• 04 May 2018 by Maria Cristina Bisi

    When you grow, it is clear that your abilities and movement coordination improve. Consequently, you are able to perform motor tasks that you could not do earlier. Ideally, this is because you acquire the ability to use more complex motor strategies as you mature. The question is, can we measure and analyse this movement complexity? And, if yes, do we expect to see an increase in motor complexity with age, independently from the motor task analysed?

    To answer these questions, we studied motor complexity during walking in children, adolescents and young adults. We assessed movement complexity from trunk acceleration data using multiscale entropy. Multiscale entropy expresses the probability that two data traces remain close to each other over time. We examined motor complexity during two different locomotor tasks: i) natural gait, which is a paradigmatic task, expected to become more automatic with age maturation, and ii) tandem gait, which is a non-paradigmatic task that challenges motor control performance, constraining the base of support both in the medio-lateral and  antero-posterior directions. We expected motor complexity to decrease during normal walking and an increase during tandem gait with age. Our hypothesis was confirmed, and results showed a significant increase of motor complexity with age in tandem walking and a decrease on the sagittal plane in normal walking. Interestingly, the ratio of motor complexity (R-Sen in Figure below) measured during both tasks started around 100% at six years of age (similar level of complexity), and showed a progressive decrease to 50% in adulthood (with higher complexity in the tandem gait condition). 

    These results indicated that multiscale entropy is capable to detect changes in movement complexity with motor control maturation. This technique offers new opportunities for improving our understanding on motor control and its development. Our results further reveal a concurrent development of automaticity and complexity. With age maturation, motor complexity decreased during normal walking but increased during tandem walking. This may results from experience obtained during daily life, which leads adults to reach an optimized solution for normal walking, thereby manifesting a decreased movement complexity, while during a novel tandem walking task, they are able to employ more complex motor strategies to successfully perform the task. Finally, our results highlight directionality of changes with age in system complexity, which may depend on the direction of the adaptations or tolerance to stressors.

    Figure. An overview of the two walking conditions (left) with normal walking (top) and tandem walking (bottom), and the effect of age on the ratio of complexity during these tasks (right) in antero-posterior and vertical directions.

     

    Publication

    M. C. Bisi & R. Stagni (2018): Changes of human movement complexity during maturation: quantitative assessment using multiscale entropy, Computer Methods in Biomechanics and Biomedical Engineering, DOI: 10.1080/10255842.2018.1448392

     

    The author

    Maria Cristina Bisi, DEI - Department of Electrical, Electronic and Information Engineering, "Guglielmo Marconi", University of Bologna, Italy.

    Maria Cristina Bisi is a post-doctoral fellow at the Department of Electrical, Electronic and Information Engineering of the University of Bologna. Her research activity is mainly focused on the development of quantitative methods for the assessment and the understanding of motor control development during maturation.

     

    Copyright

    © 2017 by the author. Except as otherwise noted, the ISPGR blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

     

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  • 23 Apr 2018 by Sue Peters

    After stroke, asymmetrical stepping and standing balance is commonly observed when weight bearing or spatiotemporal parameters are measured. These asymmetries are thought to circumvent stroke-related impairments and enable stroke survivors to walk and maintain their balance while standing. However, at the same time, motor planning is also impaired in stroke survivors which impacts the integration of incoming sensory information during functional daily movements and standing balance performance. This process is not well understood but could explain stroke-induced asymmetries. Movement-related cortical potentials (MRCPs) - measured using electroencephalography (EEG) - can be used to estimate motor planning processes in the cortex. After a stroke, longer duration and larger amplitude MRCPs are detected for planning paretic hand movements compared with the non-paretic hand. These differences to the MRCP are thought to reflect the longer time and greater cognitive effort needed to plan a movement, respectively. The aim of this study was to examine motor planning via MRCPs to understand whether motor planning can be attributed to difficulties with stepping and balance after a stroke.

     Self-initiated stepping was performed by participants with sub-acute stroke with the paretic and non-paretic legs. Both EEG and electromyography recorded brain and muscle activity, with movement onset identified by electro-goniometers affixed to the lateral knees. There were no significant differences in stepping performance between legs or in MRCP measures (p ≥ 0.069, Figure). However, when the paretic leg was stepping, the burst onset of the biceps femoris (or hamstring) muscle influenced the MRCP amplitude (p = 0.024; Figure).

