Comparing measurement errors for formants in synthetic and natural vowelsa)

The measurement of formant frequencies of vowels is among the most common measurements in speech studies, but measurements are known to be biased by the particular fundamental frequency (F0) exciting the formants. Approaches to reducing the errors were assessed in two experiments. In the first, synthetic vowels were constructed with five different first formant (F1) values and nine different F0 values; formant bandwidths, and higher formant frequencies, were constant. Input formant values were compared to manual measurements and automatic measures using the linear prediction coding-Burg algorithm, linear prediction closed-phase covariance, the weighted linear prediction-attenuated main excitation (WLP-AME) algorithm [Alku, Pohjalainen, Vainio, Laukkanen, and Story (2013). J. Acoust. Soc. Am. 134(2), 1295–1313], spectra smoothed cepstrally and by averaging repeated discrete Fourier transforms. Formants were also measured manually from pruned reassigned spectrograms (RSs) [Fulop (2011). Speech Spectrum Analysis (Springer, Berlin)]. All but WLP-AME and RS had large errors in the direction of the strongest harmonic; the smallest errors occur with WLP-AME and RS. In the second experiment, these methods were used on vowels in isolated words spoken by four speakers. Results for the natural speech show that F0 bias affects all automatic methods, including WLP-AME; only the formantsmeasured manually from RS appeared to be accurate. In addition, RS coped better with weaker formants and glottal fry.

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The benefit of head orientation to speech intelligibility in noise

Spatial release from masking is traditionally measured with speech in front. The effect of head-orientation with respect to the speech direction has rarely been studied. Speech-reception thresholds (SRTs) were measured for eight head orientations and four spatial configurations. Benefits of head orientation away from the speech source of up to 8 dB were measured. These correlated with predictions of a model based on better-ear listening and binaural unmasking (r = 0.96). Use of spontaneous head orientations was measured when listeners attended to long speech clips of gradually diminishing speech-to-noise ratio in a sound-deadened room. Speech was presented from the loudspeaker that initially faced the listener and noise from one of four other locations. In an undirected paradigm, listeners spontaneously turned their heads away from the speech in 56% of trials. When instructed to rotate their heads in the diminishing speech-to-noise ratio, all listeners turned away from the speech and reached head orientations associated with lower SRTs. Head orientation may prove valuable for hearing-impaired listeners.

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A model for wave propagation in a porous solid saturated by a three-phase fluid

This paper presents a model to describe the propagation of waves in a poroelastic medium saturated by a three-phase viscous, compressible fluid. Two capillary relations between the three fluid phases are included in the model by introducing Lagrange multipliers in the principle of virtual complementary work. This approach generalizes that of Biot for single-phase fluids and allows to determine the strain energy density, identify the generalized strains and stresses, and derive the constitutive relations of the system. The kinetic and dissipative energy density functions are obtained assuming that the relative flow within the pore space is of laminar type and obeys Darcy's law for three-phase flow in porous media. After deriving the equations of motion, a plane wave analysis predicts the existence of four compressional waves, denoted as type I, II, III, and IV waves, and one shear wave. Numerical examples showing the behavior of all waves as function of saturation and frequency are presented.

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Prediction of break-out sound from a rectangular cavity via an elastically mounted panel

The break-out sound from a cavity via an elastically mounted panel is predicted in this paper. The vibroacoustic system model is derived based on the so-called spectro-geometric method in which the solution over each sub-domain is invariably expressed as a modified Fourier series expansion. Unlike the traditional modal superposition methods, the continuity of the normal velocities is faithfully enforced on the interfaces between the flexible panel and the (interior and exterior) acoustic media. A fully coupled vibro-acoustic system is obtained by taking into account the strong coupling between the vibration of the elastic panel and the sound fields on the both sides. The typical time-consuming calculations of quadruple integrals encountered in determining the sound power radiation from a panel has been effectively avoided by reducing them, via discrete cosine transform, into a number of single integrals which are subsequently calculated analytically in a closed form. Several numerical examples are presented to validate the system model, understand the effects on the sound transmissions of panel mounting conditions, and demonstrate the dependence on the size of source room of the “measured” transmission loss.

