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PubMed2001

Hand-transmitted vibration and biodynamic response of the human hand-arm: a critical review.

Hand-arm vibration syndrome (HAVS) has been associated with prolonged exposure to vibration transmitted to the human hand-arm system from hand-held power tools, vibrating machines, or hand-held vibrating workpieces. The biodynamic response of the human hand and arm to hand transmitted vibration (HTV) forms an essential basis for effective evaluations of exposures, vibration-attenuation mechanisms, and potential injury mechanisms. The biodynamic response to HTV and its relationship to HAVS are critically reviewed and discussed to highlight the advances and the need for further research. In view of its strong dependence on the nature of HTV and the lack of general agreement on the characteristics of HTV, the reported studies are first reviewed to enhance an understanding of HTV and related issues. The characteristics of HTV and relevant unresolved issues are discussed on the basis of measured data, proposed standards, and measurement methods, while the need for further developments in measurement systems is emphasized. The studies on biodynamic response and their findings are grouped into four categories based on the methodology used and the objective. These include studies on (1) through-the-hand-arm response, expressed in terms of vibration transmissibility; (2) to-the-hand response, expressed in terms of the force-motion relationship of the hand-arm system; (3) to-the-hand biodynamic response function, expressed in terms of vibration energy absorption; and (4) computer modeling of the biodynamic response characteristics.

Arm↗

PubMed2003

Predicted costs and outcomes from reduced vibration detection in people with diabetes in the U.S.

OBJECTIVE: The ability to perceive vibration (vibration detection) has been shown to be a good predictor of the long-term complications of diabetic peripheral neuropathy (DPN). We aimed to estimate the predicted complications and costs for the U.S. health care system associated with reduced vibration detection (vibration perception threshold >or=25 V), estimated using a quantitative sensory testing device. RESEARCH DESIGN AND METHODS: A Markov model was constructed for a hypothetical cohort of people with DPN. The model was run over a 10-year period using Monte Carlo simulations to estimate disease progression, predicted costs, and complications according to vibration detection levels. RESULTS: The average individual with reduced vibration detection incurs approximately five times more direct medical costs for foot ulcer and amputations, yields 0.18 fewer quality-adjusted life-years, and lives for approximately 2 months less than an average individual with normal vibration detection. CONCLUSIONS: The treatment of foot ulceration and amputation is time-consuming and expensive. If individuals with reduced vibration detection could be identified, then preventative care could be concentrated on those patients, potentially saving valuable resources and improving health outcomes.

Aged↗

PubMed1997

Low back pain among different groups of subjects exposed to hand-arm transmitted vibration.

OBJECTIVES: The purpose of this study was to investigate the prevalence of low back pain (LBP) among various groups of subjects exposed to hand-arm transmitted vibration, and to compare the prevalence of LBP of these subjects with that of non-exposed groups. METHODS: The subjects of this study were 13 groups of males and 3 groups of females of working population leaving in a certain city located in the central part of Japan. By means of a questionnaire, interviews, field visits, or annual health examination, information on age, working career, working posture, various types of tools used, and experience of having LBP during the 12 months preceding the completion of the questionnaire were collected. The subjects' age ranged between 22 and 69 years. All subjects were classified into 5 categories, and the prevalence of LBP was obtained for them. RESULTS: On the whole, complaints of LBP among male and female green tea and strawberry farmers were most frequent. There was a large variation (16.0-72.2%) in the prevalence of LBP among subjects operating vibrating tools. Among three groups of health care professionals, the prevalence of LBP was in the range of 36.5-53.0%. The senior doctors had less complaints of LBP. The prevalence of LBP among subjects who had sedentary jobs was in the range of 41.7-45.9%, and almost as high as that in blue-collar workers using vibrating tools. The prevalence of LBP among females exposed to hand-arm transmitted vibration was between 26.1 and 63%. The prevalence rates of LBP among vibration exposed subjects were plotted against the vibration magnitude of tools used by the same subjects reported in our previous study; however, no significant correlation could be obtained between the prevalence of LBP and vibration values. CONCLUSIONS: Exposure to segmental vibration is less likely to be a risk factor in increasing prevalence of LBP. A higher prevalence of LBP in some groups provide strong evidence for a dominant work-related etiology in developing LBP. Regarding data presented in this study and by a review on scientific literature, suggestions for improving working posture were presented. It seemed that to decrease the risk of LBP among these subjects, special attention should be paid to stimulating the adoption of an ergonomic working posture and to ergonomic training.

