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PubMed1989

Vibration sensitivity of slowly and rapidly adapting cutaneous mechanoreceptors in the human foot and leg.

The activities of 30 rapidly adapting cutaneous receptors (FA) and 23 slowly adapting cutaneous receptors (SA) were recorded from the lateral peroneal nerve using the microneurographic method. Their sensitivity to mechanical vibrations with constant amplitude applied at various frequencies to the center of the receptive field was studied. These two populations of cutaneous receptors were found to be very sensitive to this stimulus: they could be driven in a one to one manner up to between 100 and 200 Hz. The difference lay in the response observed when the vibration frequency was increased to above this critical value: the FA receptors sharply stopped firing, whereas the SA receptors became progressively unlinked from the stimulus. The effects of vibration on the physiological messages were also studied. The results showed that the messages coding the properties of tactile stimuli were either completely or partly masked by the receptor response to vibration. These vibration-induced modifications of cutaneous sensory messages might be at least partly responsible for the sensorimotor alterations observed when subjects are exposed to vibration.

Electrophysiology↗
PubMed1994

Simulation study on the effect of external vibration on left ventricular function: potential indicator of LV tolerance to the sudden reduction of myocardial contractility.

In a previous study the authors reported that external mechanical vibration applied to the left ventricular (LV) epicardium induces contractility-dependent depression in LV pressure, stroke volume and stroke work. It was suggested that this depression may be caused by the direct effect of external vibration on contractile protein. In another paper in this issue, it is proved that LV function with various myocardial contractilities and the actual process of deterioration in heart failure are well simulated in the model proposed by Beyar and Sideman, after some modifications have been made. In the study reported here it is assumed that an external mechanical vibration induces sudden reduction in myocardial active stress in the model of Beyar and Sideman; in this way the contractility-dependent effect of external vibration on LV function has been simulated. The results of this simulation support the suggestion that external mechanical vibration directly affects contractile protein and reduces LV function, and it is further suggested that the reduction of LV function induced by external vibration reflects the reserve or tolerance capacity of LV to a sudden reduction of myocardial contractility.

Animals↗
PubMed1994

The effects of vertical and horizontal vibrations on the human body.

Vertical and horizontal vibrations of a 100 kg human have been investigated. A new mechanical model has been developed, and an analogous electric simulation has been carried out, which in turn has been analysed by using computer software (MICRO-CAP II). The vibration force comes from (a) hand, (b) seat and (c) combination of the two. The theoretical results obtained have been tabulated and are presented in a graphical manner. It has been found that the body segments (lower arm, head, torso, cervical spine and lumbar spine) are affected by horizontal vibrations when the input force (F(i)) comes from both hand and seat more than when (F(i)) comes from the seat alone. Similar results have been found also for the case of the lower arms and torso when the body is subjected to vertical vibrations. The head is affected by vertical vibrations when (F(i)) comes from the seat more than when (F(i)) comes from both hand and seat. An experimental set-up has been designed and measurements of vibrational signals from the human lower arm, head and torso have been carried out. Similar trends are shown for both theoretical results and experimental findings.

Adult↗
PubMed1996

The vibrational mode of the tibia and assessment of bone union in experimental fracture healing using the impulse response method.

This study attempts to clarify the use of the impulse response method in the assessment of fracture healing. The vibrational mode as well as the effect of simulated callus consolidation on the vibrational parameters of excised human tibia were studied. Two separate vibrations were found, one vibrating strongly in the lateral direction and the other vibrating weakly in the antero-posterior direction. The ability to identify the primary vibrational mode in the lateral direction would make the impulse response method suitable for use in clinical practice. The callus consolidation process was simulated by the sequential consolidation of an adhesive material in an experimentally produced fracture gap. The change in hardness of the epoxy was found to correlate well with the change of resonant frequency of the bone. The resonant frequency demonstrated a steady increase during the initial phase of consolidation of the adhesive, up to about 40% of its final hardness. With the addition of various constructs for fracture fixation to the in vitro model such as a plate, Ender's pins, a Russell-Taylor intramedullary nail, or an Orthofix external fixator, the relationship between the consolidation of the 'callus' and the change in resonant frequency of the bone was not disturbed.