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Cues for auditory stream segregation of birdsong in budgerigars and zebra finches: Effects of location, timing, amplitude, and frequency

Deciphering the auditory scene is a problem faced by many organisms. However, when faced with numerous overlapping sounds from multiple locations, listeners are still able to attribute the individual sound objects to their individual sound-producingsources. Here, the characteristics of sounds important for integrating versus segregating in birds were determined. Budgerigars and zebra finches were trained using operant conditioning procedures on an identification task to peck one key when they heard a whole zebra finch song and to peck another when they heard a zebra finch song missing a middle syllable. Once the birds were trained to a criterion performance level on those stimuli, probe trials were introduced on a small proportion of trials. The probe songs contained modifications of the incomplete training song's missing syllable. When the bird responded as if the probe was a whole song, it suggests they streamed together the altered syllable and the rest of the song. When the bird responded as if the probe was a non-whole song, it suggests they segregated the altered probe from the rest of the song. Results show that some features, such as location and intensity, are more important for segregating than other features, such as timing and frequency.

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Distortion product otoacoustic emission generation mechanisms and their dependence on stimulus level and primary frequency ratio

In this study, a systematic analysis of the dependence on stimulus level and primary frequency ratio r of the different components of human distortion product otoacoustic emissions has been performed, to check the validity of theoretical models of their generation, as regards the localization of the sources and the relative weight of distortion and reflection generation mechanisms. 2f1 – f2 and 2f2 – f1 distortion product otoacoustic emissions of 12 normal hearing ears from six human subjects have been measured at four different levels, in the range [35, 65] dB sound pressure level, at eight different ratios, in the range [1.1, 1.45]. Time-frequency filtering was used to separate distortion and reflection components. Numerical simulations have also been performed using an active nonlinear cochlear model. Both in the experiment and in the simulations, the behavior of the 2f1 – f2 distortion and reflection components was in agreement with previous measurements and with the predictions of the two-source model. The 2f2 – f1 response showed a rotating-phase component only, whose behavior was in general agreement with that predicted for a component generated and reflected within a region basal to the characteristic place of frequency 2f2 – f1, although alternative interpretations, which are also discussed, cannot be ruled out.

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Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Int J Audiol. 2016 Feb 6;:1-6

Authors: English R, Plant K, Maciejczyk M, Cowan R

Abstract
OBJECTIVE: For a group of cochlear implant recipients, who use hearing aids in the contralateral ear, the benefit of NAL-NL2 relative to a recipients' own prescription was assessed. Whether there was a preferred frequency response and/or gain deviation from NAL-NL2 was then investigated.
DESIGN: Speech recognition and self-reported ratings of benefit were examined for the recipients' own prescription compared to the NAL-NL2 prescription, in the bimodal and hearing-aid alone conditions. Paired-comparison of hearing-aid frequency response was conducted with default NAL-NL2 and two variants, a low frequency boost or cut. Using a loudness balancing procedure, the hearing-aid gain required to achieve equal loudness between the devices was measured.
STUDY SAMPLE: Sixteen adults with post-lingual hearing loss.
RESULTS: A 22% increase in group median word score in quiet with use of NAL-NL2 in the hearing-aid alone condition. In the bimodal condition there was no improvement with NAL-NL2. Default NAL-NL2 frequency response was preferred by 67% of participants. For 56% of participants, the preferred gain to achieve loudness balance across bimodal devices was within 5-dB of prescribed values.
CONCLUSIONS: The NAL-NL2 prescription provides a high level of clinical performance, and an acceptable frequency response and gain for most participants.

PMID: 26853233 [PubMed - as supplied by publisher]

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Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Int J Audiol. 2016 Feb 6;:1-6

Authors: English R, Plant K, Maciejczyk M, Cowan R

Abstract
OBJECTIVE: For a group of cochlear implant recipients, who use hearing aids in the contralateral ear, the benefit of NAL-NL2 relative to a recipients' own prescription was assessed. Whether there was a preferred frequency response and/or gain deviation from NAL-NL2 was then investigated.
DESIGN: Speech recognition and self-reported ratings of benefit were examined for the recipients' own prescription compared to the NAL-NL2 prescription, in the bimodal and hearing-aid alone conditions. Paired-comparison of hearing-aid frequency response was conducted with default NAL-NL2 and two variants, a low frequency boost or cut. Using a loudness balancing procedure, the hearing-aid gain required to achieve equal loudness between the devices was measured.
STUDY SAMPLE: Sixteen adults with post-lingual hearing loss.
RESULTS: A 22% increase in group median word score in quiet with use of NAL-NL2 in the hearing-aid alone condition. In the bimodal condition there was no improvement with NAL-NL2. Default NAL-NL2 frequency response was preferred by 67% of participants. For 56% of participants, the preferred gain to achieve loudness balance across bimodal devices was within 5-dB of prescribed values.
CONCLUSIONS: The NAL-NL2 prescription provides a high level of clinical performance, and an acceptable frequency response and gain for most participants.