    This indicates that cortical planning for initiating stepping is similar between legs after a stroke. Between-leg symmetry may indicate that a portion of the motor planning is actually to prepare for the movement as a whole (e.g. walking). Comparable motor programs may be needed to plan the shifting of the centre of mass, irrespective of whether it is to plan stepping of the paretic or non-paretic legs. It is likely that the motor plan required for stepping reflects this pattern in the sub-acute phase after stroke. The earlier hamstring muscle activity in the paretic leg may then be associated with a lower cognitive effort as measured by the MRCP. The MRCP may therefore be an important process for the timing of muscle preparation for initiating stepping in stroke survivors.

     

     

     

    Figure: In panel A, no differences are seen between the paretic and non-paretic legs for step duration, movement related cortical potential (MRCP) amplitude or biceps femoris (BF) onset. Bars indicate standard deviations. In panel B, higher cognitive effort (MRCP amplitude) related to later onset of BF burst in the paretic leg stepping condition. Data points above the horizontal line indicate individuals with the onset of BF burst after knee flexion, and points below the line specify individuals that show a BF burst in advance of knee flexion. Smaller MRCP amplitudes were found in those with earlier onset BF suggesting that lower cognitive effort is required with an anticipatory burst of hamstring muscle activity.

     

    Publication

    • Peters S, Ivanova TK, Lakhani B, Boyd LA, Staines WR, Handy TC, Garland SJ. Symmetry of cortical planning for initiating stepping in sub-acute stroke. Clinical Neurophysiology. 2018 Apr;129(4):787-796. doi: 10.1016/j.clinph.2018.01.018. Epub 2018 Feb 1.

     

    The author

    • Sue Peters, PT, PhD. Postdoctoral fellow, Simon Fraser University; Research Associate, University of British Columbia.
    • Dr. Peters is a physiotherapist, postdoctoral fellow at Simon Fraser University, and research associate at University of British Columbia. Dr. Peters completed her PhD in the neurophysiology of stepping after stroke. Her current interests are to examine the acute to chronic phases and patterns of recovery post-stroke.
    • Questions? Contact her at sue_peters@sfu.ca or s.peters@alumni.ubc.ca or follow her on twitter: @smpeters9

     

     

    Copyright

    © 2018 by the author. Except as otherwise noted, the ISPGR blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

     

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  • 16 Apr 2018 by Daina Sturnieks

    Fatigue is a common complaint for older people; more than 50 per cent of people aged 70+ report fatigue in undertaking their daily activities. Laboratory-induced fatigue has been shown to affect sensory and movement functions that are associated with falling, such as strength, balance and limb sensation. In addition, fatigue is likely to affect cognitive functions, such as processing speed and attention, which are essential to maintain balance. Therefore, a busy day of shopping, social activities or minding the grandchildren might leave an older person at risk of falling late in the day.

     

    Previous studies showing fatigue effects have employed rigorous laboratory protocols that are unlikely to accurately reflect an older person’s daily activities. So, we asked a group of 50 healthy older people to plan a busy day (where they tried to fit in as many chores or physical activities as possible) and compared changes in fall-related measures of physical and cognitive function with a planned rest day (in which they tried to avoid activity by relaxing, reading or watching TV etc.). Using activity monitors, we found our participants undertook twice as many steps and 2.5 times more minutes of activity on the busy day, compared with the rest day. Participants reported an increase in feelings of fatigue following the busy day and no change in fatigue following the rest day (see figure). However, performance on physical and cognitive tests associated with fall risk changed similarly across the busy and rest days, suggesting that a busy day has little effect on factors associated with fall risk in older people.

     

    Figure: Group mean (SD) self-reported fatigue and physiological fall risk score in the morning (am) and afternoon (pm) of the busy and rest days.

