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PubMed1995

Operating vibrating tools and prevalence of subjective complaints in vibration syndrome.

The aim of this paper is to evaluate the prevalence of subjective symptoms and signs related to vibration syndrome in various groups of subjects exposed to hand-arm vibration (HAV). In 9 groups of subjects occupationally exposed to HAV, one group of subjects previously exposed to HAV, one control group, and 2 groups of general population (males and females), the prevalence of finger blanching, numbness in the hands, stiffness in the hands, and pain in the hands were investigated. The age of subjects ranged from 25 to 59 years. In subjects exposed to HAV, hand-transmitted vibration levels (HTVLs) were measured by means of vibration dosimeters, and the frequency-weighted acceleration levels [(Lh,w)eq,t] were determined as the vibration levels. The prevalence of vibration-induced white finger (VWF) in the exposed subjects was in the range of 0.0-9.6%, and that in subjects who were previously exposed to HAV was 4.1%. The prevalence rates of finger blanching in males and females of the general population were 2.7 and 3.4%, respectively. The highest prevalence rate of VWF was observed among subjects exposed to HTVLs of 2.7-5.1 m/s2. The prevalence of numbness of the hands fluctuated among the groups; i.e., in the exposed groups: in the range of 6.5-30.4%; in those previously exposed to HAV: 16.4%; and was 13.4% in males and 29.5% in females of the general population. The prevalence rates of stiffness in the hands were in the range of 7.6-65.2% in the exposed workers, 13.7% in those previously exposed to HAV, and was 5.5% in males and 20.9% in females of the general population. The prevalence of pain in the hands was between 7.4 and 17.4% in the exposed groups, 1.4% in those who stopped exposure to vibration, and 1.2% in subjects without segmental vibration exposure. Among the subjective symptoms, only VWF showed a significant positive correlation with the measured vibration acceleration; Y = -0.9 + 1.9 X, r = 0.8, P = 0.01. It was concluded that VWF is the most appropriate signs in decisions concerning quantitative recommendations for segmental vibration exposure.

Adult↗
PubMed1990

Physical characteristics of vibration in relation to vibration-induced white finger.

Predicted and observed prevalences and latency periods of vibration-induced white finger (VWF) were examined among workers exposed to hand-arm vibration. The different physical characteristics of vibration--spectra and impulsiveness--were measured. The following groups of workers were included in the study: forest workers (n = 199), pedestal grinders (n = 12), stone workers (n = 16), shipyard workers (n = 171), and platers (n = 5). The exposure to vibration was measured according to the ISO 5349 method. The impulsiveness of vibration was defined as the difference between peak levels and RMS levels. A good agreement was observed between the predicted and observed data for prevalence and latency of VWF in the forest workers. For the tools with high impulsiveness used in grinding, stone works, and shipyard assembly hall, the results were nonconfirmative; and there was a poor correlation between vibration and VWF. The ISO 5349 standard does not consider the high peak values of the vibration signal which may comprise high-frequency components and cause short transients in the underlying tissue of the worker's hand. These characteristics in vibration may be hazardous in the genesis of VWF and cannot be predicted when measuring vibration by the present standard method.

Cross-Sectional Studies↗
PubMed1995

Dose-response relation between exposure to two types of hand-arm vibration and sensorineural perception of vibration.

OBJECTIVES: 31 railway workers and 32 lumberjacks were examined to compare the dose-response relation between the exposure to two types of hand-arm vibration and the sensory disturbances in peripheral nerves as evaluated by the vibration perception thresholds (VPTs). METHODS: Clinical examinations were carried out that included measurements of the VPTs, and electroneuromyography (ENMG), and an inquiry to confirm the use of vibrating tools. Diseases of the central nervous system and neuropathies were checked by inquiry and a clinical examination, diabetes was excluded by a blood sample analysis, and the subjects with carpal tunnel syndrome confirmed with ENMG were excluded from the study. RESULTS: Lifetime use of hand held tamping machines (railway workers) and chain saws (lumberjacks) had a significant correlation with the VPTs at frequencies from 32 to 500 Hz. The increase of the VPTs (250 Hz) in relation to use of vibrating tools was 1.8-fold higher on average in the whole group and 2.3-fold higher in the young (< 45) railway workers who had used hand held tamping machines, than in the corresponding groups of lumberjacks, who had used chain saws, whereas the frequency weighted acceleration of vibration in tamping machines was fourfold. CONCLUSION: There was a significant dose-response relation between the exposure to hand-arm vibration and the VPTs. The VPTs as a function of the frequency weighted acceleration of vibration and the exposure to vibration gave promising results for assessment of the risk of damage to sensory nerves induced by vibration.

