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PubMed1990

Skin sympathetic activity in the tibial nerve triggered by vibration applied to the hand.

The effect of vibration applied to the hand on skin sympathetic activity (SSA) in the lower limbs was studied in five healthy subjects. SSA from the right tibial nerve at the popliteal fossa, plethysmogram from the right index toe and perspiration from the sole of the right foot were measured when vibration of 100 m/s2 at 60 Hz was applied to the left palm for 1 min. The SSA response to vibration exposure differed among subjects, but every subject showed an increase in SSA from the tibial nerve when vibration was applied to the hand. Decrease in amplitude of plethysmogram from the toe was also found in all subjects. One subject displayed a remarkable increase in perspiration on the sole of the foot together with a great increase in SSA. The present findings indicated that even vibration exposure of the hand triggers sympathetic activity in the tibial nerve innervating the foot, and causes vasoconstriction of the toe and perspiration on the sole of the foot.

Adult↗
PubMed1986

A case-control study on the prognosis of vibration syndrome.

A case-control study was undertaken to evaluate some factors affecting the prognosis of vibration-induced white finger (VWF), 286 workers, who had used a chain saw in forests and had showed some symptoms and signs that were suspected to be vibration syndrome during some of the years from 1956 to 1980, were selected by medical examinations from a total of 612 forestry workers, and were divided into four groups according to the prognosis of the VWF based on a twenty-year follow-up. The study shows an association between the prognosis of VWF and vibration components, particularly vibration levels, severity of the syndromes not only in peripheral circulation but also in peripheral neuropathy before exposure to vibration ceased. There are also significant associations between the prognosis of peripheral neuromuscular symptoms and the factors of aging and duration of exposure. The study suggests that smoking habits and history of heart failure and diabetes had no effect on the prognosis of VWF.

Finger Injuries↗
PubMed1989

Heart rate variation and serum dopamine-beta-hydroxylase activity in workers exposed to vibration.

Tests of autonomic nervous function were conducted on 38 workers who had been exposed to vibration [16: VWF(+) group, 22: VWF(-) group, VWF: vibration-induced white finger] and 17 workers who had not been exposed to vibration (control group). Measurements were made of R-R interval variation of the electrocardiogram at rest and during deep breathing, and serum dopamine-beta-hydroxylase (DBH) activity during an immersion test of the hand in 10 degrees C water. Heart-rate variation related to respiratory arrhythmia indicates parasympathetic activity, and serum DBH activity is regarded as an indicator of sympathetic activity. The variations in the R-R interval during deep breathing were smallest in the VWF(+) group, followed by the VWF(-) group (P less than 0.05 and P less than 0.01, compared with the control group). The DBH activity of the VWF(+) group was larger than those of the VWF(-) group and the control group, however, the differences were small and not statistically significant. The reduced R-R interval variations in the VWF(+) and the VWF(-) groups support the hypothesis that autonomic nervous function can be affected by exposure to vibration. The change of DBH activity induced by cold exposure may be an unsuitable index of sympathetic tone. Further study of the autonomic nervous function in workers with vibration syndrome is recommended.

Adult↗
PubMed1989

Quantitative estimation of aesthesiometric thresholds for assessing impaired tactile sensation in workers exposed to vibration.

To evaluate the usefulness of aesthesiometric threshold testing in the quantitative assessment of peripheral sensorineural disorders occurring in the hand-arm vibration syndrome, two point discrimination (TPD) and depth sense perception (DSP) thresholds were measured by means of two aesthesiometers in the fingertips of 65 forestry workers exposed to chain saw vibration and 91 healthy males unexposed to local vibration or neurotoxic chemicals. Among the healthy subjects, divided into three age groups, there was no difference in the mean values of TPD and DSP thresholds. Assuming 1.28 or 2 standard deviations above the mean to be the upper limits of normality, in the present study the threshold values for TPD were 2.5 and 3.13 mm, respectively. Using the same assumptions, the normal threshold values for DSP were 0.36 and 0.49 mm. Among the 65 chain saw operators the prevalence of peripheral sensory disturbances was 70.8%. On the basis of the aesthesiometric results obtained for the group of 46 chain sawyers affected with sensorineural symptoms and a control group of 46 manual workers, the specificity of the aesthesiometric testing method was found to range between 93.4 and 100%, while the sensitivity varied from 52.2 to 71.7%. In its predictive value aesthesiometry had a positive accuracy of 84.6-96.0% and a negative accuracy of 42.8-50.0%. Aesthesiometric testing was able to differentiate between normals and vibration workers with sensory disturbances on a group basis (P less than 0.001), but due to the high rate of false negatives among vibration exposed patients, it was unsuitable to confirm objectively sensorineural symptoms on an individual basis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1981

Factors affecting the perception of low-level vibration.

