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PubMed2001

Scleroderma and occupational exposure to hand-transmitted vibration.

OBJECTIVES: To determine whether occupational exposure to hand-transmitted vibration is a risk factor for scleroderma (systemic sclerosis, SSc), two case-control studies were conducted in the provinces of Trento and Verona, northeastern Italy. METHODS: In the Trento study, 21 patients with a diagnosis of either systemic or localised scleroderma were recruited from those admitted to all hospitals of the province from 1 January 1976 to 31 December 1991. For each case, two age- and gender-matched controls were selected. In the Verona study, cases included 55 patients diagnosed with SSc and clinically followed at the rheumatology clinic of the local university hospital between 1 January 1997 and 30 June 1999. The controls included 171 subjects frequency-matched by gender and age group. In both studies, all subjects were interviewed by structured questionnaire containing items on personal characteristics, smoking and drinking habits, use of medicines, occupational history and complete medical history. Women were also investigated about silicone implants and cosmetic surgery. Jobs and job tasks involving the use of vibratory tools, with or without concomitant exposure to silica dust in mining and non-mining occupations, were carefully investigated. A minimum criterion of 6 months was required for exposure duration. RESULTS: In the Trento study, men with scleroderma were more likely than controls to have had exposure to hand-transmitted vibration (odds ratio (OR) 1.5, 95% confidence interval (95% CI) 0.1-74.1) or silica dust (OR 5.2, 95% Cl 0.5-74.1), but the association was not significant. The scleroderma patients were miners or stone workers who had operated jackhammers and rock drills. In the Verona study, a greater, although not statistically significant, odds of SSc was observed in men exposed to hand-transmitted vibration (OR 2.4, 95% CI 0.4-14.0) and in women exposed to silica (OR 2.4, 95% Cl 0.4-15.5). The SSc patients with vibration exposure were machinery operators or metal workers who had used grinders and impact wrenches. CONCLUSIONS: Our case-control studies did not show a significant association between scleroderma and hand-transmitted vibration, with or without concomitant exposure to silica dust. Owing to the rarity of the disease and the small number of cases in the present studies, a genetic susceptibility to connective tissue disorders in SSc patients with occupational exposure to hand-transmitted vibration and/or silica cannot be ruled out.

Case-Control Studies↗

PubMed2002

Finger systolic blood pressure indices for the diagnosis of vibration-induced white finger.

OBJECTIVES: To compare the accuracy of several finger systolic blood pressure indices (FSBPIs) for the diagnosis of cold-induced Raynaud's phenomenon in vibration-exposed worker groups with different prevalences of vibration-induced white finger (VWF). METHODS: The finger systolic blood pressure (FSBP) in a test finger at 10 degrees C as a percentage of the pressure at 30 degrees C, corrected for the change in systolic blood pressure in a reference finger [FSBPI(A)] or the arm [FSBPI(B)], was measured in 455 healthy controls and 874 workers exposed to hand-transmitted vibration (HTV). The following FSBPIs were also calculated: FSBPI(C), as the ratio between FSBP in the test finger at 10 degrees C and FSBP in the same finger at 30 degrees C; and FSBPI(D), as the ratio of FSBP to arm systolic blood pressure during finger cooling to 10 degrees C. The finding of zero systolic blood pressure, FSBP(0), in the cooled finger was taken as an objective sign of Raynaud's attack with complete closure of the digital arteries. RESULTS: On a group basis, all FSBPIs could discriminate between the controls and the HTV workers. In the vibration-exposed worker population, the FSBPIs were significantly lower in the subjects affected with VWF than in those without vasospastic symptoms. The lower normal limits of FSBPIs were derived from the results of the cold test in the controls and were found to vary from 50% to 60%. The FSBPI(A) showed the best sensitivity for the detection of cold-induced digital arterial hyper-responsiveness in both the total sample of HTV workers (sensitivity 87%) and most of the vibration-exposed groups with different prevalence of VWF (sensitivity from 79% to 100%). The results of the receiver operating characteristic analysis suggested a higher diagnostic accuracy of FSBPI(A) when compared with the global performance of the other FSBPIs. In the whole sample of HTV workers, the predictive value of a positive cold test varied from 73% [FSBPI(D)] to 89% [FSBP(0)] and that of a negative test ranged between 89% [FSBP(0)] and 97% [FSBPI(A)]. CONCLUSIONS: The findings of this investigation and clinical experience suggest that a discriminating threshold of FSBPI(A) <60% during finger cooling to 10 degrees C is an appropriate diagnostic criterion for the detection of abnormal cold response in the digital arteries of most vibration-exposed workers with a true history of symptoms of finger whiteness at the medical interview.