Adult↗
PubMed1975

Vertical vibration of seated subjects: effects of posture, vibration level, and frequency.

The transmissibility of 12 seated subjects to sinusoidal vertical vibration was measured at 12 frequencies in the range of 7 to 75 Hz. Transmissibility, the ratio of seat vibration to vertical head vibration measured on a bite-bar, was determined at each of six levels of vibration (0.2 to 4.0 m/s2 r.m.s.) in two body postures. The postures were defined by the body positions that maximised and minimised the sensation of vibration at the subjects' heads. Measurements of the fore-and-aft (ax), lateral (ay), and pitch motions of the head were measured on three subgroups. Posture was found to have a very large effect on the vibration of the head with an approximate 6:1 difference in the mean vertical head vibration of the subjects between the two postures in the range 35 to 50 Hz. In both postures the mean transmissibility of the subjects decreased as frequency increased from 7 to 75 Hz and there were statistically significant reductions in transmissibility with increasing levels of vibration. Some results from individuals are presented to illustrate the large differences between subjects. The reactions of the subjects to the vibration are outlined and some implications of the results are discussed.

Adult↗
PubMed1996

Comparison of different methods for vibration measurements on hand-held vibrating tools.

Vibration measurements have been done on hand-held tools in a group of 48 platers by evaluating the individual vibration acceleration and absorption of vibration energy. The measurement of acceleration has been done frequency-weighted and frequency-unweighted in accordance with ISO 5349 and NIOSH (USA) recommendations for hand-arm vibration standards, respectively. The acceleration and the energy absorption have been measured simultaneously in the three orthogonal directions, the latter by using a specially designed adapter. The exposure time has been determined by both subjective rating and objective measurements. Individual energy-equivalent accelerations and vibration dosages have been calculated from these data. The outcome shows that the type of tool was critical to vibration load when the different measures for determining vibration levels were used. Of the methods used, the evaluation specified by ISO 5349 makes most consideration of low frequencies of vibration (< 50 Hz), absorption of vibration energy middle frequencies (50-200 Hz) and NIOSH of high frequencies (> 200 Hz). The results show a poor correlation between the three methods used. Close agreement between mean subjective rating and objective measurement of the average exposure time was found. Further studies of the relation between results presented here and generated disturbance will be conducted, which may clarify any exposure-response relationship.

Acceleration↗
PubMed1990

Measuring method for vibration perception threshold of fingers and its application to vibration exposed workers.

A measuring method for the vibration perception threshold (VPT) of fingers has been developed. The VPTs of 118 and 149 professional forest workers were measured during a compulsory annual health examination in 1979 and 1983, respectively. Also the VPTs of eight pedestal grinders, who were suffering vibration-induced white finger (VWF), were measured in 1979 and 1983. The control group consisted of 20 research workers who had no vibration exposure in the past and no symptoms in their hands. The measuring system for VPT gave repeatable results. The frequency of the most sensitive VPT of vibration exposed workers alternated between 63 and 125 Hz instead of 125 Hz of subjects without vibration exposure. The VPT of the pedestal grinders and forest workers with decreased hand grip force and with vibration-induced white finger were significantly higher than those of the controls. The VPTs of the forest workers decreased slightly and that of the grinders increased from 1979 to 1983. In spite of long vibration exposure in the past and continuing lower level vibration exposure, the increased VPT of forest workers does not seem to be permanent.

