Publication date: Available online 24 February 2016
Source:Hearing Research
Author(s): David Chhan, Peter Bowers, Melissa L. McKinnon, John J. Rosowski
While the cochlea is considered the primary site of the auditory response to bone conduction (BC) stimulation, the paths by which vibratory energy applied to the skull (or other structures) reaches the inner ear are a matter of continued investigation. We present acoustical measurements of sound in the inner ear that separate out the components of BC stimulation that stimulate the inner ear via ossicular motion (compression of the walls of the ear canal or ossicular inertia) from the components that act directly on the cochlea (cochlear compression or inertia, and extra-cochlear ‘third-window’ pathways). The results are consistent with our earlier suggestion that the inner-ear mechanisms play a large role in bone-conduction stimulation in the chinchilla at all frequencies. However, the data also suggest the pathways that conduct vibration to the inner ear via ossicular-motion make a significant contribution to the response to BC stimulation in the 1 to 3 kHz range, such that interruption of these path leads to a 5 dB reduction in total stimulation in that frequency range. The mid-frequency reduction produced by ossicular manipulations is similar to the ‘Carhart’s notch’ phenomenon observed in otology and audiology clinics in cases of human ossicular disorders. We also present data consistent with much of the ossicular-conducted sound in chinchilla depending on occlusion of the ear canal.
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Τρίτη 23 Φεβρουαρίου 2016
Middle-ear and inner-ear contribution to bone bonduction in chinchilla: The development of Carhart’s notch
Publication date: Available online 24 February 2016
Source:Hearing Research
Author(s): David Chhan, Peter Bowers, Melissa L. McKinnon, John J. Rosowski
While the cochlea is considered the primary site of the auditory response to bone conduction (BC) stimulation, the paths by which vibratory energy applied to the skull (or other structures) reaches the inner ear are a matter of continued investigation. We present acoustical measurements of sound in the inner ear that separate out the components of BC stimulation that stimulate the inner ear via ossicular motion (compression of the walls of the ear canal or ossicular inertia) from the components that act directly on the cochlea (cochlear compression or inertia, and extra-cochlear ‘third-window’ pathways). The results are consistent with our earlier suggestion that the inner-ear mechanisms play a large role in bone-conduction stimulation in the chinchilla at all frequencies. However, the data also suggest the pathways that conduct vibration to the inner ear via ossicular-motion make a significant contribution to the response to BC stimulation in the 1 to 3 kHz range, such that interruption of these path leads to a 5 dB reduction in total stimulation in that frequency range. The mid-frequency reduction produced by ossicular manipulations is similar to the ‘Carhart’s notch’ phenomenon observed in otology and audiology clinics in cases of human ossicular disorders. We also present data consistent with much of the ossicular-conducted sound in chinchilla depending on occlusion of the ear canal.
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Source:Hearing Research
Author(s): David Chhan, Peter Bowers, Melissa L. McKinnon, John J. Rosowski
While the cochlea is considered the primary site of the auditory response to bone conduction (BC) stimulation, the paths by which vibratory energy applied to the skull (or other structures) reaches the inner ear are a matter of continued investigation. We present acoustical measurements of sound in the inner ear that separate out the components of BC stimulation that stimulate the inner ear via ossicular motion (compression of the walls of the ear canal or ossicular inertia) from the components that act directly on the cochlea (cochlear compression or inertia, and extra-cochlear ‘third-window’ pathways). The results are consistent with our earlier suggestion that the inner-ear mechanisms play a large role in bone-conduction stimulation in the chinchilla at all frequencies. However, the data also suggest the pathways that conduct vibration to the inner ear via ossicular-motion make a significant contribution to the response to BC stimulation in the 1 to 3 kHz range, such that interruption of these path leads to a 5 dB reduction in total stimulation in that frequency range. The mid-frequency reduction produced by ossicular manipulations is similar to the ‘Carhart’s notch’ phenomenon observed in otology and audiology clinics in cases of human ossicular disorders. We also present data consistent with much of the ossicular-conducted sound in chinchilla depending on occlusion of the ear canal.