PMID: 26853233 [PubMed - as supplied by publisher]

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Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Int J Audiol. 2016 Feb 6;:1-9

Authors: Altieri N, Hudock D

Abstract
OBJECTIVE: The ability to use visual speech cues and integrate them with auditory information is important, especially in noisy environments and for hearing-impaired (HI) listeners. Providing data on measures of integration skills that encompass accuracy and processing speed will benefit researchers and clinicians.
DESIGN: The study consisted of two experiments: First, accuracy scores were obtained using City University of New York (CUNY) sentences, and capacity measures that assessed reaction-time distributions were obtained from a monosyllabic word recognition task.
STUDY SAMPLE: We report data on two measures of integration obtained from a sample comprised of 86 young and middle-age adult listeners: Results: To summarize our results, capacity showed a positive correlation with accuracy measures of audiovisual benefit obtained from sentence recognition. More relevant, factor analysis indicated that a single-factor model captured audiovisual speech integration better than models containing more factors. Capacity exhibited strong loadings on the factor, while the accuracy-based measures from sentence recognition exhibited weaker loadings.
CONCLUSIONS: Results suggest that a listener's integration skills may be assessed optimally using a measure that incorporates both processing speed and accuracy.

PMID: 26853446 [PubMed - as supplied by publisher]

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Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Int J Audiol. 2016 Feb 6;:1-6

Authors: English R, Plant K, Maciejczyk M, Cowan R

Abstract
OBJECTIVE: For a group of cochlear implant recipients, who use hearing aids in the contralateral ear, the benefit of NAL-NL2 relative to a recipients' own prescription was assessed. Whether there was a preferred frequency response and/or gain deviation from NAL-NL2 was then investigated.
DESIGN: Speech recognition and self-reported ratings of benefit were examined for the recipients' own prescription compared to the NAL-NL2 prescription, in the bimodal and hearing-aid alone conditions. Paired-comparison of hearing-aid frequency response was conducted with default NAL-NL2 and two variants, a low frequency boost or cut. Using a loudness balancing procedure, the hearing-aid gain required to achieve equal loudness between the devices was measured.
STUDY SAMPLE: Sixteen adults with post-lingual hearing loss.
RESULTS: A 22% increase in group median word score in quiet with use of NAL-NL2 in the hearing-aid alone condition. In the bimodal condition there was no improvement with NAL-NL2. Default NAL-NL2 frequency response was preferred by 67% of participants. For 56% of participants, the preferred gain to achieve loudness balance across bimodal devices was within 5-dB of prescribed values.
CONCLUSIONS: The NAL-NL2 prescription provides a high level of clinical performance, and an acceptable frequency response and gain for most participants.

PMID: 26853233 [PubMed - as supplied by publisher]

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Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Int J Audiol. 2016 Feb 6;:1-9

Authors: Altieri N, Hudock D

Abstract
OBJECTIVE: The ability to use visual speech cues and integrate them with auditory information is important, especially in noisy environments and for hearing-impaired (HI) listeners. Providing data on measures of integration skills that encompass accuracy and processing speed will benefit researchers and clinicians.
DESIGN: The study consisted of two experiments: First, accuracy scores were obtained using City University of New York (CUNY) sentences, and capacity measures that assessed reaction-time distributions were obtained from a monosyllabic word recognition task.
STUDY SAMPLE: We report data on two measures of integration obtained from a sample comprised of 86 young and middle-age adult listeners: Results: To summarize our results, capacity showed a positive correlation with accuracy measures of audiovisual benefit obtained from sentence recognition. More relevant, factor analysis indicated that a single-factor model captured audiovisual speech integration better than models containing more factors. Capacity exhibited strong loadings on the factor, while the accuracy-based measures from sentence recognition exhibited weaker loadings.
CONCLUSIONS: Results suggest that a listener's integration skills may be assessed optimally using a measure that incorporates both processing speed and accuracy.

