Quietness better than background music for creativity

A study finds that listening to music can significantly impair performance on tasks that need creativity compared with doing them in a quiet environment.

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Quietness better than background music for creativity

A study finds that listening to music can significantly impair performance on tasks that need creativity compared with doing them in a quiet environment.

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Model-Based Hearing Diagnostics based on Wideband Tympanometry Measurements utilizing Fuzzy Arithmetic

Publication date: Available online 28 February 2019

Source: Hearing Research

Author(s): B. Sackmann, E. Dalhoff, M. Lauxmann

Abstract

Today’s audiometric methods for the diagnosis of middle ear disease are often based on a comparison of measurements with standard curves, that represent the statistical range of normal hearing responses. Because of large inter-individual variances in the middle ear, especially in wideband tympanometry (WBT), specificity and quantitative evaluation are greatly restricted. A new model-based approach could transform today’s predominantly qualitative hearing diagnostics into a quantitative and tailored, patient-specific diagnosis, by evaluating WBT measurements with the aid of a middle-ear model. For this particular investigation, a finite element model of a human ear was used. It consisted of an acoustic ear canal and a tympanic cavity model, a middle-ear with detailed nonlinear models of the tympanic membrane and annular ligament, and a simplified inner-ear model. This model has made it possible for us to simulate pathologies like the stiffening of ligaments or joints, because we can simply change the corresponding mechanical parameters of the model. On the other hand, it is also possible to identify pathologies from measurements, by analyzing the parameters obtained by a system identification procedure. This reduces the number of required model parameters through sensitivity studies and parameter clustering. Uncertainties due to the lack of knowledge, subjectivity in numerical implementation and model simplification are taken into account by the application of fuzzy arithmetic. The most confident parameter set can be determined by applying an inverse fuzzy method on the measurement data. The principle and the benefits of this model-based approach are illustrated by the example of a two-mass oscillator, and also by the simulation of the energy absorbance of an ear with malleus fixation, where the parameter changes that are introduced can be determined quantitatively through the system identification.

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Vibroplasty Combined with Tympanic Membrane Reconstruction in Middle Ear Ventilation Disorders

Publication date: Available online 27 February 2019

Source: Hearing Research

Author(s): Christoph Müller, Thomas Zahnert, Marcus Neudert, Steffen Ossmann, Matthias Bornitz

Abstract

Although the Vibrant Soundbridge is one of the most frequently used active middle ear implants, data regarding how middle ear ventilation disorders may affect the transmission behavior of its floating mass transducer are still insufficient. Studies involving coupling the floating mass transducer to the stapes head are particularly lacking.

This temporal bone study evaluated the influence of simulated middle ear ventilation disorders on the middle ear transfer function in the reconstructed middle ear. The middle ear transfer function was measured using Laser Doppler Vibrometry after vibroplasty onto the stapes head, with or without tympanic membrane reconstruction. Middle ear ventilation disorders were simulated through changes in static pressure via the external ear channel with a maximum pressure of +3 kPa. Slice thickness of tympanic membrane reconstruction material was measured using micro-CT.

When the reconstructed ossicular chain and the reconstructed tympanic membrane were mechanically excited by the floating mass transducer under conditions of ambient static pressure, the transmission behavior was found to be independent of the type of tissue used. Increase in static pressure up to + 3 kPa caused maximum low frequency transmission loss of 15 dB when elastic grafts were used and 5 dB when stiff tissue was inserted. At high frequencies, measured loss of up to 5 dB was relatively independent of the tissue stiffness.

Increase in static pressure led to displacement of the tissues towards the vestibulum and caused stiffening, especially of the annular ligament. Stiffening-induced transmission losses were mainly found at low frequencies and could not be compensated by the floating mass transducer in this range. Above 1300 Hz, the continuous force spectrum of the actuator sufficiently protected against loss of amplitude. To minimize postoperative transmission loss due to persisting ventilation disorders, choosing a very stiff tympanic membrane reconstruction material seems to be appropriate.