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Three-dimensional time reversal communications in elastic media
This letter presents a series of vibrational communication experiments, using time reversal, conducted on a set of cast iron pipes. Time reversal has been used to provide robust, private, and clean communications in many underwater acoustic applications. Here the use of time reversal to communicate along sections of pipes and through a wall is demonstrated to overcome the complications of dispersion and multiple scattering. These demonstrations utilize a single source transducer and a single sensor, a triaxial accelerometer, enabling multiple channels of simultaneous communication streams to a single location.
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Evolution of the temporal slope density function for waves propagating according to the inviscid Burgers equation
An exact formulation for the evolution of the probability density function of the time derivative of a waveform (slope density) propagating according to the one-dimensional inviscid Burgers equation is given. The formulation relies on the implicit Earnshaw solution and therefore is only valid prior to shock formation. As explicit examples, the slope density evolution of an initially sinusoidal plane wave, initially Gaussian-distributed planar noise, and an initially triangular wave are presented. The triangular wave is used to examine weak-shock limits without violating the theoretical assumptions. It is also shown that the moments of the slope density function as a function of distance may be written as an expansion in terms of the moments of the source slope density function. From this expansion, approximate expressions are presented for the above cases as well as a specific non-Gaussian noise case intended to mimic features of jet noise. Finally, analytical predictions of the propagation of initially Gaussian-distributed noise are compared favorably with plane-wave tube measurements.
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Nonlinear frequency compression: Influence of start frequency and input bandwidth on consonant and vowel recognitiona)
By varying parameters that control nonlinear frequency compression (NFC), this study examined how different ways of compressing inaudible mid- and/or high-frequency information at lower frequencies influences perception of consonants and vowels. Twenty-eight listeners with mild to moderately severe hearing loss identified consonants and vowels from nonsense syllables in noise following amplification via a hearing aid simulator. Low-pass filtering and the selection of NFC parameters fixed the output bandwidth at a frequency representing a moderately severe (3.3 kHz, group MS) or a mild-to-moderate (5.0 kHz, group MM) high-frequency loss. For each group (n = 14), effects of six combinations of NFC start frequency (SF) and input bandwidth [by varying the compression ratio (CR)] were examined. For both groups, the 1.6 kHz SF significantly reduced vowel and consonant recognition, especially as CR increased; whereas, recognition was generally unaffected if SF increased at the expense of a higher CR. Vowel recognition detriments for group MS were moderately correlated with the size of the second formant frequency shift following NFC. For both groups, significant improvement (33%–50%) with NFC was confined to final /s/ and /z/ and to some VCV tokens, perhaps because of listeners' limited exposure to each setting. No set of parameters simultaneously maximized recognition across all tokens.
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Idealized digital models for conical reed instruments, with focus on the internal pressure waveform
Two models for the generation of self-oscillations of reed conical woodwinds are presented. The models use the fewest parameters (of either the resonator or the exciter), whose influence can be quickly explored. The formulation extends iterated maps obtained for lossless cylindrical pipes without reed dynamics. It uses spherical wave variables in idealized resonators, with one parameter more than for cylinders: the missing length of the cone. The mouthpiece volume equals that of the missing part of the cone, and is implemented as either a cylindrical pipe (first model) or a lumped element (second model). Only the first model adds a length parameter for the mouthpiece and leads to the solving of an implicit equation. For the second model, any shape of nonlinear characteristic can be directly considered. The complex characteristic impedance for spherical waves requires sampling times smaller than a round trip in the resonator. The convergence of the two models is shown when the length of the cylindrical mouthpiece tends to zero. The waveform is in semi-quantitative agreement with experiment. It is concluded that the oscillations of the positive episode of the mouthpiece pressure are related to the length of the missing part, not to the reed dynamics.
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Three-dimensional parabolic equation modeling of mesoscale eddy deflection
The impact of mesoscale oceanography, including ocean fronts and eddies, on global scale low-frequency acoustics is examined using a fully three-dimensional parabolic equation model. The narrowband acoustic signal, for frequencies from 2 to 16 Hz, is simulated from a seismic event on the Kerguellen Plateau in the South Indian Ocean to an array of receivers south of Ascension Island in the South Atlantic, a distance of 9100 km. The path was chosen for its relevance to seismic detections from the HA10 Ascension Island station of the International Monitoring System, for its lack of bathymetric interaction, and for the dynamic oceanography encountered as the sound passes the Cape of Good Hope. The acoustic field was propagated through two years (1992 and 1993) of the eddy-permitting ocean state estimation ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) system. The range of deflection of the back-azimuth was 1.8° with a root-mean-square of 0.34°. The refraction due to mesoscale oceanography could therefore have significant impacts upon localization of distant low-frequency sources, such as seismic or nuclear test events.