Adult↗
PubMed1992

Vibration perception thresholds in workers exposed to vibration.

The vibration perception thresholds (VPT) at six frequencies from 16 to 500 Hz were examined in 77 workers exposed to hand-arm vibration and in 77 controls using a limits procedure. A dose-response relationship between VPTs and exposure to vibration was found, and the age-adjusted VPTs at each frequency were higher in workers exposed to vibration than in controls. Carpal tunnel syndrome (at 250 Hz) and consumption of alcohol (at 125 Hz) significantly increased the VPT, but vibration-induced white finger was not correlated with VPT. Indices for low (16 and 32 Hz) and high (63-500 Hz) VPT frequencies were calculated to evaluate the entire vibrogram, which consisted of several frequencies with two numbers. The results showed that hand-arm vibration disturbs first the high frequencies, and that the disturbance spreads thereafter to the low frequencies. The characteristics of the VPT test regarding vibration exposure and the association between VPT and nerve symptoms in the hand support the view that VPT is a useful measure for vibration-induced sensory nerve damage.

Arm↗
PubMed1999

The effect of tennis racket string vibration dampers on racket handle vibrations and discomfort following impacts.

In this study, we evaluated the effect of the use of tennis racket string vibration dampers on racket handle vibrations, and perceptions of hand and arm discomfort experienced by tennis players owing to stationary racket impacts. Twenty tennis players (10 males, 10 females) aged 18-29 years volunteered for the study. Two different racket models were impacted at the geometric centre of the racket face and 100 mm distal to the centre both with and without string vibration dampers in place. The participants could neither see nor hear the impacts, and they indicated their discomfort immediately after each impact using a visual analogue scale. An analysis of variance (2 x 2 x 2 factorial) was performed on the scaled discomfort ratings with the factors damping condition, racket type and impact location. No significant differences in discomfort ratings between damped and undamped impacts or between the two racket types were found. Also, central impacts were found to be more comfortable than impacts 100 mm distal to the centre (P< 0.05). There were no significant interaction effects. Vibration traces from an accelerometer mounted on the racket handle revealed that string vibration dampers quickly absorbed high-frequency string vibration without attenuating the lower-frequency frame vibration. In conclusion, we found no evidence to support the contention that string vibration dampers reduce hand and arm impact discomfort.

Adolescent↗
PubMed1978

Mechanism of the vibration paradox: excitatory and inhibitory effects of tendon vibration on single soleus muscle motor units in man.

1. The parameters of presynaptic inhibition of the Ia spindle afferents from soleus muscle by vibration have been investigated. The inhibitory effects increase with the amplitude of vibration, but decrease when the vibration frequency is increased.2. The monosynaptic reflex threshold of twenty-one single soleus motor units activated in the H (Hoffmann) reflex by a single electrical stimulus to the posterior tibial nerve was estimated quantitatively and expressed in relation to the size of the simultaneously recorded H reflex.3. A parametric study of the effects of various Achilles tendon vibrations on the reflex threshold of the single soleus motor units indicated that their order of derecruitment is concordant with their rank order for activation in the phasic reflexes of the soleus. The last recruited motoneurones are the most susceptible to being silenced by steady vibration.4. Muscle vibration progressively recruits single motor units according to the motoneurone size principle through polysynaptic proprioceptive pathways. However the presynaptic inhibition of Ia spindle afferents simultaneously induced by the vibration works in reverse on the same rank order of motoneurones of the soleus spinal pool, thereby limiting the polysynaptic recruitment of units in the tonic vibration reflex while depressing the autogenic phasic proprioceptive reflexes. These mechanisms elucidate the so-called vibration paradox and extend the size principle of Henneman to presynaptic inhibitory effects.

Achilles Tendon↗
PubMed1986

Temperature and vibration thresholds in vibration syndrome.