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Model-Based Hearing Diagnostics based on Wideband Tympanometry Measurements utilizing Fuzzy Arithmetic

Publication date: Available online 28 February 2019

Source: Hearing Research

Author(s): B. Sackmann, E. Dalhoff, M. Lauxmann

Abstract

Today’s audiometric methods for the diagnosis of middle ear disease are often based on a comparison of measurements with standard curves, that represent the statistical range of normal hearing responses. Because of large inter-individual variances in the middle ear, especially in wideband tympanometry (WBT), specificity and quantitative evaluation are greatly restricted. A new model-based approach could transform today’s predominantly qualitative hearing diagnostics into a quantitative and tailored, patient-specific diagnosis, by evaluating WBT measurements with the aid of a middle-ear model. For this particular investigation, a finite element model of a human ear was used. It consisted of an acoustic ear canal and a tympanic cavity model, a middle-ear with detailed nonlinear models of the tympanic membrane and annular ligament, and a simplified inner-ear model. This model has made it possible for us to simulate pathologies like the stiffening of ligaments or joints, because we can simply change the corresponding mechanical parameters of the model. On the other hand, it is also possible to identify pathologies from measurements, by analyzing the parameters obtained by a system identification procedure. This reduces the number of required model parameters through sensitivity studies and parameter clustering. Uncertainties due to the lack of knowledge, subjectivity in numerical implementation and model simplification are taken into account by the application of fuzzy arithmetic. The most confident parameter set can be determined by applying an inverse fuzzy method on the measurement data. The principle and the benefits of this model-based approach are illustrated by the example of a two-mass oscillator, and also by the simulation of the energy absorbance of an ear with malleus fixation, where the parameter changes that are introduced can be determined quantitatively through the system identification.

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Vibroplasty Combined with Tympanic Membrane Reconstruction in Middle Ear Ventilation Disorders

Publication date: Available online 27 February 2019

Source: Hearing Research

Author(s): Christoph Müller, Thomas Zahnert, Marcus Neudert, Steffen Ossmann, Matthias Bornitz

Abstract

Although the Vibrant Soundbridge is one of the most frequently used active middle ear implants, data regarding how middle ear ventilation disorders may affect the transmission behavior of its floating mass transducer are still insufficient. Studies involving coupling the floating mass transducer to the stapes head are particularly lacking.

This temporal bone study evaluated the influence of simulated middle ear ventilation disorders on the middle ear transfer function in the reconstructed middle ear. The middle ear transfer function was measured using Laser Doppler Vibrometry after vibroplasty onto the stapes head, with or without tympanic membrane reconstruction. Middle ear ventilation disorders were simulated through changes in static pressure via the external ear channel with a maximum pressure of +3 kPa. Slice thickness of tympanic membrane reconstruction material was measured using micro-CT.

When the reconstructed ossicular chain and the reconstructed tympanic membrane were mechanically excited by the floating mass transducer under conditions of ambient static pressure, the transmission behavior was found to be independent of the type of tissue used. Increase in static pressure up to + 3 kPa caused maximum low frequency transmission loss of 15 dB when elastic grafts were used and 5 dB when stiff tissue was inserted. At high frequencies, measured loss of up to 5 dB was relatively independent of the tissue stiffness.

Increase in static pressure led to displacement of the tissues towards the vestibulum and caused stiffening, especially of the annular ligament. Stiffening-induced transmission losses were mainly found at low frequencies and could not be compensated by the floating mass transducer in this range. Above 1300 Hz, the continuous force spectrum of the actuator sufficiently protected against loss of amplitude. To minimize postoperative transmission loss due to persisting ventilation disorders, choosing a very stiff tympanic membrane reconstruction material seems to be appropriate.