Adult↗

PubMed1998

The influence of the great Hanshin earthquake on human response to environmental vibration due to the Shinkansen.

A severe earthquake of magnitude 7.2 hit the west part of Japan on January 17, 1995. A part of the Shinkansen railway, which is one of the most popular high-speed mass transportation systems in Japan, was seriously damaged by the earthquake. About 80 days later, the Shinkansen service was resumed but complaints about vibration due to the passing Shinkansen increased rapidly among residents near the tracks. This paper reports the results of two investigations that were carried out in both stricken and non-stricken areas to determine the cause of complaint. In the first investigation, the ground vibration propagation induced by passing trains was measured. In the second investigation, questionnaires were distributed to the people living near the Shinkansen tracks. As a result, it was found out that the vibration levels before and after the earthquake were almost the same at most measured points in the stricken area. It was also found that the vibration levels in the stricken area and a non-stricken area were almost the same within 50 m from the Shinkansen tracks. However the results of the questionnaire survey showed that people's nuisance due to the vibration in the stricken area was clearly greater than that in the non-stricken area. This inconsistency was explained using the "category judgment method", which is generally used to determine the relationship between a physical stimulus and psychological reaction. According to the results of this analysis, the vibration level, at which 50% of the inhabitants complained about Shinkansen vibration, was approximately 54 dB in the non-stricken area and 50 dB in the stricken area. This result suggests that the people who experienced the severe earthquake became 4 dB more sensitive to the Shinkansen vibration than the people living in a non-stricken area despite the fact that this investigation was carried out 10 months after the earthquake struck.

Data Interpretation, Statistical↗

PubMed1990

Vibration stress and the autonomic nervous system.

Raynaud's phenomenon has been considered to be due to activation of the central sympathetic vasoconstrictor reflex, and may represent part of a larger dysfunction of higher autonomic centers. Symptoms, such as sweating disturbances, orthostatic hypotension, insomnia and impotence have been reported to be more common among vibration exposed workers. We studied 217 male forest workers and selected samples of this population for electromyographic (N = 80), autonomic nervous system function, controlled breathing, tilting bed and valsalva manoeuvre (N = 88) tests, and a full clinical neurological examination. Mean alcohol consumption was estimated to be 3.0 kg absolute alcohol/year. The total mean vibration exposure time was 14,100 hours. The prevalence of Raynaud's phenomenon was 5%. The variations in heart rate (HRV) at rest and during deep breathing were observed. The traditional indexes of HRV (CV, CVS, MEAN) were computerized and calculated. There was a significant difference (p less than 0.001) between the HRV indexes during the deep breathing test in those with the shortest and the longest exposure to vibration. The values of HRV indexes were age dependent; and in multiple regression analysis, the total exposure time to vibration had an independent negative association to HRV. Also association of sensory neural hearing loss to Raynaud's phenomenon among vibration exposed workers indicates that there is an involvement of the central nervous system in the pathogenesis of vibration syndrome. The question, does vibration cause permanent changes in autonomic centers of the brain or do these centers only mediate vibration stress to end organs, remains unsettled.

Adult↗

PubMed2006

[Effect of vibration caused by time-varying magnetic fields on diffusion-weighted MRI].

Diffusion-weighted images (DWIs) with high b-factor in the body are often used to detect and diagnose cancer at MRI. The echo planar imaging (EPI) sequence and high motion probing gradient pulse are used at diffusion weighted imaging, causing high table vibration. The purpose of this study was to assess whether the diffusion signal and apparent diffusion coefficient (ADC) values are influenced by this vibration because of time-varying magnetic fields. Two DWIs were compared. In one, phantoms were fixed on the MRI unit's table transmitting the vibration. In the other, phantoms were supported in air, in the absence of vibration. The phantoms called "solution phantoms" were made from agarose of a particular density. The phantoms called "jelly phantoms" were made from agarose that was heated. The diffusion signal and ADC value of each image were compared. The results showed that the signal of DWI units using the solution phantom was not affected by vibration. However, the signal of DWI and ADC were increased in the low-density jelly phantom as a result of vibration, causing the jelly phantom to vibrate. The DWIs of vibrating regions such as the breast maybe be subject to error. A countermeasure seems to be to support the region adequately.

Diffusion Magnetic Resonance Imaging↗

PubMed2000

[Measure of vibration protection effect of driver's corset and analysis of its biomechanical effect].