Adult↗

PubMed2002

National regulations for diagnostics in health surveillance, therapy and compensation of hand-transmitted vibration injury in Japan.

OBJECTIVES: During the period of technological innovation and rapid economic development, portable power tools were introduced on a large scale in Japan. Vibration disease from the operation of those tools and its prevention and therapy became urgent social problems in the 1970s. This paper aims to introduce national regulations in Japan for diagnostics in the health surveillance, certification, therapy and compensation of vibration disease and evaluates them in the present perspective. METHOD: Relevant laws, regulations and administrative directives were described in chronological order. Effect of those laws, regulations and directives were evaluated by statistics. RESULTS: Relevant regulations were established in 1947 and were revised in the 1960s and 1970s. According to those regulations, administrative directives were issued. Relevant vibration-disease statistics improved from the 1970s to 1990s. The annual ratio of workers examined was 95% to 100% in national forests (NFs), 47.3% in 1980 and 40.8% in 1990 in private industry (PI). The number of workers certified in NFs was 1,796 from 1971-1975, with a decrease to nine from 1991-1995, while in PI there were 9,783 from 1976-1980, decreasing to 2,331 from 1991-1995. However, in the construction industry the number increased again in the 1990s. The top four workers certified by the type of tool from 1994-1997 were operators of rock drills, chainsaws, pick hammers and concrete vibrators. The annual number of workers under treatment (at highest level) was 3,605 (1982; NFs) and 13,501 (1987; PI), with a decrease to 3,481 (1997; NFs) and 8,958 (1997; PI). Regulations for compensation covered 3,670 workers from 1965 to 1997 (NFs) and 22,723 from 1976 to 1997 (PI) in medical treatment benefits, and 189 (NFs) and 15,448 (PI) in disability benefits during the same term. CONCLUSION: The national regulations developed in Japan since 1965 for health surveillance, certification, therapy and compensation of hand-transmitted vibration disease have proven effective for prevention and compensation of vibration disease in many industries, but unsolved problems remain in the construction industry.

Hand↗

PubMed2002

Prolonged muscle vibration reduces maximal voluntary knee extension performance in both the ipsilateral and the contralateral limb in man.

Previous studies have shown that prolonged vibration of the rectus femoris decreases maximal voluntary knee extension performance in the ipsilateral leg. In the present study, measurements of maximal voluntary isometric knee extension contractions with the ipsilateral (right) leg and the contralateral (left) leg were made immediately before and after vibration treatment. Significant reductions in maximal force and maximum rate of force generation occurred in both the ipsilateral and contralateral legs following 30 minutes of continuous vibration at both 30 Hz and 120 Hz, with 30 Hz causing the greatest ipsilateral effects. However, although the level of neural activation (iEMG) of the vibrated muscle (right rectus femoris) was reduced following 30 Hz vibration ( P=0.026), there were no significant changes occurring in a synergistic muscle (right vastus lateralis) or in either contralateral muscle. It was concluded that muscle vibration may act through spinal reflex pathways to influence the homonymous motoneuron pool. The effects on contralateral force but not specific muscle iEMG suggest an effect on heteronymous motoneuron pools or an effect acting on central descending drive to contralateral muscles. These findings may have implications for the rehabilitation of patients with an immobilised limb.

Adult↗

PubMed2003

Blood flow in the tibialis anterior muscle by photoplethysmography during foot-transmitted vibration.

Photoplethysmography (PPG) was used to detect changes in the anterior tibial muscle blood flow (MBF) during foot-transmitted vibration in six healthy subjects. A filter was developed for reducing the vibration-induced artefacts in the PPG signal. The vibration applied was random with constant acceleration power density in the range 5-2000 Hz with an acceleration of 16-46 m s(-2) (rms). The application of the filter technique showed a dramatic reduction in the vibration-induced artefacts and distortion of the PPG signal was negligible. The mean ratio and correlation coefficient of MBF originating from filtered and non-filtered PPG signals was [mean (SD)] 0.89 (0.04) and 0.99, respectively. This made it possible to detect a relative increase in MBF of 20% during an acute vibration exposure. The results suggest that the use of the filter enables MBF to be measured by PPG during vibration, thus extending the range of applications of the PPG technique to include ergonomic conditions.