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Utilising temporal signal features in adverse noise conditions: Detection, estimation, and the reassigned spectrogram
Visual displays in passive sonar based on the Fourier spectrogram are underpinned by detection models that rely on signal and noise power statistics. Time-frequency representations specialised for sparse signals achieve a sharper signal representation, either by reassigning signal energy based on temporal structure or by conveying temporal structure directly. However, temporal representations involve nonlinear transformations that make it difficult to reason about how they respond to additive noise. This article analyses the effect of noise on temporal fine structure measurements such as zero crossings and instantaneous frequency. Detectors that rely on zero crossing intervals, intervals and peak amplitudes, and instantaneous frequency measurements are developed, and evaluated for the detection of a sinusoid in Gaussian noise, using the power detector as a baseline. Detectors that rely on fine structure outperform the power detector under certain circumstances; and detectors that rely on both fine structure and power measurements are superior. Reassigned spectrograms assume that the statistics used to reassign energy are reliable, but the derivation of the fine structure detectors indicates the opposite. The article closes by proposing and demonstrating the concept of a doubly reassigned spectrogram, wherein temporal measurements are reassigned according to a statistical model of the noise background.
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Three-dimensional time reversal communications in elastic media
This letter presents a series of vibrational communication experiments, using time reversal, conducted on a set of cast iron pipes. Time reversal has been used to provide robust, private, and clean communications in many underwater acoustic applications. Here the use of time reversal to communicate along sections of pipes and through a wall is demonstrated to overcome the complications of dispersion and multiple scattering. These demonstrations utilize a single source transducer and a single sensor, a triaxial accelerometer, enabling multiple channels of simultaneous communication streams to a single location.
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Intracochlear Drug Injections through the Round Window Membrane: Measures to Improve Drug Retention
The goal of this study was to develop an appropriate methodology to apply drugs quantitatively to the perilymph of the ear. Intratympanic applications of drugs to the inner ear often result in variable drug levels in the perilymph and can only be used for molecules that readily permeate the round window (RW) membrane. Direct intracochlear and intralabyrinthine application procedures for drugs, genes or cell-based therapies bypass the tight boundaries at the RW, oval window, otic capsule and the blood-labyrinth barrier. However, perforations can release inner ear pressure, allowing cerebrospinal fluid (CSF) to enter through the cochlear aqueduct, displacing the injected drug solution into the middle ear. Two markers, fluorescein or fluorescein isothiocyanate-labeled dextran, were used to quantify how much of an injected substance was retained in the cochlear perilymph following an intracochlear injection. We evaluated whether procedures to mitigate fluid leaks improved marker retention in perilymph. Almost all procedures to reduce volume efflux, including the use of gel for internal sealing and glue for external sealing of the injection site, resulted in improved retention of the marker in perilymph. Adhesive on the RW membrane effectively prevented leaks but also influenced fluid exchange between CSF and perilymph. We conclude that drugs can be delivered to the ear in a consistent, quantitative manner using intracochlear injections if care is taken to control the fluid leaks that result from cochlear perforation.