     

    Our busy day protocol did not result in reduced strength, balance and stepping performance in older people, which is different from studies of immediate fatigue conducted with arduous fatiguing protocols in laboratory settings, but similar to studies of physical activity that increased reported tiredness. If any detrimental effects of increased activities undertaken during the busy day occurred, they were not long lasting and had dissipated by the time that the afternoon assessments were undertaken (approx. 4pm). Overall, the findings suggest that in the afternoon of a busy day (based on older people's estimates of their busiest days), cognitive and physical functions associated with fall risk are minimally affected in healthy older people.

     

    Publication

    Sturnieks DL, Yak SL, Ratanapongleka M, Lord SR, Menant JC. A busy day has minimal effect on factors associated with falls in older people: An ecological randomised crossover trial. Exp Gerontol. 2018 12;106:192-197.

    https://doi.org/10.1016/j.exger.2018.03.009

     

    The author

    Daina Sturnieks is a Research Fellow in the Falls, Balance and Injury Research Centre at Neuroscience Research Australia, Sydney. Her research focuses on understanding sensorimotor and neurocognitive contributions to falls in older people and clinical groups, and trialling novel interventions to prevent falls with balance, stepping and cognitive exercises.

     

    Copyright

    © 2017 by the author. Except as otherwise noted, the ISPGR blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

    ISSN 2561-4703

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  • 21 Mar 2018 by Diego Kaski

    Many neurological disorders lead to gait and balance impairments. Especially in older people, these disorders are a common cause of falls, associated with significant morbidity and mortality. Despite the recognition of the socio-economic burden of falls, there are very few treatment options beyond physical therapy for neurological gait and balance impairment. From a brain perspective, human locomotion relies upon a distributed neural network including primary motor, premotor areas, basal ganglia and, importantly, white matter connections between these areas. White Matter hyperintensities and other changes in the cerebral white matter (‘leukoaraiosis’) are very common in old age and associated with gait and balance dysfunction.                    

    This review paper explores whether beneficial effects of physical training can be enhanced by using non-invasive brain stimulation, namely transcranial direct current stimulation (tDCS), in patients with neurological gait disorders. tDCS is a non-invasive neurostimulation technique that consists of delivering a weak electrical current through the scalp. This has been shown to induce bidirectional polarity-dependent changes in excitability of the underlying cortex; anodal tDCS increases cortical excitability and cathodal tDCS decreases it. The physiological and behavioural effects of tDCS have been shown to last for up to one hour, implying that tDCS also modulates the synaptic strength of intracortical and corticospinal neurons.

    Across a number of our own pilot studies, we explored whether these physiological and behavioural effects may facilitate neuroplasticity during physical therapy and thus enhance its effectiveness. We applied 15 minutes of anodal tDCS over the motor and premotor cortex of both cerebral hemispheres using a central electrode in patients with Parkinson’s disease and patients with leukoaraiosis while they were also receiving gait and balance physical therapy. We found that the combination of cortical stimulation and physical therapy improved gait velocity, stride length, time taken to complete the ‘Timed Up and Go’, and postural reactions, above and beyond the positive effects of physical therapy alone. tDCS alone (without physical therapy), however, did not improve gait in patients with Parkinson’s disease or leukoaraiosis.

    Our review paper and pilot studies suggest that non-invasive brain stimulation (such as tDCS) may enhance the effects of physical therapy in patients with neurological gait disorders. Large-scale, multicenter, randomized, double-blind, Phase III studies using standardized protocols based on the more robust published pilot data are needed before these techniques can be implemented into mainstream clinical practice.

    Figure 1. A tDCS stimulation protocol showing anodal tDCS stimulation over the primary motor and pre-motor cortices bilaterally, and reference (cathode) electrode (blue rectangle), over the inion. B Hypothesized effect on synaptic excitability depicting the additive effect of physical therapy and tDCS (red arrow) in lowering the threshold of a motor action potential (i.e. increased cortical excitability), leading to increased cortical plasticity over motor cortical regions, and improved clinical outcomes. C Mean averaged data across pilot studies discussed in the main text, showing the largest reduction in time taken to walk 6 metres in the tDCS + physical therapy arm, compared to physical therapy with sham stimulation.  