Adult↗

PubMed1999

Influence of vibration on mechanical power and electromyogram activity in human arm flexor muscles.

The aim of this study was to evaluate the influence of vibration on the mechanical properties of arm flexors. A group of 12 international level boxers, all members of the Italian national team, voluntarily participated in the experiment: all were engaged in regular boxing training. At the beginning of the study they were tested whilst performing forearm flexion with an extra load equal to 5% of the subjects' body mass. Following this. one arm was given the experimental treatment (E; mechanical vibration) and the other was the control (no treatment). The E treatment consisted of five repetitions lasting 1-min each of mechanical vibration applied during arm flexion in isometric conditions with 1 min rest between them. Further tests were performed 5 min immediately after the treatment on both limbs. The results showed statistically significant enhancement of the average power in the arm treated with vibrations. The root mean square electromyogram (EMGrms) had not changed following the treatment but, when divided by mechanical power, (P) as an index of neural efficiency, it showed statistically significant increases. It was concluded that mechanical vibrations enhanced muscle P and decreased the related EMG/P relationship in elite athletes. Moreover, the analysis of EMGrms recorded before the treatment and during the treatment itself showed an enormous increase in neural activity during vibration up to more than twice the baseline values. This would indicate that this type of treatment is able to stimulate the neuromuscular system more than other treatments used to improve neuromuscular properties.

Adult↗

PubMed2004

Identification of the head-neck complex in response to trunk horizontal vibration.

A method is proposed for identifying the head-neck complex (HNC) in the seated human body when it is exposed to the trunk horizontal (fore-and-aft) vibration. It is assumed that the HNC only has the anteroposterior (flexion/extension) motion in the sagittal plane. An electrohydraulic vibrator is used as a source of vibration. To generate the trunk horizontal vibration, the trunk of the seated subject is fixed to the seatback. The subjects are exposed to the random vibration at a magnitude of 1.60 ms(-2) rms (root-mean-square) for 50 s. The coherence and frequency response function are then obtained in the frequency range 0.5-3 Hz. The results show that the HNC behavior is quasilinear with a resonance frequency between 1 and 1.4 Hz. Accordingly, a two-dimensional single-inverted pendulum is considered as a model for the HNC. The frequency domain identification method is then used to estimate the unknown parameters, including the HNC viscoelastic and inertia parameters. The model is examined in a time domain using the random vibration. Good agreement is obtained between experimental and simulation results, indicating the reliability of the proposed method.

Acceleration↗

PubMed1997

The effect of applied mechanical vibration on two different phases of rat papillary muscle relaxation.

Applying external mechanical vibration during the relaxation phase of rat papillary muscle decreases the duration of the first part of the relaxation phase. To elucidate the basic mechanism responsible for this shortening of the relaxation period, we applied a controlled vibration to isolated twitching rat papillary muscles during various phases in the relaxation of a twitch. The first part of the relaxation phase was accelerated when length perturbations were applied in the first part of the relaxation of a twitch, dependent on both amplitude and frequency of the perturbation. When vibrations were applied in the first half of the relaxation, the second phase of relaxation was slightly slower (about 20%), but when no vibrations were applied in the first phase, relaxation could be accelerated by applying vibration in the latter half of the relaxation phase. Thus, in the latter half of relaxation, the acceleration of relaxation depended upon perturbation events earlier during that twitch. This study indicates that vibration-induced acceleration of relaxation is due (at least in part) to an apparent increase in detachment rate of attached cross-bridges from the thin filament without substantial reattachment.

Animals↗

PubMed2003

Neck muscle vibration alters visually perceived roll in normals.