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A role for the lower visual field information in stair climbing

Publication date: Available online 27 February 2019

Source: Gait & Posture

Author(s): Veronica Miyasike-daSilva, Jonathan C. Singer, William E. McIlroy

Abstract

Background

Locomotion on stairs is challenging for balance control and relates to a significant number of injurious falls. The visual system provides relevant information to guide stair locomotion and there is evidence that peripheral vision is potentially important.

Research question

This study investigated the role of the lower visual field information for the control of stair walking. It was hypothesized that restriction in the lower visual field (LVF) would significantly impact gaze and locomotor behaviour specifically during descent and during transition phases emphasizing the importance of the LVF information during online control.

Methods

Healthy young adults (n = 12) ascended and descended a 7-step staircase while wearing customized goggles that restricted the LVF. Three visual conditions were tested: full field of view (FULL); 30º (MILD), and 15º (SEVERE) of lower field of view available. Stride time, head pitch angle and handrail use were assessed during approach, transition steps (two steps at the top and bottom of the stairs) and middle step phases.

Results

Transient downward head pitch angle increased with LVF restriction, while walk speed decreased and handrail use increased. Occlusion impaired stair descent more strongly than ascent reflected by a larger downward head pitch angles and slower walk times. LVF restriction had a greater influence on stride time and head angle during the approach and first transition compared to other stair regions.

Significance

Information from the lower visual field is important to guide stair walking and particularly when negotiating the first few steps of a staircase. Restriction in the lower visual field during stair walking results in more cautious locomotor behaviour such as walking slower and using the handrails. In daily activities, tasks or conditions that restrict or alter the lower visual field information may elevate the risk for missteps and falls.

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Effects of a lower extremity exercise program on gait biomechanics and clinical outcomes in children and adolescents with obesity: A randomized controlled trial

Publication date: Available online 27 February 2019

Source: Gait & Posture

Author(s): B. Horsak, C. Schwab, A. Baca, S. Greber-Platzer, A. Kreissl, S. Nehrer, M. Keilani, R. Crevenna, A. Kranzl, B. Wondrasch

Abstract

Background

Research highlights the detrimental effects of obesity on gait biomechanics and the accompanied risk of lower-extremity skeletal malalignments, increased joint stress, pain and discomfort. Individuals with obesity typically show increased knee valgus angles combined with an increased step width. Accompanying muscular dysfunctions impede their ability to compensate for these alterations, especially in the frontal plane. To date, no studies are available, which evaluated the potential effects of an exercise program (EP) in reducing these unfavorable biomechanical changes.

Research questions

Is a 12-week EP, which includes hip abductor and knee extensor strength exercises and fosters dynamic knee alignment, effective in positively altering gait biomechanics in children and adolescents with obesity?

Methods

This study was a randomized controlled trial having children and adolescents with obesity assigned to an EP (n = 19) or control (n = 16) group. Pain, self-rated knee function, muscle strength and 3D gait analysis during walking and stair climbing were evaluated.

Results

Results indicate that the EP was able to increase muscular strength especially in the hip abductors. In addition, children from the EP group walked with less maximum hip adduction and reduced pelvic drop during weight acceptance at follow-up. No changes were present in self-rated knee function, pain or discomfort.

Significance

Even though effects were small, results indicate that an EP is an effective short-term possibility to counteract the progressive development of biomechanical malalignments of the lower extremity. Clinical parameters indicated that the program was feasible. Nonetheless, low adherence highlights the need to develop more attractive programs.

Clinical Trials Reg. Nr

clinicaltrials.gov (NCT02545764).

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A role for the lower visual field information in stair climbing

Publication date: Available online 27 February 2019

Source: Gait & Posture

Author(s): Veronica Miyasike-daSilva, Jonathan C. Singer, William E. McIlroy

Abstract

Background

Locomotion on stairs is challenging for balance control and relates to a significant number of injurious falls. The visual system provides relevant information to guide stair locomotion and there is evidence that peripheral vision is potentially important.

