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At least 1,279 records · Page 71Linked to original sources
PubMed1989

Clinical demonstration of vibration-induced depression of left ventricular function.

In experimental studies, minute sinusoidal vibration has been reported to induce functional depression of the left ventricle and to be an index for evaluation of myocardial crossbridge kinetics. Therefore, to examine whether or not this vibration-induced functional depression could also be observed in the human ventricle, motion of the left ventricular (LV) wall or LV pressure was measured by echocardiography (n = 16) or by left heart catheterization (n = 4), in which 100 Hz, 2.07 mm-amplitude sinusoidal vibration was applied to the subject's precordium. In the echocardiographic study, left ventricular wall shortening did not change by vibration in nine healthy volunteers, but was depressed in two patients with aortic regurgitation (AR) and in one patient with ischemic heart disease (IHD). In measurement of LV pressure, the decrease in LV systolic pressure caused by vibration was obviously observed in two patients (AR and IHD) but was not observed in two patients with hypertrophic cardiomyopathy. These results suggest that we might be able to extend previously proposed experimental idea on early detection of the abnormality in myocardial crossbridge kinetics to the clinical setting.

Adult↗
PubMed1993

Differences in lingual vibrotactile thresholds of sensitivity using adjusted vs fixed methods of vibrator probe-contactor alignment.

The purpose of this study was to compare lingual vibrotactile thresholds of sensitivity obtained using individual subject adjustments of vibrator probe-contractor to lingual surface, with thresholds obtained using a fixed vibrator probe-contactor position across 30 subjects ranging in age from 18 to 26 yr. (M age = 20 yr.). Analysis showed minor (less than 5 dB SPL) differences in lingual vibrotactile thresholds of sensitivity between the two methods of vibrator probe-contactor alignment. For research purposes, the vibrator probe-contactor assembly should be adjusted to each individual's lingual surface, but for clinical-behavioral purposes, it might be sensible to use a fixed vibrator probe-contactor position across subjects, especially when performing research on young children, older adults, and the communicatively handicapped.

Adolescent↗
PubMed1995

Vibrotactile temporary threshold shifts induced by hand-transmitted vibration during underwater work.

The purpose of this paper is to clarify the temporary threshold shifts (TTS) of fingertip vibratory sensation produced by hand-transmitted vibration in an underwater work environment. The hand-transmitted vibration was applied with a pneumatic tool to the right hand of four experienced male SCUBA divers. The threshold of 125 Hz vibratory sensation was measured at the tip of the right forefinger before and after vibration exposure in the atmosphere and underwater. Vibration exposure at a 4 m depth produced greater TTS than in the atmosphere. The recovery time of TTS after vibration exposure in an underwater were affected by the underwater pressure.

Adult↗
PubMed1998

The effect of backrest angles on discomfort caused by fore-and-aft back vibration.

The effect on discomfort of the frequency and the backrest angle of x-axis (fore-and-aft) vibration of backrest have been studied. The method of adjustment was employed to obtain contours of equivalent comfort for three types of rigid backrests, whose surface were vertical, inclined 20 degrees and 40 degrees from vertical. Eighteen subjects were required to adjust test vibration over the frequency range 2-80 Hz to produce discomfort equivalent to that caused by 10 Hz 0.25 m/s2 r.m.s. sinusoidal reference vibration for each backrest. The direction of vibration was perpendicular to backrest surface. Results shows that the sensitivity at 20 and 40 Hz on inclined backrests is significantly about 1.4 to 1.5 times greater than that on a vertical backrest (p < 0.01) but there is no significant difference between the two contours for inclined backrests. The contour for a 'vertical' backrest obtained in this experiment agrees with the contour calculated from the frequency weighting factors for x-axis back vibration, Wc, in ISO2631-1, but the contours for inclined backrests do not agree with the contour well.

Adult↗
PubMed1999

A pilot study on the human body vibration induced by low frequency noise.