PMID: 26853446 [PubMed - as supplied by publisher]

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Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Int J Audiol. 2016 Feb 6;:1-6

Authors: English R, Plant K, Maciejczyk M, Cowan R

Abstract
OBJECTIVE: For a group of cochlear implant recipients, who use hearing aids in the contralateral ear, the benefit of NAL-NL2 relative to a recipients' own prescription was assessed. Whether there was a preferred frequency response and/or gain deviation from NAL-NL2 was then investigated.
DESIGN: Speech recognition and self-reported ratings of benefit were examined for the recipients' own prescription compared to the NAL-NL2 prescription, in the bimodal and hearing-aid alone conditions. Paired-comparison of hearing-aid frequency response was conducted with default NAL-NL2 and two variants, a low frequency boost or cut. Using a loudness balancing procedure, the hearing-aid gain required to achieve equal loudness between the devices was measured.
STUDY SAMPLE: Sixteen adults with post-lingual hearing loss.
RESULTS: A 22% increase in group median word score in quiet with use of NAL-NL2 in the hearing-aid alone condition. In the bimodal condition there was no improvement with NAL-NL2. Default NAL-NL2 frequency response was preferred by 67% of participants. For 56% of participants, the preferred gain to achieve loudness balance across bimodal devices was within 5-dB of prescribed values.
CONCLUSIONS: The NAL-NL2 prescription provides a high level of clinical performance, and an acceptable frequency response and gain for most participants.

PMID: 26853233 [PubMed - as supplied by publisher]

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Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Int J Audiol. 2016 Feb 6;:1-9

Authors: Altieri N, Hudock D

Abstract
OBJECTIVE: The ability to use visual speech cues and integrate them with auditory information is important, especially in noisy environments and for hearing-impaired (HI) listeners. Providing data on measures of integration skills that encompass accuracy and processing speed will benefit researchers and clinicians.
DESIGN: The study consisted of two experiments: First, accuracy scores were obtained using City University of New York (CUNY) sentences, and capacity measures that assessed reaction-time distributions were obtained from a monosyllabic word recognition task.
STUDY SAMPLE: We report data on two measures of integration obtained from a sample comprised of 86 young and middle-age adult listeners: Results: To summarize our results, capacity showed a positive correlation with accuracy measures of audiovisual benefit obtained from sentence recognition. More relevant, factor analysis indicated that a single-factor model captured audiovisual speech integration better than models containing more factors. Capacity exhibited strong loadings on the factor, while the accuracy-based measures from sentence recognition exhibited weaker loadings.
CONCLUSIONS: Results suggest that a listener's integration skills may be assessed optimally using a measure that incorporates both processing speed and accuracy.

PMID: 26853446 [PubMed - as supplied by publisher]

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Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Int J Audiol. 2016 Feb 6;:1-6

Authors: English R, Plant K, Maciejczyk M, Cowan R

Abstract
OBJECTIVE: For a group of cochlear implant recipients, who use hearing aids in the contralateral ear, the benefit of NAL-NL2 relative to a recipients' own prescription was assessed. Whether there was a preferred frequency response and/or gain deviation from NAL-NL2 was then investigated.
DESIGN: Speech recognition and self-reported ratings of benefit were examined for the recipients' own prescription compared to the NAL-NL2 prescription, in the bimodal and hearing-aid alone conditions. Paired-comparison of hearing-aid frequency response was conducted with default NAL-NL2 and two variants, a low frequency boost or cut. Using a loudness balancing procedure, the hearing-aid gain required to achieve equal loudness between the devices was measured.
STUDY SAMPLE: Sixteen adults with post-lingual hearing loss.
RESULTS: A 22% increase in group median word score in quiet with use of NAL-NL2 in the hearing-aid alone condition. In the bimodal condition there was no improvement with NAL-NL2. Default NAL-NL2 frequency response was preferred by 67% of participants. For 56% of participants, the preferred gain to achieve loudness balance across bimodal devices was within 5-dB of prescribed values.
CONCLUSIONS: The NAL-NL2 prescription provides a high level of clinical performance, and an acceptable frequency response and gain for most participants.

PMID: 26853233 [PubMed - as supplied by publisher]

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Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Normative data on audiovisual speech integration using sentence recognition and capacity measures.