Research question

This study investigated the role of the lower visual field information for the control of stair walking. It was hypothesized that restriction in the lower visual field (LVF) would significantly impact gaze and locomotor behaviour specifically during descent and during transition phases emphasizing the importance of the LVF information during online control.

Methods

Healthy young adults (n = 12) ascended and descended a 7-step staircase while wearing customized goggles that restricted the LVF. Three visual conditions were tested: full field of view (FULL); 30º (MILD), and 15º (SEVERE) of lower field of view available. Stride time, head pitch angle and handrail use were assessed during approach, transition steps (two steps at the top and bottom of the stairs) and middle step phases.

Results

Transient downward head pitch angle increased with LVF restriction, while walk speed decreased and handrail use increased. Occlusion impaired stair descent more strongly than ascent reflected by a larger downward head pitch angles and slower walk times. LVF restriction had a greater influence on stride time and head angle during the approach and first transition compared to other stair regions.

Significance

Information from the lower visual field is important to guide stair walking and particularly when negotiating the first few steps of a staircase. Restriction in the lower visual field during stair walking results in more cautious locomotor behaviour such as walking slower and using the handrails. In daily activities, tasks or conditions that restrict or alter the lower visual field information may elevate the risk for missteps and falls.

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Effects of a lower extremity exercise program on gait biomechanics and clinical outcomes in children and adolescents with obesity: A randomized controlled trial

Publication date: Available online 27 February 2019

Source: Gait & Posture

Author(s): B. Horsak, C. Schwab, A. Baca, S. Greber-Platzer, A. Kreissl, S. Nehrer, M. Keilani, R. Crevenna, A. Kranzl, B. Wondrasch

Abstract

Background

Research highlights the detrimental effects of obesity on gait biomechanics and the accompanied risk of lower-extremity skeletal malalignments, increased joint stress, pain and discomfort. Individuals with obesity typically show increased knee valgus angles combined with an increased step width. Accompanying muscular dysfunctions impede their ability to compensate for these alterations, especially in the frontal plane. To date, no studies are available, which evaluated the potential effects of an exercise program (EP) in reducing these unfavorable biomechanical changes.

Research questions

Is a 12-week EP, which includes hip abductor and knee extensor strength exercises and fosters dynamic knee alignment, effective in positively altering gait biomechanics in children and adolescents with obesity?

Methods

This study was a randomized controlled trial having children and adolescents with obesity assigned to an EP (n = 19) or control (n = 16) group. Pain, self-rated knee function, muscle strength and 3D gait analysis during walking and stair climbing were evaluated.

Results

Results indicate that the EP was able to increase muscular strength especially in the hip abductors. In addition, children from the EP group walked with less maximum hip adduction and reduced pelvic drop during weight acceptance at follow-up. No changes were present in self-rated knee function, pain or discomfort.

Significance

Even though effects were small, results indicate that an EP is an effective short-term possibility to counteract the progressive development of biomechanical malalignments of the lower extremity. Clinical parameters indicated that the program was feasible. Nonetheless, low adherence highlights the need to develop more attractive programs.

Clinical Trials Reg. Nr

clinicaltrials.gov (NCT02545764).

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iHear Releases Subscription Plans for Web-Enabled Hearing Aids

​iHear Medical (https://www.ihearmedical.com/) has introduced new subscription plans for consumers to obtain advanced hearing aids and optional wireless services on a pay-as-you-go model or at a low monthly fee. iHEAR will launch its subscription service in conjunction with mobile apps for wireless programming of its hearing devices, which features Internet of Things (IoT) connectivity and enables consumers to conveniently and discreetly interact with smart devices in their environment. This new service will allow consumers to personalize their hearing experience to suit their budget and individual needs like with mobile subscriptions. John Luna, the CEO of iHEAR Medical, said this service model lowers the entry point and saves consumers money. "Consumers will have the flexibility to adjust their subscription as their needs change," he said.