    Publication

    Kaski D, Bronstein AM, 2014, Treatments for Neurological Gait and Balance Disturbance: The Use of Non-invasive Electrical Brain Stimulation, Advances in Neuroscience, Vol: 2014, Pages: 1-13, ISSN: 2356-6787

    The author

    Dr Diego Kaski

    Consultant Neurologist and Honorary Senior Lecturer, Gait and Balance Lab, Institute of Neurology, University College London, UK

    Dr Diego Kaski is a Consultant Neurologist with an interest in Neuro-otology. He completed his PhD investigating the cortical mechanisms underpinning human self-motion perception, and the neural control of gait. His current interests include central vestibular processing and the development of novel treatment strategies to improve gait and balance.

    Copyright

    © 2017 by the author. Except as otherwise noted, the ISPGR blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

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  • 26 Feb 2018 by Niklas Lofgren

    Balance deficits are among the most impairing symptoms in people with Parkinson’s disease, and impacts mobility, quality of life and ultimately independence. In order to inform clinicians of the need for rehabilitation and evaluation of its effectiveness, it is essential to investigate the robustness of prevailing balance assessment tools in people with Parkinson’s disease under circumstances similar to clinical practice and by presenting the clinically relevant measurement error. The Mini-BESTest entails 4 subcomponents: anticipatory postural adjustments, postural responses, sensory orientation and dynamic gait. These items are highly relevant for balance in people with Parkinson’s disease. However, its robustness between test administrators and at different time points has only presented as relative values that are highly dependent on the diversity in the sample and are difficult to translate into clinical practice. The aim of this study was therefore to investigate the measurement error of the Mini-Bestest in people with Parkinson’s disease, when assessed by two different test administrators and at different time points.

     

    Twenty-seven people with Parkinson’s disease were assessed with the Mini-BESTest by one experienced and one inexperienced physiotherapist. The assessments took place in different treatment rooms at a hospital in random order. One week later, the experienced physiotherapist reassessed all participants at the same time of day. The results between the physiotherapists showed a measurement error of 4.1 points for the total score of the Mini-BESTest (accounting for 15% of the total score of the test). A systematic error between the testers showed that the experienced physiotherapist rated the people with Parkinson’s disease lower than the inexperienced physiotherapist. Postural responses had the highest proportional error (38% of the score available) whereas sensory orientation had the lowest (17%). The results for the assessments by the experienced physiotherapist, 7 days apart, showed a measurement error of 3.4 points for the Mini-BESTest´s total score (12% of the total score of the test). Postural responses had the highest measurement error (27% of the score available) whereas sensory orientation had the lowest error (13%).

     

    Our results show that in spite of entailing unique and clinically relevant items such as postural responses, turning and dual-task interference, the Mini-BESTest´s measurement error was similar to that of other less sensitive balance tests. Nevertheless, the results stress the importance of thorough theoretical and practical training before using the test, particularly when assessing postural responses. Moreover, clinicians need to be aware of the measurement error when interpreting the outcomes of rehabilitation.

     

     

    Figure: Clinical balance assessment in action

     

     

    Publication

    Löfgren, N., Lenholm, E., Conradsson, D., Ståhle, A., & Franzén, E. (2014). The Mini-BESTest-a clinically reproducible tool for balance evaluations in mild to moderate Parkinson’s disease? BMC neurology, 14(1), 235. https://doi.org/10.1186/s12883-014-0235-7

     

     

    The author

    Niklas Löfgren, Allied Health Professionals Function, Function Area Occupational Therapy and Physiotherapy, Karolinska University Hospital, Stockholm, Sweden; Faculty of Health Sciences, The University of Sydney, Sydney, Australia.

     

    Niklas is a physiotherapist and currently conducts a post-doc at the University of Sydney. He previously investigated integrated single- and dual-task training in Parkinson´s disease, with particular emphasis on cognitive dual-task interference. Niklas´ main research interest concerns effects of non-motor impairments on mobility and how to address this in rehabilitation.

