lateral posterior cerebellum in human gait initiation. The supplementary motor area is important for the timing and amplitude of the preparatory phase of the gait initiation, and the posterior cerebellum contributes to the inter- and intra-limb muscle coordination, and probably coupling between the APAs and the execution phases. This study enhances our understanding of how the cortico-pontine-cerebello-thalamo-cortical pathway contributes to the preparation and the execution of the first step in humans.

     

    Figure – Effects of cTBS SMA and sham stimulation on gait initiation in an individual subject. Note that after SMA stimulation (left panel) the duration of the anticipatory postural adjustments phase (delay between t0 and FC) decreased with an advanced TA muscle activity. Such is not the case after sham stimulation (right panel).

     

    Copyright

    The ISPGR blog applies Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license to figure and text of the article.

    https://creativecommons.org/licenses/by-sa/4.0/

     

    Publication

    Richard A, Van Hamme A, Drevelle X, Golmard JL, Meunier S, Welter ML. Contribution of the supplementary motor area and the cerebellum to the anticipatory postural adjustments and execution phases of human gait initiation. Neuroscience. 2017 Sep 1;358:181-189. doi: 10.1016/j.neuroscience.2017.06.047. Epub 2017 Jul 1. PMID: 28673716 (http://www.sciencedirect.com/science/article/pii/S0306452217304529?via%3Dihub)

     

     

    The author

    Marie-Laure Welter is Professor of Medicine, Chair of Physiology at Rouen-Normandie University, and head of the Neurophysiology Unit at the University Hospital Rouen-Normandie (France).  Her research program is devoted to the understanding of the pathophysiology of complex movement disorders, such as Parkinson’s disease, essential tremor or dystonia, at the Brain and Spine Institute-French National Institute of Health and Medical Research (ICM/INSERM) . Her overarching aim is to identify new therapeutic targets, especially in the field of functional neurosurgery and gait and balance disorders, with a combined clinical and electrophysiological approach.

     

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  • 22 Sep 2017 by Zrinka Potocanac

    A common way to study balance is to perturb people by moving the surface under their feet and observe how they recover balance. Perturbations used in research are typically simple, predefined support surface translations or oscillations, which remain constant throughout the whole experiment. Because of that, they are highly representative of some circumstances of falling (e.g., losing balance while standing on a bus), but they cannot mimic the most frequent circumstance of falling amongst elderly in long-term care: incorrect weight shifting. How would one artificially create errors in weight shifting? We did this by creating a novel perturbation that amplifies one’s centre of mass (COM) movement in real-time. This perturbation would induce systematic errors throughout the movement, as opposed to predefined errors occurring at specific time points, induced by simple perturbations. 
    To create this novel perturbation, we paired a moveable robotic platform with real-time computer software (see Figure). A participant stood atop the robotic platform and the software received input of his COM movement from the motion capture cameras. It then moved the robotic platform by the same amount as the COM, but in the opposite direction, effectively duplicating the weight shift generated by the participant. In this study, we limited platform movements to mediolateral translations in response to mediolateral COM displacements. Using cross-correlations, we confirmed that the perturbations were delivered with high accuracy (correlation coefficient of -0.984) and short latencies (mean 154 ms, range 120 – 170 ms) with respect to the input COM displacement. We then performed a preliminary evaluation of how healthy young adults respond to this complex perturbation. Fifteen participants were instructed to stand as still as possible on top of the robotic platform, with their eyes closed, feet hip-width apart and arms relaxed by their body. In some trials, the platform was on and in others, it was off. We were able to demonstrate that the perturbation significantly altered postural control by increasing the range, variability, and mean power frequency of mediolateral, but not anteroposterior sway. 
    The paper describes how to create complex, yet accurate perturbations at relatively short latencies. Since we provided full technical details in the supplementary materials, we hope this novel perturbation method will be used as an additional tool in future research on balance and complex circumstances of falling. 

     

    Figure: A schematic of the setup used to generate the complex perturbations. The participant is standing on top of a robotic platform and his centre of mass (COM) position is recorded by motion capture cameras and continuously transmitted to a real-time computer. Each millisecond, the real-time computer calculates the required platform movement based on the participant’s COM position. The robotic platform moves accordingly, perturbing the participant.


    Copyright
    The ISPGR blog applies Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license to figure and text of the article. 
    https://creativecommons.org/licenses/by-sa/4.0/

    Publication
    Potocanac Z, Goljat R, Babic J (2017) A robotic system for delivering novel real-time, movement dependent perturbations. Gait Posture 58:386–389. doi: 10.1016/j.gaitpost.2017.08.038
    http://www.sciencedirect.com/science/article/pii/S0966636217308949?via%3Dihub

    The author
    Zrinka Potocanac is a Postdoctoral associate at the Department for automation, biocybernetics and robotics of Jozef Stefan Institute in Ljubljana, Slovenia. She aims to understand the neuromechanical control mechanisms underlying gait and balance and our ability to quickly adjust these to account for the ever-changing environment.

     

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  • 13 Sep 2017 by Hikaru Yokoyama

    Both animals and humans can change their gait speed over a wide range to suit the situation. The coordinated locomotor muscle activity among various speeds is mainly generated by the spinal central pattern generators (CPGs). Recent animal studies have demonstrated the following two characteristics of the speed control mechanisms of the spinal CPGs: (i) rostral spinal segment activation is essential to achieving high-speed locomotion; and (ii) different spinal neural modules are sequentially activated with increasing speed. To examine whether similar control mechanisms exist in the spinal cord of humans, we estimated spinal neural activity during varied-speed locomotion from surface electromyographic (EMG) signals.

    We recorded EMG activity from 14 lower leg muscles during a range of speeds (from very slow walking [0.3 m/s] to fast running [4.3 m/s]). We estimated spinal neural activity by mapping the EMG activations onto the estimated location in the spinal cord based on innervation relationships between muscles and spinal segments (Fig. 1A-2). We then broke down the spinal activities into fundamental units of the activity generated by each locomotor module (i.e., muscle synergy) (Fig. 1A-3). We found that the reconstructed spinal activity patterns were divided into the following three patterns depending on the locomotion speed: slow walking, fast walking and running (Fig.1B, the first column). During these three activation patterns, the activity in rostral segments was more increased than that in caudal segments as speed increased. Additionally, the different spinal activation patterns were generated by distinct combinations of locomotor modules (Fig.1B, second and subsequent columns). Most modules newly recruited in fast walking and running were activated by the upper lumbar segments.