Bony Callus↗
PubMed2004

Whole-body vibration transmitted to the framesaw operator.

At the moment there are more than 40 framesaws in use in Croatia, and many framesaw operators have a serious spine problem. Complex measurements have been carried out in order to determine the vibration level on the operator's seat. This paper reports and analyzes the measurement results of the whole-body vibration transmitted to a framesaw operator during an ordinary working day. Vibrations were measured at all operations performed during the normal framesaw working cycle. For all the measurements frequency spectra were obtained and the results graphically represented according to the ISO 2631-1-1986 recommendations. The weighted r.m.s. acceleration was also calculated and the duration of each single framesaw operation was measured. The energy-equivalent vibration level, corresponding to the total duration of exposure was calculated, too. The values so obtained were compared with the daily exposure limits according to the ISO 2631-1-1997. The measurement results showed that the framesaw operator, under the given measuring conditions, is exposed to a higher vibration level than the given daily exposure limits. Also, the energy-equivalent vibration level calculated according to the guidelines given in the new ISO 2631-1-1997 is higher than the limits recommended for an effective 4-h daily exposure.

Acceleration↗
PubMed2005

Reflex contribution of spindle group Ia and II afferent input to leg muscle spasticity as revealed by tendon vibration in hemiparesis.

OBJECTIVE: Foot dorsiflexion evokes a short- (SLR) and a medium-latency EMG response (MLR) in the soleus of standing subjects. SLR is mediated by spindle group Ia, while group II fibres contribute to MLR through an oligosynaptic circuit. We studied the effects of Achilles' tendon vibration on both responses in spastic patients to disclose any abnormal excitability of these pathways. METHODS: SLR and MLR were evoked in 11 hemiparetics and 11 normals. The vibration-induced changes in both responses were correlated to the Ashworth score of the affected leg. RESULTS: There were no differences between normals and patients in the size of control SLR or MLR. Vibration decreased SLR to 70% in normal subjects, but increased it to 110% in patients, in both affected and unaffected leg. Vibration did not affect MLR in normals, but increased it to 165% on the affected and 120% on the unaffected side of patients. Ashworth score was solely correlated with the degree of vibration-induced increase of MLR. CONCLUSIONS: While the lack of inhibitory effect of vibration on SLR confirms a reduced inhibitibility of the monosynaptic reflex, the increased MLR indicates a disinhibition of group II pathway in patients, connected to the loss of descending control on group II interneurones. Spastic hypertonia depends on release of group II rather than group Ia reflex pathways. SIGNIFICANCE: These findings give a neurophysiological support for the pharmacological treatment of spastic hypertonia and suggest a method for the assessment of its effects.

Adult↗
PubMed2005

Frequency weighting derived from power absorption of fingers-hand-arm system under z(h)-axis vibration.

The objectives of this study are to derive the frequency weighting from three vibration power absorption (VPA) methods (finger VPA, palm VPA, and total or hand VPA), and to explore whether these energy methods are better than the currently accepted acceleration method. To calculate the VPA weightings, the mechanical impedance of eight subjects exposed to a broadband random vibration spectrum in the z(h)-axis using 18 combinations of hand couplings and applied forces was measured. The VPA weightings were compared with the frequency weighting specified in ISO 5349-1 [2001. Mechanical Vibration--Measurement and Evaluation of Human Exposure to Hand--Transmitted Vibration--Part 1: General Requirements. International Organization for Standardization, Geneva, Switzerland]. This study found that the hand and palm VPA weightings are very similar to the ISO weighting but the finger VPA weighting for the combined grip and push action is much higher than the ISO weighting at frequencies higher than 25 Hz. Therefore, this study predicted that the total power absorption of the entire hand-arm system is likely to be correlated with psychophysical response or subjective sensation. However, if the ISO weighting method cannot yield good predictions of the vibration-induced disorders in the fingers and hand, the hand and palm energy methods are unlikely to yield significantly better predictions. The finger VPA is a vibration measure between unweighted and ISO weighted accelerations. The palm VPA method may have some value for studying the disorders in the wrist-arm system.