Int J Audiol. 2016 Feb 6;:1-9

Authors: Altieri N, Hudock D

Abstract
OBJECTIVE: The ability to use visual speech cues and integrate them with auditory information is important, especially in noisy environments and for hearing-impaired (HI) listeners. Providing data on measures of integration skills that encompass accuracy and processing speed will benefit researchers and clinicians.
DESIGN: The study consisted of two experiments: First, accuracy scores were obtained using City University of New York (CUNY) sentences, and capacity measures that assessed reaction-time distributions were obtained from a monosyllabic word recognition task.
STUDY SAMPLE: We report data on two measures of integration obtained from a sample comprised of 86 young and middle-age adult listeners: Results: To summarize our results, capacity showed a positive correlation with accuracy measures of audiovisual benefit obtained from sentence recognition. More relevant, factor analysis indicated that a single-factor model captured audiovisual speech integration better than models containing more factors. Capacity exhibited strong loadings on the factor, while the accuracy-based measures from sentence recognition exhibited weaker loadings.
CONCLUSIONS: Results suggest that a listener's integration skills may be assessed optimally using a measure that incorporates both processing speed and accuracy.

PMID: 26853446 [PubMed - as supplied by publisher]

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Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Fitting recommendations and clinical benefit associated with use of the NAL-NL2 hearing-aid prescription in Nucleus cochlear implant recipients.

Int J Audiol. 2016 Feb 6;:1-6

Authors: English R, Plant K, Maciejczyk M, Cowan R

Abstract
OBJECTIVE: For a group of cochlear implant recipients, who use hearing aids in the contralateral ear, the benefit of NAL-NL2 relative to a recipients' own prescription was assessed. Whether there was a preferred frequency response and/or gain deviation from NAL-NL2 was then investigated.
DESIGN: Speech recognition and self-reported ratings of benefit were examined for the recipients' own prescription compared to the NAL-NL2 prescription, in the bimodal and hearing-aid alone conditions. Paired-comparison of hearing-aid frequency response was conducted with default NAL-NL2 and two variants, a low frequency boost or cut. Using a loudness balancing procedure, the hearing-aid gain required to achieve equal loudness between the devices was measured.
STUDY SAMPLE: Sixteen adults with post-lingual hearing loss.
RESULTS: A 22% increase in group median word score in quiet with use of NAL-NL2 in the hearing-aid alone condition. In the bimodal condition there was no improvement with NAL-NL2. Default NAL-NL2 frequency response was preferred by 67% of participants. For 56% of participants, the preferred gain to achieve loudness balance across bimodal devices was within 5-dB of prescribed values.
CONCLUSIONS: The NAL-NL2 prescription provides a high level of clinical performance, and an acceptable frequency response and gain for most participants.

PMID: 26853233 [PubMed - as supplied by publisher]

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Repeatability of muscle synergies within and between days for typically developing children and children with cerebral palsy

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Benjamin Shuman, Marije Goudriaan, Lynn Bar-On, Michael H. Schwartz, Kaat Desloovere, Katherine M. Steele
Muscle synergies are typically calculated from electromyographic (EMG) signals using nonnegative matrix factorization. Synergies identify weighted groups of muscles that are commonly activated together during a task, such as walking. Synergy analysis has become an emerging tool to evaluate neuromuscular control; however, the repeatability of synergies between trials and days has not been evaluated. The goal of this study was to evaluate the repeatability of synergy complexity and structure in unimpaired individuals and individuals with cerebral palsy (CP). EMG data were collected from eight lower-limb muscles during gait for six typically developing (TD) children and five children with CP on two separate days, over three walking speeds. To evaluate synergy complexity, we calculated the total variance accounted for by one synergy (tVAF1). On a given day, the average range in tVAF1 between gait cycles was 18.2% for TD and 19.1% for CP. The average standard deviation in tVAF1 between gait cycles was 4.9% for TD and 5.0% for CP. Average tVAF1 calculated across gait cycles was not significantly different between days for TD or CP participants. Comparing synergy structure, the average (standard deviation) within day correlation coefficients of synergy weights for two or more synergies were 0.89 (0.15) for TD and 0.88 (0.15) for CP. Between days, the average correlation coefficient of synergy weights for two or more synergies was greater than 0.89 for TD and 0.74 for CP. These results demonstrate that synergy complexity and structure averaged over multiple gait cycles are repeatable between days in both TD and CP groups.