     

    Figure 1. (A) Procedures of reconstruction of spinal activity patterns from surface EMG signals. (B) Reconstructed spinal activity patterns (the first column) are divided into several locomotor modules (second and subsequent columns from the left) at slow walking, fast walking and running. The locomotor modules were obtained by non-negative matrix factorization method. Muscle weighting component (top bars) and its corresponding temporal pattern component (the same color waveform) for each locomotor module is also shown in the figure. 

     

    To summarize the results, we found the following spinal activation patterns regarding speed control of human locomotion: (i) spinal activity in the rostral segments increased compared with the caudal segments with increasing locomotion speed; and (ii) the different spinal activation patterns recruited distinct combinations of locomotor modules. These results are consistent with the speed control characteristics of vertebrate CPGs. This commonality supports a hypothesis that basic locomotor neural circuits are highly conserved among in humans, mammals, and birds over vertebrate evolution. Our results provide fascinating insight into not only human locomotor control but also the evolution of vertebrate locomotion.

     

    Copyright

    © 2017 by the author.
    The ISPGR blog applies Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license to figure and text of the article.
    https://creativecommons.org/licenses/by-sa/4.0/

     

    Publication

    Yokoyama H, Ogawa T, Shinya M, Kawashima N, Nakazawa K (2017). Speed dependency in α-motoneuron activity and locomotor modules in human locomotion: indirect evidence for phylogenetically conserved spinal circuits. Proc Roy Soc B. 284(1851), 20170290. doi: 10.1098/rspb.2017.0290. 
    Link: http://dx.doi.org/10.1098/rspb.2017.0290

     

    The author

    Hikaru Yokoyama, 

    Ph.D. student. Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Japan. 

    His research interests are the neural control mechanisms of locomotion in humans. He is currently studying on the cortical control of locomotor muscle activity using machine learning and electrophysiological techniques.

     

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  • 08 Sep 2017 by Jos Vanrenterghem

    Perhaps you, like many members of our ISPGR community, have been engaged in the development and evaluation of interventions to improve postural balance and ambulation? Most likely, this was for frail members of our society who have an increased risk of falling due to reduced muscle strength/power, or in patient populations who suffer from musculoskeletal disease or degeneration?  In that case it is unlikely that you often venture into the sports medicine literature, let alone literature that establishes a theoretical framework for sport scientists who are engaged in the daily monitoring of elite athletes. In this blog, I would like to offer some creative ideas on how to evaluate physiological adaptations from a strength training programme for the frail elderly person, or how to monitor neuromechanical adaptations from ballroom dancing classes for the baby boomers.

    In our recent perspective paper in Sports Medicine, we reviewed some of the sports science and sports medical literature on the recent developments of player load monitoring. The scientific field of player load monitoring has grown rapidly, and we believed that there was a lack of theoretical framework to justify the daily monitoring of a vast amount of variables in sports environments, ranging from subjective ratings of perceived exertion to a host of complicated derivatives from GPS-based position tracking. Historically, this has been the domain of exercise physiologists, who have gained extensive knowledge on physiological processes and the effects of different types of training regimes. Very few biomechanists have looked into this, and the knowledge on so-called ‘mechanobiological’ adaptations from training and exercise is still very limited. In order to address this important knowledge gap, we developed a theoretical framework that firstly separates a biomechanical load-adaptation pathway from the physiological load-adaptation pathway (see Figure). Secondly, the framework helps to identify observations that are associated with the external load (how is the body moving through and interacting with its environment), and observations that represent internal load (what is the stress on the internal structures and systems). The availability (and affordability) of wearable sensor technologies has made it possible to monitor external load more easily. Monitoring of the internal load and of the adaptations that are constantly taking place as a consequence of those loads, however, remain a huge challenge. For example, whilst sports scientists embrace the concept of supercompensation to explain the progressive physiological benefits from training and exercise, there are few experimental observations available that allow one to monitor this wonderful phenomenon actually taking place. Therefore, our perspective paper also addresses the practical implications and to some extent the pitfalls around measuring loads and adaptation outside a laboratory, some of which may well apply to other contexts than elite athlete monitoring.


       

    Figure: A theoretical framework that separates a physiological load-adaptation pathway (left) from a biomechanical load-adaptation pathway (right). Measures that are indicative of what the body is doing (external load) are also separated from measures that represent the internal consequences to our body (internal load). Eventually, this internal load will cause adaptations which can be associated to each of these pathways, even if not exclusively so.        


    We hope that our perspective paper will assist the ISPGR community to consider using established methodologies from sports and exercise contexts into more clinical applications. For example, technologies developed by (and for) sports science could be used to evaluate physical loads due to therapeutic interventions. Or, established ratings of perceived effort multiplied by session time, may well be a useful tool in exercise programmes for the elderly or patient populations. Finally, we hope that the complex systems approaches to evaluate intricate interactions between various types of loads and load-adaptation pathways, could provide members of the ISPGR community with new ideas to better interrogate the multifactorial responses to multi-component exercise programmes within their clinical trials.

    Copyright

    © 2017 by the author.
    The ISPGR blog applies Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license to figure and text of the article.
    https://creativecommons.org/licenses/by-sa/4.0/

     

    Publication

    Vanrenterghem, J., Nedergaard, N.J., Robinson, M.A., Drust, B. (2017) Training load monitoring in team sports : A novel framework separating physiological and biomechanical load-adaptation pathways. Sports Medicine, Published Online First.

     

    About the author

    Jos Vanrenterghem is Associate Professor in the Department of Rehabilitation Sciences at KU Leuven in Belgium. His research focuses on the advancement of data analysis techniques in biomechanics and on the interplay between neuromuscular control strategies and musculoskeletal loading mechanisms.

     

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  • 22 Aug 2017 by Brett Fling

    Multiple sclerosis (MS) is characterized by central nervous system white matter lesions that affect people’s ability to move independently. Further, people with MS often report significant asymmetries in muscle strength and function in the left versus the right leg. These are often associated with increased postural sway (i.e. worse balance) and less symmetrical stepping patterns during walking (i.e. worse walking). It is no surprise that such lower limb asymmetries are frequently associated with poorer balance control, falls, and reduced quality of life. Currently there is limited understanding as to why these limb asymmetries exist in MS and which areas within the central nervous system contribute to these mobility-limiting issues. It is also unknown whether improving these lower limb asymmetries may concomitantly improve balance and mobility during activities of daily living.