The level at which vibration becomes a nuisance is low, well below the vibration intensity discussed with regard to the health of industrial workers in the International Standard ISO-2631 draft. The relationships between the various factors and the human response to low-level vibration generated by vehicular traffic, are discussed from the results obtained from questionnaires. A female may respond to a lower level than male. There is no difference in response to low-level vibration between standing and sitting postures. Accompanying noise distracts the perception of low-level vibration, however at high levels, the effect of distraction is reduced.

Adolescent↗
PubMed1979

[Ergonomical studies about the superposition of control activity and mechanical vibration (author's transl)].

The effects of combined stresses due to control activity and vertical mechanical vibration on man are analysed. In the first part, the processes in the human being at those superposed stresses are shown in a deterministic way, starting from morphological and physiological facts, which leads to a division of the organismic data processing in the fields of information reception, central information processing and information output. Hypothesis of the effects of vibration in the parts of information reception and information output as well as indications to measurable variables at laboratory experiments can be deduced from the model formulation. In the experimental part about factorized laboratory experiments with combined stresses consisting of an ideal-typical compensatory-tracking-task and mechanical vibration is reported, which can be divided into short-time experiments with measurement of the statistical control-factor and perseverance experiments with additional measurements of physiological variables. As established in the first part, influences of vibration in the regions of information reception and information output were found as well as thresholds for the performance-reducing effects of mechanical vibrations. The magnitudes of the thresholds are dependent on the task difficulty.

Ergonomics↗
PubMed1991

Experimental studies on the effects of vibration and noise on sympathetic nerve activity in skin.

Multi-unit sympathetic activity was recorded at elbow level from median nerve fascicles supplying glabrous skin of the left hand in five healthy subjects. The resultant vasomotor responses accompanying the neural activity were monitored by simultaneous recordings of skin blood flow using the laser doppler method and skin temperature in the innervation zones. No significant change in sympathetic activity was observed during handgrip exercise of the right hand under a constant gripping force of 2 kg. Subjects maintained the same gripping force of the right hand during exposure in random order to local vibration and/or noise, each type of exposure lasting 5 min with intervals of 20 min. A two-peaked significant increase in outflow from sympathetic nerves was observed during local exposure of the right hand to vibration with a frequency of 60 Hz and an acceleration of 50 m.s-2, followed by a postexposure period which revealed a relative suppression of sympathetic nerve activity and a significant increase in blood flow. Noise at 100 dB(A) showed only an initial effect on skin sympathetic nerve activity (SSA), whereas when combined with local vibration at 60 Hz, a pronounced increase in neural activity was noticed, indicating a combined effect of vibration and noise. These results from direct recordings of SSA suggest a sympathetic vasomotor reflex mechanism triggered by local vibration stimuli to the hand.

Adult↗
PubMed2004

Quickly changing acceleration forces (QCAFs) vibration analysis on the A300 ZERO-G.

Experiments that are done under microgravity, e.g. during space or parabola flights, are invariably accompanied and affected by ubiquitous vibrations of the surroundings. Vibrations induce Quickly Changing Acceleration Forces (QCAFs) that interfere with the perception of the earth gravitational field. To investigate their impact on experiments under microgravity we monitored the vibrations of the airplane A300 ZERO-G during parabola flights and analyzed them in their spectral and frequency domains. Power spectra obtained with Fast-Fourier Transforms (FFT) display a complex pattern of various vibrations whose origin, relative phases and intensities remain unidentified. During the zero-g phases (parabolas), when the engines of the airplane are throttled, the vibrations still elicit residual QCAFs of at least +/- 1 g. By means of adequate damping procedures the QCAFs could, however, be reduced by approximately 95%.

Acceleration↗
PubMed1996

[Endoscopic imaging of vocal cord vibrations. Digital high speed recording with various systems].