Arm↗
PubMed2005

Nuclear resonance vibrational spectroscopy--NRVS.

The recent, synchrotron-based vibrational technique nuclear resonance vibrational spectroscopy (NRVS) is introduced. The method can be used for a number of Mössbauer active isotopes including 57Fe, which has yielded most of the results to date. The NRVS experiment can be thought of as Mössbauer spectroscopy with vibrational sidebands. Importantly, the NRVS experiment provides the complete set of bands corresponding to modes that involve motion of the iron atom. The method has a selectivity reminiscent of that of resonance Raman spectroscopy, but with the significant advantage that NRVS is not subject to the optical selection rules of Raman or infrared spectroscopy. Indeed, NRVS provides the ultimate limit in selectivity because only the vibrational dynamics of the probe nucleus contribute to the observed signal. All iron-ligand modes will be observed, including many that had not been previously observed. For hemes, these include in-plane iron vibrations that have not yet been reported by resonance Raman studies and the iron-imidazole stretch that has not been identified in six-coordinate porphyrins. Other modes that can be investigated include that of heme doming that is expected to be a low-frequency mode. The experimental setup at a beam line and sample requirements for iron-based derivatives are presented. Both powder and polarized single-crystal measurements can be made. The general features of data extraction and analysis are given. Data for heme and heme proteins are given. Examples of assignment of spectra for nitrosyl and carbonyl derivatives are given. These data demonstrate the importance of peripheral substituents on the vibrational spectrum of heme derivatives. Delocalization of modes appears to be common. Although this technique has only been available for a relatively short time, this early progress report indicates that NRVS has significant potential for probing the dynamics of Fe-containing molecules of biological interest.

Animals↗
PubMed2005

A portable vibrator for muscle performance enhancement by means of direct muscle tendon stimulation.

Combining vibration stimulation with conventional resistance training has gained in popularity. However, no portable vibrator capable of directly stimulating muscle tendon appears to feature in the literature. The aim of this study was the development of such a unit. The unit developed makes use of a rotating eccentric mass system to produce desired amplitude and frequency range capable of investigating the diverse vibration characteristics used in previous research studies. The effects of strapping force, joint angle and day-to-day repeatability on these vibration characteristics were investigated. In addition, muscle electromyography (EMG) activity was subsequently used to identify the optimum vibration amplitude and frequency. Finally, the repeatability of these EMG responses and effect of joint angle were examined. The unit was able to produce desired vibration characteristics (amplitude: 0.2-2 mm; frequency: 30-200 Hz). Test day, strapping force and joint angle had no significant effect on these characteristics (p>0.05). Both amplitudes (0.5 and 1.2 mm) and all three frequencies (30, 65 and 100 Hz) tested, significantly enhanced EMG activity (p<0.05), with 1.2 mm and both 65 and 100 Hz resulting in significantly greater enhancements (p<0.05). Joint angle had no significant effect on these EMG results (p>0.05). The day-to-day repeatability of EMG response was shown to be high (r=0.76-0.90).

Adaptation, Physiological↗
PubMed2006

Analysis of the point mechanical impedance of fingerpad in vibration.

Biodynamic responses of the finger-hand-arm system, such as apparent mass and mechanical impedance, characterize the relationship between the motion of the finger-hand-arm system and the dynamic force acting on the driving point, and they are useful for vibration exposure assessment. In the present study, a two-dimensional finite element (FE) model has been proposed to simulate the biodynamic responses of the fingerpad in vibration tests. The fingernail was supported by the rigid ground while the fingerpad was activated by a vibration probe. The fingertip model is composed of skin, subcutaneous tissue, bone, and nail. The soft tissues (i.e., skin and subcutaneous tissues) were assumed to be non-linearly elastic and linearly viscoelastic. The FE model was applied to predict the effects of pre-indentation of the vibration probe onto the fingerpad, the damping of the soft tissues, and probe mass on the magnitude and phase angle of the mechanical impedance and the apparent mass, as measured in the vibration tests. The model predictions showed that the probe mass has non-negligible effects on the measured biodynamic responses in the vibration tests. In order to determine "true" biodynamic responses of the finger-hand-arm system, the mass effects have to be cancelled using an appropriate approach. The present analysis provided a theoretical explanation, from a biomechanical point-of-view, for the inconsistencies in the published experimental data for the biodynamic responses of fingerpad.