    To address these questions, participants stood on a platform and tried to maintain their balance while the  platform continually slid forward and backward at a fixed frequency of differing amplitudes. We measured their ability to anticipate changes in direction (i.e. temporal performance) and their ability to control the amplitude of sway (i.e. spatial performance) with repeated exposures to this moving platform. To understand the neural underpinnings of postural motor learning, we correlated the acquisition and retention of practice-related improvements in postural control to brain white matter microstructural integrity acquired via diffusion weighted magnetic resonance images using a tract-based spatial statistical approach. Despite having worse postural control than control participants, those with MS exhibited improvements in temporal performance (over one day of practice) and retention (ability to maintain improvements 24 hours later) in a similar manner as control participants. Improvements in temporal performance were directly correlated to microstructural integrity of white matter tracts in the corpus callosum, posterior parieto-sensorimotor fibers and the brainstem in people with MS. Within the corpus callosum, fibers connecting the primary motor cortices (red fibers in Figure 1) were most strongly correlated to temporal improvements in postural control, in contrast to those connecting pre-supplementary or supplementary motor areas (yellow and orange fibers in Figure 1).

    For movements that require precise coordination between the two sides of the body (e.g. walking, postural control of balance, typing) a delicate balance of excitation and inhibition is required between the right and left sensorimotor cortices. This interhemispheric communication is principally accomplished through the corpus callosum. Reduced quality of the corpus callosum is common in people with MS and has been directly related to poorer communication between the two sides of the brain and upper extremity motor performance. We suggest that impairments in gait and balance control are also, at least in part, a result of reduced structure and altered communication between the two sides of the brain in people with MS. However, our understanding of how changes in communication between the two sides of the brain contribute to lower limb asymmetries and the resultant declines in mobility for those with MS remains incomplete.

    Figure 1 – Interhemispheric white matter fiber tracts connecting the right and left pre-supplementary motor areas (yellow), supplementary motor areas (orange), and primary motor cortices (red).

     

     

    Copyright:

    The ISPGR blog applied Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license to figure and text of the article.

    https://creativecommons.org/licenses/by-sa/4.0/

     

    Publication:

    Daniel S. Peterson, Geetanjali Gera, Fay B. Horak, Brett W. Fling. Corpus Callosum Structural Integrity Is Associated With Postural Control Improvement in Persons With Multiple Sclerosis Who Have Minimal Disability. Neurorehabilitation and Neural Repair, Vol 31, Issue 4, pp. 343 – 353

    http://journals.sagepub.com/doi/abs/10.1177/1545968316680487

     

    The Author:

    Brett W. Fling, Ph.D. Assistant Professor – Health and Exercise Science Department & Molecular, Cellular & Integrative Neurosciences Program. Director – Sensorimotor Neuroimaging Laboratory. Colorado State University, Fort Collins, Colorado.

     

    Research within the Sensorimotor Neuroimaging Laboratory at Colorado State University is designed to understand the contributions of the brain’s structural and functional neural networks to everyday movements. We leverage this understanding of the nervous system to develop new therapeutic interventions for individuals with sensorimotor dysfunction. Our laboratory utilizes a range of neuroimaging techniques including functional and structural magnetic resonance imaging, diffusion tensor imaging, electroencephalography, and transcranial magnetic stimulation to assess neuroanatomy and neurophysiologic function. These state of the art imaging techniques are integrated with experimental paradigms relying on the biomechanical analysis of sensorimotor control to provide a comprehensive view of the neural control of movement.

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  • 31 Jul 2017 by Hanatsu Nagano

    For the senior population, fall-related injuries often lead to loss of independent lifestyles and enormous medical costs. Tripping is the leading cause of falls, and often results in a forward loss of balance. Dynamic balance after a trip could still be restored by an effective recovery step to prevent the fall. The effectiveness of the recovery step depends on both position and timing factors – the foot should be ‘positioned sufficiently” in front of the whole body centre of mass within a certain ‘time limit’. In the process of balance recovery, the recovery leg needs to absorb the falling momentum by knee and ankle eccentric work. We aimed to identify the biomechanical requirements of such recovery steps during unanticipated forward falling in older adults. For this investigation, biomechanical characteristics of the initial recovery step were compared between single- and multi-step recovery actions. A single step recovery should essentially fulfil all requirements of balance restoration, while a multi-step recovery distributes the entire burden over several steps. Compared to multi-step recoveries, the single-step response was, therefore, hypothesised to play a larger role for balance recovery.

    We employed a commonly-used tether-release protocol to test our hypothesis. Fifteen healthy older participants maintained forward leaning position with a cable supporting them from the back (see figure). At random timing, the cable was released to induce a forward fall, essentially requiring recovery actions. These recovery actions were recorded using a Vicon 3D motion capture system and AMTI force platforms to analyse the biomechanical characteristics of the recovery steps. We determined the margin of stability as the distance from the extrapolated centre of mass position to the base of support boundary, indicating spatial stability. Dynamic balance is secured when margin of stability is positive. Available response time was computed as the estimated time for centre of mass to reach the base of support boundary.

    Figure: (left) whole body model during a multiple-step recovery, (right) ankle and knee eccentric work and power absorption during the first recovery step.


    For both single and multiple step responses, the margin of stability was negative at recovery foot contact, which indicates that balance was not yet secured. To avoid a fall, a positive margin of stability should be established within available response time, which was on average 0.204s in the single step responses. Correlation analysis suggested that knee and ankle eccentric work may absorb the excessive falling momentum. Larger step length and velocity were also found to possibly support balance recovery. Practical training for effective recovery step may, therefore, incorporate eccentric work of the stepping limb while other concentric actions would be also important for limb swing to achieve long fast recovery step. Future studies should test this hypothesis in populations with lower limb joint degeneration (e.g. osteoarthritis patients).

     

    Publication

    Nagano, H., Levinger, P., Downie, C., Hayes, A., Begg, R.K. 2015. Contribution of Lower Limb Eccentric Work and Different Step Responses to Balance Recovery among Older Adults. Gait and Posture, 42 (3): 257-262. DOI: 10.1016/j.gaitpost.2015.05.014

     

    The author

    Dr Hanatsu Nagano

    Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Australia.

     

    Dr Nagano is a postdoctoral research fellow at the Institute of Sport, Exercise and Active Living. His area of expertise is gait biomechanics specialising in falls prevention among senior adults. He is an honorary physiologist at Austin Health.

     

    Copyright

    © 2017 by the author.

    Except as otherwise noted, this blog, including its text and figures, is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/legalcode.

     

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  • 26 Jul 2017 by Joe Verghese

    Falls are increasingly prevalent with advancing age and the consequences are often devastating, resulting in loss of independence, institutionalization and premature mortality. Evidence supports impairments in cognitive functions, specifically executive functions, as major contributors to falls. Worse performance on dual-task assessments that involve executive functions, such as walking while performing an attention demanding task, predict falls in non-demented older adults. The prefrontal cortex (PFC), a key structure for performing executive functions, also plays a vital role in control of cognition and mobility, indicating its important role in fall risk. Although the PFC is recognized as a potentially important contributor to falls, conventional neuroimaging techniques cannot image the brain during motion, leaving a gap in the understanding of underlying neural processes that might predict fall risk, and necessitated the use of newer approaches that can be used to study people while they walk, such as the functional Near Infrared Spectroscopy (fNIRS).