Vocal fold vibration patterns during phonation are presented with different digital imaging systems. With newly developed technical equipment color images up to 1000 digital images/s were obtained without light intensifying enhancement techniques via rigid and flexible endoscopy. With this color high-speed system, morphologic structures, such as small blood vessels, were visualized in high-resolution quality as a result of additional color information. In another system, zooming of endoscopic pictures via pixel interpolation algorithms provided full-monitor presentation of vocal fold vibratory patterns. This system allows PC-based synchronization with microphone and electroglottographic signals in a frame-by-frame technique. Although only processing gray scale images, analyses of dynamic changes in modes of vibration were facilitated by the higher frame rate recording of up to 2000 frames/s and, in addition, they display corresponding analog signals. Both methods provide clinically important information. Furthermore, we demonstrated irregular vocal fold vibration patterns in a healthy adult volunteer. In this experiment, the irregular vibratory modes were induced by voluntarily applying asymmetric vocal fold tension. The asymmetric vocal fold vibration pattern resulted in (functionally induced) roughness of the voice as predicted by computer models of asymmetric vocal fold vibration. Digital high-speed cinematography proved to be a highly promising technique in the analysis of dysphonia and provided physiological examples that could be compared with models of coupled nonlinear oscillators.

Adult↗
PubMed1999

Visual and oculomotor responses induced by neck vibration in normal subjects and labyrinthine-defective patients.

Three-dimensional scleral search coil eye movement recordings were obtained in five normal subjects and four patients with absent vestibular function, during unilateral vibration of the neck in the supine position. The purpose of the experiments was to investigate any role played by eye movements in the illusion that a small fixation target, viewed in an otherwise dark room, moves when vibration is applied to the neck (propriogyral illusion). Vibration was applied to the right dorsal neck muscles in three visual conditions: total darkness, fixating a light-emitting diode (LED) in an otherwise totally dark room and LED fixation in the normally lit room. Normal subjects reported that during vibration, with LED fixation in an otherwise dark room, the target appeared to move predominantly leftwards and patients reported a predominantly downward movement. Eye movements were consistently elicited in all subjects. In normal subjects there was a slow-phase eye movement predominantly to the right, interrupted by nystagmic quick phases in the opposite direction, whereas in the patients slow phases were predominantly upward with quick phases downward. Eye movements were larger in the dark but the velocity of the initial slow-phase component (<200 ms) did not change with visual conditions. Mean latencies of the eye movements were typically 80 ms but in individual trials could be as short as 40- 60 ms. The eye movements were considerably larger in the patients (e.g. mean cumulative slow-phase displacement in the dark 12 degrees vs 2 degrees; maximum velocity ca. 5 degrees /s vs 1 degrees /s). These results indicate that the propriogyral illusion is secondary to vibration-induced eye movements, presumably mediated by the cervico-ocular reflex (COR). The difference in direction of the illusion and eye movements in the patients may be related to a predominant enhancement of the vertical COR, secondary to the prominent exposure to vertical retinal slippage experienced by these patients during daily activities such as locomotion.

Adult↗
PubMed2001

Proprioceptive control of cyclical bimanual forearm movements across different movement frequencies as revealed by means of tendon vibration.

The effect of unilateral tendon vibration on the performance of cyclical bimanual forearm movements was investigated across different cycling frequencies (from 0.67 to 2.53 Hz). The spatiotemporal features of the individual limb motions as well as their coordination were studied. Tendon vibration was found to result in a substantial reduction in the amplitude of the vibrated arm, leaving the nonvibrated arm unaffected. The vibration-induced amplitude reduction decreased from 26% to 11% as cycling frequency increased even though significant reductions were still observed at the highest cycling frequencies. Tendon vibration was also found to result in an increase of the phase lead of the dominant arm with respect to the nondominant arm, but this effect was not modulated by cycling frequency. The data argue in favor of a closed-loop mode of movement control during cyclical high-speed movements. It is suggested that kinesthetic afferent information is processed and used to guide action up to near-maximal movement speeds, reinforcing recent claims with respect to visual information processing.

Adolescent↗
PubMed2006

Temperature affects interaction of visual and vibrational cues in parasitoid host location.