     

     

    Copyright

    © 2017 by the author. Except as otherwise noted, the ISPGR blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

     

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  • 21 Feb 2018 by On-Yee "Amy" Lo

    Walking is a common yet complex activity. Accumulating evidence suggests that walking is not fully autonomous, and instead, relies upon considerable cognitive input and its underlying cortical structures. We now know that the brain is organized into distinct functional networks comprised of spatially separated, yet functionally connected regions. However, it remains unclear whether and how these functional brain networks are involved in the control of walking. Besides, walking has distinct features such as gait speed and gait variability. Is it possible that these features are controlled by distinct functional brain networks? If so, in what way? In this study, we start to answer some of these questions by using a neuroimaging technique that evaluates connectivity between brain regions that share functional properties; namely, resting-state functional magnetic resonance imaging (rs-fMRI).

    Twelve older adults with relatively slow walking speed and mild-to-moderate cognitive impairment, yet without overt neurological disease, completed a gait assessment and a rs-fMRI visit. Preferred gait speed (m/s) and gait variability (%, coefficient of variation of stride time) were evaluated. Functional connectivity within and between seven known functional brain networks was estimated and compared to gait outcomes. We discovered that gait speed and variability were linked to distinct networks (see Figure). Specifically, gait speed was correlated with the strength of functional connectivity within the fronto-parietal network, suggesting that this gait feature depends upon the integrity of communication within brain regions linked to executive functions. Gait variability, on the other hand, correlated with the degree to which spontaneous brain activity within the dorsal attention network and the default network were anti-correlated. This suggests that one’s gait variability, or steadiness of walking, may depend upon the capacity of the brain to dissociate the neural activity of these two networks—a capacity that has been closely linked to sustained attention. 

    This small study demonstrated for the first time that clinically-meaningful gait features are linked to the functional integrity of distinct brain networks. Future studies are warranted to 1) examine these relationships in other populations such as Alzheimer’s disease or related dementias, and 2) determine if gait speed and variability can be differentially targeted by non-invasive brain stimulation. These results, while preliminary, also suggest that clinicians should treat gait speed and variability as distinct features of locomotor control that are controlled by cognitive functions.

    Figure. Gait speed (A, C) and gait variability (B, D) are linked to distinct functional brain networks in functionally-limited older adults. In particular, gait speed is significantly linked to functional connectivity within the frontoparietal network (A, upper left, shown in red). Gait variability is significantly linked to functional connectivity between the dorsal attention network and the default network (D, lower right, shown in red).

     

    Publication

    Lo O, Halko MA, Zhou J, Harrison R, Lipsitz LA, Manor B (2017). Gait speed and gait variability are associated with different functional brain networks. Frontiers in Aging Neuroscience, 9:390. https://www.frontiersin.org/articles/10.3389/fnagi.2017.00390/full

     

    The author

    On-Yee “Amy” Lo, PT, PhD

    Institute for Aging Research, Hebrew SeniorLife, Harvard Medical School, Boston, MA USA

    Amy was first trained as a physical therapist followed by graduate trainings in biomechanics and neuroscience. She is currently a post-doctoral research fellow in the Harvard Translational Research in Aging Program. Her career goal is to understand the neural control of locomotion and to translate research findings to enhance functional independence in older adults.

     

    Copyright

    © 2018 by the author. Except as otherwise noted, the ISPGR blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this license, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

     

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  • 24 Jan 2018 by Xianta Jiang

     

    Walking is one of the most fundamental human activities in daily life. Objective and accurate assessment of human gait provides valuable information to evaluate an individual’s gait pattern, diagnose gait abnormalities, and devise rehabilitation to restore or optimise the gait pattern. Currently, the majority of gait event detection methods are based on kinematic characteristics of trunk or foot movements, which can be obtained using inertial sensors, insoles with built-in pressure sensors or a combination of the above. All these devices have their own disadvantages. The inertial-based devices are accurate for detecting gait events during moderate and fast walking. However, their performance noticeably degrades at lower walking speeds, which is usually the pace for individuals with difficulty in walking. Foot switches and insole pressure sensors are not able to detect gait events during the swing phase, when the foot is not in contact with the floor.

