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PubMed2001

Soft-tissue vibrations in the quadriceps measured with skin mounted transducers.

The purpose of this study was to develop a method to characterize the frequency and damping of vibrations in the soft tissues of the leg. Vibrations were measured from a surface-mounted accelerometer attached to the skin overlying the quadriceps muscles. The free vibrations in this soft tissue were recorded after impact whilst the muscle was performing isometric contractions at 0, 50, and 100% maximum voluntary force and with the knee held at 20, 40, and 60 degrees angles of flexion. The acceleration signals indicated that the soft tissue oscillated as under-damped vibrations. The frequency and damping coefficients for these vibrations were estimated from a model of sinusoidal oscillations with an exponential decay. This technique resolved the vibration coefficients to 2 and 7% of the mean values for frequency and damping, respectively.

Adult↗
PubMed2001

Lumbar back muscle activity of helicopter pilots and whole-body vibration.

Several studies have attributed the prevalence of low back pain (LBP) in helicopter pilots mainly to poor posture in-flight and whole-body vibration, with the latter hypothesis particularly related to a cyclic response of the erector spine (ES) muscle to vibration. This work aims to determine if helicopter vibration and the pilot's normal posture during flight have significant effects on the electromyogram (EMG) of the ES muscle. The bilateral surface EMG of the ES muscle at the L3 level was collected in 10 young pilots before and during a short flight in UH-50 helicopters. The vibration was monitored by a triaxial accelerometer fixed to the pilots' seat. Prior to the flight, the EMG was recorded for relaxed seated and standing postures with 0 degrees (P0) and 35 degrees (P35) of trunk flexion. The effect of the posture during the flight was tested by comparing left and right EMG (normalized with respect to P35). The in-flight muscle stress was evaluated by histograms of EMG activity, and compared to P0 values. Only one pilot in ten showed significant (p<0.05) correlation between the vibration and the EMG over cycles of vibration, and no consistent causal effect was found. The pilots' posture did not show significant asymmetric muscular activity, and low EMG levels were observed during most of the duration of the flight. The results do not provide evidence that LBP in helicopter pilots is caused by ES muscle stress in the conditions studied.

Adult↗
PubMed1999

Acoustic myography during voluntary isometric contraction reveals non-propagative lateral vibration.

When isolated muscle synchronous contraction is evoked during in vitro twitches, mechanical vibrations at the surface of the muscle reflect resonant behavior. In contrast, voluntary contraction corresponds to the asynchronous contraction of recruited motor units, therefore, this kind of excitation could lead to different muscle vibrational behavior. We have studied human biceps brachii muscle during voluntary contraction in 10 healthy subjects. Low and high levels of voluntary contraction were explored with simultaneous recording of surface vibration by two sensors located longitudinally or perpendicular to the muscle's main axis. Cross-correlation and coherence functions were computed. Coherence functions revealed a common vibration frequency band between 17 and 28 Hz. Cross correlation functions revealed in-phase vibration for longitudinal sensors and opposite phase vibration for perpendicular sensors thus confirming a lateral bending movement. This behavior suggests that the acoustic myogram is the response of the muscle as a global resonant structure to the local fluctuations of pressure.

Acoustics↗
PubMed1996

Effect of ultrasonic vibration on post removal in extracted human premolar teeth.

The purpose of this study was to determine the effectiveness of ultrasonic vibration in removing Paraposts from extracted teeth. Paraposts were cemented in mandibular premolars to a depth of 9 mm with zinc phosphate cement and the teeth placed in four groups. Group 1 received no vibration. Group 2 received vibration for 4 min, group 3 received vibration for 12 min, and group 4 received vibration for 16 min. Tensile forces were applied to the posts and mean dislodgment forces compared. The mean force (kg) required to dislodge the Parapost in group 1 was 24.92 +/- 1.64 SEM; in group 2, 25.01 +/- 1.80; in group 3, 24.08 +/- 2.29; and in group 4, 12.41 +/- 2.60. There was a significant difference between group 4 and groups 1 to 3 (p = 0.0003). Results of this study indicate that 16 min ultrasonic vibration is an effective method for removing Paraposts from human premolar teeth.

Analysis of Variance↗
PubMed1996

Practical approach to measurement and evaluation of exposure to whole-body vibration in the workplace.

This article will present an overview of the history and current state-of-the-art of occupationally induced human whole-body vibration. A recommended step-by-step approach for recognizing, measuring, evaluating, and controlling whole-body vibration will be outlined. The fundamentals of vibration physics, potential vibration sources to which laborers may be exposed, and the propagation characteristics of vibration through the human body will be presented. Currently available national and international whole-body severity criteria and standards will be summarized, and the components constituting a vibration measurement instrumentation chain will be discussed in detail.

