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PubMed2002

Effect of vibration-induced postural illusion on anticipatory postural adjustment of voluntary arm movement in standing humans.

We investigated the contribution of sensory signals arising from muscle proprioceptive receptors to anticipatory postural adjustments (APAs). During vibration applied to ankle (tibialis anterior; TA, soleus; Sol) or neck muscles, subjects generally describe having illusory sensations of whole-body movement, namely, whole-body movement in a backward and forward direction induced by vibration of the Sol or TA, respectively, and the front or back surface of the neck muscles, respectively. Preceding electromyographic (EMG) activity of the ipsilateral biceps femoris (BFi) muscle induced by rapid voluntary arm movement and the typical phenomenon of APA were changed dependent on these illusory whole-body movements, with preceding EMG activities of BFi appearing earlier in vibration applied to TA and later in vibration applied to Sol muscle. In vibration applied to the back surface of neck muscle, preceding EMG activities of BFi appeared earlier, as with vibration applied to TA. On the contrary, in vibration applied to the front surface of neck muscles, preceding EMG activities of BFi appeared later, as with vibration applied to Sol. Based on these results, we discuss changes in the central processing of proprioceptive signals used for coding of the spatial orientation of the body and its contribution to postural stabilization.

Adult↗

PubMed2006

Quantum chemistry-based analysis of the vibrational spectra of five-coordinate metalloporphyrins [M(TPP)Cl].

Vibrational properties of the five-coordinate porphyrin complexes [M(TPP)(Cl)] (M = Fe, Mn, Co) are analyzed in detail. For [Fe(TPP)(Cl)] (1), a complete vibrational data set is obtained, including nonresonance (NR) Raman, and resonance Raman (RR) spectra at multiple excitation wavelengths as well as IR spectra. These data are completely assigned using density functional (DFT) calculations and polarization measurements. Compared to earlier works, a number of bands are reassigned in this one. These include the important, structure-sensitive band at 390 cm(-1), which is reassigned here to the totally symmetric nu(breathing)(Fe-N) vibration for complex 1. This is in agreement with the assignments for [Ni(TPP)]. In general, the assignments are on the basis of an idealized [M(TPP)]+ core with D(4h) symmetry. In this Work, small deviations from D(4h) are observed in the vibrational spectra and analyzed in detail. On the basis of the assignments of the vibrational spectra of 1, [Mn(TPP)(Cl)] (2), and diamagnetic [Co(TPP)(Cl)] (3), eight metal-sensitive bands are identified. Two of them correspond to the nu(M-N) stretching modes with B(1g) and Eu symmetries and are assigned here for the first time. The shifts of the metal sensitive modes are interpreted on the basis of differences in the porphyrin C-C, C-N, and M-N distances. Besides the porphyrin core vibrations, the M-Cl stretching modes also show strong metal sensitivity. The strength of the M-Cl bond in 1-3 is further investigated. From normal coordinate analysis (NCA), force constants of 1.796 (Fe), 0.932 (Mn), and 1.717 (Co) mdyn/A are obtained for 1-3, respectively. The weakness of the Mn-Cl bond is attributed to the fact that it only corresponds to half a sigma bond. Finally, RR spectroscopy is used to gain detailed insight into the nature of the electronically excited states. This relates to the mechanism of resonance enhancement and the actual nature of the enhanced vibrations. It is of importance that anomalous polarized bands (A(2g) vibrations), which are diagnostic for vibronic mixing, are especially useful for this purpose.

Metals, Heavy↗

PubMed2006

Temperature-dependent protein dynamics: a simulation-based probabilistic diffusion-vibration Langevin description.

An enduring challenge in the understanding of internal protein motions is the effective separation and characterization of diffusive and vibrational dynamical components. To address this problem, here nanosecond molecular dynamics trajectories of myoglobin in aqueous solution, performed over a range of temperatures between 120 and 300 K, are subjected to principal component analysis, and the coordinate autocorrelation functions of the resulting principal modes are interpreted using a model combining damped Langevin vibration within potential wells and barrier-crossing diffusion between them. Both the vibrational frequency and the fraction of the mean-square fluctuation arising from vibrational motion undergo transitions with temperature at about 180 K. In contrast, the vibrational friction remains linear with temperature. The diffusional component of the mean-square fluctuation increases dramatically at the dynamical transition. The heights of the energy barriers between the potential wells are estimated, and the associated diffusion constants are calculated using Kramers' rate theory. Model functions of the frequency dependence of the frictional and diffusional quantities are obtained. The dynamic structure factor from the full molecular dynamics trajectory is well reproduced by the model. Overall, the results indicate that a global description of nanosecond temperature-dependent diffusion and vibrational internal protein dynamics can be obtained by applying the results of the present diffusion-vibration model to the vibrational motions obtained from a normal-mode analysis.