    Force myography (FMG) can be a promising solution for gait event detection. FMG is a muscle activity sensing technology that often utilizes an array of force pressure sensors surrounding a limb to register volumetric changes of the underlying musculotendinous complex during activity. FMG has recently gain interest, and has been investigated primarily for upper extremity gesture recognition and prosthesis control. The MENRVA lab (http://www.sfu.ca/menrva.html) has conducted a series of studies to explore the feasibility of a FMG ankle band for gait analysis, including detecting ankle movements, counting steps, and gait event detection. In this study, we used a FMG ankle band with an array of eight force sensing resistors (FSRs) on the ankle (Fig.1) to record the pressure changes during walking. Healthy young volunteers were recruited to walk slowly on a treadmill. A machine learning model was built on a part of the collected FMG data to detect gait events and partition gait phases. The preliminary results show that over 98.5% steps were correctly detected. 

    The current FMG ankle band is designed to accurately monitoring slow gait in senior people. We plan to further improve the performance of the strap and test the accuracy of this novel method to a wider population including stroke survivors, Parkinson’s disease, and multiple sclerosis. This technology is anticipated to be transferred to clinical settings and has the potential to improve the rehabilitation process and quality of life of those affected by gait impairments caused by various neurological conditions. 

     

    Figure: 1) The FSR (force sensing resistors) band for signal acquisition; 2) the strap placement on the ankle; and 3) the FMG (force myography) signals corresponding to detected gait phases. IC: Initial-Contact, MSt: Mid-Stance, PS: Pre-Swing, Sw: Swing.

     

    Publication
    K.H. Chu, X. Jiang, C. Menon, Wearable step counting using a force myography-based ankle strap, J. Rehabil. Assist. Technol. Eng. 4 (2017) 1–11. doi:10.1177/2055668317746307. URL

     

    The author
    Xianta Jiang, Ph.D., MENRVA Lab, Engineering Science, Simon Fraser University
    Xianta Jiang is a Post-Doctoral Fellow in Engineering Science of Simon Fraser University (SFU), BC, Canada, working with Dr. Carlo Menon. He received his MSc from Zhejiang University in 1998 and his PhD from Simon Fraser University in 2015. His research interests include Human-Computer Interactions (HCI), Physiological Signals, Gait Analysis, Hand Gesture Recognition, Eye-tracking, Force Myography. He is an IEEE, ACM, and ISPGR member.

     

    Copyright
    © 2017 by the author. Except as otherwise noted, this blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode. 

     

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  • 22 Jan 2018 by Nick Kluft

    As we grow older our cognitive and physical abilities decline, but do we adjust our behaviour accordingly? If one’s perception of their declined physical ability is not adjusted to the new situation, unsafe behaviour could occur. A disparity between one’s perceived and actual ability, also known as misjudgment, may lead to risk-taking or inefficiency. As a consequence, this disparity might explain why some older adults fall while their peers with similar cognitive and physical ability do not. Fall prediction algorithms might benefit from a misjudgment term if it is a trait variable that is consistent between tasks. On the contrary, a lack of consistency between tasks would indicate that the degree of misjudgment on one task cannot be predicted by evaluation of prior tasks and suggests that a misjudgment term may have limited benefit for fall prediction. To this end, we investigated whether the degree of misjudgment of stepping ability is consistent between several stepping tasks in young and older adults. 

    We introduced four tasks (see figure) in which the participant’s perceived ability and actual stepping ability were determined. The tasks consisted of: A) stepping over a raised bar, B) stepping over a twelve-meter-long converging piece of paper at a self-selected width, while starting at the broad end of 2-meter width, C) making a recovery step after release from an inclined position, and D) crossing a declining cord at a self-selected height, while starting at the highest end of 1.2 meter. For each task, a linear model was used to determine the relationship between the perceived and actual ability, where the distance between the perceived ability and the corresponding predicted actual ability served as the degree to which a participant misjudged their physical ability. Moreover, the validity of the tasks were examined using the following criteria: “1) the perceived and actual physical ability measure of one task should relate highly to the same measures of another task, 2) the relation between perceived and actual physical ability should be linear,” 3) the linear regression model should be parallel to the identity line.