History, 20th Century↗
PubMed2001

Application of finite-element models to predict forces acting on the lumbar spine during whole-body vibration.

OBJECTIVE: To predict forces acting on the spine during whole-body vibration for a variety of boundary conditions - body mass, height and posture.Design. Representative anthropometric data and models for an upright, relaxed and bent forward sitting posture were used to derive model families with 30 variants of a finite-element model. BACKGROUND: A given exposure to whole-body vibration can cause a variable health risk depending on the concomitant conditions. The latter could contribute to the considerable uncertainty of the current evaluation of whole-body vibration. METHODS: Plane symmetric linear finite-element models were used for the prediction of static and dynamic compression and shear forces acting on the lumbar discs during whole-body vibration. Transfer functions from seat acceleration to forces were determined. RESULTS: A bent forward posture augments essentially the compressive and shear stress, predicted for erect and relaxed sitting postures. The normal variation of body mass and height causes a considerable variation of static internal shear stress, but a minor variation of compressive pressure. The dynamic internal stress varies nearly proportionally to the body mass. The transfer functions from seat acceleration to compressive force depend significantly on the posture. CONCLUSIONS: The variability of the spinal loads for a given whole-body vibration and associated with a normal range of several biological factors suggests a ratio between the minimum and maximum internal loads of about 1:2. RELEVANCE: Finite-element models can be used to compare the health risk arising from different whole-body vibration exposures and individual conditions. These results help to prevent work-related disorders of the lumbar spine.

Adult↗
PubMed1998

Vibration sonoelastography and the detectability of lesions.

Vibration sonoelastography has been developed for the detection of hard lesions in relatively soft tissue. The basic concept is to propagate low-amplitude and low-frequency shear waves (with displacements below 0.1 mm and frequencies typically below 1000 Hz) through deep organs, and displaying the vibration response in real-time using advanced color Doppler imaging techniques. A hard inhomogeneity, such as a tumor, will produce a localized disturbance in the vibration pattern, forming the basis for detection even when the tumor is isoechoic on B-scan images. This paper focuses on the important quantitative issues concerning the detectability or inherent contrast of lesions. The specific factors of lesion size, relative stiffness and vibration frequency are studied using theoretical models, finite element methods and experimental measurements on tissue-mimicking materials. The results indicate that detectability increases with vibration (shear wave) frequency; however, loss mechanisms ultimately limit the penetration of higher vibration frequencies (in the kHz range).

Elasticity↗
PubMed2003

Reduction of TMD pain by high-frequency vibration: a spatial and temporal analysis.

Under some conditions, vibration delivered to the skin can reduce pain (vibratory analgesia). Previous studies of this phenomenon in a clinical context have been somewhat variable in terms of stimulus control, and have not examined the way in which the spatial distribution of pain is affected. In the present study, we used rigorously controlled conditions to examine vibratory analgesia in participants (N=17) with painful temporomandibular disorders (TMD). Results of 20- and 100-Hz vibration were compared with data from a no-vibration control condition. The results document for the first time that vibratory analgesia occurs in TMD chronic pain conditions. We measured its time course using continuous visual analog scale (VAS) recording, and its spatial aspects by asking subjects to indicate painful regions on standardized drawings. VAS ratings and drawings both showed that pain is reduced by 100-Hz, but not by 20-Hz, vibration. The effectiveness of the high-frequency vibration cannot be attributed to a mechanism involving Pacinian corpuscles, since these receptors are lacking in the skin of the orofacial region. Spatial analyses revealed that ipsilateral and contralateral effects of vibration were statistically equivalent, suggesting that vibratory analgesia relies at least in part on central nervous system processes rather than local mechanisms.

Adolescent↗
PubMed1997

Modulatory influence on somatosensory perception from vibration and heterotopic noxious conditioning stimulation (HNCS) in fibromyalgia patients and healthy subjects.