Audiol Neurotol 2016;21:72-79
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Audiol Neurotol 2016;21:72-79
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Corrigendum to “The relationships between foot-joints range of motion and plantar pressure in the normal foot” [Gait Posture 42 (September (Suppl. 2)) (2015) S24]
Publication date: Available online 23 February 2016
Source:Gait & Posture
Author(s): Paolo Caravaggi, Alberto Leardini, Claudia Giacomozzi
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Source:Gait & Posture
Author(s): Paolo Caravaggi, Alberto Leardini, Claudia Giacomozzi
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Calibration of an instrumented treadmill using a precision-controlled device with artificial neural network-based error corrections
Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Hong-Jung Hsieh, Hsiu-Chen Lin, Hsuan-Lun Lu, Ting-Yi Chen, Tung-Wu Lu
Instrumented treadmills (ITs) are used to measure reaction forces (RF) and center of pressure (COP) movements for gait and balance assessment. Regular in situ calibration is essential to ensure their accuracy and to identify conditions when a factory re-calibration is needed. The current study aimed to develop and calibrate in situ an IT using a portable, precision-controlled calibration device with an artificial neural network (ANN)-based correction method. The calibration device was used to apply static and dynamic calibrating loads to the surface of the IT at 189 and 25 grid-points, respectively, at four belt speeds (0, 4, 6 and 8km/h) without the need of a preset template. Part of the applied and measured RF and COP were used to train a threelayered, back-propagation ANN model while the rest of the data were used to evaluate the performance of the ANN. The percent errors of Fz and errors of the Px and Py were significantly decreased from a maximum of −1.15%, −1.64mm and −0.73mm to 0.02%, 0.02mm and 0.03mm during static calibration, respectively. During dynamic calibration, the corresponding values were decreasing from −3.65%, 2.58mm and −4.92mm to 0.30%, −0.14mm and −0.47mm, respectively. The results suggest that the calibration device and associated ANN will be useful for correcting measurement errors in vertical loads and COP for ITs.
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Source:Gait & Posture, Volume 45
Author(s): Hong-Jung Hsieh, Hsiu-Chen Lin, Hsuan-Lun Lu, Ting-Yi Chen, Tung-Wu Lu
Instrumented treadmills (ITs) are used to measure reaction forces (RF) and center of pressure (COP) movements for gait and balance assessment. Regular in situ calibration is essential to ensure their accuracy and to identify conditions when a factory re-calibration is needed. The current study aimed to develop and calibrate in situ an IT using a portable, precision-controlled calibration device with an artificial neural network (ANN)-based correction method. The calibration device was used to apply static and dynamic calibrating loads to the surface of the IT at 189 and 25 grid-points, respectively, at four belt speeds (0, 4, 6 and 8km/h) without the need of a preset template. Part of the applied and measured RF and COP were used to train a threelayered, back-propagation ANN model while the rest of the data were used to evaluate the performance of the ANN. The percent errors of Fz and errors of the Px and Py were significantly decreased from a maximum of −1.15%, −1.64mm and −0.73mm to 0.02%, 0.02mm and 0.03mm during static calibration, respectively. During dynamic calibration, the corresponding values were decreasing from −3.65%, 2.58mm and −4.92mm to 0.30%, −0.14mm and −0.47mm, respectively. The results suggest that the calibration device and associated ANN will be useful for correcting measurement errors in vertical loads and COP for ITs.
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Comparison of the correlations between impact loading rates and peak accelerations measured at two different body sites: intra- and inter-subject analysis
Publication date: Available online 23 February 2016
Source:Gait & Posture
Author(s): Janet H. Zhang, Winko W. An, Ivan P.H. Au, Tony L. Chen, Roy T.H. Cheung
BackgroundHigh average (VALR) and instantaneous vertical loading rates (VILR) during impact have been associated with many running-related injuries. Peak acceleration (PA), measured with an accelerometer, has provided an alternative method to estimate impact loading during outdoor running. This study sought to compare both intra- and inter-subject correlations between vertical loading rates and PA measured at two body sites during running.MethodsGround reaction force data were collected from 10 healthy adults (age=23.6±3.8 years) during treadmill running at different speeds and inclination surfaces. Concurrently, PAs at the lateral malleoli and the distal tibia were measured using synchronized accelerometers.ResultsWe found significant positive intra-subject correlation between loading rates and PA at the lateral malleoli (r=0.561-0.950, p<0.001) and the distal tibia (r=0.486-0.913, p<0.001). PA measured at the lateral malleoli showed stronger correlation with loading rates (p=0.004) than the measurement at the distal tibia. On the other hand, inter-subject variances were observed in the association between PA and vertical loading rates. The inter-subject variances at the distal tibia were 3.88± 3.09 BW/s and 5.69±3.05 BW/s in VALR and VLIR respectively. Similarly, the inter-subject variances in the measurement at lateral malleoli were 5.24±2.85 BW/s and 6.67±2.83 BW/s in VALR and VLIR respectively.ConclusionsPA measured at lateral malleoli has stronger correlation with VALR or VILR than the measurement at distal tibia. Caution is advised when using PA to conduct inter-subject comparisons of vertical loading rates during running.