Algorithms↗

PubMed1983

Chest wall vibrations in singers.

The chest wall vibrations generated by phonation were examined with respect to origin, amplitude, and spectrum in seven singers. The vibrations were picked up in male and female singer subjects by means of small accelerometers, which were fastened to the skin on the center of the sternum, and, for the purpose of comparison, on the thyroid cartilage and on the trachea a few cm below the larynx. Among the factors which influence the chest wall vibrations, the subglottal pressure oscillations seem to represent the most important excitation, while the mechanical shocks from the vocal fold vibrations seem secondary. Supra- and subglottal resonances seem moderately influential. The results of the investigation suggest that it is the voice source, particularly the amplitude of its fundamental, which is reflected in the chest wall vibrations. The amplitude of these vibrations seem to lie above the threshold of the Pacinian receptors for vibratory sensation as long as the fundamental frequency is below approximately 300 Hz. The amplitude of the voice source fundamental and hence the sensation of chest vibrations vary considerably as phonation is changed along the phonatory dimension which ranges from "pressed/tense/strained" through "flow" to "breathy" phonation. For this reason it seems likely that the sensation of chest vibrations can serve as a useful nonauditory and hence room-independent signal for the voluntary control of phonation.

Adult↗

PubMed2005

Digital vibration threshold testing and ergonomic stressors in automobile manufacturing workers: a cross-sectional assessment.

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n = 1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.

Adult↗

PubMed1991

Implementation of double-pulsed holography in evaluation of whole-body vibration.

This study used a unique holographic technique to evaluate the effects of vibration on soft tissues and bones. It was possible to record forced whole-body vibration in humans by holograph interferometry using a double-pulsed ruby laser. The study investigated the manner in which the muscles of the back and vertebral column are affected by vibrations applied to the human buttocks in the sitting position. The subject was exposed to vibration at two frequencies: 40 and 60 Hz (vertical Z axis). Transmission of the vibrations along the subject's back was recorded by means of double-pulsed holography and electromyography. Evaluation of the vibration pattern showed that the vibrations are transmitted along the back all the way up to the neck and head. The pattern of vibration in the muscles of the back and vertebral column showed that the greatest effect was exerted on the lumbar region of the back and the area of transition between the thoracic and cervical regions.

Adult↗

PubMed1995

Predicting the discomfort caused by tractor vibration.

A field study was conducted to investigate how the discomfort caused by the vibration of an agricultural tractor can be predicted from objective measurements of the vibration in the cabin. Eleven professional drivers judged the vibration discomfort produced by four different tractors on sixteen different test runs. At the same time, for all the tests, the multi-axis vibration in the cabin was measured on the floor, the seat pan and the seat backrest. For each of the 704 tests carried out, the discomfort caused by the vibration was predicted from the measured vibration in the cabin using a total of twenty different analysis procedures. The relative merits of the different prediction procedures were investigated by comparing, on an individual basis for each driver/tractor combination, the statistical significance of the correlations between the subjective judgements and the predicted values. There was considerable variability in the drivers' subjective responses, but it was concluded that, overall, the best procedure for predicting the vibration discomfort in an agricultural tractor is that recommended by ISO 2631 (International Organization for Standardization 1978), using the frequency weighted rms values of the vibration (0.5-20 Hz) measured on the seat pan in the three orthogonal directions, and taking the square-root-of-the-sum-of-the-squares of the values in order to combine the directions as recommended in Amendment 1 to ISO 2631 (International Organization for Standardization 1982).

Agriculture↗

PubMed2005

Vibration exposure of individuals using wheelchairs over sidewalk surfaces.

According to the International Standards Organization 2631-1 standard on human vibration, individuals in a seated position are at risk of injury due to whole-body vibrations when exposed for long periods of time. Wheelchair users fit this description perfectly; however, little research has been conducted to evaluate the amount of vibration transmitted to a wheelchair user. The vibration exposure produced by traversing nine surfaces was evaluated by having 10 individuals without disabilities propel over them in both a manual wheelchair at 1 m/s and a powered wheelchair at 1 and 2 m/s. Root-mean squared (RMS) vertical vibration was examined to determine if differences existed between surfaces. At 1 m/s for both the manual and the powered wheelchair the 8-mm bevel interlocking concrete surface produced significantly higher RMS vertical vibration than the other surfaces. At 2 m/s in the powered wheelchair, the poured concrete surface (control) produced the significantly highest RMS vertical vibration. Based on the manual and power wheelchair results of this study, use of selected ICPI pavers would be acceptable for any route traveled by individuals using wheelchair. Furthermore, a 90 degrees herringbone pattern is preferred over the 45 degrees pattern, and it is recommended that for safety reasons regarding vibration exposure a bevel of less than 6 mm should be used.