Parasitoid host location in nature is facilitated by simultaneously using different information sources. How multisensory orientation on the same spatial scale is influenced by environmental conditions is however poorly understood. Here we test whether changes in reliability of cues can cause parasitoids to alter multisensory orientation and to switch to cues that are more reliable under extreme temperatures. In the ichneumonid wasp Pimpla turionellae, multisensory use of thermally insensitive vision and thermally sensitive mechanosensory host location by vibrational sounding (echolocation on solid substrate) was investigated with choice experiments on plant-stem models under optimum temperature (18 degrees C), at high- (28 degrees C) and low-temperature limits (8 degrees C) of vibrational sounding. Temperature affected relative importance of vibrational sounding whereas visual orientation did not vary. At 18 degrees C, parasitoids used visual and vibrational cues with comparable relative importance. At 8 and 28 degrees C, the role of vibrational sounding in multisensory orientation was significantly reduced in line with decreased reliability. Wasps nearly exclusively chose visual cues at 8 degrees C. The parasitoids switch between cues and sensory systems depending on temperature. As overall precision of ovipositor insertions was not affected by temperature, the parasitoids fully compensate the loss of one cue provided another reliable cue is available on the same spatial scale.

Animals↗
PubMed2003

Vocal fold vibration irregularities caused by different types of laryngeal asymmetry.

The common symptom of hoarseness is regarded to be caused by (1) turbulences and air loss due to incomplete glottic closure and (2) irregular vibrations of the vocal folds. With real time resolution, the latter can only be observed using high-speed recording techniques (> or =2,000 images/s). In this paper an actual recording method is described, called high-speed glottography (HGG), which quantifies vibration irregularities. It combines imaging and image processing techniques with a functional endoscopy of the disordered voice and delivers motion curves separately for each vocal fold. They are fitted with a computer simulation in order to identify the underlying driving parameters of the vibration. A vocal fold is assumed to vibrate as a system of two coupled oscillators ("two-mass model"). From the model fit to bilateral motion curves, the subglottal pressure, muscular tension and oscillating masses of the vocal folds can be computed with reasonable accuracy. Besides normal voices, HGG has been applied to selected clinical cases of voice disorders. Two types of irregularities have been measured: there is a frequency difference either between left and right vocal folds (horizontal asymmetry) or on one side between the ventral and dorsal third (vertical asymmetry). By modeling, both categories of irregular motion curves can be explained in detail. It is presumed that laryngeal asymmetry (either in mass or tension) causes irregular vibrations.

Adult↗
PubMed1999

Neoglottic vibration in tracheoesophageal shunt phonation.

The purpose of the present study was to examine vibratory patterns of the neoglottis and to ascertain the neoglottic conditions that could cause failure in tracheoesophageal shunt phonation. We studied 30 tracheoesophageal shunt speakers while using "trap-door" type voice prostheses. Videostroboscopy was undertaken to investigate vibratory patterns of the neoglottis during phonation of the sustained vowel sound /e/ in these patients. The voice qualities of the patients were judged perceptually. A regular neoglottic vibration was observed in 21 patients. Nine patients had irregular neoglottic vibrations. In this latter group, two patients had incomplete neoglottic closures with breathy voices, four patients had multiple contacts of several mucosal walls with rough voices, and three patients had tight neoglottic closures with strained voices. During stroboscopic evaluation of tracheoesophageal shunt phonation, regularity of the neoglottic vibration may be the most significant finding. These findings show that it is as important to evaluate neoglottic vibration in alaryngeal voicing as it is to study glottic vibration in laryngeal voicing. Stroboscopic examination may be a help to elucidate a cause of failure in cases of poor tracheoesophageal shunt speech.

Aged↗
PubMed1999

Changes of visual localization induced by eye and neck muscle vibration in normal and strabismic subjects.

BACKGROUND: It has been reported that vibratory activation of eye- and neck-muscle proprioception can induce eye position changes in normal and strabismic subjects. This study investigated the effects of proprioception in the eye and neck muscles on space localization. METHOD: Vibration was applied to either the eye or neck muscle in normal subjects, intermittent exotropes, and constant exotropes/esotropes. The subjects pointed at the immediately remembered position of an extinguished visual target with the hand both before and immediately after vibration of the muscles under binocular and monocular viewing conditions. The hand-pointing performance in darkness was recorded by an infrared camera, and the pointing shifts were analyzed qualitatively and quantitatively. RESULTS: With vibration of the vertically moving muscles of the eye and neck, the direction of the pointing shifts was the same in all groups of the subjects and under all viewing conditions. With vibration of the horizontally moving muscles of the eye and neck, the directions were the same in the normals and in most of the intermittent exotropes. However, in the constant exotropes and esotropes, the directional shifts were dependent on which eye was vibrated, and the directions were more variable, always directed only to one side. CONCLUSION: Proprioception in the eye and neck muscles participates in visual space localization, but the effects of proprioceptive activation were differed in normal subjects from those in patients having constant strabismus. The differences may be related to the level of binocular function.