The objective of this study was to determine whether vibration of dorsal neck muscles or of the mastoid bone or of both modified the perception of visual orientation in the head roll-tilt plane in normal subjects. Measurements of the subjective visual vertical (SVV) were obtained from 26 normal human subjects. Subjects reported the SVV in the upright and in the left and right 30 degrees static head roll-tilt positions. Subjects then reported the SVV while vibration was applied to the left or right dorsal neck or left or right mastoid. Both head position and vibration independently modified settings of the SVV. In head-tilted positions, vibration of the upper dorsal neck muscles (on the side of the head opposite to the head tilt) caused a significantly greater shift of the SVV in the opposite direction of head roll-tilt compared to vibration of the lower dorsal neck muscles or of the mastoid. These results support a role for cervical somatosensory information in perception of visual orientation in the roll plane. Our findings may help explain the differences observed in visual orientation perception in normal subjects between head alone and whole-body roll-tilt. Finally, vibration of neck muscles in the head roll-tilted plane may be a useful method to test cervical somatosensory function possibly by increasing their response to external stimulation.

Adult↗

PubMed2006

Vibrational analysis of mandible trauma: experimental and numerical approaches.

The aim of this study was to evaluate the effectiveness of vibrational assessment of the mandible fracture patterns. Measurement of natural frequencies and associated vibrational mode shapes was performed to determine the relationship between the dynamic behavior of the human mandible and incidence of mandibular fractures using both in vitro modal testing and finite element analysis. Our results show that the natural frequencies of the human mandible in dry and wet conditions are 567 Hz and 501 Hz, respectively. The first vibrational mode of human mandible is a bending vibration with nodes located at the mandibular body where bone fracture is less likely to occur. By contrast, high vibration amplitudes were identified in the symphysis/parasymphysis and subcondyle regions where bone fractures tend occur. These findings indicate that the vibrational characteristics of the mandible are potential parameters for assessment of the mechanisms of injury.

Finite Element Analysis↗

PubMed1988

Effects of vibration on steady flow downstream of a stenosis.

A physical model was used to test the effects of vibrations on the position of transition to turbulence (zt) downstream of a constriction. Constrictions were inserted in a length of clear plastic (Tygon) tubing and vibrated. Water was the fluid medium and flow was visualized with India ink. The frequency and velocity of vibration were monitored. For a given constriction and flow velocity, there was a band of frequencies which caused zt to move upstream. This band corresponded to frequencies of flow disturbances as measured with a hot-film anemometer without vibration. Both flow-visualization and hot-film frequencies were correlated via a Strouhal number to the Reynolds number and contraction ratio of the flow. Values of zt decreased with increasing vibration amplitude. The critical Reynolds number for turbulence was also decreased by vibration. These results are of importance in the diagnosis of vascular disease and the design of physical models of stenotic flows.

Arterial Occlusive Diseases↗

PubMed1990

Monitoring of fracture healing by lateral and axial vibration analysis.

The ability to monitor the healing of bone fractures is crucially important in their treatment. The aim of the present study was to develop and validate an objective method for monitoring fracture healing based on bone vibrational response. An analytic model was formulated, with which the mechanical parameters at the fracture site could be studied in relation to both lateral and axial bone vibration. Non-uniformities in the stiffness of the bone at the fracture site can be detected since they produce shifting of the vibration and the phase spectrum and result in strong coupling between the lateral and axial vibration response spectra. The validity of the model was tested in experiments using fresh cadaver tibiae with transverse osteotomy and materials simulating fracture callus. The results of the study of vibration amplitude and phase angle and the coupling of axial and lateral vibration in these experiments confirm our analytic projection. Preliminary results of in vivo investigations using the described method are encouraging.

Adolescent↗

PubMed1989

One-year reliability of vibration sensitivity thresholds in human beings.

Vibration sensitivity of the 3rd and 5th digits was evaluated in 36 female volunteers (between 22 and 36 years of age at the beginning of the study) previously screened for the absence of neurological disorders. Both fingers were tested in the same subjects on weeks 1, 2 and 52 in a balanced crossover design. Twenty-nine volunteers completed all 3 sessions. All participants gave their informed consent prior to participation. The test session was divided into trials. Each trial consisted of 2 sequential intervals, identified by a signal, and vibration was applied to the fingertip during either the first or the second interval. The subject was instructed to press the push button corresponding to the interval that contained vibration (two-interval forced-choice procedure). Vibration amplitudes were varied according to the up-down transformed rule for the estimation of the amplitude corresponding to 75% correct detection. Vibration sensitivity thresholds were stable as reflected by the lack of a trend over time, and by the compound symmetry of the variance-covariance matrix, which reflects stability of threshold variances as well as of intersession correlations over time. Reliability of vibration sensitivity makes this test potentially suitable for longitudinal evaluation of somatosensory functions.