Published: 2/27/2019 1:54:00 PM

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iHear Releases Subscription Plans for Web-Enabled Hearing Aids

​iHear Medical (https://www.ihearmedical.com/) has introduced new subscription plans for consumers to obtain advanced hearing aids and optional wireless services on a pay-as-you-go model or at a low monthly fee. iHEAR will launch its subscription service in conjunction with mobile apps for wireless programming of its hearing devices, which features Internet of Things (IoT) connectivity and enables consumers to conveniently and discreetly interact with smart devices in their environment. This new service will allow consumers to personalize their hearing experience to suit their budget and individual needs like with mobile subscriptions. John Luna, the CEO of iHEAR Medical, said this service model lowers the entry point and saves consumers money. "Consumers will have the flexibility to adjust their subscription as their needs change," he said.

Published: 2/27/2019 1:54:00 PM

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Auditory brainstem stimulation with a conformable microfabricated array elicits responses with tonotopically organized components

Publication date: Available online 26 February 2019

Source: Hearing Research

Author(s): Amélie A. Guex, Ariel Edward Hight, Shreya Narasimhan, Nicolas Vachicouras, Daniel J. Lee, Stéphanie P. Lacour, M. Christian Brown

Abstract

Auditory brainstem implants (ABIs) restore hearing to deaf individuals not eligible for cochlear implants. Speech comprehension in ABI users is generally poor compared to that of cochlear implant users, and side effects are common. The poor performance may result from activating broad areas and multiple neuronal populations of the cochlear nucleus, however detailed studies of the responses to surface stimulation of the cochlear nucleus are lacking. A conformable electrode array was microfabricated to fit on the rat’s dorsal cochlear nucleus (DCN). It hosts 20 small electrodes (each 100 μm diam.). The array was tested by recording evoked potentials and neural activity along the tonotopic axis of the inferior colliculus (IC). Almost all bipolar electrode pairs elicited responses, in some cases with an even, or relatively constant, pattern of thresholds and supra-threshold measures along the long axis of the array. This pattern suggests that conformable arrays can provide relatively constant excitation along the surface of the DCN and thus might decrease the ABI side effects caused by spread of high current to adjacent structures. We also examined tonotopic patterns of the IC responses. Compared to sound-evoked responses, electrically-evoked response mappings had less tonotopic organization and were broader in width. They became more tonotopic when the evoked activity common to all electrodes and the late phase of response were subtracted out, perhaps because the remaining activity is from tonotopically organized principal cells of the DCN. Responses became less tonotopic when inter-electrode distance was increased from 400 μm to 800 μm but were relatively unaffected by changing to monopolar stimulation. The results illustrate the challenges of using a surface array to present tonotopic cues and improve speech comprehension in humans who use the ABI.

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Auditory brainstem stimulation with a conformable microfabricated array elicits responses with tonotopically organized components

Publication date: Available online 26 February 2019

Source: Hearing Research

Author(s): Amélie A. Guex, Ariel Edward Hight, Shreya Narasimhan, Nicolas Vachicouras, Daniel J. Lee, Stéphanie P. Lacour, M. Christian Brown

Abstract

Auditory brainstem implants (ABIs) restore hearing to deaf individuals not eligible for cochlear implants. Speech comprehension in ABI users is generally poor compared to that of cochlear implant users, and side effects are common. The poor performance may result from activating broad areas and multiple neuronal populations of the cochlear nucleus, however detailed studies of the responses to surface stimulation of the cochlear nucleus are lacking. A conformable electrode array was microfabricated to fit on the rat’s dorsal cochlear nucleus (DCN). It hosts 20 small electrodes (each 100 μm diam.). The array was tested by recording evoked potentials and neural activity along the tonotopic axis of the inferior colliculus (IC). Almost all bipolar electrode pairs elicited responses, in some cases with an even, or relatively constant, pattern of thresholds and supra-threshold measures along the long axis of the array. This pattern suggests that conformable arrays can provide relatively constant excitation along the surface of the DCN and thus might decrease the ABI side effects caused by spread of high current to adjacent structures. We also examined tonotopic patterns of the IC responses. Compared to sound-evoked responses, electrically-evoked response mappings had less tonotopic organization and were broader in width. They became more tonotopic when the evoked activity common to all electrodes and the late phase of response were subtracted out, perhaps because the remaining activity is from tonotopically organized principal cells of the DCN. Responses became less tonotopic when inter-electrode distance was increased from 400 μm to 800 μm but were relatively unaffected by changing to monopolar stimulation. The results illustrate the challenges of using a surface array to present tonotopic cues and improve speech comprehension in humans who use the ABI.