To understand the basic characteristics of the human body vibration induced by low frequency noise and to use it to evaluate the effects on health, we designed a measuring method with a miniature accelerometer and carried out preliminary measurements. Vibration was measured on the chest and abdomen of 6 male subjects who were exposed to pure tones in the frequency range of 20 to 50 Hz, where the method we designed was proved to be sensitive enough to detect vibration on the body surface. The level and rate of increase with frequency of the vibration turned out to be higher on the chest than on the abdomen. This difference was considered to be due to the mechanical structure of the human body. It also turned out that the measured noise-induced vibration negatively correlated with the subject's BMI (Body Mass Index), which suggested that the health effects of low frequency noise depended not only on the mechanical structure but also on the physical constitution of the human body.

Abdomen↗
PubMed2000

Thermal perception threshold testing for the evaluation of small sensory nerve fiber injury in patients with hand-arm vibration syndrome.

The aim of the present study was to investigate whether thermal perception threshold testing is a useful method that could replace pain threshold testing in the evaluation of small sensory nerve fiber injury in vibration-induced neuropathy. Vibration, pain, and thermal (warm and cold) perception thresholds were examined on both middle fingers of 50 patients with hand-arm vibration syndrome and 29 healthy controls of similar age. The patients were divided into three subgroups according to the Stockholm Workshop sensorineural scale. Thermal (warm and cold) thresholds as well as vibration and pain thresholds were significantly more deteriorated among the patients than in the controls. Among the patients, warm thresholds elevated and cold thresholds lowered according to the Stockholm Workshop scale. Thermal thresholds were significantly correlated with pain thresholds, and the sensitivity of the thermal threshold testing tended to be greater than that of the pain threshold testing. The present findings indicate that thermal threshold testing for warm and cold perception can be a useful substitute for pain threshold testing to examine small nerve fiber injury in vibration-induced neuropathy.

Arm↗
PubMed2002

Influence of frequency on difference thresholds for magnitude of vertical sinusoidal whole-body vibration.

Differences in vibration magnitude required for a human subject to differentiate whole-body vertical sinusoidal vibrations, difference thresholds for amplitude of sinusoidal vibration, have been determined at a vibration magnitude of 0.7 m/s2 r.m.s. at five octave band center frequencies from 4 to 63 Hz and at 80 Hz. The median difference thresholds of 16 male subjects seated on a flat rigid seat were found between 0.037 and 0.046 m/s2 r.m.s. at the frequencies used in this study. The subjects tended to be more sensitive to the change in vibration magnitude at 4 Hz than at 16, 31.5 and 63 Hz and less sensitive to the magnitude difference at 31.5 Hz than at 4, 8 and 80 Hz. The median relative difference thresholds, Weber's ratios, varied from 5.2% to 6.5% which were lower compared to the relative difference thresholds determined in the previous studies at frequencies where comparable data were available. The causes of the difference in the relative difference thresholds observed between this study and previous studies may include the difference in the psychophysical method used to determine the difference threshold.

Adult↗
PubMed2005

Evaluation of whole-body vibration by the category judgment method.

The purpose of this research is to establish a scale for comfort with regard to whole-body vibration by the category judgment method. Experiments were conducted with random signals as stimuli. These stimuli consisted of three types of signal, namely stimulus F, with flat PSD (Power Spectrum Density) ranging from 1 to 100 Hz, stimulus H with PSD, which became 20 dB higher at 100 Hz than at 1 Hz, and stimulus L that had a PSD 20 dB lower at 100 Hz. These signals were modified by Wk frequency weighting in accordance with ISO 2631-1, and the R.M.S. values were adjusted to be equal. In addition, the signal levels were varied over a range of five steps to create 15 kinds of individual stimuli. The subjects sat on a flat, horizontal metal plate mounted directly on the vibrator and were exposed to vertical vibrations before being asked to choose a numerical category to best indicate their perceived level of comfort (or otherwise) during each stimulus. The creation of this assessment scale, including the aforementioned categories, enabled not only clarification of the relationship between the vibration stimuli and the degree of comfort but also discovery of the connection between the frequency-weighted R.M.S. acceleration and the corresponding categories representing each degree of comfort without overlap. Moreover, it became clear that the subjects' assessment of the degree of comfort perceived differed with differences in the vibration spectrum.