In a study to investigate whether the quantitative assessment of temperature and vibration thresholds can improve the evaluation of the neurological symptoms in vibration syndrome 37 patients with neurological symptoms (paraesthesias, numbness, pain) in the hands who had worked with hand held vibrating tools and 46 healthy controls not exposed to vibration were examined. Temperature thresholds were measured on the thenar eminence and on the volar side of the second and third fingers held together. Vibration thresholds were determined on the dorsum of the hand and on the dorsal side of the second and fifth fingers proximal to the nail. The neutral zone between thresholds for warmth and cold was much wider in the patients than in the controls. Patients older than 45 had higher vibration thresholds than controls. Electroneurography was abnormal in 18 of 34 patients and a carpal tunnel syndrome was diagnosed in six subjects. This investigation is thus indicated in patients with neurological symptoms. Seven of the patients with normal electroneurographic findings had impaired temperature or vibration thresholds or both. Determination of sensory thresholds seems to add valuable information and the methods are, by contrast with electroneurography, easily adapted to the screening of exposed groups outside hospital. Our results indicate that thin myelinated and unmyelinated nerve fibres might be damaged in the vibration syndrome.

Adult↗
PubMed1986

Impulsiveness of vibration as an additional factor in the hazards associated with hand-arm vibration.

Impulsiveness is defined as the difference between peak and root-mean-square signals. As the difference varies in time, the cumulative distribution function has been used to describe the probability of achieving a certain value of impulsiveness. To make numerical comparison of different vibration signals possible, an impulse index has been selected from the cumulative distribution function. Symptoms of vibration-induced white finger were observed and compared to those expected on the basis of measurements taken according to guidelines of the International Organization for Standardization (ISO). Agreement was found for chain-saw vibration. In the case of pedestal grinding, the ISO draft underestimated the hazardous effects of vibration. Stone workers using pneumatic hammers were exposed to highly impulsive but asymmetrical vibration. The corresponding asymmetry was not, however, observed between the symptoms of the left and right hands, a finding which indicates that coupling between the tool and the hand is important for impulse vibration. The results suggest that the impulse character of vibration increases the risk of vibration-induced pathology. The analysis of high-impulse acceleration peaks obtained by the method presented in this study could provide additional data necessary to improve risk assessment.

Fingers↗
PubMed1998

Vibration-induced white finger and cold response of digital arterial vessels in occupational groups with various patterns of exposure to hand-transmitted vibration.

OBJECTIVE: This study investigated the relation between vibration exposure, the prevalence of white fingers, and the cold response of digital arterial vessels in workers using vibrating tools. METHODS: The change in finger systolic blood pressure (FSBP) at 15 and 10 degrees C as the percentage of the pressure at 30 degrees C (FSBP%) was measured in 455 healthy referents and 822 workers exposed to hand-transmitted vibration. Exposure to hand-transmitted vibration was assessed in terms of 8-hour energy-equivalent frequency-weighted acceleration [A(8)] and total operating time with vibrating tools. RESULTS: The prevalence of white fingers was 1.1% for the referents and ranged from 9.0% to 51.6% for the vibration-exposed groups. The estimated mean value of A(8) ranged between 1.6 (referents) and 8.3 (quarry drillers) m/s2. After adjustment for age, smoking, and drinking habits, the FSBP% was significantly lower in the vibration-exposed groups than in the reference group. Groupwise, the FSBP%(10 degrees) was inversely related to the prevalence of white fingers, the estimated A(8), and total operating time. With FSBP%(10 degrees) <70% or <60% as the lower normal limit, the sensitivity of the cold test varied from 86% to 100%, with a specificity of 90% to 94%, and a positive predictive value of 68% to 74%. CONCLUSIONS: FSBP measurement during cold provocation is a useful laboratory test for white fingers. A quantitative relationship between cold-induced digital arterial hyperresponsiveness and occupational exposure to hand-transmitted vibration was suggested.

Adult↗
PubMed1986

Subjective effects of combined-axis vibration: III. Comparison of Y-axis and Y-plus-yaw vibrations.