In order to assess the function of endogenous mechanisms modulating somatosensory input in fibromyalgia (FM), the effect of vibratory stimulation (VS) and heterotopic noxious conditioning stimulation (HNCS) on perception of various somatosensory modalities was assessed. Ten female FM patients and 10 healthy, age-matched, females participated. VS (100 Hz) was applied to the left forearm for 45 min and quantitative sensory testing (QST) was performed within the vibrated area and in the right thigh before, during and 45 min following vibration. Pressure pain thresholds (PPTs) were assessed by pressure algometry. Perception thresholds to non-painful cold (CT) and warmth (WT), heat pain thresholds (HPTs), cold pain thresholds (CPTs) and stimulus-response curves of pain intensity as a function of graded nociceptive heat stimulation were assessed using a Peltier element based thermal stimulator. The effects of HNCS were tested using the upper extremity submaximal effort tourniquet test. Subjects rated tourniquet induced pain intensity on a visual analogue scale (VAS). QST was performed in the right thigh before, during and 60 min following the tourniquet. FM patients did not differ from controls in the response to VS. There was a local increase of PPTs during vibration (P < 0.001) and of WTs following vibration (P < 0.001). HPTs increased in the forearm and in the thigh (P < 0.009) during vibration. CTs and sensitivity to suprathreshold heat pain were not influenced by VS. The intensity of pain induced by the tourniquet did not differ between groups. PPTs increased during the tourniquet in controls (P < 0.001) but not in FM patients (difference between groups P < 0.001). Decreased sensitivity to non-painful cold (P < 0.001) and non-painful warmth (P < 0.001) was seen during and following (P < 0.001; P < 0.05, respectively) the tourniquet in both groups alike. HPTs and perception of suprathreshold heat pain remained unaffected in both groups. In conclusion, FM patients did not differ from healthy controls in their response to vibration, but no modulation of pressure pain was induced by HNCS, as opposed to controls, suggesting a dysfunction in systems subserving 'diffuse noxious inhibitory controls' (DNIC).

Adult↗
PubMed1989

Vibration disease.

Today, in this age of technology, vibration caused by machinery is an almost universal hazard. Vibration transferred from a machine to the human body may cause discomfort, a reduction of performance, and even injury. Vibratory manual tools may cause damage to the circulatory system of the upper extremities (Raynaud's syndrome), to the peripheral nerves (peripheral neuropathy), and to the bones and joints (aseptic necrosis, fatigue fractures, degenerative joint disease). Vehicles and machines causing floor vibration cause degenerative disc disease of the lumbar spine. The pathogenesis of vibration injuries is still not completely clear and there is no effective treatment. Some of the abnormalities are irreversible and may cause permanent decrease of working ability, and even unemployment. This is why prevention is so important. Prevention is complex, including technical and organizational measures, use of individual protective clothing and footwear, and medical supervision both before and during employment. Workers who are exposed to vibration should be protected against other aggravating factors such as cold and noise, etc. Vibration-induced injuries are recognized in law in many countries as grounds for financial compensation. Their cost to industry is rising and, unless a means of prevention or cure is found, will continue to do so in the foreseeable future.

Humans↗
PubMed2002

Ab initio calculations of anharmonic vibrational spectroscopy for hydrogen fluoride (HF)n (n = 3, 4) and mixed hydrogen fluoride/water (HF)n(H2O)n (n = 1, 2, 4) clusters.

Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n, with n = 3, 4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n = 1, 2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the Møller-Plesset (MP2) potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments.

Chemical Phenomena↗
PubMed2003

Vibratory antinociception: effects of vibration amplitude and frequency.

The ability of cutaneous vibration to compromise detection of a nociceptive stimulus was examined in 2 sets of psychophysical experiments. The noxious stimulus was a 10-millisecond burst of radiant heat from a CO(2) laser; at the near-threshold levels used it generally yielded a mild pricking sensation. In both experiments, the detectability (d(e)') of the laser was measured in the presence of different vibratory stimuli and in the absence of vibration. Periods of vibration lasted 10 seconds, bracketing the time of occurrence of the laser. Vibratory and laser stimuli were presented 2.3 cm apart on the dorsal surface of the forearm. Confidence rating procedures yielded receiver operating characteristic curves from which detectability of the laser was calculated. In an amplitude study, vibrations ranging from 10 to 45 dB above threshold were used; results indicated that nociceptive sensitivity gradually declined as vibration amplitude increased. In a frequency study, vibrations ranging from 20 to 230 Hz were used; all interfered with nociception. Combining the results of the 2 studies permitted the conclusion that signals in multiple vibrotactile channels are able to modulate nociception. No one mechanoreceptive channel appears to have a privileged role.

Adolescent↗
PubMed2004

Quantitative vibrational dynamics of iron in nitrosyl porphyrins.