Acceleration↗
PubMed2005

Biodynamic response at the palm of the human hand subjected to a random vibration.

This study investigated the biodynamic response (BR) distributed at the palm of the hand subjected to a random vibration. Twelve male subjects were used in the experiment. Each subject applied three coupling actions (grip-only, push-only, and combined grip and push) on a simulated tool handle at three different levels (50, 75, and 100 N) of palm force. This study found that the hand-arm system resonated mostly in the frequency range of 20 to 50 Hz, depending on the specific test treatment and individual characteristics. The maximum vibration power transmission through the palm occurred at the resonant frequency. Increasing the effective palm force generally increased the BR magnitude and resonant frequency. The apparent stiffness measured at the middle frequencies (80-100 Hz) is correlated to the BR in almost the entire frequency range (20-1,000 Hz). Under the same palm force, the push-only action corresponded to the highest BR values while the grip-only action generally produced the lowest values. Since the resonant frequency range matches the dominant vibration frequency range of many percussive tools, it is anticipated that the palm BR and vibration power transmission may have an association with vibration-induced injuries or disorders in the wrist-arm system among the workers using these tools.

Arm↗
PubMed1990

Hyperreactivity of the central sympathetic nervous system in vibration-induced white finger.

Vibration exposed workers with and without vibration-induced white finger (VWF), subjects with primary Raynaud's phenomenon and non-exposed controls were investigated in the present studies. The applied stimuli comprised cold stimuli, vibration exposure, and postural stimuli. The digital vasomotor responses to these stimuli were objectively quantified by measurements of finger systolic blood pressure and relative capillary blood flow rate in the skin of the finger. The results indicate that hyperreactivity of the central sympathetic nervous system may function as an/the abnormal element of the reflex mechanisms triggering the predominant portion of the vasoconstriction in episodic arterial closure of VWF. The hyperreactivity of the central sympathetic nervous system may be induced by prolonged exposure to hand-arm vibration, possibly by activation of the vibration elicited central sympathetic vasoconstrictor reflex mechanisms.

Adult↗
PubMed1990

Cardiovascular reflexes during vibration stress.

Vibration disease due to hand-held vibratory tools has various symptoms and signs which can be characterized by the severity. They include disorders of the central and autonomic nervous systems, as well as peripheral system disorders. The mechanism of Raynaud's phenomenon in vibration disease is proposed to be: Vibration and cold affect the local vessels and nerves directly, leading to enhanced release of chemical vasoconstrictors. Vibration, noise, cold, ergonomic and biodynamic conditions, and emotional stress during work result in disorders of the central and autonomic nervous systems. In the early stages, the autonomic nervous system may be stimulated, and in the later stages it is suppressed. When local vessel injuries and disorders of the central and local autonomic nervous mechanisms controlling the vessels occur, vasospasms in the fingers develop when the whole body is exposed to cold. The cardiovascular system, other than the peripheral circulatory system, may adapt to vibration stress. The adaptation subsides 7 to 8 years after discontinuation of the use of hand-held vibratory tools.

Cardiovascular System↗
PubMed1990

Autonomic stimulation and cardiovascular reflex activity in the hand-arm vibration syndrome.