The purpose of this study was to evaluate the vibration protection and biomechanical effect of driver's corset. The frequencies of vertfical and horizontal vibrations were measured at low back of driver. The vehicle driven was ISUZU truck (loading capacity 8 tons). Vibration of the driver's lumbar back was measured real time with wear corset and without wear corset when the truck loaded with 6 tons was driven at the spead of ten, thirty and sixty kilometers an hour on the asphalt road. The results showed: 1. Vibration frequencies at driver's low back was under 10 Hz. It is a low frequency vibration. 2. The value of vertical vibration was higher than the value of horizontal (back and forth) vibration. 3. The vibration value of wear corset was higher than un-wear corset. These indicate the driver's corset is effective for protecting lumbar spine by means of change in the biomechanical characteristics and the resonace requencies of lumbar spine. So the driver's corset is one of the good methods for preventing the back pain of drivers.

Automobile Driving↗

PubMed1975

Levels of whole-body vibration affecting human vision.

A visual task was devised to determine the minimum levels of whole-body vibration that affect human vision. This task was the perception of the blur-due to eye motion-of an image of a stationary point source of light and is considered to be as sensitive as any alternative measure of the effects of vibration on visual acuity. Minimum levels of sinusoidal vertical vibration required to produce blur have been determined in a group of 12 subjects seated in a posture that maximised the sensation of vibration at their heads. The effect of vibration frequency (from 7 to 75 Hz) differed between subjects and there was a large individual variability in the levels of both head and seat vibration required to produce blur at any frequency. This intersubject variability has been compared with the potentially large intrasubject variability due to changes in body posture. The experimental results have led to the tentative recommendation of vibration levels below which vibration is not normally expected to reduce visual acuity.

Head↗

PubMed2001

[Standardized new method for measuring vibration perception].

The examination of the vibration perception is one of the basic measurements applied in the evaluation of the peripheral neuropathies in hand-arm vibration syndrome (HAVS) The detailed guidelines on how this kind of examinations should be performed, presented in the 1998 ISO standard, differ substantially from those currently binding in Poland. The aim of this study was to standardize the method of vibration perception measurements, taking account of the parameters consistent with the ISO recommendations, such as algorithm (stimulus presentation method), vibration frequency, the size and contact force of vibrating probe, as well as the comparison of the results obtained by means of both methods (ISO-recommended method and standard Polish method). It was found that the algorithm change (ascending method replaced by Bekesy's technique, recommended by ISO) did not affect the of the vibration perception thresholds values within the wide range of frequencies (32-500 Hz), whereas the decreased size of probe, pressed with smaller contact force, resulted in significantly higher values of perception thresholds within the frequency range of 125-400 Hz. The comparison of the outcomes of the ISO-recommended and Polish standard methods revealed that the perception thresholds did not differ at the frequency of 125 Hz, but at the frequencies of 250 and 400 Hz, the ISO-recommended method produced higher values. Moreover, at the frequencies ranging from 125 to 400 Hz, the results of the perception threshold measurements, taken several times in the same persons (intrasubject variability) by means of both methods, were more scattered. It was revealed that the measurements at the frequency range of 4-125 Hz should be included in the vibration perception examinations, and the certification of the ability to work in the conditions of exposure to hand-arm vibration should be based on their results. It is also essential that in the standard examination, a smaller vibratory probe (phi = 5 mm) and lighter contact force (0.1 N) than those currently used, should be applied.

Adult↗

PubMedDate not supplied

[The European Directive 2002/44/CE on the protection of workers from risks resulting from mechanical vibration].

This paper provides comments on the European Directive 2002/44/CE of 25 June 2002 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (vibration) (sixteenth individual Directive according to Article 16(1) of Directive 89/291/EEC). The European Directive on mechanical vibration was published in the Official Journal of the European Communities L 177/13 on 6 July 2002. The Directive includes the definitions of hand-arm vibration and whole-body vibration, establishes the daily exposure limit values and action values for mechanical vibration, and gives provisions related to (i) determination and assessment of risks, (ii) measures aimed at avoiding or reducing exposure, (iii) information, training, consultation and participation of workers, (iv) health surveillance of the exposed workers, and (v) derogations and transitional periods for the implementation of the obligations of employers when the daily exposure limit values are exceeded. The author discusses the strong link which exists between the assessment of risk due to vibration exposure at the workplace and the health surveillance of the exposed workers. The occupational health physician, as a specialist with expertise in human factors and in the early detection of vibration-related adverse health effects, will have an important role in the assessment of risks arising from mechanical vibration in order to implement an effective health surveillance of the exposed workers. The Member States must bring into force the requirements of the Directive no later than 6 July 2005.