We use quantitative experimental and theoretical approaches to characterize the vibrational dynamics of the Fe atom in porphyrins designed to model heme protein active sites. Nuclear resonance vibrational spectroscopy (NRVS) yields frequencies, amplitudes, and directions for 57Fe vibrations in a series of ferrous nitrosyl porphyrins, which provide a benchmark for evaluation of quantum chemical vibrational calculations. Detailed normal mode predictions result from DFT calculations on ferrous nitrosyl tetraphenylporphyrin Fe(TPP)(NO), its cation [Fe(TPP)(NO)]+, and ferrous nitrosyl porphine Fe(P)(NO). Differing functionals lead to significant variability in the predicted Fe-NO bond length and frequency for Fe(TPP)(NO). Otherwise, quantitative comparison of calculated and measured Fe dynamics on an absolute scale reveals good overall agreement, suggesting that DFT calculations provide a reliable guide to the character of observed Fe vibrational modes. These include a series of modes involving Fe motion in the plane of the porphyrin, which are rarely identified using infrared and Raman spectroscopies. The NO binding geometry breaks the four-fold symmetry of the Fe environment, and the resulting frequency splittings of the in-plane modes predicted for Fe(TPP)(NO) agree with observations. In contrast to expectations of a simple three-body model, mode energy remains localized on the FeNO fragment for only two modes, an N-O stretch and a mode with mixed Fe-NO stretch and FeNO bend character. Bending of the FeNO unit also contributes to several of the in-plane modes, but no primary FeNO bending mode is identified for Fe(TPP)(NO). Vibrations associated with hindered rotation of the NO and heme doming are predicted at low frequencies, where Fe motion perpendicular to the heme is identified experimentally at 73 and 128 cm-1. Identification of the latter two modes is a crucial first step toward quantifying the reactive energetics of Fe porphyrins and heme proteins.

Animals↗
PubMed2005

End-cap effects on vibrational structures of finite-length carbon nanotubes.

Vibrational structures of C60-related finite-length nanotubes, C(40+20n) and C(42+18n) (1 < or = n < or = 4), in which n is, respectively, the number of cyclic cis- and trans-polyene chains inserted between fullerene hemispheres, are analyzed from density functional theory (DFT) calculations. To illuminate the end-cap effects on their vibrational structures, the corresponding tubes terminated by H atoms C(20n)H20 and C(18n)H18 (1 < or = n < or = 5) are also investigated. DFT calculations show a broad range of vibrational frequencies for the finite-size nanotubes: high-frequency modes (1100-1600 cm(-1)) containing oscillations along tangential directions (tangential modes), medium-frequency modes (700-850 cm(-1)) whose oscillations are located on the edges or end caps, and low-frequency modes (300-600 cm(-1)) involving oscillations along the radial directions (radial modes). Broadening of the calculated frequencies is due to the number of nodes in the standing waves of normal modes in the finite-size tubes. In the capped tubes, calculated vibrational frequencies are insensitive to the number of chains (n), whereas in the uncapped tubes, most vibrational frequencies change significantly with an increase in tube length. The discrepancy in the size dependency is reasonably understood by their C-C bonding networks; the capped tubes have similar bond-length alternation patterns within the polyene chains irrespective of n, whereas the uncapped tubes have various bond-deformation patterns. Thus, DFT calculations illuminate that the edge effects have strong impacts on the vibrational frequencies in the finite-size nanotubes.

Models, Chemical↗
PubMed2005

Theory of the photodissociation of ozone in the Hartley continuum; effect of vibrational excitation and O(1D) atom velocity distribution.

The effect of vibrational excitation on the photodissociation cross section of ozone in the Hartley continuum is examined. The calculations make use of newly computed potential energy and transition dipole moment surfaces. The initial vibrational states of the ozone are computed using grid based techniques and the first few ab initio computed vibrational energy level spacings agree to within 10 cm(-1) with experimental values. The computed total absorption cross sections arising from different initial vibrational states of ozone are discussed in the light of the nature of the transition dipole moment surface. The computed cross section for excitation from the ground vibrational-rotational state is in good agreement with the experimentally measured cross section. Excitation of the asymmetric stretching vibration of ozone has a marked effect on both the form and magnitude of the photodissociation cross section. The velocity distributions of highly reactive O(1D) atoms arising from the photodissociation process in different wavelength ranges is also presented. The results show that the O(1D) atoms travel with a most probable translational velocity of 2.030 km s(-1) corresponding to a translational energy of 0.342 eV or 33.0 kJ mol(-1).

Mathematical Computing↗
PubMed2001

Whole-body vibration exercise leads to alterations in muscle blood volume.