    The primary goal of the study was to determine whether brain activity in the PFC measured during walking predicts falls in high-functioning older adults. We selected a high-functioning group of community-dwelling older adults enrolled in a prospective aging study at Albert Einstein College of Medicine to evaluate early brain activation changes that predict falls. Task-related changes in oxygen levels in the PFC were measured using fNIRS during single-task conditions (normal pace walking and standing while reciting alternate letters of the alphabet), and a dual-task condition (walking while reciting alternate letters of the alphabet). Over the 50-month study period 71 of the 166 participants reported 116 falls. People who had increases in brain activity levels during the dual-task condition were 32 percent more likely to fall. Brain activity levels during both the cognitive or motor single task conditions did not predict fall risk.

    These findings provide evidence that brain activity patterns during cognitively demanding assessments predict falls in older adults and may not be elicited by more simple tasks. From a clinical perspective, these findings suggest that there may be changes in brain activity before visible signs of clinical dysfunction and physical symptoms manifest in high-functioning people who are at risk of falls. In the future, a brain scan assessment such as fNIRS might be used to help predict falls in older adults. Clinicians may be able to use this information to recommend behavioral and lifestyle modifications or treatments for their patients that may reduce the risk of future falls.

    Figure 1. Participant completing fNIRS assessment.

     

     

    Publication:

    Verghese J, Wang C, Ayers E, Izzetoglu M, Holtzer R. Brain activation in high-functioning older adults and falls Prospective cohort study. Neurology. 2017 Jan 10;88(2):191-7. http://www.neurology.org/content/88/2/191

    Authors:

    Emmeline Ayers, MPH and Joe Verghese, MBBS

    Affiliations:

    Departments of Neurology1 and Medicine,2 Albert Einstein College of Medicine, Bronx, New York, USA

    Bios:

    Emmeline Ayers is an Associate, The Saul R. Korey Department of Neurology. Her research interests are in understanding the role of gait and mobility in progression to dementia and cognitive decline in older adults.

    Dr. Verghese is Professor of Neurology and Medicine, Murray D. Gross Memorial Faculty Scholar in Gerontology, Director, Resnick Gerontology Center, and Chief of the Integrated Divisions of Cognitive and Motor Aging (Neurology) and Geriatrics (Medicine). He is an expert in aging and the effects on mobility and cognition.

     

     

     

     

     

     

     

     

     

    Copyright

    © 2017 by the author.

    Except as otherwise noted, this blog, including its text and figures, is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/legalcode.

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  • 19 Jun 2017 by Natalia Rinaldi

    Older adults with history of falls often slow down and have a more variable gait when performing another task at the same time (dual task walking). However, most studies involving dual task paradigms have investigated primarily the walking task, while little attention has been given to performance in the secondary task. The combined task of walking while reaching and grasping an object (prehension) is widely performed during daily life activities, such as picking up a glass, shopping, eating, and others. Importantly, older adults need to adapt their walking patterns to make sure that their gait is stable while conducting such a prehension task. Our study investigated the level of interference between the combined task of walking and prehension with different levels of manual task difficulty.

     

    Fallers and non-fallers were invited to perform three tasks: (1) simple walking (control condition), (2) reaching-to-grasping a dowel during quiet standing, and (3) grasping a dowel wile walking. The dowel was placed on a cylindrical support with different types of bases (wide and narrow) and was surrounded by two obstacles with two different distances between them (short and long). Whole body center of mass and spatiotemporal gait parameters were analyzed to explore changes in walking, reaching (duration and velocity) and grasping (hand grip aperture and velocity). Participants with history of falls walked slower and took wider steps during the dual task walk for the most difficult manual conditions. While reaching, fallers also reduced their body velocity and increased the body stability (margin of dynamic stability) to grasp the dowel compared to non-fallers. When looking at the center of mass anterior-posterior velocity, fallers almost stopped walking to perform the prehension task. Fallers presented slower movement time and lower peak wrist velocity, peak grip aperture velocity, and time-to-peak grip aperture, which indicated a generalized slowing down in movement performance.

     

    In conclusion, fallers showed a more conservative walking strategy. They also decoupled the prehension task from the walking when compared to non-fallers and had to increase body stability in order to perform grasping successfully. Our results suggest that manual tasks may be used as an assessment tool for fall risk prediction. Given that prehension movement is widely used during daily life activities, we suggest that preventive and rehabilitation programs should also emphasize movement exercises to improve the control of upper limbs, especially while performing locomotor tasks. 

     

     

     

     

     

     

     

     

     

    Publication:

    Rinaldi NM, Moraes, R. Older adults with history of falls are unable to perform walking and prehension movements simultaneously. Neuroscience. 2016; 249-260.

    http://www.sciencedirect.com/science/article/pii/S0306452215011306

     

    The author:

    Dr Natalia Madalena Rinaldi is a Professor in the Center of Physical Education and Sports of Federal University of Espirito Santo, Brazil. Her research focuses on the effects of aging on gait and posture and the effects of motor interventions to improve the functional capacity in older adults (natalia.rinaldi@ufes.br).

     

     

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  • 12 Jul 2017 by Avril Mansfield

    People who have had a stroke fall frequently. Many previous studies with older adults have found that exercise, particularly balance training, reduces fall risk. However, comparable studies in stroke survivors indicate that similar exercise training does not prevents falls in this group. People fall when they fail to recover from a loss of balance. Recently, studies have found that ‘perturbation-based balance training’ (PBT), which involves people experiencing repeated balance losses, can improve control of reactions to a loss of balance. Some studies have found that PBT reduces fall rates in healthy older adults or in people with Parkinson’s disease. We wanted to know if PBT could reduce fall rates in people with sub-acute stroke.

     

    Physiotherapists at our institution had started PBT with some of their eligible clients as part of routine care for stroke rehabilitation. Therefore, we conducted a non-randomized study to establish the benefit of PBT compared to non-PBT rehabilitation. We recruited participants with sub-acute stroke at discharge from in-patient rehabilitation if they completed PBT during their routine rehabilitation. We then asked these individuals to report any falls that they experienced in the following six months. We compared fall rates to a matched historical control group who were recruited for another study before physiotherapists had implemented PBT, but who also reported falls in daily life for six months after discharge. Five (out of 31) participants in the PBT group reported 10 falls in the six months post-discharge, whereas ten (out of 31) participants in the historical control group reported 31 falls in the six months. The fall rates in the PBT group were significantly lower than in the control group, when accounting for some characteristics that differed between the two groups at baseline.