Two experiments were carried out to investigate the cardiovascular responses of vibration-exposed workers to autonomic stimulation. In the first experiment blood pressures, heart rate and systolic time intervals (STI) were measured during a cold test in 63 vibration-exposed foundry workers and 41 controls. STI, such as total electromechanical systole (QS2I) and left ventricular ejection time index (LVETI), were found to be shorter in the vibration-exposed workers with and without vibration white finger (VWF) than in the controls, both at rest and during cold provocation and recovery (p less than 0.001). A significant inverse relationship between urinary excretion of free catecholamines and the duration of STI was observed under resting conditions (0.001 less than p less than 0.03). In the second experiment, the above mentioned cardiovascular parameters were measured in 11 grinding operators with VWF and 11 controls during a hand grip test, an arithmetic test and an orthostatic test. Finger systolic pressures (FSP) during local cooling to 30, 15 and 10 degrees C were also measured. QS2I and LVETI were more abbreviated in the VWF subjects than in the controls at rest and during both the circulatory stress tests and the recovery periods (0.001 less than p less than 0.05). The reduction in FSP by local cooling from 30 degrees C to 15 and 10 degrees C was greater in the VWF workers than in the controls (p less than 0.001). Significant correlations were observed between the reduction in FSP at 15 and 10 degrees C and the duration of STI during circulatory stress activities (p less than 0.01). A multiple regression analysis pointed out that vibration exposure was the major determinant of STI during circulatory stress, while the importance of age and smoking and drinking habits in predicting STI was negligible. The findings of these studies suggest that the level of cardiac sympathetic activity is increased in VWF workers in comparison with controls. These experimental results are consistent with those of other investigators, indicating that excessive sympathetic reflex activity plays an important role in the pathogenesis of VWF.

Fingers↗
PubMedDate not supplied

Effect of crossed stapedius reflex on vibration of mallear handle in man.

The ear drum was made to vibrate using frequency-modulated sound pulses of 40 ms duration, and the vibration velocity of the tip of the mallear handle (umbo) was measured with laser vibrometry before and during stapedius muscle contractions (elicited by sound of 100 dB HL in the contralateral ear). The stapedius reflex caused: an attenuation of the mallear vibrations below 1 kHz, a slight enhancement of the vibrations between 300 Hz and 1,500 Hz. These effects of the stapedius reflex appear to be caused by an increased stiffness in the structures affecting the mallear vibrations.

Adult↗
PubMed1993

Spontaneous cellular vibrations in the guinea-pig cochlea.

Mechanical vibrations of Hensen cells were measured with a laser-heterodyne interferometer in the third turn of the guinea-pig temporal-bone preparation without the application of an external stimulus. Smoothed periodograms (spectral-density estimates vs frequency) were constructed from the velocity vs time waveforms recorded from individual cells. For some cells, several peaks appear in the periodograms at levels as high as 10 dB above the noise floor, indicating the presence of spontaneous vibrations. The frequencies at which the peaks are located differ in different preparations, indicating that the observed peaks are not caused by the presence of ambient noise or ambient vibrations. It is demonstrated that smoothed-periodogram analysis is superior to fast-Fourier-transform analysis for discerning these spontaneous spectral components. The frequency tuning curves of cells from which spontaneous vibrations were measured (determined by applying an external stimulus to the ear) have single principal peaks. When the spontaneous spectral features are present, their frequencies lie, for the most part, within the principal-peak region of the tuning curve. We propose that these spontaneous vibrations originate at the outer hair cells and are the source of spontaneous otoacoustic emissions in the ear.

Animals↗
PubMed1981

Influence of vibration on asymptotic threshold shift produced by impulse noise.