Biomechanical Phenomena↗
PubMed2006

Comparison of vibration perception thresholds in individuals with diffuse upper limb pain and carpal tunnel syndrome.

The study objective was to compare vibration perception and patterns of blood flow in outpatients with diffuse upper limb pain disorder (ULPD), carpal tunnel syndrome (CTS) and age and sex matched healthy controls. Vibration perception and discrimination thresholds were compared in subjects with ULPD (n=27), CTS (n=27) and healthy matched controls (n=54). Vibration measurements were taken bilaterally at three sites: (a) over the dorsum of the second and (b) fifth metacarpals and (c) the palmar aspect of the first and second metacarpals, corresponding to the innervation territories of the radial, ulnar and median nerves, respectively. Non-invasive assessments of peripheral blood flow were also performed in both limbs. When compared to healthy controls, subjects with ULPD had widespread elevation of vibration thresholds both ipsilateral and contralateral to the symptomatic limb. Subjects with CTS had similarly elevated vibration thresholds at sites both adjacent to and distant from the site of peripheral nerve injury. The responses to cold pressor testing of the upper limbs were physiologically normal in both the CTS and ULPD patient groups. Furthermore, there were no significant differences in the haemodynamic responses between the patient groups. The global elevation of vibration thresholds in subjects with both ULPD and CTS is consistent with altered central nervous system mechanisms, common to both conditions, which may be either adaptive to or maintaining the perception of pain.

Adaptation, Physiological↗
PubMed2005

Vibration sensitivity of the scanning near-field optical microscope with a tapered optical fiber probe.

In this paper the Rayleigh-Ritz method was used to study the scanning near-field optical microscope (SNOM) with a tapered optical fiber probe's flexural and axial sensitivity to vibration. Not only the contact stiffness but also the geometric parameters of the probe can influence the flexural and axial sensitivity to vibration. According to the analysis, the lateral and axial contact stiffness had a significant effect on the sensitivity of vibration of the SNOM's probe, each mode had a different level of sensitivity and in the first mode the tapered optical fiber probe was the most acceptive to higher levels of flexural and axial vibration. Generally, when the contact stiffness was lower, the tapered probe was more sensitive to higher levels of both axial and flexural vibration than the uniform probe. However, the situation was reversed when the contact stiffness was larger. Furthermore, the effect that the probe's length and its tapered angle had on the SNOM's probe axial and flexural vibration were significant and these two conditions should be incorporated into the design of new SNOM probes.

Algorithms↗
PubMed2005

Ultrasonic vibration dectection with wavelets: preliminary results.

Several arterial disorders are known to cause systolic audio vibrations in tissue: they include stenoses, vasospasm, aneurysms, bleeds and arteriovenous fistulas. High-amplitude vibrations can be discovered with conventional Doppler ultrasound (US) instruments; however, differentiating brief, low-amplitude vibrations from other nonstationary echo sources is difficult. Further, characterizing the frequency and amplitude of vibrations is not feasible with conventional Doppler US. The automated detection and estimation of both the frequency and amplitude of vibrations with durations less than 100 ms and amplitudes of a micrometer or less have remained a signal-processing challenge. These vibrations may be associated with both nonstationary colored noise and strong low-frequency clutter. The normalized continuous Morlet wavelet power-spectrum analysis of quadrature Doppler echoes, followed by a binary hypothesis test for noise, results in simulated detection rates above 99.9%, with 0.1% false alarms for signal-on signal-to-noise ratios (SNRs) as low as one. Two clinical examples are included.

Algorithms↗
PubMed1996

Acceleration of fetal head induced by vibration of maternal abdominal wall in sheep.