Adult↗

PubMed1976

Changes in the pattern of breathing caused by chest vibration.

Vibration of 100 Hz was delivered longitudinally onto the sternum of anaesthetized cats and rabbits. Vibration consistently reduced the tidal volume by 10-15% without altering the end-expiratory point, and occasionally reduced the respiratory rate. Vibration applied during inspiration reduced the tidal volume as much as if delivered over several breaths. Expiratory vibration did not alter the course of the expiration, nor the volume of the following inspiration. The inhibition of inspiration was unaffected by deafferentation of chest wall skin, bilateral vagotomy, bilateral division of the phrenic nerves and low thoracic spinal transection. Spinal transection above the thoracic cord (C8/T1) abolished usual responses to vibration. The receptors for this reflex probably lie in the chest wall. Vibration inhibited the development of alae nasi tension during inspiration indicating that supraspinal reflex loops were involved. A role for intercostal muscle spindles is suggested.

Adult↗

PubMed1996

Increase in plasma thrombomodulin level in patients with vibration syndrome.

To determine whether endothelial cells are injured in vibration syndrome, we measured plasma levels of thrombomodulin (TM) in 100 patients with this syndrome using one-step sandwich enzyme immunoassay. Plasma level of TM in patients with vibration syndrome was significantly higher than that in normal control (p < 0.0001). There was no significant difference in the plasma TM level between patients with vibration syndrome and those with collagen disease. Plasma TM concentration in chain-saw operators was significantly higher than that in rock-drill operators (p < 0.05). Plasma TM value did not significantly differ between patients with vibration-induced white finger (VWF) and those without VWF. These results suggest that endothelial injury is present in patients with vibration syndrome, the degree of endothelial injury in patients with vibration syndrome equals that in patients with collagen disease, and the endothelial injury in chain-saw operators is greater than that in rock-drill operators. However, there was no difference in the degree of endothelial injury between patients with VWF and those without VWF.

Adult↗

PubMed1993

Development and evaluation of a novel sterilizer with rotary vibrators.

A novel steam-air sterilizer with rotary vibrators was developed with the aim of promoting heat transfer and the effective sterilization of foods. To evaluate the effects of the sterilizer, experiments to examine heat transfer and sterilization tests were carried out. In the experiments to examine heat transfer, heat penetration factors of sterilizer with vibration, j and fh values, were 1.70 and 1.50, respectively, while those of sterilizer without vibration were 1.83 and 2.32, respectively. In the sterilization with vibration, no surviving cells were detected after 3 min, whereas 7 min were required for sterilization without vibration. The rate of the amino carbonyl reaction was repressed by heat treatment with vibration.

Amines↗

PubMed1992

Nerve conduction in the hands of vibration exposed workers.

Symptoms of peripheral neuropathy in the hands are common among workers using vibrating tools. The mechanism for this and its relation to carpal tunnel syndrome (CTS) was studied in workers exposed to vibration at their workplace (17), along with a control group of healthy construction workers with heavy manual work but without vibration exposure (10). Patients with uni- or bilateral CTS (11) and a group of healthy volunteers without manual work (9) were included for comparison. Median nerve conduction velocities were measured both over the carpal tunnel and in a more distal segment. Vibration exposed workers had similar conduction velocities to unexposed construction workers. The subgroup of vibration exposed patients with symptoms from the hands had normal conduction in the ulnar nerve but demonstrated a decrease in median nerve conduction comparable (but less pronounced) with the CTS group. On a group basis these results indicated that the median nerve is most vulnerable for hand-arm vibrations. However, the conduction defects were not pronounced enough to diagnose CTS in most individual cases.

Adult↗

PubMed1985

Disturbed proprioception following a period of muscle vibration in humans.

Forearm position matching tasks were performed by blindfolded subjects before and after applying vibration for 60 s to the biceps or triceps muscle of one arm. Following cessation of vibration, statistically significant alignment (proprioceptive) errors occurred when a movement lengthened the previously vibrated muscle. The error was such that the length of the post-vibrated muscle was greater than the length of the same muscle in the non-vibrated arm. This effect is the opposite to that which occurs during vibration.

Adult↗