Adult↗

PubMed2003

Analysis of whole-body vibration during manual wheelchair propulsion: a comparison of seat cushions and back supports for individuals without a disability.

Whole-body vibration exposure has been found to be detrimental to the health of humans owing to effects such as degraded comfort, disc degeneration, and lower back pain. The purpose of this study was to determine if selected seat cushions and back supports minimize the transmission of vibrations during manual wheelchair propulsion. Ten unimpaired participants traversed an activities of daily living course using four seat cushions and four back supports. Vibrations were measured using triaxial accelerometers. The time domain and frequency domain transmissibility was used to determine if differences exist among seat cushions and back supports. Differences were found among the four seat cushions and four back supports. Seat cushion and back support manufacturers should concentrate on single-event shocks and repeated shocks, as opposed to oscillatory motions and self-generated vibrations, because the vibrations generated by these events tend to reside in the range of frequencies most sensitive to humans. Vibrations in this range of frequencies have the greatest effect on the transmission of whole-body vibration during manual wheelchair propulsion. Differences among the seat cushions and back supports appear to be due to the seat cushion/back support design and postural support. From a clinical perspective, the time domain transmissibility best describes the transmission of whole-body vibration.

Acceleration↗

PubMedDate not supplied

Vibration of dental handpieces.

The vibration of new (n=4) and used (n=16) dental handpieces was tested in three directions during idling. In addition, work was simulated by drilling on plastic plate with all new and five used handpieces. The weighted vibration according to standard ISO 5349:1986 and the total acceleration of high-frequency vibration ("ultravibration") in the frequency range of 1.43-11.06 kHz were analyzed. Neither the water and air injection nor the grip force of fingers had any significant effect on the vibration level. The work simulation did increase the vibration of the handpieces, and the vibration became more broadband. The weighted accelerations were plainly below the hazardous acceleration determined in ISO 5349 and the ACGIH-TLV. The vibration spectra of the handpieces contained powerful vibration at high frequencies, but the effects of this ultravibration and exposure during work are not well known.

Dental High-Speed Equipment↗

PubMed1990

Vibration exposure for selected power hand tools used in automobile assembly.

A practical method for assessing vibration exposure for workers operating vibrating hand tools on an automobile assembly line is presented. Vibration exposure is difficult to assess directly using many fast Fourier transform (FFT) spectral analyzers because of long task cycle times. Exposure time cannot be accurately estimated using time standards because of the high variability between operators and work methods. Furthermore, because workers frequently move about and get into inaccessible spaces, it is difficult to record vibration without interfering with the operation. A work sampling method was used for determining vibration exposure time by attaching accelerometers to the tools and suspending a battery-operated digital data logger from the air hose. Vibration acceleration and frequency spectra for each tool were obtained off-line replicating actual working conditions and analyzed together with exposure time data for determining individual worker vibration exposure. Eight pneumatic vibrating power hand tools, representing tools commonly used in an automobile assembly plant, were studied. Spectra for the rotary and reciprocating power tools and had large distinct dominant fundamental frequencies occurring in a narrow frequency range between 35 Hz and 150 Hz. These frequencies corresponded closely to tool free-running speeds, suggesting that major spectral component frequencies may be predicted on the basis of speed for some tools.

Automobiles↗

PubMed2003

An exploratory study of whole-body vibration exposure and dose while operating heavy equipment in the construction industry.

Whole-body vibration measurements were recorded for various types of heavy equipment used within the construction industry. The purpose of these measurements was to provide more information about the potential levels of whole-body vibration experienced by equipment operators in the construction industry, as well as to identify types of equipment warranting further research. In total, 67 pieces of equipment were tested from 14 different equipment types. Testing took place at various construction sites including corporate, public, and residential work projects. Measurements were made (following the 1997 International Standards Organization's 2631-1 whole-body vibration standards) for 20-minute testing periods using a Larson Davis HVM100 vibration monitor and a triaxial accelerometer. The mobile equipment tested was associated with greater levels of whole-body vibration than the stationary equipment. When whole-body vibration levels were compared to the International Standards Organization's 2631-1 standards, wheel loaders, off-road dump trucks, scrapers, skid steer vehicles, backhoes, bulldozers, crawler loaders, and concrete trowel vehicles exceeded the recommendations based on measured vibration dose values. Further research incorporating larger sample sizes and controlled testing conditions is required to better understand the levels of exposure experienced by operators as well as the amount to which seating, terrain, mobility, and vehicle structure might affect whole-body vibration.