OBJECTIVE: The human body is often exposed to significant vibration stress in the workplace, at home, and during recreational activities. The current study was designed to evaluate whether low- to midfrequency vibrations present at the extraabdominal wall would be attenuated across this wall and what the levels of exposure would be once these vibrations reached the fetal head. STUDY DESIGN: Four pregnant sheep were instrumented with acceleration transducers to obtain acceleration levels at the extraabdominal and intraabdominal walls and at the fetal head. Sine-wave vibration stimulation was applied over a frequency range of 3 to 150 Hz at a constant acceleration level of 2.5 m/sec2 (root-mean-square). RESULTS: Vibration of the extraabdominal wall resulted in a frequency-dependent rise in vibration levels at the intraabdominal wall, from 4% to 140% of the input level. At the fetal head a broad peak in response was noted between 6 and 12 Hz, but the overall levels never exceeded 4% of the input level. CONCLUSION: Fetal exposure to localized vibratory stimulation of the maternal abdomen is maximal in the range of 6 to 12 Hz.

Abdominal Muscles↗
PubMed2001

Associations between hand-wrist musculoskeletal and sensorineural complaints and biomechanical and vibration work constraints.

A 3-year prospective epidemiological study was conducted to investigate the relationship between musculoskeletal complaints (MS) and sensorineural complaints (SN) of the workers in the hand-wrist region. A group of 69 workers (G1) using vibrating tools in eight different working situations was compared to a group of 62 workers (G2) performing heavy work without vibration and 46 workers (G3) performing light work without vibration. Biomechanical constraints (force, postures, repetitiveness and movement velocities) were analysed for each working situation and the vibration exposure at the eight workplaces with the 69 workers. MS and SN data were collected using the nordic questionnaire, modified to collect information about the frequency intensity and duration of complaints. The prevalence of complaints at the start of the study was significantly greater for G1 (72.5%) than for G2 (56.5%), itself greater than for G3 (30.4%). The prevalence of SN was about 40% for G1 and 2.5 times smaller in the two other groups. During the two years follow-up, new cases of 'serious' MS and SN developed. The annual incidence was respectively 8.3 and 5.4% on average. The incidence of MS was slightly but not statistically significantly greater for G1, while the incidence of SN was statistically higher (P<0.01) for G1 (10.9%) than for the two other groups (4.1 and 2.1%). Forces and angular repetitiveness were the only biomechanical factors significantly greater for G1. The vibration exposure duration of the G1 workers varied, in average, from 10 to 70% of the work time and the weighted personal exposure amplitude (A(EPw)) varied from 0.5 to 25.4 ms(-2). The probabilities of complaints at the beginning of the study (cross-sectional study) were estimated using multiple logistic regression models. The prevalence odds ratio (POR) for MS was equal to 4 for G1 compared to G2 and equal to 9 compared to G3. Force and vibration exposure were the main constraint parameters associated with this likelihood. As far as the SN are concerned, G2 and G3 were not statistically different, but the POR for the G1 workers was 4.5 compared to both groups. The most significant constraint factor was the weighted personal exposure acceleration. The same procedure was used to estimate the likelihood of development of 'serious' complaints (longitudinal study). The three groups did not appear significantly different concerning the 'serious' MS, while the incidence odds ratio (IOR) of 'serious' SN was very high (28.5) and significantly greater for G1 than for the two other groups. The likelihood of development of 'serious' SN increased with A(EPw). According to this prediction model, the risk of 'serious' SN would be about 6% at the proposed European 'action' value (2.5 ms(-2)) and about 10% at the 'limit' value (5 ms(-2)).

Adult↗
PubMed1998

Assessing the performance of anti-vibration gloves--a possible alternative to ISO 10819, 1996.