     

    The results of this study suggest that PBT might help to prevent falls in people with sub-acute stroke. Because the study was not randomized, the results should be interpreted with some caution. However, since the results are consistent with other studies showing reduced fall rates with PBT, the evidence from this study may be sufficient to recommend PBT in clinical practice. Other studies of PBT used programmable treadmills or custom-built moving platforms to provide the balance perturbations in training. In the current study, the physiotherapist provided manual perturbations (e.g., push or pull; see Figure). This meant that PBT only required equipment that is already in most physiotherapy practices. For this reason, we think it would be relatively easy to implement our PBT program in other settings.

     

     

    Figure: Physiotherapist delivers a rightward pull perturbation while the participant walks over foam obstacles.

     

    Publication

    Mansfield A, Schinkel-Ivy A, Danells CJ, Aqui A, Aryan R, Biasin L, DePaul VG, Inness EL. Does perturbation training prevent falls after discharge from stroke rehabilitation? A prospective cohort study with historical control. J Stroke Cerebrovasc Dis. 2017; doi: 10.1016/j.strokecerebrovasdis.2017.04.041

     

    The author

    Avril Mansfield; Scientist, Toronto Rehabilitation Institute – University Health Network; Affiliate Scientist, Evaluative Clinical Sciences, Hurvitz Brain Sciences Program, Sunnybrook Research Institute; Associate Professor (status only), Department of Physical Therapy, University of Toronto

    Avril’s research aims to determine how aging and neurologic injury or disease affect balance control and mobility, and how to exploit principles of optimal learning to develop exercise programs that improve balance and mobility. She is particularly interested in applying this work to develop clinically feasible fall-prevention programs.

     

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  • 17 Jun 2017 by Dominic Pérennou

    Following a stroke, it is important to assess a person’s perception of verticality. This assessment can help us to find what causes the bodily disorientation with respect to vertical (lateropulsion) and can guide post-stroke rehabilitation and monitor postural recovery. The visual vertical (VV) is the most commonly used test to assess verticality perception, both in research and in clinical practice. It is a simple test that consists of adjusting a luminous rod to the vertical in darkness; however, specific guidelines for use in clinical practice are lacking. Published studies have used different methodologies and the impact of these different methodologies on the assessment outcome is not well-understood. For example, should the trunk and head be free to move during the test or should they be fixed in the upright position? This question is critical for stroke survivors. It is well-known that spontaneous lateral whole body tilts are common after stroke and this may compromise their ability to sit on their own and might further impact their perception of verticality. In the present study, we aimed to analyse the impact of controlling body orientation on stroke patients’ ability to estimate VV and their ability to sit unsupported.

     VV perception was assessed in 20 controls and 36 subacute patients undergoing rehabilitation after a first hemisphere stroke, under 3 different scenarios: body not fixed (trunk and head free), partially fixed (trunk fixed, head free), or both trunk and head were fixed. We quantified both trunk and head orientations and analysed VV as a function of trunk and head tilt. Patients were classified into 2 groups according to their ability to maintain (n=25) or not (n=11) an independent upright sitting posture. Our results confirmed for the first time the clinical intuition: it is spontaneous upright trunk (and not head) orientation which is necessary for recovering an independent sitting posture after stroke. This suggests that postural orientation deficits, especially trunk orientation, are a major cause of lateral postural disorders after a stroke. The level of fixation strongly affects the estimation of VV in stroke patients who have difficulties maintaining a seated posture. Our results suggest that a fixed trunk and head in the upright position was the most optimal setting for assessing VV. We proposed that measuring VV without any body fixation is only valid in patients with satisfactory balance abilities. Our results contribute to a better standardization of VV assessment to optimize its integration in research and clinical practice.

    Figure. Individual mean spontaneous orientations of trunk axis and head axis. The data were classified from the most pronounced contralesional tilt (negative values) to the most pronounced ipsilesional tilt (positive values), for trunk orientation, and this order was maintained for the classification of head orientation data. (B) Visual vertical perception, orientation (mean) and uncertainty (variability) as a function of group and setting.

    Publications

    Piscicelli C, Barra J, Sibille B, Bourdillon C, Guerraz M, Pérennou D. (2016). Maintaining trunk and head upright optimizes visual vertical measurement after stroke, Neurorehabil Neural Repair, 30(1):9-18. https://doi.org/10.1177/1545968315583722

    Piscicelli C, Pérennou D. (2017). Visual verticality perception after stroke: A systematic review of methodological approaches and suggestions for standardization. Ann Phys Rehabil Med, 11. pii: S1877-0657(16)00042-7. https://doi.org/10.1016/j.rehab.2016.02.004

     

    The authors

     

     

     

     

     

     

     

     

    Céline Piscicelli and Dominic Pérennou
    Department of NeuroRehabilitation, Institute of Rehabilitation, University Hospital Grenoble-Alpes

    Laboratory Psychology and Neurocognition, UMR 5105 CNRS and Grenoble-Alpes University, Grenoble, France.

    Celine Piscicelli received her PhD in Cognitive Psychology and Neuroscience from Grenoble-Alpes University. She currently works as a neuropsychologist in the Physical and Rehabilitation Medicine Unit at University Hospital Grenoble-Alpes and is an associate member in the Psychology and Neurocognition Lab at Grenoble-Alpes University. Her research focuses on spatial cognition and its interaction with posture and action.  

    Dominic Pérennou is Professor of Medicine, Chair of Physical Medicine and Rehabilitation at Grenoble-Alpes University, and head of the Department of Neurorehabilitation at the University Hospital Grenoble-Alpes (France). He is Editor in Chief of the Annals of Physical Medicine and Rehabilitation, and Associate Editor of Gait & Posture. His main research focuses on internals models of verticality for postural and gait control.

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  • 14 Jun 2017 by Yoshiro Okubo

    Step training has recently been shown effective in preventing falls most likely because of its high task-specificity to rapid movements required to avoid falls. Step training systems using interactive video game technology have the potential for widespread implementation because they are low-cost and can be used unsupervised by older people at home. While this is all very promising, there is one thing we need to consider. Most stepping systems only train in a few directions (e.g., anterior-posterior and lateral directions). This is concerning because a randomised controlled trial (RCT) showed that upper-limb resistance training with limited directions deteriorated rapid movements in untrained directions in older adults. Therefore, to ensure the safety of home-based step training system, we conducted this study to examine transfer effects of step training on stepping performance in untrained directions among older adults.