Adaptation, Ocular↗
PubMed2004

Effect of different vibration frequencies on heart rate variability and driving fatigue in healthy drivers.

OBJECTIVE: This investigation was to assess the effect of different vibration frequencies on heart rate variability (HRV) and driving fatigue in healthy subjects during simulated driving, by the use of power spectrum analysis and subjective evaluation. MATERIALS AND METHODS: Sixty healthy subjects (29.6+/-3.3 years) were randomly divided into three groups, A, B and C, and the subjects of each group participated in the simulated driving for 90 min with vertical sinusoidal vibration (acceleration 0.05 g) of 1.8 Hz (group A), 6 Hz (group B) and no vibration (group C), respectively. Low-frequency (LF) and high-frequency (HF) components of HRV, reflecting sympathetic and parasympathetic activities, and the LF:HF ratio, indicating sympathovagal balance, were measured throughout all periods. All indices of HRV were calculated in the pre-experiment period, mid-experiment period and end-experiment period, and were analyzed by repeated measures analysis of variance. Subjective responses to a questionnaire were obtained after the simulated task for the three groups. RESULTS: Significant differences in all indices of HRV were observed between different experiment periods and between any two groups. The ratings of subjective fatigue exhibited significant differences between any two groups. CONCLUSION: The drivers' fatigue ratings were associated with vibration frequencies in simulated driving. The study quantitatively demonstrated that different effects on autonomic nerve activities were induced by different vibration frequencies.

Adult↗
PubMed2000

Pathophysiology and classification of the vibration white finger.

Skin, arteries and nerves of the upper extremities can be affected by vibration exposure. Recent advances in skin and vascular biology as well as new investigative methods, have shown that neurovascular symptoms may be due to different vascular and neurological disorders which should be differentiated if proper management is to be evaluated. Three types of vascular disorder can be observed in the vibration white finger: digital organic microangiopathy, a digital vasospastic phenomenon and arterial thrombosis in the upper extremities. An imbalance between endothelin-1 and calcitonin-gene-related peptide is probably responsible for the vasospastic phenomenon. Moreover, paresthesiae can be due to either a diffuse vibration neuropathy or a carpal tunnel syndrome. A precise diagnosis is then necessary to adapt the treatment to individual cases. A classification describing the type and severity of the vascular lesions is presented. Asymptomatic lesions are included for adequate epidemiological studies and risk assessment of vibrating tools. Monitoring of vibration exposed workers should include not only a questionnaire about symptoms, but also a clinical evaluation including diagnostic tests for the screening of early asymptomatic neurovascular injuries.

Diagnosis, Differential↗
PubMed1997

Effects of occupational use of vibrating tools in the autonomic, central and peripheral nervous system.

OBJECTIVES: The objective of this study was to clarify the autonomic, central and peripheral nervous effects of vibrating-tool operation. METHODS: The ECG R-R interval variability (CVRR), including the C-CVHF, C-CVLF (two component CVs of the CVRR reflecting parasympathetic and sympathetic activities, respectively) and the power spectral densities (PSDHF and PSDLF) after autoregressive analysis, short-latency somatosensory evoked potentials (SSEP), distribution of nerve conduction velocities (DCV), and median and radial nerve conduction velocities (NCVs) were measured in 17 vibrating-tool operators and the same number of age-matched control subjects. Some of the operators complained of white finger even in summer as soon as they arrived at the cold workplace. DESIGN: The significance of the differences in neurophysiological data between the exposed and unexposed groups and the associations between these data in the former were investigated. RESULTS: The CVRR, C-CVHF and PSDHF were significantly lower in the vibrating-tool operators than in the matched controls. The N9-N13 interpeak latency of the SSEP, i.e., conduction time of the cervico-spinobulbar pathway, in the operators was significantly prolonged as compared with the controls; the faster velocities of the DCV and the NCVs were significantly slowed in the operators. The N9-N13 interpeak latency in the operators was significantly correlated with the C-CVHF. CONCLUSION: Complex stressors of local vibration, cold, noise and heavy work, seem to affect the cervico-spinobulbar, parasympathetic and peripheral nerve functions. Also, parasympathetic hypofunction may imply a consequence in brainstem pathology induced by cold exposure in addition to vibration.

Adult↗