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Is adult gait less susceptible than paediatric gait to hip joint centre regression equation error?

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): D. Kiernan, J. Hosking, T. O’Brien
Hip joint centre (HJC) regression equation error during paediatric gait has recently been shown to have clinical significance. In relation to adult gait, it has been inferred that comparable errors with children in absolute HJC position may in fact result in less significant kinematic and kinetic error. This study investigated the clinical agreement of three commonly used regression equation sets (Bell et al., Davis et al. and Orthotrak) for adult subjects against the equations of Harrington et al. The relationship between HJC position error and subject size was also investigated for the Davis et al. set. Full 3-dimensional gait analysis was performed on 12 healthy adult subjects with data for each set compared to Harrington et al. The Gait Profile Score, Gait Variable Score and GDI-kinetic were used to assess clinical significance while differences in HJC position between the Davis and Harrington sets were compared to leg length and subject height using regression analysis. A number of statistically significant differences were present in absolute HJC position. However, all sets fell below the clinically significant thresholds (GPS <1.6°, GDI-Kinetic <3.6 points). Linear regression revealed a statistically significant relationship for both increasing leg length and increasing subject height with decreasing error in anterior/posterior and superior/inferior directions. Results confirm a negligible clinical error for adult subjects suggesting that any of the examined sets could be used interchangeably. Decreasing error with both increasing leg length and increasing subject height suggests that the Davis set should be used cautiously on smaller subjects.



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Accuracy and concurrent validity of a sensor-based analysis of sit-to-stand movements in older adults

Publication date: Available online 8 February 2016
Source:Gait & Posture
Author(s): G. Ruben H. Regterschot, Wei Zhang, Heribert Baldus, Martin Stevens, Wiebren Zijlstra
Body-fixed motion sensors have been applied for the assessment of sit-to-stand (STS) performance. However, the accuracy and concurrent validity of sensor-based estimations of the body's center of mass (CoM) motion during STS are unclear. Therefore, this study investigated the accuracy and concurrent validity of sensor-based measures of CoM motion during STS in older adults. Accuracy and concurrent validity were investigated by comparing the sensor-based method to a force plate method. Twenty-seven older adults (20 females, 7 males; age: 72-94 years) performed five STS movements while data were collected with force plates and motion sensors on the hip and chest. Hip maximal acceleration provided an accurate estimation of the center of mass (CoM) maximal acceleration (limits of agreement (LOA) smaller than 5% of the CoM maximal acceleration; estimated and real CoM maximal acceleration did not differ (p=0.823)). Other hip STS measures and the chest STS measures did not provide accurate estimations of CoM motion (LOA ranged from -155.6% to 333.3% of the CoM value; sensor-based measures overestimated CoM motion (range p: <0.001 to 0.01)). However, the hip sensor did not overestimate maximal jerk of the CoM (p=0.679). Moderate to very strong associations were observed between sensor-based estimations and actual CoM motion (range r=0.64-0.94, p<0.001). Hence, sensor-based estimations of CoM motion during STS are possible, but accuracy is limited. The sensor-based method cannot replace laboratory methods for a mechanical analysis of CoM motion during STS but it may be a practical alternative for the clinical assessment of STS performance in older persons.



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Repeatability of muscle synergies within and between days for typically developing children and children with cerebral palsy

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Benjamin Shuman, Marije Goudriaan, Lynn Bar-On, Michael H. Schwartz, Kaat Desloovere, Katherine M. Steele
Muscle synergies are typically calculated from electromyographic (EMG) signals using nonnegative matrix factorization. Synergies identify weighted groups of muscles that are commonly activated together during a task, such as walking. Synergy analysis has become an emerging tool to evaluate neuromuscular control; however, the repeatability of synergies between trials and days has not been evaluated. The goal of this study was to evaluate the repeatability of synergy complexity and structure in unimpaired individuals and individuals with cerebral palsy (CP). EMG data were collected from eight lower-limb muscles during gait for six typically developing (TD) children and five children with CP on two separate days, over three walking speeds. To evaluate synergy complexity, we calculated the total variance accounted for by one synergy (tVAF1). On a given day, the average range in tVAF1 between gait cycles was 18.2% for TD and 19.1% for CP. The average standard deviation in tVAF1 between gait cycles was 4.9% for TD and 5.0% for CP. Average tVAF1 calculated across gait cycles was not significantly different between days for TD or CP participants. Comparing synergy structure, the average (standard deviation) within day correlation coefficients of synergy weights for two or more synergies were 0.89 (0.15) for TD and 0.88 (0.15) for CP. Between days, the average correlation coefficient of synergy weights for two or more synergies was greater than 0.89 for TD and 0.74 for CP. These results demonstrate that synergy complexity and structure averaged over multiple gait cycles are repeatable between days in both TD and CP groups.