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Influence of Age and Falls Incidence on Tau Guidance of Centre of Pressure Movement during Gait Initiation

Publication date: Available online 27 February 2019

Source: Gait & Posture

Author(s): Steven van Andel, Michael H. Cole, Gert-Jan Pepping

Abstract

Background

Prospective balance control can be assessed in terms of the characteristics of a tau-guidance function that summarizes the velocity profile of Centre of Pressure (CoP) movement during gait initiation. This allows the nature of CoP movement to be assessed on a continuum between controlled ‘soft’- and unstable ‘hard’ CoP-motion gap-closure. Previous research has shown less stable movement patterns with harder closures with increasing age, which makes movements more prone to overshooting and could possibly explain the increasing falls risk with age.

Research questions

The primary research question was ‘what is the relationship between falls incidence and tau-guidance in the mediolateral centre of pressure movements during gait initiation?’ The secondary research question was ‘what are the influences of age and task demands on the variability of tau-guidance characteristics?’.

Methods

Sixteen young adults and 76 older adults performed 33 gait initiations from a force platform, stepping onto stepping-targets imposing differing task demands. Older participants completed a one-year follow-up screening for falls. An analysis was performed investigating linear relationships between a tau-guidance function and the time-to-closure (tau) of the mediolateral centre of pressure motion-gap with coupling constant K (dependent variable).

Results

Gait-related falls during the 12-month follow-up period were associated with higher tau-K values. Furthermore, longer movement preparation time was associated with lower K values, particularly in fallers. Previously-reported age-related increases of the tau-coupling constant values which were found in studies of unconstrained gait initiation were not present in our results.

Significance

The presence of the targeting task provided a more prescriptive environment compared to unconstrained gait initiation and could explain the absence of age-related changes to the produced K values. Falls incidence was found to be associated with higher values of K, indicating less stable movement. Future studies should investigate the practical implications of these findings for falls prevention.

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Fractal analysis of gait in people with Parkinson’s disease: three minutes is not enough

Publication date: Available online 26 February 2019

Source: Gait & Posture

Author(s): Vivien Marmelat, Ryan L. Meidinger

Abstract

Background

The fractal dynamics of gait variability in people with Parkinson’s disease has been studied by applying the detrended fluctuations analysis (DFA) to short time series (<200 strides). However, DFA is sensitive to time series length, and it is unclear if DFA results from short time series are reliable and if they reflect the fractal dynamics of longer time series.

Research question

Is DFA reliable when applied to short time series?

Methods

We applied DFA to stride time series from five 3-min trials and one 15-min trial in 12 people with Parkinson’s disease, 14 healthy older adults and 14 healthy young adults walking overground. Within each group, intraclass correlations (ICC 3,1) were performed to assess the reliability of i) the five 3-min trials together, ii) each 3-min trials to the 15-min trial, and iii) the first 150 strides from the 15-min trial to the full 15-min trial.

Results

Our three main findings are that 1) stride time α-DFA values are not consistent from trial-to-trial for short stride time series, 2) stride time α-DFA values from each 3-min trials are not consistent when compared to stride time α-DFA values from a 15-min trial, and 3) stride time α-DFA values from the first 150 strides of the 15-min trial are not consistent when compared to α-DFA values from the full 15-min trial.