Europe↗

PubMed2003

Encoding of whisker vibration by rat barrel cortex neurons: implications for texture discrimination.

Rats, using their whiskers, have excellent capabilities in texture discrimination. What is the representation of texture in rat somatosensory cortex? We hypothesize that as rats "whisk" over a surface, the spatial frequency of a grooved or pebbled texture is converted to a temporal frequency of whisker vibration. Surface features such as groove depth or grain size modulate the amplitude of this vibration. Validation of the hypothesis depends on showing that vibration parameters have distinct neuronal representations in cortex. To test this, we delivered sinusoidal vibrations to the whisker shaft and analyzed cortical neuronal activity. Seven amplitudes and seven frequencies were combined to construct 49 stimuli while recording activity through a 10 x 10 microelectrode array inserted into the middle layers of barrel cortex. We find that cortical neurons do not explicitly encode vibration frequency (f) or amplitude (A) by any coding measure (average spike counts over different time windows, spike timing patterns in the peristimulus time histograms or in autocorrelograms). Instead, neurons explicitly encode the product of frequency and amplitude, which is proportional to the mean speed of the vibration. The quantity Af is an invariant because neuronal response encodes this feature independently of the values of the individual terms A and f. This was true across a wide time scale of firing rate measurements, from 5 to 500 msec. We conclude that vibration kinetics are rapidly and reliably encoded in the firing rate of cortical ensembles. Therefore, the cortical representation of vibration speed could underlie texture discrimination.

Action Potentials↗

PubMed2006

Seat vibration in military propeller aircraft: characterization, exposure assessment, and mitigation.

INTRODUCTION: There have been increasing reports of annoyance, fatigue, and even neck and back pain during prolonged operation of military propeller aircraft, where persistent multi-axis vibration occurs at higher frequencies beyond human whole-body resonance. This paper characterizes and assesses the higher frequency vibration transmitted to the occupants onboard these aircraft. METHODS: Multi-axis accelerations were measured at the occupied seating surfaces onboard the WC/C-130J, C-130H3, and E-2C Hawkeye. The effects of the vibration were assessed in accordance with current international guidelines (ISO 2631-1:1997). The relative psychophysical effects of the frequency components and the effects of selected mitigation strategies were also investigated. RESULTS: The accelerations associated with the blade passage frequency measured on the passenger seat pans located on the side of the fuselage near the propeller plane of the C-130J (102 Hz) and C-130H3 (68 Hz) were noteworthy (5.19 +/- 1.72 ms(-2) rms and 7.65 +/- 0.71 ms(-2) rms, respectively, in the lateral direction of the aircraft). The psychophysical results indicated that the higher frequency component would dominate the side passengers' perception of the vibration. Balancing the props significantly reduced the lower frequency propeller rotation vibration (17 Hz), but had little effect on the blade passage frequency vibration. CONCLUSIONS: The relationships among the frequency, vibration direction, and seat measurement sites were complex, challenging the development of seating systems and mitigation strategies. Psychophysical metrics could provide a tool for optimizing mitigation strategies, but the current international vibration standard may not provide optimum assessment methods for evaluating higher frequency operational exposures.

Acceleration↗

PubMedDate not supplied

[The role of the occupational health physician in the implementation of the European and Italian regulations on mechanical vibration at work].

The European Directive 2002/44/EC and the Italian Decree 187/2005 establish the minimum health and safety requirements regarding the exposure of workers to the risks arising from mechanical vibration. Excessive exposure to hand-arm vibration from powered processes or tools can cause disorders in the vascular, neurological and musculoskeletal systems of the upper limbs. Long-term occupational exposure to intense whole-body vibration is associated with an increased risk for disorders of the lumbar spine and the connected nervous system. The prevention of injuries or disorders caused by mechanical vibration at the workplace requires the implementation of administrative, technical and medical procedures. The role of the occupational health physician in the implementation of the health surveillance of vibration-exposed workers is discussed in the light of the requirements established by the European and Italian regulations. The health surveillance of vibration-exposed workers consists of pre-employment medical screening and subsequent clinical examinations at regular intervals. The aims of health surveillance are to make the worker aware of the hazards connected with exposure to mechanical vibration, to obtain baseline health data for comparison with the findings of subsequent periodical health examinations, to verify the presence of pathological conditions which may increase the risk of adverse health effects due to vibration exposure, to make a diagnosis of occupational or work-related disease, and to check the long-term effectiveness of preventive measures.

Europe↗

PubMedDate not supplied

Vibration effects on fatty acid composition of organ and cell membrane lipids.