Two psychophysical matching experiments (Exps. III and IV in a series) were conducted to compare the perceived intensity of Y-axis and Y-plus-yaw vibrations. Seated subjects matched their perceptions of the intensity of single-axis vibrations in the Y-axis, or combined-axis vibrations made up of Y-axis and yaw motions, by adjusting the intensity of a sinusoidal, 5 Hz, Z-axis response vibration. Stimulus vibrations were sinusoidal at 3.15, 4, 5, 6.3, and 8 Hz. For each frequency, both types of stimulus vibrations were presented at three acceleration levels related to three axis-to-seat distances for the yaw motions. In Exp. III the subjects were seated forward of the rotation axis, and in Exp. IV they were seated aft of the axis. For both experiments the results showed that as frequency increased the acceleration of the matching response decreased for both types of stimuli. In addition, as stimulus acceleration (axis-to-seat distance) increased, response acceleration showed substantial increases at every frequency. However, the effects of vibration type were dependent on the location of the subject. In Exp. III the combined-axis stimuli produced higher response accelerations, but in Exp. IV matching responses were the same for both vibration types.

Acceleration↗
PubMed1985

Subjective effects of combined-axis vibration: II. Comparison of X-axis and X-plus-pitch vibrations.

Seated subjects matched their perceptions of the intensity of single-axis vibrations in the X axis, or combined-axis vibrations made up of X-axis and pitch motions, by adjusting the intensity of a sinusoidal, 5 Hz, Z-axis response vibration. Stimulus vibrations were sinusoidal at 3.15, 4, 5, 6.3 and 8 Hz. For each frequency, both types of vibration were presented at three acceleration levels related to three axis-to-seat distances for the pitch vibrations. Results showed that Z-axis response accelerations were essentially constant across frequency. However, matching responses were significantly higher for X-plus-pitch than for X-axis vibrations. These findings are in contrast to those of a previous experiment involving Y-axis and roll vibrations, and are probably due to additional input from the seat back for X and pitch motions. The two experiments do agree on the importance of the distance of the subject from the axis of rotation for angular motions. In both experiments, as stimulus acceleration (axis-to-seat distance) increased, response acceleration increased substantially at every frequency.

Acceleration↗
PubMed1978

[Spectrum character of vibration and clinical form of vibration disease].

300 workers of metalurgical plant exposed to vibrations were divided according to the chief work tool into the three groups: 1) moulder, 2) mould cleaner and 3) ironworker--grinder. The velocity of vibration was measured and the spectrum of vibrations examined. The product of vibration velocity excesses was evaluated within the following three bands of frequency: 16--63 Hz, 125--250 Hz, 500--2000 Hz and the frequency of occurrence of the two main forms of vibration disease, i.e. angioneurosis and osteoarthrosis was calculated. The osteoarthretic form of vibration disease was significantly more frequent when the multiplicity of surpassing the velocity of vibration occurred with low frequencies (moulders), and angioneurotic form was more frequent at high and very high frequencies. It seems, that "the safe limit" of vibration frequency should be transferred to frequencies higher than 500 Hz.

Angioedema↗
PubMed1998

Efficacy of vibration, electric current and thermal perception tests in diagnosis of hand-arm vibration syndrome.

Vibration perception test is usually proposed as a useful tool for quantitative assessment of neurological disturbances induced by hand-arm vibration syndrome (HAVS). The increased mean vibration perception threshold (VPT) is an early manifestation of this syndrome. However, we have identified a group of exposed subjects with normal VPT who showed electric current and/or thermal sensitivity impairment. The use of three tests instead of a single vibration test increased by 27% the number of persons with detected quantitative skin sensory disorders. The intensity of quantitative disorders of vibration and electric current sensitivity was closely related to the duration of vibration exposure. The thermal perception was diminished in subjects working for a longer period of time, but there was no relationship between intensity of disorders and the duration of exposure. In an early stage of hand-arm vibration syndrome (prevention of HAVS) the use of three tests helps to identify a larger number of workers at risk who should undergo thorough diagnostic examinations. In our study the proportion of identified workers increased from 27% (32 subjects with vibration sensory impairment) to 45% (53 persons with disorders detected in one, two or even three tests).

Adult↗