Special gloves (commonly referred to as anti-vibration gloves) have been offered for many years as personal protection against hand-arm vibration generated, for example, by powered hand tools. An internationally agreed means of quantifying the vibration-reducing performance of such gloves was not available until the publication of International Standard ISO 10819, 1996. The evaluation of the Standard reported here has led to the conclusion that the test could be improved to give more information to the potential glove user about how the glove might perform. Investigations of the main factors which can influence the results of glove transmissibility tests have formed the basis for a proposal to develop the Standard. The proposed alternative test measures the performance of a glove in octave bands and the resultant data can be used to estimate the potential that the glove has to protect against any given vibration source. Examples of the application of the proposed alternative test for selection of anti-vibration gloves matched to particular vibration sources (powered hand tools) are given. The advantages and disadvantages of the two test methods are discussed. The evaluation of the Standard and proposals for its development are under discussion with members of the committee which developed ISO 10819, 1996.

Gloves, Protective↗
PubMed1994

Pressure-induced correlation field splitting of vibrational modes: structural and dynamic properties in lipid bilayers and biomembranes.

Correlation field splittings of the vibrational modes of methylene chains in lipid bilayers, isolated lipid molecules in perdeuterated lipid bilayers, crystalline lipid, and interdigitated lipid bilayers have been investigated by pressure-tuning Fourier-transform infrared spectroscopy. The correlation field splittings of these modes are originating from the vibrational coupling interactions between the fully extended methylene chains with different site symmetry along each bilayer leaflet. The interchain-interactions of the methylene chains with the same site symmetry only contribute to frequency shift of the vibrational modes. The magnitude of the correlation field splitting is a measure of the strength of the interchain-interactions, and the relative intensities of the correlation field component bands provide information concerning the relative orientation of the zig-zag planes of the interacting methylene chains. It has been demonstrated in the present work that the correlation field splitting of the CH2 bending and rocking modes commonly observed in the vibrational spectra of lipid bilayers is the result of the intermolecular interchain-interactions among the methylene chains of the neighboring molecules. The intramolecular interchain-interactions between the sn-1 and sn-2 methylene chains within each molecule are weak. The correlation field splitting resulting from the intramolecular interchain-interactions exhibits a much smaller magnitude than that from the intermolecular interchain-interactions and is observed only at very high pressure. Interdigitation of the opposing bilayer leaflets disturbs significantly the intermolecular interchain-interactions and results in dramatic changes in the pressure profiles of the correlation field component bands of both the CH2 bending and rocking modes. The relative intensities of the correlation field component bands of these modes and the magnitude of the splitting are also altered significantly. These results provide further evidence that the correlation field splitting of the CH2 bending and rocking modes in the vibrational spectra of lipid bilayers is due to the intermolecular interchain-interactions. The present work has also demonstrated that the correlation field splitting of the vibrational modes in lipid bilayers is mainly contributed by the intermolecular interchain-interactions among the nearest neighboring molecules and that the long-range correlation interactions beyond the second neighboring molecules are insignificant.

Biophysical Phenomena↗
PubMed2000

Non-linearities in apparent mass and transmissibility during exposure to whole-body vertical vibration.

The causes of low back pain associated with prolonged exposure to whole-body vibration are not understood. An understanding of non-linearities in the biomechanical responses is required to identify the mechanisms responsible for the dynamic characteristics of the body, to allow for the non-linearities when predicting the influence of seating dynamics, and to predict the adverse effects caused by various magnitudes of vibration. Twelve subjects were exposed to six magnitudes, 0.25-2.5ms(-2) rms, of vertical random vibration in the frequency range 0.2-20Hz. The apparent masses of the subjects were determined together with transmissibilities measured from the seat to various locations on the body surface: the upper and lower abdominal wall, at L3, over the posterior superior iliac spine and the iliac crest. There were significant reductions in resonance frequencies for both the apparent mass and the transmissibilities to the lower abdomen with increases in vibration magnitude. The apparent mass resonance frequency reduced from 5.4-4. 2Hz as the magnitude of the vibration increased from 0.25-2.5ms(-2) rms. Vertical motion of the lumbar spine and pelvis showed resonances at about 4Hz and between 8 and 10Hz. When exposed to vertical vibration, the human body shows appreciable non-linearities in its biodynamic responses. Biodynamic models should be developed to reflect the non-linearity.

Abdominal Muscles↗