     

    We conducted an RCT with 54 older adults aged 65 years or older. The participants were randomly allocated to one of three groups; forward step training (FT), lateral plus forward step training (FLT) and no training (NT) groups. A choice stepping reaction time (SCRT) system was used for the training as well as assessments (see Figure). The FT group completed 200 forward steps, while the FLT group completed 100 forward steps and 100 lateral steps. The NT group rested for 15-min between the pre- and post-assessments. Prior to and immediately after the training or rest periods, the participants underwent a 2-min CSRT assessment. During the assessments, participants wore 14-mm diameter reflective markers to the lower limbs and their stepping movements were recorded using a 6-camera Vicon Bonita motion capture system. We used choice stepping reaction time and stepping kinematics in untrained, diagonal and lateral directions as outcome measures. Results indicated that FT induced delayed response time (a negative transfer effect) and faster peak stepping speed (a positive transfer effect) in the diagonal direction during the first step after the training. However, these effects were no longer apparent in the subsequent steps. Moreover, no such effects were seen in the FLT group.

     

    Figure. A) The step mat and screen display used in the step training and stepping performance assessments. B) A typical example of stepping trajectory for one participant.

     

    Our results suggest that if participants receive a step training program that only trains steps in the forward direction, this will improve stepping speed but may acutely slow response times in the untrained diagonal direction. However, this acute effect appears to dissipate after a few repeated steps. Step training in both forward and lateral directions appears to induce no negative transfer effects in untrained diagonal stepping. These findings suggest home-based step training systems (usually with 6 directions) present low risk of harm through negative transfer effects in untrained stepping directions.

     

    Publication

    Okubo Y, Menant J, Udyavar M, Brodie MA, Barry BK, Lord SR, Sturnieks DL. Transfer effects of step training on stepping performance in untrained directions in older adults: A randomized controlled trial. Gait & Posture 54 (2017) 50–55

    http://www.gaitposture.com/article/S0966-6362(17)30048-6/abstract

     

    The author

    Yoshiro Okubo, Postdoctoral Fellow, Falls, Balance and Injury Research Centre, Neuroscience Research Australia

     

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  • 12 Jun 2017 by Gammon Earhart

    People with Parkinson disease (PD) often report difficulty walking as an early and troublesome problem.  Emergence of gait problems is considered a red flag indicating onset of disability, and can contribute to reduced quality of life.  Gait in people with PD is often slower, with reduced stride lengths and increased variability that may be attributed to loss of ability to maintain a steady gait rhythm.  To address this loss of rhythmicity, many studies have employed use of external rhythmic cues, such as music or a metronome, to help stabilize gait.  However, we know very little about the impact of self-generated rhythmic cues, such as singing, on gait.  The goal of this study was to test the feasibility of singing during walking in people with PD, gathering preliminary evidence regarding the efficacy of this novel cueing technique.

     

    Twenty-three people with Parkinson disease participated.  Each person walked at their normal, comfortable pace for the Baseline condition, which was used to determine preferred walking cadence.  Cue rate, or beats per minute of the song, was then set to match preferred cadence.  Participants then walked in three cued conditions and a dual task condition (see Figure).  When walking to music, participants maintained velocity but increased spatial and temporal variability.  Variability was further increased when participants walked while singing along to music.  Singing in the absence of music, however, did not increase variability.  In contrast, when dual tasking (i.e. completing a word generation task while walking) participants showed reductions in velocity along with large increases in variability. 

     

    Of all the conditions tested, singing was the only cue condition that did not result in increased variability.  We think that matching a self-generated rhythm may facilitate rhythmicity more than matching an external cue.  Future work should explore use of faster cueing rates and use of mental rather than overt singing, in addition to determining the utility of singing during walking in everyday, real-world situations. If singing continues to hold promise in future studies, this could represent a substantial advance as singing is universally available, inexpensive, and adaptable.

     

     

    Copyright

    The ISPGR blog applies Creative Commons Attribution (CC BY) license to figure and text of the article.

    https://creativecommons.org/licenses/by/4.0/

     

    Publication

    Harrison, E. C., McNeely, M. E., & Earhart, G. M. (2017). The feasibility of singing to improve gait in Parkinson disease. Gait & Posture53, 224-229.

    https://www.ncbi.nlm.nih.gov/pubmed/28226309

     

    The authors

    Gammon M. Earhart, PT, PhD, Program in Physical Therapy, Washington University in St. Louis

    Dr. Earhart is Professor and Director of the Program in Physical Therapy at Washington University in St. Louis.  Her research focuses on the neural control of movement in health and disease, with an emphasis on postural and locomotor control in Parkinson disease.   

     

    Elinor C.  Harrison, BA, Program in Physical Therapy, Washington University in St. Louis

    Elinor Harrison is a professional performance artist turned graduate student.  She is working toward completion of a PhD in Movement Science.  Her dissertation focuses on the use of singing as a means to facilitate movement in people with Parkinson disease.

     

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  • 09 Jun 2017 by Patrick Sparto

    Concussion results in a wide variety of impairments such as cognitive deficits in memory, reaction time and processing speed. Moreover, post-concussion dizziness and balance impairments are found to be common and predictive of worse recovery times.  Therefore, an increasing number of patients with concussion are referred for vestibular physical therapy.
    Although it is likely that cognitive and vestibular impairments after concussion are related, they have only been examined in isolation. This study examined the relationship between cognitive performance and various gait and balance measures in patients referred for vestibular physical therapy after concussion.

    Our study investigated the relationship between gait and balance performance with cognitive performance in a group of 60 adolescents referred for vestibular therapy after concussion. We tested our participants on a range of functional gait and balance measures, such as the Functional Gait Assessment, Timed “UP & GO”, and Five Times Sit to Stand. Our results suggest that, after concussion, both memory deficits and impaired gait and balance can occur in individuals. Our results further show that they are associated with each other. First, we demonstrated that functional balance and gait measures were associated with worse verbal and visual memory on the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT). For example, in the figure below, we observed that better performance in visual memory (i.e. higher scores) and verbal memory was related to better performance in the Five Times Sit to Stand (i.e. less time). We also found that higher scores on the Post-Concussion Symptom Scale were associated with lower scores on the Activities-specific Balance Confidence scale and higher scores on the Dizziness Handicap Inventory.

    Spatial navigation is frequently affected after concussion and is important for both gait and balance tasks as well as memory tasks. Clinicians working with patients after concussion should check whether any observed cognitive impairments might be partially attributed to declines in spatial navigation rather than an isolated memory decline. Vestibular therapists should consider giving dual-task exercises, combining balance and cognition, during the rehabilitation process to reduce the impact of cognitive performance on gait and balance function. It will be interesting to see in future studies whether the associations between cognitive and balance affect recovery trajectories after concussion.
     