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Source:Gait & Posture
Author(s): Janet H. Zhang, Winko W. An, Ivan P.H. Au, Tony L. Chen, Roy T.H. Cheung
BackgroundHigh average (VALR) and instantaneous vertical loading rates (VILR) during impact have been associated with many running-related injuries. Peak acceleration (PA), measured with an accelerometer, has provided an alternative method to estimate impact loading during outdoor running. This study sought to compare both intra- and inter-subject correlations between vertical loading rates and PA measured at two body sites during running.MethodsGround reaction force data were collected from 10 healthy adults (age=23.6±3.8 years) during treadmill running at different speeds and inclination surfaces. Concurrently, PAs at the lateral malleoli and the distal tibia were measured using synchronized accelerometers.ResultsWe found significant positive intra-subject correlation between loading rates and PA at the lateral malleoli (r=0.561-0.950, p<0.001) and the distal tibia (r=0.486-0.913, p<0.001). PA measured at the lateral malleoli showed stronger correlation with loading rates (p=0.004) than the measurement at the distal tibia. On the other hand, inter-subject variances were observed in the association between PA and vertical loading rates. The inter-subject variances at the distal tibia were 3.88± 3.09 BW/s and 5.69±3.05 BW/s in VALR and VLIR respectively. Similarly, the inter-subject variances in the measurement at lateral malleoli were 5.24±2.85 BW/s and 6.67±2.83 BW/s in VALR and VLIR respectively.ConclusionsPA measured at lateral malleoli has stronger correlation with VALR or VILR than the measurement at distal tibia. Caution is advised when using PA to conduct inter-subject comparisons of vertical loading rates during running.
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Treadmill Walking is not Equivalent to Overground Walking for the Study of Walking Smoothness and Rhythmicity in Older Adults
Publication date: Available online 22 February 2016
Source:Gait & Posture
Author(s): Brandi S. Row Lazzarini, Theodore J. Kataras
Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.
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Source:Gait & Posture
Author(s): Brandi S. Row Lazzarini, Theodore J. Kataras
Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.
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Corrigendum to “The relationships between foot-joints range of motion and plantar pressure in the normal foot” [Gait Posture 42 (September (Suppl. 2)) (2015) S24]
Publication date: Available online 23 February 2016
Source:Gait & Posture
Author(s): Paolo Caravaggi, Alberto Leardini, Claudia Giacomozzi
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Source:Gait & Posture
Author(s): Paolo Caravaggi, Alberto Leardini, Claudia Giacomozzi
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Calibration of an instrumented treadmill using a precision-controlled device with artificial neural network-based error corrections
Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Hong-Jung Hsieh, Hsiu-Chen Lin, Hsuan-Lun Lu, Ting-Yi Chen, Tung-Wu Lu
Instrumented treadmills (ITs) are used to measure reaction forces (RF) and center of pressure (COP) movements for gait and balance assessment. Regular in situ calibration is essential to ensure their accuracy and to identify conditions when a factory re-calibration is needed. The current study aimed to develop and calibrate in situ an IT using a portable, precision-controlled calibration device with an artificial neural network (ANN)-based correction method. The calibration device was used to apply static and dynamic calibrating loads to the surface of the IT at 189 and 25 grid-points, respectively, at four belt speeds (0, 4, 6 and 8km/h) without the need of a preset template. Part of the applied and measured RF and COP were used to train a threelayered, back-propagation ANN model while the rest of the data were used to evaluate the performance of the ANN. The percent errors of Fz and errors of the Px and Py were significantly decreased from a maximum of −1.15%, −1.64mm and −0.73mm to 0.02%, 0.02mm and 0.03mm during static calibration, respectively. During dynamic calibration, the corresponding values were decreasing from −3.65%, 2.58mm and −4.92mm to 0.30%, −0.14mm and −0.47mm, respectively. The results suggest that the calibration device and associated ANN will be useful for correcting measurement errors in vertical loads and COP for ITs.