The influence of middle and high frequency vibrations (50 and 150 Hz) on the fatty acid pattern of structural lipids in white rat liver, kidney, heart, aorta and muscular tissue was studied in a 3-month experiment. The study also examined the fatty acid composition of phospholipids in erythrocyte cell membranes of workers occupationally exposed to vibrations and of patients suffering from vibration disease. Statistically significant changes in the per cent distribution of fatty acids were observed, which were more evident in the liver and kidney of experimental animals, and also after high frequency (150 Hz) vibration exposure. Changes in human subjects were greater in workers exposed to hand-arm vibrations and in patients suffering from vibration disease. Routine and more precise methods are needed to assess occupational risk via determination of the lipid metabolism state in workers exposed to vibrations and in patients suffering from vibration disease.

Adult↗

PubMed1991

The interaction of hand vibration with oculomanual coordination in pursuit tracking.

The effects of high frequency hand vibration (150 Hz) on simultaneous ocular and manual tracking performances were investigated in trained human subjects. First, a zero-order pursuit tracking task was performed with and without direct visual control of the hand. Second, eye tracking of an imaginary target linked to the hand was also performed. The results show that hand vibration significantly alters eye and hand tracking performances when the hand is out of sight. However, when the hand is placed in the visual field, tracking performances are less affected by vibration. Visual cues on limb segments may compensate to some extent for the vibration-induced alteration of proprioceptive information otherwise used to control movements. Eye movements are altered during vibration while the subject is tracking or fixating an imaginary target attached to the hand. These findings explicitly show that hand vibration can perturb oculo-manual coordination control. The present results imply that vibration-induced activity of somesthetic mechanoreceptors is likely to contribute to oculomanual coordination alteration and tracking decrement in vibratory environments. Furthermore, direct visual control of the hand and/or arm may be of particular interest in manipulation tasks executed under vibration.

Adult↗

PubMed1990

[The assessment of the vibration load in tractor drivers].

The assessment of the vibration loading of a group of tractor-drivers from the enterprise for melioration and erosion control is made on the basis of: measurement of general and local vibrations and noise of 5 tractors type C 100, C 100M and T 130; determination of the total vibration loading on the basis of data of measurements and average weekly hour individual engagement; comparison of the admissible values of vibration loading with the real determined at work with machines of different vibration characters at different hour engagement. A surpass of the admissible vibration loading is established which reaches up to 3.3 (at average weekly exposure to 30 hrs.) and to 4.7 hrs (at average weekly exposure 42.5 hrs.) with the tractors with higher surpass of MAC for the general vibrations. An admissible exposure for 1 day and for 1 year work for the separate tractors is determined in relation to the data for general and local vibrations and individual hour engagement.

Agriculture↗

PubMed1989

[The impulse activity of the motor units of the human soleus muscle in the tonic vibration reflex].

The tonic vibration reflex was evoked in the human soleus muscle, the range of vibration frequencies was 30-180 Hz. The potentials of single motor units (MUs) were picked up. At low frequencies (to 70-80 Hz) the potentials of all MUs under study correlated with vibration stimuli. This showed the existence of ripples in the excitatory inflow to motoneurons. With an increase of the vibration frequency the correlation disappeared. In the voluntarily contracted muscle the correlation was revealed at higher vibration frequencies than in the relaxed muscle. Since the vibration is known to depress monosynaptic reflexes from primary spindle endings, it is suggested that the correlation of motoneuron discharges and vibration stimuli at low vibration frequency is, apparently, a result of the activation of secondary spindle endings which via short synaptic pathways evoked discrete EPSPs in motoneurons.

Action Potentials↗

PubMed1979

[Dynamics of changes in vibration sensitivity in syringomyelia].

The state of vibrational sensibility was studied in 35 patients with syringomyelia, with the aid of a special device, which evoked in the tuning fork a vibration of the same amplitude (128) in repeated studies. The indices of vibrational sensibility in patients with syringomyelia were compared to normal figures. As a norm the author employed the medium indices of vibrational sensibility in seconds in 50 normals. According to the vibrational sensibility all the patients were divided into 4 groups. The absence of vibrational perception, its drop below the norm and appearance of hyperpallesthesia corresponded to the most severe forms of the disease. In a drop of temporal indices, but not lower than the norm, the side, where the pathological process was more marked under the treatment influence, showed a restituted vibrational feeling. Disordered vibrational sensibility was found not only to the level of affected segments, but beyond them, which supports the conductive character of these disturbances.

Adult↗