Construction Materials↗

PubMed1989

Exposure to shock and vibration and symptoms in workers using impact power tools.

In The Netherlands damage to health due to occupational exposure to shock and vibration is seldom reported. A survey was therefore made of the nature, extent and severity of exposure to shock and vibration. This paper presents the results of an epidemiological study, by questionnaire, among workers using impact power tools. Data were collected about exposure time, symptoms and the subjective workload. A prevalence rate of 17% for symptoms of white finger was found. In the logistic regression symptoms of back pain showed an increased prevalence with increasing total time exposed to vibration. This study shows that exposure to vibration due to working with impact power tools, either alone or in combination with ergonomically bad working conditions, probably contributes to these symptoms. An estimate of the population at risk showed that over 30,000 workers in The Netherlands who use impact power tools are exposed to a vibration intensity of 10-40 m s-2. This intensity exceeds the standards advocated in draft standards in the U.K. (BSI, 1987) and U.S.A. (ACGIH, 1984). The results also provide evidence that in The Netherlands exposure to hand-arm vibration damages health. It is suggested that damage to health due to occupational exposure to vibration is underestimated by the Dutch occupational health services. It was concluded that more investigation is needed to evaluate the precise nature of occupational exposure to vibration in order to provide a basis for its reduction or elimination.

Finger Injuries↗

PubMed1991

Exposure to vibration and self-reported health complaints of riveters in the aircraft industry.

Workers using vibrating tools may experience neurological and vascular symptoms in the fingers and hands. The effect of vibration exposure on bone and joint disorders in the hand, arm and shoulder is less clear. In a cross-sectional study, riveters and controls in an aircraft company were investigated for vibration exposure and health complaints. Vibration measurements showed that frequency-weighted acceleration levels for riveting hammers and bucking bars ranged from 5.5 to 12.3 m s -2. The calculated equivalent frequency-weighted acceleration for a period of 4 h was the questionnaire survey 101 riveters reported statistically significant more complaints of pain and stiffness in their hands and arms when compared with 76 controls with no, or little, exposure to vibration. After 10 years of exposure statistically significant age-adjusted odds ratios (P less than 0.05) were found for vibration-induced white finger (VWF) (1.9) and pain or stiffness of the wrist (3.2). Although they were not statistically significant (0.05 less than P less than 0.10) odds ratios appreciably greater than 1 were found for numbness in fingers (1.6) and pain or stiffness in the elbow (1.6) and the shoulder (1.5), and these complaints were strongly associated with duration of exposure to vibration. With logistic regression the probabilities for a riveter of having symptoms of VWF after 10 and 20 years of exposure was estimated to be P = 0.18 and P = 0.29, respectively, which can be compared with the prevalences predicted by the dose-response relationship for VWF in ISO 5349, which are 10 and 30%. The results of this study suggest that exposure to vibration from working with impact power tools can contribute to complaints of pain and stiffness in the hand, arm and shoulder, and especially in the wrist.

Adult↗

PubMed2004

Whole-body vibration exposure and non-neutral neck postures during occupational use of all-terrain vehicles.

OBJECTIVES: The purpose of this study was to characterize whole-body vibration (WBV) exposure from various all-terrain vehicles (ATVs) like snowgroomers, snowmobiles and forwarders, and to investigate how frequently the drivers' cervical spine is positioned in a non-neutral rotational position during operation. METHODS: Field measurements of WBV were measured according to the international standard ISO 2631-1 in 19 ATVs. Simultaneous recordings of frequency and duration of rotational neck movements exceeding 15 degrees were achieved through an observational method, PEOflex. RESULTS: The sum of the vectors of frequency-weighted r.m.s. acceleration varied between 0.5 and 3.5 m s(-2), which meant that for most vehicles they exceeded the action value stated by the European Union (0.5 m s(r.m.s.)(-2)). In general, snowmobiles achieved the highest vibration total value. The dominant vibration direction for the snowmobile was the x-axis but the z-axis also had relatively high vibration dose values and maximal transient vibration values. The z-axis was the dominant vibration direction for the snowgroomer and the y-axis for the forwarder. Frequency and duration of non-neutral rotational neck postures were relatively low for all driver categories. CONCLUSIONS: Vibration magnitudes in ATVs are considerably high than the EU's action value and the health guidance caution zones in ISO 2631-1. The dominant vibration direction varies depending on the machine type. Duration and frequency of non-neutral rotational positions do not seem to constitute single ergonomic risk factors for musculoskeletal symptoms in the neck among professional drivers of ATVs. However, synergistic effects with other factors are conceivable.