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Source:Gait & Posture, Volume 45
Author(s): Hong-Jung Hsieh, Hsiu-Chen Lin, Hsuan-Lun Lu, Ting-Yi Chen, Tung-Wu Lu
Instrumented treadmills (ITs) are used to measure reaction forces (RF) and center of pressure (COP) movements for gait and balance assessment. Regular in situ calibration is essential to ensure their accuracy and to identify conditions when a factory re-calibration is needed. The current study aimed to develop and calibrate in situ an IT using a portable, precision-controlled calibration device with an artificial neural network (ANN)-based correction method. The calibration device was used to apply static and dynamic calibrating loads to the surface of the IT at 189 and 25 grid-points, respectively, at four belt speeds (0, 4, 6 and 8km/h) without the need of a preset template. Part of the applied and measured RF and COP were used to train a threelayered, back-propagation ANN model while the rest of the data were used to evaluate the performance of the ANN. The percent errors of Fz and errors of the Px and Py were significantly decreased from a maximum of −1.15%, −1.64mm and −0.73mm to 0.02%, 0.02mm and 0.03mm during static calibration, respectively. During dynamic calibration, the corresponding values were decreasing from −3.65%, 2.58mm and −4.92mm to 0.30%, −0.14mm and −0.47mm, respectively. The results suggest that the calibration device and associated ANN will be useful for correcting measurement errors in vertical loads and COP for ITs.
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Comparison of the correlations between impact loading rates and peak accelerations measured at two different body sites: intra- and inter-subject analysis
Publication date: Available online 23 February 2016
Source:Gait & Posture
Author(s): Janet H. Zhang, Winko W. An, Ivan P.H. Au, Tony L. Chen, Roy T.H. Cheung
BackgroundHigh average (VALR) and instantaneous vertical loading rates (VILR) during impact have been associated with many running-related injuries. Peak acceleration (PA), measured with an accelerometer, has provided an alternative method to estimate impact loading during outdoor running. This study sought to compare both intra- and inter-subject correlations between vertical loading rates and PA measured at two body sites during running.MethodsGround reaction force data were collected from 10 healthy adults (age=23.6±3.8 years) during treadmill running at different speeds and inclination surfaces. Concurrently, PAs at the lateral malleoli and the distal tibia were measured using synchronized accelerometers.ResultsWe found significant positive intra-subject correlation between loading rates and PA at the lateral malleoli (r=0.561-0.950, p<0.001) and the distal tibia (r=0.486-0.913, p<0.001). PA measured at the lateral malleoli showed stronger correlation with loading rates (p=0.004) than the measurement at the distal tibia. On the other hand, inter-subject variances were observed in the association between PA and vertical loading rates. The inter-subject variances at the distal tibia were 3.88± 3.09 BW/s and 5.69±3.05 BW/s in VALR and VLIR respectively. Similarly, the inter-subject variances in the measurement at lateral malleoli were 5.24±2.85 BW/s and 6.67±2.83 BW/s in VALR and VLIR respectively.ConclusionsPA measured at lateral malleoli has stronger correlation with VALR or VILR than the measurement at distal tibia. Caution is advised when using PA to conduct inter-subject comparisons of vertical loading rates during running.
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Source:Gait & Posture
Author(s): Janet H. Zhang, Winko W. An, Ivan P.H. Au, Tony L. Chen, Roy T.H. Cheung
BackgroundHigh average (VALR) and instantaneous vertical loading rates (VILR) during impact have been associated with many running-related injuries. Peak acceleration (PA), measured with an accelerometer, has provided an alternative method to estimate impact loading during outdoor running. This study sought to compare both intra- and inter-subject correlations between vertical loading rates and PA measured at two body sites during running.MethodsGround reaction force data were collected from 10 healthy adults (age=23.6±3.8 years) during treadmill running at different speeds and inclination surfaces. Concurrently, PAs at the lateral malleoli and the distal tibia were measured using synchronized accelerometers.ResultsWe found significant positive intra-subject correlation between loading rates and PA at the lateral malleoli (r=0.561-0.950, p<0.001) and the distal tibia (r=0.486-0.913, p<0.001). PA measured at the lateral malleoli showed stronger correlation with loading rates (p=0.004) than the measurement at the distal tibia. On the other hand, inter-subject variances were observed in the association between PA and vertical loading rates. The inter-subject variances at the distal tibia were 3.88± 3.09 BW/s and 5.69±3.05 BW/s in VALR and VLIR respectively. Similarly, the inter-subject variances in the measurement at lateral malleoli were 5.24±2.85 BW/s and 6.67±2.83 BW/s in VALR and VLIR respectively.ConclusionsPA measured at lateral malleoli has stronger correlation with VALR or VILR than the measurement at distal tibia. Caution is advised when using PA to conduct inter-subject comparisons of vertical loading rates during running.