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Is adult gait less susceptible than paediatric gait to hip joint centre regression equation error?

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): D. Kiernan, J. Hosking, T. O’Brien
Hip joint centre (HJC) regression equation error during paediatric gait has recently been shown to have clinical significance. In relation to adult gait, it has been inferred that comparable errors with children in absolute HJC position may in fact result in less significant kinematic and kinetic error. This study investigated the clinical agreement of three commonly used regression equation sets (Bell et al., Davis et al. and Orthotrak) for adult subjects against the equations of Harrington et al. The relationship between HJC position error and subject size was also investigated for the Davis et al. set. Full 3-dimensional gait analysis was performed on 12 healthy adult subjects with data for each set compared to Harrington et al. The Gait Profile Score, Gait Variable Score and GDI-kinetic were used to assess clinical significance while differences in HJC position between the Davis and Harrington sets were compared to leg length and subject height using regression analysis. A number of statistically significant differences were present in absolute HJC position. However, all sets fell below the clinically significant thresholds (GPS <1.6°, GDI-Kinetic <3.6 points). Linear regression revealed a statistically significant relationship for both increasing leg length and increasing subject height with decreasing error in anterior/posterior and superior/inferior directions. Results confirm a negligible clinical error for adult subjects suggesting that any of the examined sets could be used interchangeably. Decreasing error with both increasing leg length and increasing subject height suggests that the Davis set should be used cautiously on smaller subjects.



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Accuracy and concurrent validity of a sensor-based analysis of sit-to-stand movements in older adults

Publication date: Available online 8 February 2016
Source:Gait & Posture
Author(s): G. Ruben H. Regterschot, Wei Zhang, Heribert Baldus, Martin Stevens, Wiebren Zijlstra
Body-fixed motion sensors have been applied for the assessment of sit-to-stand (STS) performance. However, the accuracy and concurrent validity of sensor-based estimations of the body's center of mass (CoM) motion during STS are unclear. Therefore, this study investigated the accuracy and concurrent validity of sensor-based measures of CoM motion during STS in older adults. Accuracy and concurrent validity were investigated by comparing the sensor-based method to a force plate method. Twenty-seven older adults (20 females, 7 males; age: 72-94 years) performed five STS movements while data were collected with force plates and motion sensors on the hip and chest. Hip maximal acceleration provided an accurate estimation of the center of mass (CoM) maximal acceleration (limits of agreement (LOA) smaller than 5% of the CoM maximal acceleration; estimated and real CoM maximal acceleration did not differ (p=0.823)). Other hip STS measures and the chest STS measures did not provide accurate estimations of CoM motion (LOA ranged from -155.6% to 333.3% of the CoM value; sensor-based measures overestimated CoM motion (range p: <0.001 to 0.01)). However, the hip sensor did not overestimate maximal jerk of the CoM (p=0.679). Moderate to very strong associations were observed between sensor-based estimations and actual CoM motion (range r=0.64-0.94, p<0.001). Hence, sensor-based estimations of CoM motion during STS are possible, but accuracy is limited. The sensor-based method cannot replace laboratory methods for a mechanical analysis of CoM motion during STS but it may be a practical alternative for the clinical assessment of STS performance in older persons.