Analysis of Variance↗

PubMed2007

Rock drills used in South African mines: a comparative study of noise and vibration levels.

OBJECTIVES: To compare the noise and vibration levels associated with three hand-held rock drills (pneumatic, hydraulic and electric) currently used in South African mines, and a prototype acoustically shielded self-propelled rock drill. METHODS: Equivalent A-weighted sound pressure levels were recorded on a geometrical grid, using Rion NL-11 and NL-14 sound level meters. Vibration measurements were conducted on the pneumatic, hydraulic and electric drills in accordance with the ISO5349-1 (2001) international standard on human exposure to hand-transmitted vibration, using a Brupsilonel and Kjaer UA0894 hand adaptor. PCB Piezo accelerometers were used to measure vibration in three orthogonal directions. No vibration measurements were conducted on the self-propelled drill. RESULTS: All four drills emitted noise exceeding 85 dB(A). The pneumatic drill reached levels of up to 114 dB(A), while the shielded self-propelled drill almost complied with the 85 dB(A) 8 h exposure limit. Vibration levels of up to 31 m s(-2) were recorded. These levels greatly exceed recommended and legislated levels. CONCLUSIONS: Significant engineering advances will need to be made in the manufacture of rock drills to impact on noise induced hearing loss and hand arm vibration syndrome. Isolating the operator from the drill, as for the self-propelled drill, addresses the problems of both vibration and noise exposure, and is a possible direction for future development.

Humans↗

PubMed2005

Vibration enhances interleukin-8 release in a cell model of snoring-induced airway inflammation.

STUDY OBJECTIVES: To test a cell model of snoring-induced airway inflammation and to assess whether a vibration stimulus simulating the one experienced by airway tissues in snoring patients induces inflammation in airway epithelial cells. DESIGN: Prospective controlled study in cell culture. SETTING: University laboratory. PATIENTS OR PARTICIPANTS: Human bronchial epithelial cells (BEAS-2B cell line). INTERVENTIONS: Cell cultures were subjected to vibration (60 Hz, +/- 0.3 mm) for time periods of 6 hours, 12 hours, and 24 hours. The vibratory stimulus was applied with and without treatment with inhibitors of the 3 main pathways of mitogen-activated protein kinases (MAPK): p38, MEK1/2, and JNK. MEASUREMENTS AND RESULTS: The effect of vibration was assessed by comparing cell proliferation and release of interleukin-8 (IL-8; measured by enzyme-linked immunosorbent assay) in cells subjected to the vibratory stimulus (both when treated and untreated with MAPK inhibitors) and in controls. Application of vibration up to 24 hours did not significantly modify cell proliferation. By contrast, the concentration of IL-8 in the supernatant was significantly increased after 12 hours and 24 hours of vibration. The inhibition of the p38, MEK1/2, and JNK MAPK pathways significantly reduced the overexpression of IL-8 resulting from the vibration stimulus. CONCLUSIONS: A mechanical vibration simulating snoring triggered an inflammatory cascade, as reflected by the increase in IL-8 release mediated by MAPK pathways. The novel model developed is potentially applicable to studying the effects of the vibration due to snoring in the different cell types (epithelial, endothelial, muscular, neuronal) involved in airway pathophysiology during respiratory sleep disturbances.

Biomarkers↗

PubMed1992

Measurement of height loss during whole body vibrations.

An experimental, in vivo study was performed to measure height changes in subjects exposed to whole body vibrations while seated. Twelve women, with an average age of 22 years, were exposed to sinusoidal vibrations for 5 mins. The vibration frequency was 5 Hz, and the acceleration was 0.1 g Rms. The height loss stemming from vibration exposure was compared with that experienced while sitting without being subjected to vibrations. The height losses that always occurred from the two exposures were corrected for the effect of posture change. The height loss from vibration was significantly greater than when no vibration was present. Height loss due to posture change was responsible for approximately 50% of the total height loss. From this study it was concluded that whole body vibrations cause increased height loss.

Adult↗