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Treadmill Walking is not Equivalent to Overground Walking for the Study of Walking Smoothness and Rhythmicity in Older Adults
Publication date: Available online 22 February 2016
Source:Gait & Posture
Author(s): Brandi S. Row Lazzarini, Theodore J. Kataras
Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.
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Source:Gait & Posture
Author(s): Brandi S. Row Lazzarini, Theodore J. Kataras
Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.
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Corrigendum to “The relationships between foot-joints range of motion and plantar pressure in the normal foot” [Gait Posture 42 (September (Suppl. 2)) (2015) S24]
Publication date: Available online 23 February 2016
Source:Gait & Posture
Author(s): Paolo Caravaggi, Alberto Leardini, Claudia Giacomozzi
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Source:Gait & Posture
Author(s): Paolo Caravaggi, Alberto Leardini, Claudia Giacomozzi
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Calibration of an instrumented treadmill using a precision-controlled device with artificial neural network-based error corrections
Publication date: March 2016
Source:Gait & Posture, Volume 45
Author(s): Hong-Jung Hsieh, Hsiu-Chen Lin, Hsuan-Lun Lu, Ting-Yi Chen, Tung-Wu Lu
Instrumented treadmills (ITs) are used to measure reaction forces (RF) and center of pressure (COP) movements for gait and balance assessment. Regular in situ calibration is essential to ensure their accuracy and to identify conditions when a factory re-calibration is needed. The current study aimed to develop and calibrate in situ an IT using a portable, precision-controlled calibration device with an artificial neural network (ANN)-based correction method. The calibration device was used to apply static and dynamic calibrating loads to the surface of the IT at 189 and 25 grid-points, respectively, at four belt speeds (0, 4, 6 and 8km/h) without the need of a preset template. Part of the applied and measured RF and COP were used to train a threelayered, back-propagation ANN model while the rest of the data were used to evaluate the performance of the ANN. The percent errors of Fz and errors of the Px and Py were significantly decreased from a maximum of −1.15%, −1.64mm and −0.73mm to 0.02%, 0.02mm and 0.03mm during static calibration, respectively. During dynamic calibration, the corresponding values were decreasing from −3.65%, 2.58mm and −4.92mm to 0.30%, −0.14mm and −0.47mm, respectively. The results suggest that the calibration device and associated ANN will be useful for correcting measurement errors in vertical loads and COP for ITs.
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Source:Gait & Posture, Volume 45
Author(s): Hong-Jung Hsieh, Hsiu-Chen Lin, Hsuan-Lun Lu, Ting-Yi Chen, Tung-Wu Lu
Instrumented treadmills (ITs) are used to measure reaction forces (RF) and center of pressure (COP) movements for gait and balance assessment. Regular in situ calibration is essential to ensure their accuracy and to identify conditions when a factory re-calibration is needed. The current study aimed to develop and calibrate in situ an IT using a portable, precision-controlled calibration device with an artificial neural network (ANN)-based correction method. The calibration device was used to apply static and dynamic calibrating loads to the surface of the IT at 189 and 25 grid-points, respectively, at four belt speeds (0, 4, 6 and 8km/h) without the need of a preset template. Part of the applied and measured RF and COP were used to train a threelayered, back-propagation ANN model while the rest of the data were used to evaluate the performance of the ANN. The percent errors of Fz and errors of the Px and Py were significantly decreased from a maximum of −1.15%, −1.64mm and −0.73mm to 0.02%, 0.02mm and 0.03mm during static calibration, respectively. During dynamic calibration, the corresponding values were decreasing from −3.65%, 2.58mm and −4.92mm to 0.30%, −0.14mm and −0.47mm, respectively. The results suggest that the calibration device and associated ANN will be useful for correcting measurement errors in vertical loads and COP for ITs.