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Repeatability of muscle synergies within and between days for typically developing children and children with cerebral palsy

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Benjamin Shuman, Marije Goudriaan, Lynn Bar-On, Michael H. Schwartz, Kaat Desloovere, Katherine M. Steele
Muscle synergies are typically calculated from electromyographic (EMG) signals using nonnegative matrix factorization. Synergies identify weighted groups of muscles that are commonly activated together during a task, such as walking. Synergy analysis has become an emerging tool to evaluate neuromuscular control; however, the repeatability of synergies between trials and days has not been evaluated. The goal of this study was to evaluate the repeatability of synergy complexity and structure in unimpaired individuals and individuals with cerebral palsy (CP). EMG data were collected from eight lower-limb muscles during gait for six typically developing (TD) children and five children with CP on two separate days, over three walking speeds. To evaluate synergy complexity, we calculated the total variance accounted for by one synergy (tVAF1). On a given day, the average range in tVAF1 between gait cycles was 18.2% for TD and 19.1% for CP. The average standard deviation in tVAF1 between gait cycles was 4.9% for TD and 5.0% for CP. Average tVAF1 calculated across gait cycles was not significantly different between days for TD or CP participants. Comparing synergy structure, the average (standard deviation) within day correlation coefficients of synergy weights for two or more synergies were 0.89 (0.15) for TD and 0.88 (0.15) for CP. Between days, the average correlation coefficient of synergy weights for two or more synergies was greater than 0.89 for TD and 0.74 for CP. These results demonstrate that synergy complexity and structure averaged over multiple gait cycles are repeatable between days in both TD and CP groups.



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Is adult gait less susceptible than paediatric gait to hip joint centre regression equation error?

Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): D. Kiernan, J. Hosking, T. O’Brien
Hip joint centre (HJC) regression equation error during paediatric gait has recently been shown to have clinical significance. In relation to adult gait, it has been inferred that comparable errors with children in absolute HJC position may in fact result in less significant kinematic and kinetic error. This study investigated the clinical agreement of three commonly used regression equation sets (Bell et al., Davis et al. and Orthotrak) for adult subjects against the equations of Harrington et al. The relationship between HJC position error and subject size was also investigated for the Davis et al. set. Full 3-dimensional gait analysis was performed on 12 healthy adult subjects with data for each set compared to Harrington et al. The Gait Profile Score, Gait Variable Score and GDI-kinetic were used to assess clinical significance while differences in HJC position between the Davis and Harrington sets were compared to leg length and subject height using regression analysis. A number of statistically significant differences were present in absolute HJC position. However, all sets fell below the clinically significant thresholds (GPS <1.6°, GDI-Kinetic <3.6 points). Linear regression revealed a statistically significant relationship for both increasing leg length and increasing subject height with decreasing error in anterior/posterior and superior/inferior directions. Results confirm a negligible clinical error for adult subjects suggesting that any of the examined sets could be used interchangeably. Decreasing error with both increasing leg length and increasing subject height suggests that the Davis set should be used cautiously on smaller subjects.



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via IFTTT

Accuracy and concurrent validity of a sensor-based analysis of sit-to-stand movements in older adults

Publication date: Available online 8 February 2016
Source:Gait & Posture
Author(s): G. Ruben H. Regterschot, Wei Zhang, Heribert Baldus, Martin Stevens, Wiebren Zijlstra
Body-fixed motion sensors have been applied for the assessment of sit-to-stand (STS) performance. However, the accuracy and concurrent validity of sensor-based estimations of the body's center of mass (CoM) motion during STS are unclear. Therefore, this study investigated the accuracy and concurrent validity of sensor-based measures of CoM motion during STS in older adults. Accuracy and concurrent validity were investigated by comparing the sensor-based method to a force plate method. Twenty-seven older adults (20 females, 7 males; age: 72-94 years) performed five STS movements while data were collected with force plates and motion sensors on the hip and chest. Hip maximal acceleration provided an accurate estimation of the center of mass (CoM) maximal acceleration (limits of agreement (LOA) smaller than 5% of the CoM maximal acceleration; estimated and real CoM maximal acceleration did not differ (p=0.823)). Other hip STS measures and the chest STS measures did not provide accurate estimations of CoM motion (LOA ranged from -155.6% to 333.3% of the CoM value; sensor-based measures overestimated CoM motion (range p: <0.001 to 0.01)). However, the hip sensor did not overestimate maximal jerk of the CoM (p=0.679). Moderate to very strong associations were observed between sensor-based estimations and actual CoM motion (range r=0.64-0.94, p<0.001). Hence, sensor-based estimations of CoM motion during STS are possible, but accuracy is limited. The sensor-based method cannot replace laboratory methods for a mechanical analysis of CoM motion during STS but it may be a practical alternative for the clinical assessment of STS performance in older persons.



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