Significance

Our results confirm that α-DFA values from 3-min walking trials are not reliable, and that they do not reflect the scale invariant properties of longer time series. This suggests that previous studies assessing the fractal dynamics of gait variability from about 3-min walking must be interpreted with caution. A major clinical implication is that DFA cannot be used to study gait in people unable to perform 500 strides continuously.

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The ability of the instrumented tandem walking tests to discriminate fully ambulatory people with MS from healthy adults

Publication date: Available online 26 February 2019

Source: Gait & Posture

Author(s): Yevgenia Grinberg, Shani Berkowitz, Leora Hershkovitz, Ofir Malcay, Alon Kalron

Abstract

Background

People with multiple sclerosis (PwMS) experience walking and balance deficits at the initial phases of the disease, even when classified as only minimally disabled. Complex balance tasks, such as tandem walking, are probably more sensitive in detecting mild balance difficulties compared to the standard traditional tests in this population.

Research question

The aim was to investigate different types of 3-meter tandem walking tests in fully ambulatory PwMS.

Methods

This observational case-control study included 50 participants; 25 PwMS, 17 women and 8 men, aged 35.2 (S.D = 8.6) and 25 healthy subjects, 18 women and 7 men, aged 34.3 (S.D = 6.1). The 3-meter tandem walk tests were performed during a single session. Each subject completed a sequence of 3 consecutive tests under 3 different task conditions: normal tandem walking, backward tandem walking and cognitive tandem walking. Tandem walking tests were evaluated via three small, lightweight axial wearable accelerometers (APDM, Oregon, USA).

Results

The mean EDSS for the MS group was 1.6 (S.D = 0.6) indicating minimal disability. PwMS walked slower and at a slower pace, with a prolonged double support and decreased swing phase compared to healthy subjects in normal and backward conditions. In contrast, during the cognitive task, non-significant differences were found in gait measures between the PwMS and the healthy controls. Significant differences were found between task conditions for all participants. All reduced their walking speed and walked at a slower pace in both the cognitive and backward conditions compared to the normal tandem walk condition. However, non-significant scores were found for the condition X group factor.

Significance

The study provides new insights into the 3-meter tandem walk test. Findings should improve evaluation and training of dynamic balance in fully ambulatory PwMS.

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Influence of Age and Falls Incidence on Tau Guidance of Centre of Pressure Movement during Gait Initiation

Publication date: Available online 27 February 2019

Source: Gait & Posture

Author(s): Steven van Andel, Michael H. Cole, Gert-Jan Pepping

Abstract

Background

Prospective balance control can be assessed in terms of the characteristics of a tau-guidance function that summarizes the velocity profile of Centre of Pressure (CoP) movement during gait initiation. This allows the nature of CoP movement to be assessed on a continuum between controlled ‘soft’- and unstable ‘hard’ CoP-motion gap-closure. Previous research has shown less stable movement patterns with harder closures with increasing age, which makes movements more prone to overshooting and could possibly explain the increasing falls risk with age.

Research questions

The primary research question was ‘what is the relationship between falls incidence and tau-guidance in the mediolateral centre of pressure movements during gait initiation?’ The secondary research question was ‘what are the influences of age and task demands on the variability of tau-guidance characteristics?’.

Methods

Sixteen young adults and 76 older adults performed 33 gait initiations from a force platform, stepping onto stepping-targets imposing differing task demands. Older participants completed a one-year follow-up screening for falls. An analysis was performed investigating linear relationships between a tau-guidance function and the time-to-closure (tau) of the mediolateral centre of pressure motion-gap with coupling constant K (dependent variable).

Results

Gait-related falls during the 12-month follow-up period were associated with higher tau-K values. Furthermore, longer movement preparation time was associated with lower K values, particularly in fallers. Previously-reported age-related increases of the tau-coupling constant values which were found in studies of unconstrained gait initiation were not present in our results.