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Comparison of the correlations between impact loading rates and peak accelerations measured at two different body sites: intra- and inter-subject analysis
Publication date: Available online 23 February 2016
Source:Gait & Posture
Author(s): Janet H. Zhang, Winko W. An, Ivan P.H. Au, Tony L. Chen, Roy T.H. Cheung
BackgroundHigh average (VALR) and instantaneous vertical loading rates (VILR) during impact have been associated with many running-related injuries. Peak acceleration (PA), measured with an accelerometer, has provided an alternative method to estimate impact loading during outdoor running. This study sought to compare both intra- and inter-subject correlations between vertical loading rates and PA measured at two body sites during running.MethodsGround reaction force data were collected from 10 healthy adults (age=23.6±3.8 years) during treadmill running at different speeds and inclination surfaces. Concurrently, PAs at the lateral malleoli and the distal tibia were measured using synchronized accelerometers.ResultsWe found significant positive intra-subject correlation between loading rates and PA at the lateral malleoli (r=0.561-0.950, p<0.001) and the distal tibia (r=0.486-0.913, p<0.001). PA measured at the lateral malleoli showed stronger correlation with loading rates (p=0.004) than the measurement at the distal tibia. On the other hand, inter-subject variances were observed in the association between PA and vertical loading rates. The inter-subject variances at the distal tibia were 3.88± 3.09 BW/s and 5.69±3.05 BW/s in VALR and VLIR respectively. Similarly, the inter-subject variances in the measurement at lateral malleoli were 5.24±2.85 BW/s and 6.67±2.83 BW/s in VALR and VLIR respectively.ConclusionsPA measured at lateral malleoli has stronger correlation with VALR or VILR than the measurement at distal tibia. Caution is advised when using PA to conduct inter-subject comparisons of vertical loading rates during running.
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Source:Gait & Posture
Author(s): Janet H. Zhang, Winko W. An, Ivan P.H. Au, Tony L. Chen, Roy T.H. Cheung
BackgroundHigh average (VALR) and instantaneous vertical loading rates (VILR) during impact have been associated with many running-related injuries. Peak acceleration (PA), measured with an accelerometer, has provided an alternative method to estimate impact loading during outdoor running. This study sought to compare both intra- and inter-subject correlations between vertical loading rates and PA measured at two body sites during running.MethodsGround reaction force data were collected from 10 healthy adults (age=23.6±3.8 years) during treadmill running at different speeds and inclination surfaces. Concurrently, PAs at the lateral malleoli and the distal tibia were measured using synchronized accelerometers.ResultsWe found significant positive intra-subject correlation between loading rates and PA at the lateral malleoli (r=0.561-0.950, p<0.001) and the distal tibia (r=0.486-0.913, p<0.001). PA measured at the lateral malleoli showed stronger correlation with loading rates (p=0.004) than the measurement at the distal tibia. On the other hand, inter-subject variances were observed in the association between PA and vertical loading rates. The inter-subject variances at the distal tibia were 3.88± 3.09 BW/s and 5.69±3.05 BW/s in VALR and VLIR respectively. Similarly, the inter-subject variances in the measurement at lateral malleoli were 5.24±2.85 BW/s and 6.67±2.83 BW/s in VALR and VLIR respectively.ConclusionsPA measured at lateral malleoli has stronger correlation with VALR or VILR than the measurement at distal tibia. Caution is advised when using PA to conduct inter-subject comparisons of vertical loading rates during running.
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Treadmill Walking is not Equivalent to Overground Walking for the Study of Walking Smoothness and Rhythmicity in Older Adults
Publication date: Available online 22 February 2016
Source:Gait & Posture
Author(s): Brandi S. Row Lazzarini, Theodore J. Kataras
Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.
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Source:Gait & Posture
Author(s): Brandi S. Row Lazzarini, Theodore J. Kataras
Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.
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