    Figure: Association between Five Times Sit to Stand Performance and Visual and Verbal Memory performance in 60 adolescents with a concussion who were referred for vestibular physical therapy. Higher visual and verbal memory scores were related to better performance on the Five Times Sit to Stand.


    Publication
    Alsalaheen BA, Whitney SL, Marchetti GF, Furman GM, Kontos AP, Collins MW, Sparto PJ:  Relationship between cognitive assessment and balance measures in adolescents treated with vestibular physical therapy after concussion. Clin J Sport Med. 2016. 26(1):46-52. PMCID:  PMC4856020

    http://journals.lww.com/cjsportsmed/Citation/2016/01000/Relationship_Between_Cognitive_Assessment_and.7.aspx

    The authors

    Bara Alsalaheen, PT, PhD is an Assistant Professor of Physical Therapy at University of Michigan-Flint, Michigan, USA. His research focuses on understanding factors associated with variations in concussion risks, recovery times and rehabilitation outcomes. This research was completed when Dr. Alsalaheen was a doctoral student at Dr. Sparto’s laboratory at University of Pittsburgh.


    Patrick Sparto, PT, PhD is an Associate Professor of Physical Therapy at the University of Pittsburgh. His research interests include the neuroimaging of postural control, the biomechanics of step initiation, and balance impairments after concussion.

     

     

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  • 30 May 2017 by Takeshi Yamaguchi

    Preventing falls is one of the major challenges of our ISPGR community. As part of addressing this challenge, the dynamic postural stability of human gait has been attracting attention from many researchers. When slippery or uneven surfaces cause a large balance perturbation during gait, such as a slip or trip, current postural stability measures indicate whether postural stability is maintained. They do not, however, indicate the degree of instability. In this study, we introduced a desired center of pressure (dCOP) to assess the degree of dynamic postural instability. The dCOP is defined as a virtual point on the ground where the moment around the body center of mass (COM) becomes zero, which occurs when the dCOP and the measured COP (mCOP) coincide. We hypothesized that, when the misalignment of the dCOP and mCOP (dCOP-mCOP) increases to a certain value due to a large perturbation, it becomes difficult to take the reactive step necessary to recover balance and continue walking. The objective of this study was to test this hypothesis in healthy participants during an induced slip while turning.

    Twelve healthy young adult males participated and were asked to: 1) walk straight and turn 60 degrees to the right with the right foot (spin turn) on a dry surface, and 2) walk straight and perform a 60-degree spin turn to the right on a slippery surface. The dCOP-mCOP during turning in the slip trials was significantly larger in trials where a fall occurred compared to the no-slip trials and slip trials where balance was maintained. This was particularly the case in x-direction (i.e., the medial-lateral direction during forward gait). The receiver operating characteristic (ROC) analysis indicated that the dCOP-mCOP in the x-direction was a good indicator of fall risk due to a slip during turning (area under the curve, AUC =0.93). The threshold of dCOP-mCOP in the x-direction for distinguishing trials at risk of a fall from those at no risk of a fall was 0.55 m.

     

    Figure: A) Inverted pendulum model and the desired center of pressure (dCOP) in the sagittal plane. B) Experimental set-up and movement instruction: 1) straight walk and 60-degree spin turn on the dummy sheet, and 2) straight walk and 60-degree spin turn on the slippery sheet. C) Relative location of dCOP with respect to mCOP for spin turn trials. The origin corresponds to the location of mCOP, and each plot indicates the dCOP location relative to the mCOP at which the dCOP–mCOP took the largest value in each trial.

     

    Our study shows that participants were not able to recover walking by taking a successful reactive step after slipping when the dCOP-mCOP reached a certain value, particularly in the x-direction. Furthermore, we were able to differentiate between successful and unsuccessful recoveries using our dCOP-mCOP concept. These results indicate the feasibility of our dCOP concept in assessing the risk of fall due to an induced slip during turning. The misalignment of dCOP and mCOP may provide insight into the variability of gait parameters such as the step length and width of older adults or patients with movement disorders. The dCOP could also yield insight into the desired foot placement for stable gait and contribute to the development of fall prevention interventions.

     

    Publication

    Yamaguchi T, Higuchi H, Onodera H, Hokkirigawa K, Masani K. (2016) Misalignment of the Desired and Measured Center of Pressure Describes Falls Caused by Slip during Turning. PLOS ONE 11: e0155418.  https://doi.org/10.1371/journal.pone.0155418

     

    The author

    Takeshi Yamaguchi

    Associate Professor, Graduate School of Engineering, Graduate School of Biomedical Engineering, Tohoku University, Japan

    Takeshi Yamaguchi is an associate professor at the graduate school of engineering and graduate school of biomedical engineering, Tohoku University. His primary research interests involve the tribology of the shoe and floor interface and biomechanics of gait with the goal of finding ways to reduce slips and fall accidents.

     

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  • 19 May 2017 by Lis Boulton

    Balance, strength and physical activity are important factors for healthy ageing and preventing age-related functional decline. In order to be effective, preventive interventions must target risk factors for functional decline, be tailored to the needs and preferences of the individual, and be designed to change behaviour to a sustained healthier lifestyle. Smartphones and smartwatches are used by an increasing number of people, with thousands of smartphone applications available to promote healthy lifestyles. However, few of these applications are evidence based, meaning that their contribution to overcoming the challenges presented by an ageing population is limited.

    The European Project ‘PreventIT’ (EU Horizon 2020 Grant Agreement No. 689238) aims to address this issue, by developing an evidence-based mHealth behaviour change intervention. PreventIT has adapted the Lifestyle-integrated Functional Exercise (LiFE) programme, which reduced falls in people 75 years and over (BMJ 2012; 345:e4547), for a younger cohort (aLiFE). The aLiFE programme incorporates challenging strength and balance/agility tasks, as well as specific recommendations for increasing physical activity in young-older adults, aged 60-70 years. Personalised advice is given on how to integrate strength, balance and physical activities into existing daily routines. aLiFE was then operationalised to be delivered using smartphones and smartwatches (eLiFE), providing the opportunity to send timely motivational messages and real-time feedback to the user. Both aLiFE and eLiFE are behaviour change interventions, supporting older adults to form long term physical activity habits. PreventIT has taken the original LiFE concept and further developed the behaviour change elements, explicitly relating and mapping them to Social Cognitive Theory and behaviour change techniques. Goal setting, planning, prompts and real-time feedback are used to deliver a person-centred experience for participants in the intervention. Findings from the aLiFE and eLiFE pilot studies highlighted the feasibility and acceptability of the PreventIT motivational strategy, with the vast majority of the participants rating the programmes positively (satisfaction score median: 6 points, out of maximum 7).