Occupationally used high-frequency vibration is supposed to have negative effects on blood flow and muscle strength. Conversely, low-frequency vibration used as a training tool appears to increase muscle strength, but nothing is known about its effects on peripheral circulation. The aim of this investigation was to quantify alterations in muscle blood volume after whole muscle vibration--after exercising on the training device Galileo 2000 (Novotec GmbH, Pforzheim, Germany). Twenty healthy adults performed a 9-min standing test. They stood with both feet on a platform, producing oscillating mechanical vibrations of 26 Hz. Alterations in muscle blood volume of the quadriceps and gastrocnemius muscles were assessed with power Doppler sonography and arterial blood flow of the popliteal artery with a Doppler ultrasound machine. Measurements were performed before and immediately after exercising. Power Doppler indices indicative of muscular blood circulation in the calf and thigh significantly increased after exercise. The mean blood flow velocity in the popliteal artery increased from 6.5 to 13.0 cm x s(-1) and its resistive index was significantly reduced. The results indicate that low-frequency vibration does not have the negative effects on peripheral circulation known from occupational high-frequency vibration.

Adult↗
PubMed2001

Factor analysis of thermal and vibration thresholds in young patients with Type 1 diabetes mellitus.

AIMS: To identify factors that represent relationships among sets of interrelated thermal and vibration threshold variables and to find clinical correlates that are significantly associated with these factors. METHODS: Thermal and vibration perception thresholds were tested in the hands and feet of Type 1 diabetic patients treated in an outpatient clinic for juvenile-onset diabetes. Factor analysis was used to identify factors that represent relationships among sets of thermal and vibration threshold variables. RESULTS: One hundred and forty-eight patients (47.3% males, median current age 22.3 years and median duration of diabetes 11.4 years) were evaluated. Three factors explained 77% of the total variance: 'hand sensation' factor, underlying cold, warmth and vibration perception thresholds in the hand; 'foot sensation' factor, underlying the same sensory thresholds in the foot; and 'heat-related pain' factor, underlying heat pain perception threshold in both limbs. The 'foot sensation' factor was the only factor that significantly correlated with diabetes-related variables (e.g. duration and cumulative glycaemic control of the disease) and concurrent diabetic microangiopathy. Male sex was associated with higher values of the 'heat-related' factor, while the 'hand sensation' factor did not correlate with any of the study variables. CONCLUSIONS: The distribution of the various thermal and vibration threshold variables according to the three factors may point at length-dependent mechanism of axonal degeneration. Cold, warmth and vibration perception thresholds in the foot may be the only valuable psychophysical parameters in the evaluation of early sensory impairment associated with diabetes.

Adolescent↗
PubMed1998

Cutaneous responses to endothelin-1 and histamine in patients with vibration white finger.

Vibration white finger (VWF) is the episodic blanching of the fingers that occurs in response to cold in those who work with hand-held vibrating tools. Clinically the condition differs from primary Raynaud's phenomenon as persistent pain and paresthesia are common in the hands and arms and occur independently of the "white attacks." We have previously reported a decrease in protein gene product 9.5 and calcitonin gene-related peptide-immunoreactive nerve fibers in the digital skin of individuals with VWF. In this study, we have sought to determine whether this deficit of immunoreactive sensory-motor nerves has a functional counterpart in vivo. Histamine produces a rapid wheal and flare response following intradermal injection, whereas endothelin-1 (ET-1) produces a central area of pallor with a surrounding neurogenic flare. In contrast, calcitonin gene-related peptide produces a non-neurogenic erythema. In this study, histamine and ET-1 were injected into the dorsum of the middle phalanx and the local neurovascular response was assessed by measuring the area of the visible flare or pallor. Basal finger blood flow was also measured by laser Doppler flowmetry in each of the digits prior to intradermal injection. The experiments were performed at 21 degrees C and 4 degrees C. Patients with VWF and asymptomatic vibration-exposed workers had significantly lower resting skin blood flow at both 21 degrees C and 4 degrees C than heavy manual workers with no vibration exposure. The size of the histamine- and ET-1-induced flares at both 21 degrees C and 4 degrees C was significantly smaller in patients with VWF when compared with the asymptomatic vibration-exposed workers and heavy manual workers. The size of the ET-1-induced pallor was smaller in patients with VWF when compared with the heavy manual workers at both 21 degrees C and 4 degrees C. In contrast, the area of erythema induced by intradermal injection of calcitonin gene-related peptide at both 21 degrees C and 4 degrees C was of a similar size in patients with VWF and in heavy manual workers. These results indicate that the neuroneal deficit identified by immunohistochemistry in the digital skin of patients with VWF has a functional counterpart in vivo and is evident as a reduced ability to propagate an axon-reflex vasodilator response when challenged with histamine and ET-1. Furthermore, these results enable patients with VWF to be differentiated from both asymptomatic vibration-exposed workers, in whom the histamine- and ET-1-induced flares are normal, and those with primary Raynaud's disease, in whom the ET-1 flare is reduced and the histamine-induced flare is normal.

Adult↗