Monaural chinchillas were exposed for 10 days to one of these conditions: (1) whole-body vibration (30 Hz, 1 g rms acceleration); (2) impact noise (113 dB peak SPL 1/s) or (3) a combination of whole-body vibration and impact noise. Thresholds were monitored before, during and after the exposure using the auditory-evoked response or behavioral conditioning techniques. Vibration alone had essentially no effect on threshold. Exposure to impact noise produced a stable asymptotic level of threshold shift 2-8 h after exposure onset. The asymptotic threshold shift was roughly 35 and 43 dB SPL at 0.5 and 8.0 kHz, respectively. Exposure to impact noise plus vibration produced an asymptotic threshold shift at 0.5 and 8.0 kHz that was approximately 10 dB greater than noise alone. The combination group also showed greater permanent threshold shifts and greater hair cell losses than the group exposed only to impact noise. The results imply that impact noise and whole-body vibration, at levels commonly found in industrial settings, can interact to increase the susceptibility of the chinchilla cochlea to noise-induced hearing loss.

Animals↗
PubMed1993

Neurophysiological investigation of hands damaged by vibration: comparison with idiopathic carpal tunnel syndrome.

Forty-seven men with numbness and paresthesiae in their hands after long-term occupational exposure to vibrating hand-held tools were examined neurophysiologically and clinically. The vibration thresholds of the finger tips were assessed and fractionated neurography of the median nerve motor and sensory fibres carried out. They were compared with control groups of healthy subjects and patients with idiopathic carpal tunnel syndrome. The patients exposed to vibration had major increases in their finger vibration thresholds, shown with both the Goldberg-Lindblom vibrameter and the Lundborg vibrogram. They also had a moderately increased motor distal latency at the wrist, but significantly less than patients with idiopathic carpal tunnel syndrome. Similar changes were seen in the sensory conduction velocities from finger to wrist. Measurement of fractionated conduction velocity across the carpal tunnel showed a bimodal distribution; one group of patients exposed to vibration had a significant reduction in conduction velocity similar to that in the genuine carpal tunnel syndrome, and one group had no localised affection at the carpal tunnel, suggesting more distal dysfunction at the level of palm or finger, or at the receptor level. A careful neurophysiological assessment of these cases is necessary before treatment is planned. It is particularly important to confirm median nerve damage at the wrist level if the carpal tunnel ligament is to be sectioned.

Adult↗
PubMed1982

A system for generating a variable mechanical impedance and its use in an investigation of the electromechanical properties of the B71 audiometric bone vibrator.

A method of presenting a bone vibrator with a variable mechanical load is described. Reciprocal relationships between electrical and mechanical properties of the B71 vibrator have been investigated and it is concluded that the vibrator behaves as a linear, reversible electrodynamic system. The mechanical impedance of the vibrator has been measured in the frequency range 250-4000 Hz. The relevance of these measurements to audiometer calibration and to sound radiation from the vibrator is discussed.

Acoustic Impedance Tests↗
PubMed1990

The influence of spatial contrast on the frequency-dependent nature of vibration sensitivity.

Several stimulus configurations have been described for measuring the threshold for vibration perception. One such configuration, used primarily for screening for peripheral nervous system function, for example, consists of a matrix of 24 rows and 6 columns of tiny pins vibrating at 230 Hz, with the even rows of pins vibrating in opposite phase to the uneven rows. In order to determine which class of mechanoreceptors is being tested with such a stimulus, the frequency dependence of the threshold for vibration perception was measured with a similar stimulus configuration in a group of younger subjects and in a group of older subjects. Moreover, the stimulus configuration could be changed from opposite phase stimulation to equal phase stimulation, wherein all pins vibrated with equal phase. In the range above 160 Hz, it appeared that in younger subjects the threshold of the Pacinian receptor system was evaluated with both modes of stimulation, although the sensitivity for opposite phase stimulation was reduced relative to the sensitivity for equal phase stimulation. In the older subjects, equal phase stimulation also appeared to evaluate the Pacinian receptor system. However, with the opposite phase stimulation, the non-Pacinian receptors tended to be evaluated. Below 100 Hz, sensitivity was greater for opposite phase than for equal phase stimulation in both groups. Moreover, with both modes of stimulation, a sensitivity maximum at 40 Hz could be obtained, which was tentatively ascribed to the rapidly adapting class of mechanoreceptors.

Adult↗