    Figure. A) stepping over a raised bar, B) stepping over a converging piece of paper at a self-selected width, C) making a recovery step after release from an inclined position, D) crossing a declining cord at a self-selected height.

    We showed that the actual ability measures and perceived ability measures were consistent across tasks. However, the degree of misjudgment was not consistent between different stepping tasks, but rather task-specific and could not be generalised to other stepping tasks. Furthermore, only one of the tasks satisfied our validity criteria of, which hampers comparison of the degree of misjudgment over tasks. Future research should implement novel and valid tasks to investigate the added value of a misjudgment term in fall prediction models.

     

    Publication

    Kluft N, Bruijn SM, Weijer RHA, van Dieën JH, Pijnappels M (2017). On the validity and consistency of misjudgment of stepping ability in young and older adults. PLOS ONE 12(12): e0190088. https://doi.org/10.1371/journal.pone.0190088

     

    About the author

    Nick Kluft is a PhD candidate at the Department of Human Movement Sciences at 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 91714344). 

     

    Copyright

    © 2017 by the author. Except as otherwise noted, this blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this license, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

     

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  • 22 Nov 2017 by George Mochizuki

    Lower limb spasticity is a common consequence of stroke. The persistent muscle overactivity, paresis, increased stretch sensitivity and altered tissue properties, which characterize spasticity, affect the ability to effectively modulate muscle activity. In turn, the ability to control the position of the centre of mass is altered and may lead to an increased likelihood of falling. Because unilateral impairments are common after stroke (Figure 1A), posturographic measures quantifying the contributions of each limb to balance control may have utility in characterizing specific deficits in spatio-temporal parameters of control. More importantly, there is an added need to use these measures to characterize change in balance control over time, as a way of informing clinical decision-making. Precise quantitative measures of changes in individual limb contributions to balance control over time have the potential of providing specific and sensitive information on the efficacy of interventions.

     

    Using data that tracked recovery over a 2-year window, we retrospectively analyzed changes in balance-related outcomes that took individual-limb contributions to balance into consideration over time, to characterize the natural time course of balance recovery in individuals with post-stroke spasticity. Inter-limb synchronization (the amount of similarity in forward and backward sway between the left and right legs over a 30 second trial) was determined by calculating the peak of the cross-correlation function between the anteroposterior centre of pressure traces on 2 force plates (one for each leg). Spatial symmetry, weight-bearing symmetry, and Berg Balance Scale scores were also tracked. Hierarchical growth curve modelling was used to estimate the recovery trajectories of 92 stroke-survivors with (n=45) and without (n=47) post-stroke spasticity of the lower limb (assessed as Modified Ashworth Scale ≥ 1 at the ankle alone with or without knee spasticity). Separate trajectories were modelled for individuals with and without spasticity. Models were additionally generated based on the severity of spasticity. These analyses identified early improvement followed by a slowing and plateau in rates of recovery. Individuals with spasticity had greater deficits than those individuals without spasticity, but the recovery trajectories between groups did not differ. Inter-limb synchronization was negatively influenced by the severity of spasticity (Figure 1B).

     

    Spasticity affects balance control by reducing the extent of inter-limb synchronization of the centres of pressure. This reduction in synchronization persists well into the recovery window. Further research is needed to determine whether these recovery trajectories can be modified with interventions that aim to reduce spasticity or enhance motor recovery of the lower limbs. From this perspective, the information derived from this study can serve as indicators of the natural time course of recovery using specific metrics of balance control.

     

     

    Figure 1. A) Typical example of a stabilogram of the affected (left) and less-affected (right) legs of an individual with lower limb spasticity. B) Comparison of recovery trajectories on 3 outcome measures for individuals with (left) and without (right) lower limb spasticity after stroke.

     

    Copyright

    © 2017 by the author. Except as otherwise noted, this blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode.