Significance

The presence of the targeting task provided a more prescriptive environment compared to unconstrained gait initiation and could explain the absence of age-related changes to the produced K values. Falls incidence was found to be associated with higher values of K, indicating less stable movement. Future studies should investigate the practical implications of these findings for falls prevention.

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Fractal analysis of gait in people with Parkinson’s disease: three minutes is not enough

Publication date: Available online 26 February 2019

Source: Gait & Posture

Author(s): Vivien Marmelat, Ryan L. Meidinger

Abstract

Background

The fractal dynamics of gait variability in people with Parkinson’s disease has been studied by applying the detrended fluctuations analysis (DFA) to short time series (<200 strides). However, DFA is sensitive to time series length, and it is unclear if DFA results from short time series are reliable and if they reflect the fractal dynamics of longer time series.

Research question

Is DFA reliable when applied to short time series?

Methods

We applied DFA to stride time series from five 3-min trials and one 15-min trial in 12 people with Parkinson’s disease, 14 healthy older adults and 14 healthy young adults walking overground. Within each group, intraclass correlations (ICC 3,1) were performed to assess the reliability of i) the five 3-min trials together, ii) each 3-min trials to the 15-min trial, and iii) the first 150 strides from the 15-min trial to the full 15-min trial.

Results

Our three main findings are that 1) stride time α-DFA values are not consistent from trial-to-trial for short stride time series, 2) stride time α-DFA values from each 3-min trials are not consistent when compared to stride time α-DFA values from a 15-min trial, and 3) stride time α-DFA values from the first 150 strides of the 15-min trial are not consistent when compared to α-DFA values from the full 15-min trial.

Significance

Our results confirm that α-DFA values from 3-min walking trials are not reliable, and that they do not reflect the scale invariant properties of longer time series. This suggests that previous studies assessing the fractal dynamics of gait variability from about 3-min walking must be interpreted with caution. A major clinical implication is that DFA cannot be used to study gait in people unable to perform 500 strides continuously.

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The ability of the instrumented tandem walking tests to discriminate fully ambulatory people with MS from healthy adults

Publication date: Available online 26 February 2019

Source: Gait & Posture

Author(s): Yevgenia Grinberg, Shani Berkowitz, Leora Hershkovitz, Ofir Malcay, Alon Kalron

Abstract

Background

People with multiple sclerosis (PwMS) experience walking and balance deficits at the initial phases of the disease, even when classified as only minimally disabled. Complex balance tasks, such as tandem walking, are probably more sensitive in detecting mild balance difficulties compared to the standard traditional tests in this population.

Research question

The aim was to investigate different types of 3-meter tandem walking tests in fully ambulatory PwMS.

Methods

This observational case-control study included 50 participants; 25 PwMS, 17 women and 8 men, aged 35.2 (S.D = 8.6) and 25 healthy subjects, 18 women and 7 men, aged 34.3 (S.D = 6.1). The 3-meter tandem walk tests were performed during a single session. Each subject completed a sequence of 3 consecutive tests under 3 different task conditions: normal tandem walking, backward tandem walking and cognitive tandem walking. Tandem walking tests were evaluated via three small, lightweight axial wearable accelerometers (APDM, Oregon, USA).

Results

The mean EDSS for the MS group was 1.6 (S.D = 0.6) indicating minimal disability. PwMS walked slower and at a slower pace, with a prolonged double support and decreased swing phase compared to healthy subjects in normal and backward conditions. In contrast, during the cognitive task, non-significant differences were found in gait measures between the PwMS and the healthy controls. Significant differences were found between task conditions for all participants. All reduced their walking speed and walked at a slower pace in both the cognitive and backward conditions compared to the normal tandem walk condition. However, non-significant scores were found for the condition X group factor.

Significance

The study provides new insights into the 3-meter tandem walk test. Findings should improve evaluation and training of dynamic balance in fully ambulatory PwMS.

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