    Mobile technology such as smartphones and smartwatches can be used effectively to monitor behaviour and to deliver a personalised intervention. The PreventIT mHealth intervention focusses on behaviour change from initiation to long-term maintenance, addressing the different phases of adopting a healthier lifestyle. As such, it makes a strong contribution to the developing field of evidence-based mHealth. The interventions (aLiFE and eLiFE) are currently being trialled in a three-site, three-arm feasibility randomised controlled trial in Norway, the Netherlands and Germany. An overview of the project can been viewed on YouTube: https://www.youtube.com/watch?v=upAfGHbNvdU

     

     

     

     

     

     

     

    Publication:

    Helbostad JL, Vereijken B, Becker C, Todd C, Taraldsen K, Pijnappels M, Aminian K, Mellone S. Mobile Health Applications to Promote Active and Healthy Ageing. Sensors. 2017; 17(3):622. http://www.mdpi.com/1424-8220/17/3/622

    Author:

    Dr Lis Boulton is a Research Associate in the School of Health Sciences at the University of Manchester, UK, and is a member of the EU-PreventIT consortium. Her research focusses on the use of technologies to facilitate behavioural change, to encourage older adults to be more physically active. Lis works with Professor Chris Todd in developing and operationalising the motivational strategy for PreventIT. (elisabeth.boulton@manchester.ac.uk)

     

     

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  • 08 May 2017 by Ruopeng Sun

    During daily life, locomotion tasks are often accompanied by a concurrent task such as talking, texting or recalling a shopping list. There is a wide body of empirical evidence on the profound negative effects of concurrent cognitive challenges on gait, the cognitive task itself, and other clinical outcomes such as falls. Such reductions in performance are commonly interpreted as competition for attentional resources between the postural and cognitive task. Various cognitive tasks have been utilized in dual-task research, such as backwards counting, reaction time, memory recall, Stroop and verbal fluency tasks. Performance for these tasks is traditionally measured through the rate of error or the response time. However, such descriptive measures lack the temporal resolution to track the dynamics of attention allocation during postural control. Hence, we aimed to evaluate the timing of postural prioritization during stepping using a continuous finger-tapping task.

    Ten healthy young adults with a mean age of 21 years participated in this study. Participants were asked to perform a rapid voluntary step with either their left or right foot after hearing an auditory tone (simple/choice reaction paradigm), while also tapping their right index finger continuously on a handhold numeric keypad (Figure A). Three variants of concurrent attentional tasks were used: (1) single task: holding keypad only, no finger-tapping; (2) low attention-demanding: one-button tapping task; (3) high attention-demanding: four-button tapping task. We performed wavelet analysis on the stimulus-locked finger-tapping data to determine the temporal change of tapping frequency related to reactive stepping (Figure B). Results showed that the postural performance was negatively affected only by the high attention-demanding task. Significant reduction of post-stimulus tapping speed was observed across all test conditions, indicating attention shift during the execution of a step. In addition, the high attention-demanding task induced early postural prioritization during the choice reaction stepping condition when different motor programs needed to be prepared and executed.

    Our study shows that a continuous finger-tapping task can be used to track attention allocation during step initiation, by detecting the reduction of tapping speed in response to the stimulus presentation. The results suggest that the postural task is prioritized during step planning and execution, especially when the motor program cannot be pre-selected in case of the choice reaction condition. Our novel method can be used to probe when and how attention shifts during other locomotion tasks, as well as track attention allocation in various aging and pathological populations.

    Publication

    Sun, R, & Shea, J. B. (2016). Probing attention prioritization during dual-task step initiation: a novel method. Experimental brain research234(4), 1047-1056. https://link.springer.com/article/10.1007/s00221-015-4534-z

    The Author

    Ruopeng (Robin) Sun, Ph.D. Motor Control Research Lab, Department of Kinesiology and Community Health, University of Illinois Urbana-Champaign

    Ruopeng (Robin) Sun received his Ph.D. in kinesiology from Indiana University Bloomington and currently works as a Postdoctoral Research Associate in the Motor Control Research Lab at University of Illinois Urbana-Champaign (http://publish.illinois.edu/motorcontrol). His research interests are: novel technology in fall risk assessment, gait adaptability in complex locomotion task, and cognitive-motor interference in daily locomotion. 

     

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  • 18 Apr 2017 by Nick Kluft

    Moving safely through the environment requires adequate perception of our abilities in relation to the task at hand. If we have the ability to overcome the biomechanical task demands, execution of the planned task is most likely successful. Knowledge of our own ability is therefore crucial in motor planning. Yet, are we still capable of accurately judging our abilities when we grow older and face the concomitant physical and cognitive declines? Inaccurate judgment of our own ability could either lead to overestimation (e.g., excessive risk taking) or underestimation (e.g., activity avoidance). How can we directly quantify the amount of over-and underestimation in gait? We aimed to quantify the degree of misjudgment between the perceived and actual gait ability in older adults.

    We investigated two paradigms to determine the degree of misjudgment: one used a path width manipulation and the other used a speed manipulation (Figure 1a). We asked 27 older adults to walk within paths of different widths projected on a treadmill. We quantified the actual ability by evaluating the participant’s stepping accuracy on a range of path widths and treadmill speeds. Prior to this actual ability measurement, we asked the participants to indicate the smallest path and highest treadmill speed at which they believed they could still walk within the boundaries of the path to unravel their perceived ability. By doing so, we were able to define the degree of misjudgment as the difference between one’s perceived and actual ability (Figure 1b).

     

    Figure 1: Experimental setup and results

    Our results show that stepping accuracy increased when we broadened the path width, while the stepping accuracy did not decrease when treadmill speed increased (i.e., it was not more challenging to walk on a path at a higher speed). Because stepping accuracy was not affected by treadmill speed but was affected by path width, the latter manipulation was used to determine the degree of misjudgment. In agreement with other studies, we showed disparities between perceived ability and actual ability for some of the participants. Altogether, we directly quantified older adults’ misjudgment of gait ability using a path width paradigm. Such quantification of over-and underestimation of gait abilities in older adults could be beneficial in fall-risk assessment and allow for more tailored interventions.

     

    Publication

    Kluft N, van Dieën JH, Pijnappels M (2017). The degree of misjudgment between perceived and actual gait ability in older adults. Gait & Posture, 51, 275-280. doi: 10.1016/j.gaitpost.2016.10.019

     

    About the author

    Nick Kluft is a PhD candidate at the Department of Human Movement Sciences of the Vrije Universiteit Amsterdam in The Netherlands. His research focuses on the discrepancy between perceived and actual physical ability, and how this misjudgment affects gait, stepping behaviour and responses to gait perturbations in older adults. This research was supported by the Dutch Organisation for Scientific Research (NWO). 

     

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  • 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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