     

    Publication

    Singer JC, Nishihara K, Mochizuki G (2016). Does post-stroke lower limb spasticity influence the recovery of standing balance control? A multilevel growth model of stability control measures over two years. Neurorehabilitation and Neural Repair, 30(7):626-634. http://journals.sagepub.com/doi/pdf/10.1177/1545968315613862

     

    Author

    Dr. George Mochizuki is a Scientist with the Canadian Partnership for Stroke Recovery in the Hurvitz Brain Sciences Research Program at the Sunnybrook Research Institute in Toronto, Canada. He also holds the rank of Associate Professor (status-only) in the Department of Physical Therapy at the University of Toronto. His research aims to identify the contributions of the central nervous system to balance control and to characterize impairment and recovery of balance control following neurological injury.

     

    ISSN 2561-4703

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  • 19 Nov 2017 by David Conradsson

    Difficulty with turning while walking is a common and delibitating problem for individuals with Parkinson’s disease (PD). A possible explanation for this problem may be the inability to adequately regulate step width during the turn. Although the characteristics of turning impairments in PD are well documented, few studies have investigated how step width is regulated during turning. Dopaminergic medication is commonly prescribed to decrease the severity of PD symptoms and has been shown to improve gait. However, it is unclear whether and how dopaminergic medication affects turning ability. Therefore, this study aimed to compare regulation of step width during pre- and unplanned walking turns in individuals with PD to healthy controls and to investigate whether dopaminergic medication improves step width regulation or not.

    Seventeen individuals with PD (ON and OFF dopaminergic medication) and 17 healthy controls performed each of the following three tasks, presented randomly: walking and turning 180° to the right or left, and walking straight. To evaluate both proactive and reactive turning behavior, the task was visually cued before starting to walk (preplanned turns) or at one step before reaching the turning point (unplanned turns). Walking kinematics were measured by 3D motion analysis. Turns initiated with the step and spin strategy (see example in Figure 1A-B) were analysed separately. Our findings reveal that both individuals with PD and controls alternated their step width while turning, i.e. from wide-to-narrow-to-wide base of support for the step strategy and narrow-to-wide-to-narrow base of support for the spin strategy (Figure 2A-B). However, irrespective of turning strategy, individuals with PD turned with narrower steps whilst using crossing steps (i.e. step width closer to a value of zero). The effects of dopaminergic medication were sparse; significant interaction effects were found for the step strategy (Figure 2A) but post-hoc testing did not reveal any significant differences between PD OFF and ON.

    To conclude, problems regulating step width while executing cross-over steps with a narrow base of support appears to be a critical feature for turning in PD. This finding could reflect a safety strategy among individuals with PD in order to decrease the postural demands associated with the drastic change of base of support while performing crossing steps. As dopaminergic medication showed limited effect on step width regulation, rehabilitation plays an important role to promote safe turning strategies with a specific emphasis on sustaining a wide support base.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    Figure 1. Schematic drawing of A) the step strategy (i.e. first turning step ipsilateral to the turning direction) and B) the spin strategy (i.e. first turning step contralateral to the turning direction) during a right turn. Note that similar to straight walking, the step strategy leads to positive step width as the base of support is widened, whereas the spin strategy results in a narrow or negative step width as the turning foot crosses over and lands close to or medial to the line of progression of the internal leg.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    Figure 2. Step width (meter) of three turning steps for PD-OFF, PD-ON and the control group while using A) the step and B) spin strategy to initiate pre- and unplanned turns. Positive values reflect widening of the base of support whereas negative values reflect crossing-over of the base of support. Error bars represent 95% confidence interval. *p ≤ .025; **p ≤ .01.

     

    Publication

    Conradsson D, Paquette C, Lökk J, Franzén E. Pre- and unplanned walking turns in Parkinson's disease - Effects of dopaminergic medication. Neuroscience. 26;341:18-26. 2017

    http://doi.org/10.1016/j.neuroscience.2016.11.016

     

    The author

    David Conradsson, Division of Physiotherapy, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden and Department of Kinesiology and Physical Education, McGill University, Montreal, Canada

    David is a registered physiotherapist who investigated dual-task training for individuals with Parkinson's disease during his PhD training at the Karolinska Institutet. As a post-doc at McGill University, his current research focus on the effects of non-invasive brain stimulation on motor recovery after stroke.

     

    Copyright

    © 2017 by the author. Except as otherwise noted, this blog, including its text and figures, is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-sa/4.0/legalcode. 

     

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  • 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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  • 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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